Chapter 2 All

:

CHAPTER 2:

CELL STRUCTURE & FUNCTIONS

(8 HRS)

2.0 Cell Structure & Functions (8 hrs)

2.1 Prokaryotic & Eukaryotic Cells ()

2.2 Structure and functions: cell membrane and

organelles (2)

2.3 Cells are grouped into tissues (3)

2.4 Cell Transport (2)

Learning outcomes

2.1 Prokaryotic & Eukaryotic Cells

a) State cell theory.

b) Describe the structures of prokaryotic & eukaryotic

cells.

c) Compare the structures of prokaryotic and eukaryotic

cells.

4

Robert Hooke observed cork sample

Composed of a lot of tiny, empty box structures ~ cell

Cell ~ basic unit of living things

What Is Cell?

Learning Outcomes : 2.1 (a) State cell theory

Cork tissue

5

Introduced by Schleiden (1838), Schwann (1839) & Rudolf Virchow (1855)

Their work ~ cell theory

Cell Theory


1. Cell is the building block of structure in living things

2. New cells come from preexisting cells

Cells can divide to form new cells

All living things are made of 1 or more cells

6

Cell Theory


3. Cells contain hereditary information (DNA) which

is passed from cell to cell during cell division

4. Cell is the functioning unit of life

Cell is the smallest unit that can conduct all activities of

life (metabolism)

Based on structural organisation

Types of Cell

Prokaryotic cell Eukaryotic cell

Types of Cell

Learning Outcomes : 2.1 (b) Describe the structures of prokaryotic & eukaryotic cells

8

Eg: bacteria, cyanobacteria (blue green algae)

Prokaryotic Cell

Main Features

Lack a membrane-bounded nucleus

Genetic material is not enclosed by a nuclear membrane

Lies freely in cytoplasm, in a region called nucleoid


9

Capsule

Cell Wall Plasma

membrane

Cytoplasm

Chromosomal DNA

Flagellum

Plasmid DNA

Pili

Structures of Prokaryotic Cell

Ribosome

Learning Outcomes : 2.1 (b) Describe & compare the structures of prokaryotic & eukaryotic cell

10

Structure Explanation

Chromosomal

DNA

Single, circular, double stranded DNA

Plasmid DNA

(if present)

Small, circular, double stranded extra DNA

Usually gives resistance to antibiotics in some bacteria

Flagella (if

present)

Long threadlike structure for locomotion

Pili Shorter & straighter than flagella (numerous)

Adhesion to surface or to each other

Capsule (if

present)

Gel-like layer outside cell wall

Adhesion to surface or to each other, provide protection

Structures of Prokaryotic Cell


11

Eg: protists, fungi, plants & animals

Eukaryotic Cell

Main Features

Has membrane-bounded nucleus

Genetic material is enclosed by a nuclear membrane

Has many membrane bounded organelles

Organelle is a small structure suspended in cytoplasm that conduct certain function


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Structures of Eukaryotic Cell


13

Feature Prokaryotic Cells Eukaryotic Cells

Cell Size Smaller, diameter 1-10 m Larger, diameter 10-100 m

Nucleus No membrane-bounded

nucleus

Genetic material lies freely

in cytoplasm (nucleoid)

Has membrane-bounded

nucleus

Genetic material is enclosed

by nuclear membrane

Genetic

material

Circular DNA Linear DNA

DNA does not associate

with histone protein

DNA associates with histone

protein

Differences Between Prokaryotic & Eukaryotic Cell

Learning Outcomes : 2.1 (c) Compare the structures of prokaryotic & eukaryotic cells


Circular DNA Linear DNA


DNA associates with histone protein

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Organelle No membrane bounded

organelle

Has many membrane-

bounded organelles

Ribosome Smaller, subunit 70S Larger, subunit 80S

Cell wall Composed mainly of

peptidoglycan & murein /

amino acids

Composed mainly of

cellulose (plant) & chitin

(fungi)

Structure of

flagella

Simple, lack of 9+2

microtubules

arrangement

Complex, has 9+2

microtubules arrangement



Structure of Flagella


Flagella 9+2 microtubules arrangement

18


Cell division Mitosis & meiosis does not

occur.

Mostly by binary fission

without spindle formation

By mitosis, meiosis or

both.

Spindle is formed

Type of

organism

Unicellular or filamentous

organisms

Unicellular, filamentous

or multicellular

organism



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Both cells are bounded by a plasma membrane

Both cells contain genetic material

Both cells have cytoplasm

Both cells have ribosomes

Similarities Between Prokaryotic & Eukaryotic Cell





organelles (2)



Learning outcomes

2.2 Cell Membrane & Organelles

a) Illustrate the detailed structures of typical plant and animal

cells.

b) Describe the structure of the plasma membrane and the

functions of each of its components.

c) Describe the structure and functions of the following

organelles:

nucleus lysosome

rough endoplasmic reticulum ribosome

smooth endoplasmic reticulum mitochondria

Golgi body chloroplast

centriole

Based on structure, 2 types:-

Eukaryotic Cell

Animal cell Plant cell

Eukaryotic Cell

Learning Outcomes : 2.2 (a) Illustrate the detailed structures of typical plant & animal cells

Structure of Animal Cell (Electron Microscope)


Structure of Plant Cell (Electron Microscope)


Plant Cell (Light Microscope)


Animal Cell (Light Microscope)


Cell wall

Plasma membrane

Cytoplasm

Structures Seen Under Light Microscope

Chloroplast

Vacuole

Plasma membrane

Cytoplasm

Nucleus

Plant Cell Animal Cell

Nucleus


Plasma membrane separates the living cell from its nonliving surroundings

Size ~ 7.5-8 nm thick

Plasma membrane that surround the cell & membrane that surround the organelles has the same structure

Structure of plasma membrane is proposed by Singer & Nicolson (1972) ~ Fluid-Mosaic model

Plasma Membrane

Learning Outcomes : 2.2 (b) Describe the structure of the plasma membrane & the functions of each of its component

Globular protein Phospholipids Carbohydrate Cholesterol

Fluid Mosaic Model ~ Structure

Major Others

Components


Phospholipids

hydrophobic

tails

hydrophilic heads


Phospholipid bilayer (2 layers of phospholipids)

Phospholipid has 2 parts:

head ~ polar, hydrophilic region tail ~ non-polar, hydrophobic region

Phospholipids have both hydrophobic & hydrophilic regions

Amphipathic molecules

The polar, hydrophilic heads points outward into cytoplasm &

extracellular fluid (outside the cell)

The non-polar, hydrophobic tails face inwards (away from

water)

Creating a hydrophobic region in the middle

Phospholipids


Types of Protein

Integral / Intrinsic Peripheral / Extrinsic

Globular Protein


Phospholipid

bilayer

Extrinsic protein

Intrinsic protein

Globular Protein


Intrinsic protein ~ partially / fully embedded within the

phospholipid bilayer (firmly

bound)

Extrinsic proteins ~ attached loosely to the surface of

phospholipids or protein

Fully embedded protein that penetrates the entire phospholipid

bilayer transmembrane protein

Intrinsic protein amphipathic

Globular Protein


Embedded proteins within phospholipid bilayer

creates a mosaic pattern (when viewed from the above)

Why Mosaic Pattern?


Why Fluid?

Fluid ~ mosaic pattern is dynamic

Phospholipid & extrinsic proteins can move laterally along the membrane

Lateral movement

Time


Why Fluid?


Protein form glycoprotein

Phospholipid form glycolipids

Carbohydrate

Other Components ~ Carbohydrate

Location: on the outer surface of the membrane,

Carbohydrate chain may combine with:-


Function: act as identification tag (described later)

Other Components ~ Carbohydrate


Found between phospholipids molecules

Function: to regulate membrane fluidity by restricting the movement of phospholipids (stabilize membrane structure)

Cholesterol

Other Components ~ Cholesterol


1. Act as Transport Protein

6. Attachment site of cytoskeleton

& extracellular matrix

3. Act as Receptor Protein

2. Act as Enzyme

4. Intercellular Joining

5. Cell-cell Recognition

Roles of Cell Membrane Components


Hydrophilic

channel

Selective permeable

1. Act as Transport Protein

Transmembrane protein transport

molecules across membrane

Transport protein has hydrophilic

channels that allow polar

molecules / ion to pass through

Eg: channel protein, carrier

protein


Globular protein has active site which can bind to a specific substrate

Catalyze specific chemical reaction

A B C

2. Act as Enzyme


3. Act as Receptor Protein

Has a binding site with a specific shape for chemical messenger

Eg: hormone / neurotransmitter

Send information into the cell


4. Intercellular Joining

Membrane proteins of adjacent cell may join together

Eg: gap junction


Act as identification tag

Specifically recognized by other cells

Eg: antigen is recognized by human cells as foreign

GLYCOPROTEIN

5. Cell-cell Recognition


6. Attachment site of cytoskeleton & extracellular matrix

Outer surface ~ attach to extracellular matrix

Inner surface ~ attach to cytoskeleton

Maintain cell shape


Learning outcomes

2.2 Cell Membrane & Organelles

a) Illustrate the detailed structures of typical plant and animal

cells.

b) Describe the structure of the plasma membrane and the

functions of each of its components.

c) Describe the structure and functions of the following

organelles:

nucleus lysosome

rough endoplasmic reticulum ribosome

smooth endoplasmic reticulum mitochondria

Golgi body chloroplast

centriole

Nucleus

Learning Outcomes : 2.2 (c) Describe the structures & functions of nucleus

Largest organelle

Spherical-shaped

Inner parts of nucleus contain nucleoplasm

Structure

Enclosed by 2 layers of nuclear membrane

Which fused at intervals to form nuclear pores

Nuclear pore regulate movement of molecules across

nuclear membrane

Nucleus

Structure


Nucleus


Outer membrane is continuous with

endoplasmic reticulum

(ER)

Structure

Nucleolus

Spherical-shaped Non-membranous Dense mass structures Contain DNA, RNA & proteins

Nucleoplasm

A jellylike fluid contain nucleolus & chromatin

Chromatin

Long thin strands of DNA & histone protein

Function (nucleolus)

Site of rRNA synthesis Combine protein with rRNA

to form ribosome (ribosome subunit assembly)

Nucleus


Nucleus

Function

Control cell activities & cell division

Store genetic material

Site of RNAs synthesis & ribosomes subunit assembly


Extensive network of membranous tubules ~

cisternae (interconnected)

Continuous with the outer nuclear membrane

Enclosed by a single membrane

Space within ER ~ cisternal space / lumen

Endoplasmic Reticulum (ER)

Structure

Learning Outcomes : 2.2 (c) Describe the structures & functions of endoplasmic reticulum

Consist of more tubular sacs

Lack of ribosomes on outer surface

~ appear smooth

Rough ER Smooth ER

Types of ER

Consist of flattened sacs

Has ribosomes; attached on the

outer surface ~ appear granular

Endoplasmic Reticulum


Rough Endoplasmic Reticulum

Function

Intracellular transport of protein (package & transport

protein to Golgi body within transport vesicle)


Smooth Endoplasmic Reticulum

Function

Site of lipid synthesis

Detoxification of toxic waste (drugs & poison)

Storage of calcium ions in skeletal muscle cells


Enclosed by a single membrane

Consist of stacked flattened membranous

sacs ~ cisternae

Golgi Body

Structure

Learning Outcomes : 2.2 (c) Describe the structures & functions of Golgi body

The sacs are not physically connected

Space within Golgi body ~ cisternal space / lumen

Each Golgi stack has cis face & trans face

Cis face is facing towards the ER /

nucleus

Trans face is facing towards the plasma

membrane

Golgi Body

Structure


Golgi

body

Nucleus Rough

ER

Secretory

vesicle

Plasma

membrane

Glycoprotein

cis face

trans face

Golgi Body


Secretory

vesicles

Transport

vesicles

ER pinches off to form transport vesicles

Which move towards Golgi body

It fuses with the cis-face

Contents (eg: protein/ carbohydrate/lipid) is released

into lumen

Golgi body modifies the substances as it moves from

cis-face to the trans-face

Golgi Body


Secretory

vesicle

Transport

vesicle

The tips of trans-face cisternae

pinches off to form secretory

vesicles

Secretory vesicles may:-

Move towards plasma

membrane & fuse with it to

release substances by

exocytosis

Remain in the cell ~ become

lysosome

Golgi Body

Function

Process, modify,

sorting, package

& transport

protein

Form lysosomes


Small, spherical-shaped

Enclosed by a special single membrane

Contain many hydrolytic/digestive enzymes

Lysosome

Structure

Learning Outcomes : 2.2 (c) Describe the structures & functions of lysosome

Lysosome

Intracellular digestion

Digest macromolecules which enter the cell by phagocytosis process

Recycle cells own organic material Digest old / damaged organelles to recycle organic

material by autophagy process

Programmed cell destruction

Digest the whole cell by autolysis process

Function


Plasma membrane engulfs large molecules & pinches off to form food vacuole / phagosome by phagocytosis process

Primary lysosome fuses with food vacuole secondary lysosome

Hydrolytic enzymes digest large molecules

Useful substances are absorbed into cytosol

1. Intracellular Digestion


1. Intracellular Digestion


Eg: Amoeba & macrophage (engulf bacteria & digest them for defense or protection)

Amoeba engulf red yeast for food Macrophage engulf bacteria for protection

Old or damaged organelle is enclosed by a single

membrane to form autophagic vacuole / autophagosome

Lysosome fuse with autophagic vacuole & digest the

organelle with hydrolytic enzymes by autophagy process

2. Recycle cells own organic material


3. Programmed Cell Destruction

In old / damaged cell, lysosome membrane ruptures

Hydrolytic enzymes are released into the cytoplasm

Digest the whole cell by autolysis process

Eg : destroy old / damaged cell

: destroy leukocyte that phagocytize pathogen

: during metamorphosis & development


Autolysis during human embryo development Autolysis in tadpole tails

Endomembrane System

The membrane of the organelles are related through

direct physical continuity or by transfer of membrane

segments as vesicles

Endomembrane system include:-

nuclear membrane

endoplasmic reticulum

Golgi body

lysosome

vesicle / vacuole

plasma membrane


Small granule

Spherical-shaped

Non-membranous

Made of rRNA & protein

Consist of 2 subunits (large & small)

Ribosome

Structure

Learning Outcomes : 2.2 (c) Describe the structures & functions of ribosome

attached to nuclear membrane or RER

synthesize proteins for export / cell

membrane / lysosome

Free ribosome Bound ribosome

Types of ribosome

lies freely in cytoplasm

synthesize proteins that function

in cytosol


Function

Site of protein synthesis

Act as enzyme (ribozyme) to catalyze the formation of peptide bond

Ribosome


Mitochondria

Structure

Learning Outcomes : 2.2(c) Describe the structures & functions of mitochondria

Shape ~ oblong / biconvex /

cylindrical

Enclosed by 2 layers of

membrane

Space between outer & inner

membrane ~ intermembrane

space

Outer membrane is smooth

& point towards cytoplasm

Mitochondria

Learning Outcomes : 2.2 (c) Describe the structures & functions of mitochondria

Inner membrane is folded inwards to form cristae

Cristae increase the surface area for attachment of

enzymes involved in Electron Transport Chain (ETC)

Structure

Mitochondria

Inner membrane enclosed a

fluid-filled space ~ matrix

Matrix contains :-

bacterial-like DNA &

ribosome to synthesize own

protein & enzymes

enzymes involved in Krebs

cycle

Structure


Mitochondria

Site of ATP synthesis / cellular respiration

Krebs cycle occur in matrix

ETC occurs in cristae

Function


Chloroplast

Learning Outcomes : 2.2 (c) Describe the structures & functions of chloroplast

Shape ~ oblong /

biconvex

Enclosed by 2 layers

of membrane

Space between

outer & inner

membrane ~

intermembrane

space

Structure

Outer membrane points towards cytoplasm

Inner membrane enclosed a fluid-filled space ~ stroma

Chloroplast


Stroma contains :-

bacterial-like DNA & ribosome to synthesise own protein &

enzymes

enzymes involved in Calvin cycle

Structure

Chloroplast

Structure


Grana are interconnected by intergrana membrane / lamella

Chlorophyll & photosynthetic pigments are embedded within

thylakoid membrane

Embedded within

stroma, are

membranous system

called thylakoids

Thylakoids ~ flat discs

which are stacked to

form grana

Chloroplast

Site of photosynthesis

Light dependent reaction occurs in grana /

thylakoid

Light independent reaction occurs in stroma

Store starch (in stroma)

Function


Semiautonomous Organelle

Both mitochondria & chloroplast can duplicate &

reproduce independently within the cell

semiautonomous organelle

Learning Outcomes : 2.2 (c) Describe the structures & functions of organelle

Centriole

Exist in pair, orientated at

90 angle to another

Located in a region called

centrosome ~ near nucleus

of animal cell

Each centriole composed of

9 sets of triplet

microtubules, arranged in a

circle (9x3)

Structure

Learning Outcomes : 2.2 (c) Describe the structures & functions of centriole

Centriole

Function

Organize microtubules assembly during cell division

(microtubules organizing center ~ MTOC)

Form the bases of cilia & flagella

Learning Outcomes : 2.2 (c) Describe the structures & functions of centriole




organelles (2)






organelles (2)


Animal cells & tissues Plant cells & tissues

Epithelial cells Meristem

Nerve cells Parenchyma

Muscle cells Collenchyma

Connective tissues Sclerenchyma

Xylem & Phloem


Learning outcomes

2.3 Cells are grouped into tissues

Describe the following types of cells and tissues:

Animal cells & tissues

epithelial muscle

nerve connective

Plant cells & tissues

meristem sclerenchyma

parenchyma xylem

collenchyma phloem

Muscle Tissue

Most abundant tissue

Cytoplasm contain many :

mitochondria

glycogen

myoglobin

myofilament (actin & myosin) ~

specialised for contraction

Main function ~ movement

Learning Outcomes : 2.3 Describe the structures, function and distribution of muscle cells

Muscle Tissue

Types of Muscle Tissue

Skeletal / Striated Cardiac Smooth

Plasma membrane ~ sarcolemma

Cytoplasm ~ sarcoplasm

Endoplasmic reticulum ~ sarcoplasmic reticulum

Modified Terms


Muscle Tissue


(a) Skeletal muscle

Spindle-shaped, elongated, pointed ends

Unbranched fibre, cells are arranged in parallel

Uninucleated, centrally located

No striations (no sarcomere)

Smooth Muscle

Structure

Learning Outcomes : 2.3 Describe the structures, function and distribution of muscle cells ~ smooth muscle

Smooth Muscle

Action

Type of control : involuntary / autonomic

Speed of contraction : slowest

Resistance to fatigue : greatest (do not tired easily)


Walls of digestive tract (alimentary canal) / urinary bladder / uterus / urinogenital tract / respiratory tract / blood vessel

(endothelium)

Smooth Muscle

Location


Cylindrical-shaped, very long, blunt ends

Unbranched fibre

Multinucleated, peripherally located (beneath sarcolemma)

Obvious striations (has sarcomere)

Extensive sarcoplasmic reticulum

Skeletal Muscle

Structure

Learning Outcomes : 2.3 Describe the structures, function and distribution of muscle cells ~ skeletal muscle

Skeletal Muscle


Skeletal Muscle

Striations ~ repeating series of light bands (I band) & dark

bands (A band)

Due to arrangement of myofilaments

Thin filament (mainly actin)

Thick filament (mainly myosin)


Skeletal Muscle

Action

Type of control : voluntary / somatic

Speed of contraction : fastest

Resistant to fatigue : least (easily tired)

Location

Attached to the skeleton / bones by tendon


Cardiac Muscle

Structure

Learning Outcomes : 2.3 Describe the structures, function and distribution of muscle cells ~ cardiac muscle

Cylindrical-shaped, elongated, blunt ends

Branched fibre

Joined together from end to end at intercalated disc

Uni / binucleated, centrally located

Striated

Cardiac Muscle

Location

Walls of heart (for contraction of heart)

Action

Type of control : involuntary / autonomic

Speed of contraction : intermediate

Resistant to fatigue : intermediate


Cardiac Muscle

Intercalated disc has gap junction

Speed up impulse transmission throughout heart muscle

Contract as a single unit

Heart muscle is myogenic (can initiate own impulse for

contraction without the help of Central Nervous System)


Features Smooth

muscle

Skeletal muscle Cardiac

muscle

Shape Spindle-shaped,

elongated,

pointed ends

Cylindrical-

shaped,

elongated, blunt

ends

Cylindrical-

shaped,

elongated, blunt

ends

Branching Unbranched fibre Unbranched fibre Branched fibre,

fused together

Number of

nucleus per

cell

One

(Uninucleated)

Many nucleus

(multinucleated)

One or two

Location of

nucleus

Central Peripheral Central

Striations Absent Present Present

Differences of Muscle Cells


Features Smooth

muscle

Skeletal muscle Cardiac

muscle

Type of

control

Involuntary Voluntary Involuntary

Speed of

contraction

Slowest Most rapid Intermediate

(varies)

Resistance

to fatigue

Greatest Least Intermediate

Location

Wall of digestive

tract

Attached to the

bone / skeletal

Wall of heart

Differences of Muscle Cells


Three types of connective tissues are:

Connective Tissue

Hyaline Cartilage

Blood

Compact Bone

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues

Composition

Matrix Fiber

Connective Tissue

Cell

Non-living substance

around cells

Provide support

(eg: collagen, elastin)

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues

All connective tissue has 3 features in common:-

Composition

Matrix Fiber

Compact Bone

Cell

Hard calcified matrix Collagen Osteocyte

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues -compact bone

105

Compact Bone ~ Structure

Bone cell ~ osteocyte

Has many tiny cytoplasmic extension ~ canaliculi

Osteocytes are found in a cavity ~ lacunae

Osteocytes are arranged in circles

They are interconnected by canaliculi which enable the transfer of nutrients & wastes from one osteocytes to another

They secrete hard matrix composed of collagen fiber & inorganic mineral salts (mainly calcium) / hydroxyapatites

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues-compact bone

canaliculi lacuna

osteocyte

106


Matrix are arranged in a circular tube ~ lamella

Several layers of lamella are found around the same central Haversian canal

These structure is called osteon / Haversian system ~ structural unit of bone


lamella lamella

osteon Haversian canal

Haversian canal contains nerve, blood & lymph vessel

Haversian canals are interconnected by Volkmanns canal

A unit of bone is covered by periosteum membrane



Blood vessel

Periosteum

membrane

Volkmanns canal

108

Compact Bone ~ Function

Cellular level (osteocyte) ~ secrete hard matrix & maintain the bone matrix

Tissue level

Hard bone matrix gives basic shape to the body

Provide a hard framework that support the body

Protect soft internal organs in vertebrates

Storage of calcium / mineral salt

Site of blood cell synthesis within the bone marrow


Composition

Matrix Fiber

Hyaline Cartilage

Cell

Soft & elastic matrix

(chondrin) Collagen Chondrocyte

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues-hyaline cartilage

110

Hyaline Cartilage ~ Structure

Protected by an outer perichondrium layer

Which produces chondrocyte

Chondrocyte near the outer layer are flattened in shape but the inner region are angular

Chondrocyte are found in lacunae


111

Hyaline Cartilage ~ Structure

Each lacuna contain 1, 2 or 4 chondrocytes

Chondrocyte secretes soft & elastic matrix ~ chondrin

Composed of chondroitin sulphate & collagen

No blood vessel within matrix (O2 & nutrients diffuse from perichondrium through the matrix)


112

Hyaline Cartilage ~ Function

Cellular level (chondrocyte)

Secrete chondrin

Tissue level

Tough & flexible support

Cushioning properties

Location

Tip of nose, trachea, larynx

End of long bones

Function

Connect the ribs to sternum

Inter-vertebral disc


Composition

Matrix Fiber

Blood

Cell

The only fluid tissue containing blood cells suspended in plasma

Erythrocyte Plasma Collagen Leukocyte Platelet

~45% ~55%

Blood

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues -blood

Erythrocyte

Biconcave shaped ~ increase surface area

Thin at the center, thicker at the edge

No nucleus & organelles at maturity

Contain hemoglobin (respiratory pigment)

Function

Transport O2 & CO2

(respiratory gases)

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues - blood

Structure

Leukocyte

Have nucleus & organelles (the only true cell)

Spherical or irregular shaped

Larger than erythrocyte

Function

Defense against disease


Structure

Blood Cell

Leukocyte Platelet

Granulocyte Agranulocyte

Neutrophil Eosinophil Basophil

Types of Leukocyte

Erythrocyte

Lymphocyte Monocyte

most abundant

Lack granule

Nucleus round

Many granules

Nucleus multi-lobed


118

Neutrophil

Nucleus : multi-lobed (3-6 lobes)

Granule : very small

Function : phagocytize microorganisms / dead cells


119

Eosinophil

Nucleus : bi-lobed (2 lobes)

Granule : large size

Function : reduce the effect of allergy reactions

: attack parasitic worms


120

Basophil

Nucleus : U or S-shaped lobed (2 or 3-lobed)

Granule : many large granule

Function : release histamine (inflammatory substance)

: contain heparin (anticoagulant ~ prevent blood clotting)


121

Lymphocyte

Nucleus : large, spherical-shaped

Location : mostly in lymphoid tissue

Types : 2 (B & T-lymphocyte)

Function : specific defense mechanism / immune response


122

Monocyte

Largest leukocyte

Nucleus : U or kidney-shaped

It can differentiates into active macrophage

Function : phagocytize microorganisms / pathogen


123

Platelets

Cytoplasmic fragments of a large cell, megakaryocyte

No nucleus & organelle

Function : promotes blood clotting


Matrix ~ Plasma

Consist mainly of water, inorganic mineral salts & dissolved protein

& small amount of collagen

Learning Outcomes : 2.3 Describe the structures, function and distribution of connective tissues-blood

Learning outcomes




epithelial muscle

nerve connective



parenchyma xylem

collenchyma phloem

Classification

Number of cell layers Cell shape

Simple Stratified Squamous Cuboidal Columnar

Epithelial Tissue

Learning Outcomes : 2.3 Describe the structure, function & distribution of animal tissues ~ epithelial

127

Epithelial Tissue

Stratified epithelium Simple epithelium

1 layer of cells More than 1 layer of cells


128

Epithelial Tissue

Lower layer of cells

attached to the basement membrane

Uppermost layer

free surface (face lumen/cavity)

Basement

membrane

Free surface


129

Cell Shape

Cuboidal

Squamous

Columnar

Cells : thin, flat

Nucleus : disc-shaped, central

Cells : cube-shaped

Nucleus : spherical-shaped, central

Cells : elongated, column-shaped

Nucleus : oval-shaped, close to the cell base

Large cytoplasm


130

1. Simple Squamous Epithelium

Single layer of flat cells

With disc-shaped central nuclei

Location

Structure

Function

Alveoli of lungs

Lining of blood vessel (endothelium)

Glomerulus & Bowman capsule (in kidney)

Facilitate diffusion & filtration of

substances (very thin & permeable)


1. Simple Squamous Epithelium


132

2. Simple Cuboidal Epithelium

Single layer of cube cells

With spherical-shaped central nuclei

Location

Structure

Function

Lining of kidney tubules

Small glands

Ovary surface

Facilitate absorption & secretion


133

3. Simple Columnar Epithelium

Single layer of columnar cells

With oval-nuclei located near to the base

Location

Structure

Function

Lining of digestive tract, gallbladder &

some glands

Facilitate absorption & secretion


134

Special Structures of Epithelium ~ Microvilli

Microvilli ~ small finger-like projections due to the folding of plasma

membrane

Function:

Increase surface area for absorption

May present in:-

Simple cuboidal epithelial

Location: kidney tubules

Function: to absorb useful substances before excreted out in urine

Simple columnar epithelial

Location: digestive tract lining

Function: to absorb nutrients before excreted out in feces


Special Structures of Epithelium ~ Cilia

Cilia ~ small & short hairlike structure

Beating of cilia create motion to move materials

Eg: Simple ciliated columnar epithelial


Location: fallopian tubes or

oviduct, uterine tubes

Function: to move fertilized egg

from oviduct to the uterus

Location: lining of bronchi

Function: to remove mucus dust

trapped within mucus in

respiratory tract

Goblet Cells


Goblet cells is cup-shaped cells

Location: digestive tract & respiratory tract

Function: secrete mucus to lubricate movement of digested material &

to trap dust & particles which enter respiratory tract

137

Only lower layer is metabolically active

Divide & push older cells upward

Replace uppermost older cells

More durable

Common in high abrasion areas

Function ~ protection

Eg: skin surface

Stratified Epithelium


138

4. Stratified Squamous Epithelium

Thick ~ composed of many layers of

cells & uppermost layer is flat squamous

cells

Location

Structure

Function

Skin (keratinized), mouth, esophagus & vaginal lining

Protection from mechanical injury or invading

microorganisms, prevent excessive water loss (keratinized)


139

Nerve Cell (Neuron) ~ Structure

Neuron is the nerve cell that generate & conduct nerve impulses

Enable communications between the body & brain to response to stimulus

Cell body

Dendrites

Axon

Learning Outcomes : 2.3 Describe the structure, function & distribution of animal tissues ~ nerve cell

All neurons have 3 things in common:-

140

Large nucleus

Have organelles (except centriole), numerous mitochondria

Extensive rough endoplasmic reticulum (Nissl granules)

Dendrites ~ short highly-branched cytoplasm arise from the cell body

Function ~ receive message from other cells & carry the message to the cell body

Cell body

Dendrites

Motor Neuron ~ Structure


141

Long cytoplasmic branch arising from the cell body

Site where axon joins the cell body ~ axon hillock

Axon



Axon endings (synaptic knob) send signals from the neuron to other cells by releasing neurotransmitters

Function ~ carry impulse away from cell body

At certain parts of the axon, some neurons are enclosed in a myelin sheath myelinated neuron

142

Myelin sheath is formed by Schwann cell

Roll around axon

Form overlapping layers of membranes (myelin sheath)

Outermost membrane of Schwann cell ~ neurilemma

Composed of lipid & protein

Myelin sheath act as electrical insulator to speed up impulse transmission



Adjacent Schwann cells do not touch one another create gaps (axon is not completely covered by myelin sheath)

Small, uncovered part of axon between the Schwann cells ~ nodes of Ranvier

Nerve impulse jump from node to node along the axon

Speed up impulse transmission along the axon



144

Motor Neuron

Function

Transmit impulse from central nervous system to effector or motor organs, eg: muscle & glands


Location

Most cell bodies of motor neuron is found within CNS & few in ganglion & its axon is found throughout the motor organs

Learning outcomes




epithelial muscle

nerve connective



parenchyma xylem

collenchyma phloem

In multicellular organisms, most cells differentiates in structure specialised cells

New structure is suitable to carry out specific function

A group of cells which are similar in structure & conduct specific function tissue

What is Tissue ?

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ meristem

Meristem

PLANT TISSUE

Permanent

Dermal Vascular

i. Parenchyma

ii. Collenchyma

iii. sclerenchyma

Ground

Types of Plant Tissue


i. Epidermis

ii. Periderm

i. Xylem

ii. Phloem

i. Apical

ii. Lateral

Young cells Actively dividing cells Unspecialized

Types: Apical meristem Lateral meristem

Meristem Tissue


Small

Isodiametric / cube

Thin primary cell wall

Large, central nucleus

Dense cytoplasm

Small vacuoles

Closely packed / no intercellular air spaces

Meristem ~ Structure


Types of

meristem

Location

Function

Apical Shoot tips & root tips Increase the length of stems

& roots (primary growth)

Lateral Cylinders around the

stem & root (cambium)

Increase the diameter of

stems & roots (secondary

growth)

Meristem ~ Distribution & Function


Functions :

Retain the ability to divide continuously by mitosis to produce new cells

For growth, reproduction & replacement of old, damaged cells

Permanent Plant Tissue

Mature & specialised cells

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ dermal

Outermost layer of cells @ surface of plant body

Dermal Tissue

Distribution

Tightly packed forming a protective layer on the surface

Structure

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ dermal

Function

Defense against :-

mechanical damaged, pathogenic organisms / disease & water loss

Least specialised cells Living cells at maturity (maintain cytoplasm) Carry out most of the metabolic functions of plant

Parenchyma Tissue

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ parenchyma

Parenchyma Tissue ~ Structure

Has nucleus (living cells)

Isodiametric/spherical-shaped

Thin & flexible primary cell wall, consist of cellulose,

hemicellulose & pectin

Large central vacuole

Cells are loosely packed/ large intercellular air spaces


Store food / organic substances (large vacuole)

Carry out photosynthesis for cells containing chloroplast (eg: mesophyll cells)

Allow gaseous exchange as there are large intercellular spaces

In flowers & fruits, cell contain chromoplast to attract pollinating agents & help in dispersal of fruits & seeds

Parenchyma Tissue ~ Function


In dicot stem :-

Cortex

Pith

Scattered within vascular bundle

Parenchyma Tissue ~ Distribution

Dicotyledon stem


Tissue Modified Parenchyma

Mesophyll Endodermis Pericycle

Cell

shape

Palisade

mesophyll ~

column-shaped

Spongy mesophyll

~ spherical /

irregular-shaped

Flat & elongated

(deposited with

suberin)

As

parenchyma

Distribu-

tion

Between upper &

lower epidermis of

leaves

Around vascular

tissue of root

(innermost layer

of root cortex)

Between

vascular tissue

& endodermis

of root

Modified Parenchyma


Modified Parenchyma


Mesophyll Endodermis & pericycle

Collenchyma ~ Structure

Has nucleus (living cells)

Polygonal-shaped, elongated with tapered ends

Cell walls are unevenly thickened at their corners with deposits of cellulose, hemicellulose & pectin

Pits are present in the cell walls

Cells are closely packed / less intercellular space

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ collenchyma

As supporting tissue to herbaceous plants / young parts of the plant

Gives flexible mechanical support (allow cells to expand & stretched as young stems grow)

Collenchyma ~ Function


1. Below the epidermis of

herbaceous plants

Collenchyma ~ Distribution

2. Midrib of leaves


3. Leaf petioles / stalk of leaves (eg: celery)

Sclerenchyma ~ Structure

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ sclerenchyma

No nucleus at maturity (dead cells)

Has primary & secondary cell walls

Secondary cell wall is evenly thickened with lignin

Small lumen

Pits are present in cell walls

Cells are tightly packed / no intercellular space

Function:

Gives support to the tissue

Gives mechanical strength & rigidity to the plant

Protect from mechanical damage

Sclerenchyma ~ Function & Distribution

Distribution:

Leaf veins / vascular bundle

Wood, inner bark


Structure:

Polygonal-shaped Elongated with tapered ends Which overlap & interlock with

one another (increase strength)

Fewer pits than sclereids Eg: jute fibers for making rope

Sclerenchyma ~ Fibers


Structure:

Irregular-shaped

Shorter than fibers

Unevenly thickened with lignin

Pits maybe branched or not

Cells with unbranched pits ~ stone cells

Eg: in pears (cause gritty texture)

Distribution:

Hard shells of seeds & nuts in fruits

Sclerenchyma ~ Sclereids

Cherry pit

Pear stone cells


Complex tissue

Consist of 4 tissues ~ tracheid, vessel, fiber & parenchyma

Dead at functional maturity

Xylem

Structure:

No nucleus (dead cells) at maturity

Elongated, thin

Tapered ends which overlap & interlock with one another

Small empty lumen

Thick lignified secondary wall

Have pits in cell walls

Which allow water to flow from 1 tracheid to the other

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ xylem

No nucleus (dead cells) at maturity

Shorter & wider than tracheid

Tubular / less tapered than tracheid

Wide empty lumen

Thick lignified secondary wall

Both ends are highly perforated / open

Cells are stacked from end to end to form a continuous hollow tube

Pits are present to allow lateral movements of water

Vessels ~ Structure


Young mature vessel

Xylem ~ Vessels

i. Annular / ring

ii. Spiral / helix

iii. Scalariform

iv. Reticulate

v. Pitted

Uneven deposition of lignin creates different pattern in vessel:-


Function

Transport water & minerals from root to other parts of plant

Give mechanical support (lignified vessels & tracheid can resist compression & tension)

Distribution

Vascular bundle

Xylem ~ Function & Distribution


Complex tissue

Consist of 4 tissues ~ sieve tube cell, companion cell, fiber & parenchyma

Phloem

Learning Outcomes : 2.3 Describe the structure, function & distribution of plant tissues ~ phloem

Living cells at maturity

But nucleus & most organelles degenerate

Thin layer of cytoplasm remains at the periphery of the cell

Has only primary cell wall (no lignin)

Long cylindrical structure

End walls are perforated forming sieve plate

Sieve plate has pores which allows cytoplasm to extend between sieve tube cells

Sieve tube cell are stacked end to end to form a long sieve tube

Phloem ~ Sieve tube cells structure


A modified parenchyma which is found next to sieve tube cell

Metabolically active

Phloem ~ Companion cell structure

Structure:

Have nucleus (living cells) at maturity

Dense cytoplasm

Small vacuoles

Many mitochondria & ribosomes

Thin primary cell wall

Interconnected to sieve tube cell by numerous plasmodesmata


Function

Transport organic substance from leaves to other parts of plant

Companion cell helps sieve tube elements to transport organic substances

Distribution

Vascular bundle

Phloem ~ Function & Distribution





organelles (2)



2.4 Cell Transport

Explain the various transport mechanisms across the membrane

Passive transport - Simple diffusion - Facilitated diffusion - Osmosis

Active transport - Sodium potassium pump - Bulk Transport (endocytosis & exocytosis)

Learning outcomes

Types of Transport Across Membrane

Passive Transport

Endocytosis Exocytosis

Simple Diffusion

Facilitated Diffusion

Osmosis

Active Transport

Na-K Pump

Phagocytosis Pinocytosis

Learning Outcomes : 2.4 Explain the various transport mechanisms across the membrane

Bulk Transport

Characteristic of Cell Membrane

Cell membrane is selectively permeable

Allow some substances to pass through

But does not allow other substances to pass through

Cell membrane is permeable to lipid soluble molecule & small non-polar substance due to its hydrophobic region of phospholipid bilayer

Impermeable to polar molecules & ions

Enable cell to retain polar molecules & ions within the cell (mostly are important for the cell)

Learning Outcomes : 2.4 Explain passive transport across membrane

Passive Transport

Movement of a substance from higher concentration to lower concentration gradient

Or movement of a substance down a

concentration gradient

Across a selective permeable membrane

Without using energy

Learning Outcomes : 2.4 Explain passive transport across membrane

Simple Diffusion

(extracellular fluid)

(cytoplasm)

Some molecules diffuse freely across

phospholipid bilayer

Movement of a substance from higher concentration to lower concentration gradient across phospholipid bilayer


Without the help of transport protein

Learning Outcomes : 2.4 Explain passive transport across membrane ~ simple diffusion

Simple Diffusion

Molecules that can diffuse easily across phospholipid bilayer:-

Lipid soluble molecules (eg: cholesterol, steroid)

Small, non-polar/uncharged molecules (O2, CO2)

Small, polar molecules (eg: H2O, glycerol)


Simple Diffusion

Although water are polar, they are small enough to pass through the space between the fluid fatty acids as they move

Rate of diffusion increase when:-

Temperature increase

Molecules involved is in gas state rather than liquid

Size of molecules reduce (faster for smaller molecules)

Large differences in concentration gradient between inside & outside the cell


Simple Diffusion ~ Importance

Enable atoms & small molecules diffuse faster across membrane

Eg: O2, CO2 as respiratory gases, important in ATP synthesis

Eg: H2O, important to facilitate chemical reaction

Enable lipid soluble molecules to diffuse freely

Eg: steroid hormone (testosterone) for homeostatic regulation



Movement of a substance from higher concentration to lower concentration gradient across plasma membrane

With the help of transport protein


Involve ions & polar molecules (eg: Na+, Cl-, glucose, amino acids)

Learning Outcomes : 2.4 Explain passive transport across membrane ~ facilitated diffusion



1. Channel protein

2. Carrier protein

Transport protein:- 2 main types

Facilitated Diffusion ~ Importance

Transport ions & polar molecules or water soluble molecules across membrane

Eg: water, ions (Na+, Cl-), sugars (glucose) & amino acids


Osmosis

Movement of water molecules

From higher water potential to lower water potential region



Learning Outcomes : 2.4 Explain passive transport across membrane ~ osmosis

Water Potential

Definition:

Tendency of water molecules to move from 1 area to another area

Symbol ~

Pure water has the highest water potential, = 0 kPa


Solute Potential

A measure of the change in water potential of a solution due to the presence of solute molecules

When solute molecules is dissolved in pure water, it reduces its water potential, becoming negative (-ve)

Symbol, s (always has ve value)

A solution with less solute than the other has higher water potential


189

Types of Solution

Hypertonic

Hypotonic

Low concentration of solute relative to another solution

High concentration of solute relative to another solution

Isotonic

Same concentration of solute relative to another solution


Osmosis


Less solute More solute

Net movement of water molecules

Pressure applied to piston to resist upward movement

Water plus solute

Pure water

Water molecule

Molecule of solute

Selectively permeable membrane

When water diffuse into the plant cell, it enters vacuole

Vacuole enlarge & creates a pressure towards cytoplasm & cell wall turgor pressure

Also called as pressure potential, p

p always has +ve value

The point at which plasmolysis is just about to happen incipient plasmolysis, p = 0


192

Water potential inside & outside the cell is equal

Water moves into & out of the cell at the same rate by osmosis

Animal / plant cell does not change its shape

When a cell is put into an isotonic solution

No net movement of water into or out of the cell


193

The cell has higher water potential than outside the cell

Water moves out from the cell by osmosis

Animal cell becomes crenated / shrink


When a cell is put into a hypertonic solution

194

When a cell is put into a hypertonic solution

In plant cell, water moves out from vacuole vacuole shrinks

Plasma membrane detached & pulled away from the cell wall

Plant cell becomes plasmolysed / flaccid

The starting point of plasmolysis ~ incipient plasmolysis


Plasma membrane

Vacuole

Vacuolar membrane (tonoplast)

Cytoplasm Plasma membrane

Vacuole Nucleus

(a) (b) (c)

Turgid Plasmolyzed Plasmolyzed


196

Water potential outside the cell is higher than in the cell

Water from outside moves into the cell by osmosis

Plant cell becomes turgid

When a cell is put in a hypotonic solution

Animal cell swell (if too much water moves in, it may lysed / burst)

If erythrocyte burst ~ haemolysis


Outside cell

Outside cell

Outside cell

Inside cell

Inside cell

Inside cell

No net water movement

Net water movement out of the cell

Net water movement into the cell

Isotonic solution Hypertonic solution Hypotonic solution

(a)

(b)

(c)


198

Calculation of Water Potential in Plant Cell

Water potential = solute potential + pressure potential

Which cell has higher water potential?

A ~ = -200 kPa

B ~ = -400 kPa

C ~ = -500 kPa

D ~ = -600 kPa

= s + p


Cell A Cell B

s = -8 MPa p = 3 MPa

= -10 Mpa s = -10 Mpa

= ? p = ? -5 MPa 0 MPa

Example 1


Cell A

Sucrose solution, s = -1000 kPa

s = -500 kPa p = 200 kPa

Calculate the water potential of this cell.

State whether water will move in or out of the cell. Explain.

What happen to the volume of the cell?

= s + p = -500 + 200 kPa = -300 kPa

Water moves out from the cell by osmosis

Because cell A has higher water potential than surrounding solution

Decrease


Example 2

Cell A

Cell B

s = -2200 kPa p = 1000 kPa

s = -1600 kPa p = 800 kPa

Calculate the water potential of cell A & cell B

Example 3 (a)

Cell A, = s + s

= -2200 + 1000 kPa

= -1200 kPa

Cell B, = s + s

= -1600 + 800 kPa

= -800 kPa


Cell A

Cell B

s = -2200 kPa p = 1000 kPa

s = -1600 kPa p = 800 kPa

Exercise 3 (b)

State the direction of water flow between the 2 cells. Give reason.

Cell A, = -1200 kPa

Cell B, = -800 kPa

Water flows from cell B to cell A

Because cell B has higher water potential than cell A


Cell A

Cell B

s = -2200 kPa p = 1000 kPa

s = -1600 kPa p = 800 kPa

Exercise 3 (c)

Calculate the final values of water potential & pressure potential after equilibrium is reached. Assume that no changes occurs to s

Cell A, = -1200 kPa

Cell B, = -800 kPa

For cell A, at equilibrium,

= s + p

P = - s

= -1000 (-2200) kPa

= -1000 + 2200 kPa

= 1200 kPa

At equilibrium, A = B = cell A + cell B

= -1200 + (-800) kPa

= -1000 kPa

2

2


Cell A

Cell B

s = -2200 kPa p = 1000 kPa

s = -1600 kPa p = 800 kPa

Exercise 3 (c)

Calculate the final values of water potential & pressure potential after equilibrium is reached. Assume that no changes occurs to s

Cell A, = -1200 kPa

Cell B, = -800 kPa

At equilibrium, A = B = cell A + cell B

= -1200 + (-800) kPa

= -1000 kPa

2

2


For cell B, at equilibrium,

= s + p

P = - s

= -1000 (-1600) kPa

= -1000 + 1600 kPa

= 600 kPa

Active Transport

Movement of a substances against concentration gradient or from lower concentration to higher concentration gradient


Which needs energy

Involve transport protein

Learning Outcomes : 2.4 Explain active transport across membrane ~ Na-K Pump

Endocytosis Exocytosis

Active Transport

Na-K Pump

Allow cell to maintain useful nutrients in the cell against concentration gradient

Na-K Pump

Outside the cell : [Na+] , [K+]

Inside the cell : [Na+] , [K+]

3 Na+ in the cell binds to a specific site of transport protein

The binding of Na+ stimulates the hydrolysis of ATP (in the cell) into ADP (adenosine diphosphate) + Pi (inorganic phosphate)

Pi binds to transport protein (phosphorylation) & change its conformation

Causes it to pump 3 Na+ to the outside

Increasing its concentration outside the cell


Na-K Pump


Na-K Pump

2 K+ outside the cell binds to a specific site of transport protein

Stimulates the release of phosphate group from the transport protein (dephosphorylation)

Causes transport protein to restore its original conformation

2 K+ is pumped into the cell

Increasing its concentration inside the cell

Na-K pump is important for transmission of nerve impulses


Endocytosis

A process in which bulk substances are taken into the cell

Requires energy

Involves invagination (folding) of cell membrane (cannot occur in plant cell due to the presence of cell wall)

2 types of endocytosis:

Learning Outcomes : 2.4 Explain active transport across membrane ~ bulk transport (endocytosis)

Endocytosis

Phagocytosis Pinocytosis

Phagocytosis

A process in which large, solid particles is taken into the cell

Presence of large particles causes the cell membrane to invaginate

Forming cytoplasmic extension ~ pseudopodia which surround the large particle & trapped them

Pseudopodia fuse together to form food vacuole / phagocytic vacuole / phagosome

Learning Outcomes : 2.4 Explain active transport across membrane ~ endocytosis (phagocytosis)

2. The vacuole then pinches off inside the cell.

1. Folds of the plasma membrane surround the particle to be ingested, forming a small vacuole around it.

Phagocytosis

Primary lysosome will fuse with phagocytic vacuole & activates the enzyme inside lysosome

Secondary lysosome releases its enzyme to digest the particles

Useful substance is absorbed into cytoplasm

Waste substance is released by exocytosis outside the cell

Learning Outcomes : 2.4 Explain active transport across membrane ~ endocytosis (phagocytosis)

3. Lysosomes may fuse with the vacuole and digest the substance

Eg: macrophage engulf bacteria Eg: Amoeba engulf Paramecium / food

Pinocytosis

A process in which dissolved solutes are taken into the cell

Presence of dissolved solutes causes the cell membrane to invaginate

To form a tiny canals of cytoplasmic extension

Dissolved solutes are trapped within tiny canals / microvilli

Learning Outcomes : 2.4 Explain active transport across membrane ~ endocytosis (pinocytosis)

Cytosol

Pinocytosis

Learning Outcomes : 2.4 Explain active transport across membrane ~ endocytosis (pinocytosis)

At the end of tiny canals / cytoplasmic extensions, it pinches off to form pinocytic vesicles / pinosome

The dissolved solutes is directly absorbed into cytoplasm

Eg: uptake of dissolved solutes in kidney tubules & intestines

Microvilli Pinocytic vesicle

Phagocytosis & Pinocytosis

Learning Outcomes : 2.4 Explain active transport across membrane ~ endocytosis

Exocytosis

A process in which cells release substance out of the cell

Vesicle move towards cell membrane & fuse with it

Substance within vesicles are released outside the cell (during secretion)

1. A vesicle move towards the plasma membrane

2. fuses with it

3. release its contents outside the cell.

Learning Outcomes : 2.4 Explain active transport across membrane ~bulk transport (exocytosis)

Reference

Campbell N.A & Reece, J.B., Biology, 6th ed. (2002), Pearson Education, Inc.

Solomon E.P & Berg, L.R, Biology, 7th ed. (2005) Thomson Learning, Inc.

Mader, S.S Biology, 8th ed. (2004) McGraw-Hill Companies, Inc.

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