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Transmission electron microscopy (TEM) micrograph of a peroxisome from the marine snail Gibulla umbilicalis.

Head Louse

INTRODUCTION TO THE CELL

Copyright © 2009 Pearson Education, Inc.

Nucleoid

Ribosomes

Plasma membrane

Cell wall

Capsule

Flagella

Bacterialchromosome

A typical rod-shapedbacterium

Pili

A thin section through thebacterium Bacillus coagulans(TEM)

Smooth endoplasmicreticulum

Roughendoplasmicreticulum

CYTOSKELETON:

NUCLEUS:

Chromosomes

Nucleolus

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Lysosome

Microtubule

Intermediatefilament

Microfilament

Animal Cell Organelles

Smooth endoplasmicreticulum

Rough endoplasmicreticulum

CYTOSKELETON:

NUCLEUS:

Chromosome

NucleolusRibosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Peroxisome

Cell wall

Central vacuoleMicrotubule

Intermediatefilament

Microfilament

Cell wall ofadjacent cell

Chloroplast

Plant Cell Organelles

4.4 Eukaryotic cells are partitioned into functional compartments

There are four life processes in eukaryotic cells that depend upon structures and organelles

– Manufacturing

– Breakdown of molecules

– Energy processing

– Structural support, movement, and communication



Manufacturing involves the nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus

– Manufacture of a protein, perhaps an enzyme, involves all of these


Cellular Organelles - Nucleus

The nucleus contains most of the DNA in a eukaryotic cell

In the nucleus, DNA and proteins form genetic material called chromatin

Chromatin condenses to form discrete chromosomes (during cell division)

Two membranes ofnuclear envelope Nucleus

Nucleolus

Chromatin

Pore

Endoplasmicreticulum

Ribosomes

Ribosomes: Protein Factories

• Ribosomes are particles made of ribosomal RNA and protein

• Ribosomes carry out protein synthesis

• Cells that must synthesize large amounts of protein have a large number of ribosomes

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 6-11

Cytosol

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small subunit

Diagram of a ribosomeTEM showing ER and ribosomes

0.5 µm

The endomembrane system: all these membranes are related through direct contact or through vesicles

• Components of the endomembrane system:– Nuclear envelope

– Endoplasmic reticulum

– Golgi apparatus

– Lysosomes

– Vacuoles

– Plasma membrane

• A vesicle is a tiny spherical package of molecules surrounded by a membrane


The Endoplasmic Reticulum: Biosynthetic Factory

• There are two distinct regions of ER:

– Smooth ER, which lacks ribosomes

– Rough ER, with ribosomes studding its surface

– One synthesizes lipids and the other functions in protein synthesis. Which do you think is which?


4.9 The endoplasmic reticulum is a biosynthetic factory

• Smooth ER is involved in a variety of diverse metabolic processes

– involved in the synthesis of lipids, oils, phospholipids, and steroids


4.9 The endoplasmic reticulum is a biosynthetic factory

• Rough ER makes additional membrane for itself and proteins destined for secretion

– Once proteins are synthesized, they are transported in vesicles to other parts of the endomembrane system


4.10 The Golgi apparatus finishes, sorts, and ships cell products

• The Golgi apparatus functions in conjunction with the ER by modifying products of the ER

– Products travel in transport vesicles from the ER to the Golgi apparatus

– One side of the Golgi apparatus functions as a receiving dock for the product and the other as a shipping dock

– Products are modified as they go from one side of the Golgi apparatus to the other and travel in vesicles to other sites


Golgi apparatusGolgi apparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

“Shipping” sideof Golgi apparatus

Transportvesicle fromthe Golgi

Lysosomes: Digestive Compartments

• A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules

• Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids


• Some types of cell can engulf another cell/bacteria by phagocytosis; this forms a vacuole

• A lysosome fuses with the vacuole and digests the molecules

• Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy


Fig. 6-14

Nucleus 1 µm

Lysosome

Digestiveenzymes

Lysosome

Plasmamembrane

Food vacuole

(a) Phagocytosis

Digestion

(b) Autophagy

Peroxisome

Vesicle

Lysosome

Mitochondrion

Peroxisomefragment

Mitochondrionfragment

Vesicle containingtwo damaged organelles

1 µm

Digestion

Video• Examples

• Lets follow the path of insulin

– This is a protein that will be secreted from the pancreatic cell

• Antibodies

– These are defensive proteins that will be secreted from the white blood cell

Transport vesiclebuds off

Secretoryproteininside trans-port vesicle

GlycoproteinPolypeptide

Ribosome

Sugarchain

Rough ER

1

2

3

4

Video


Breakdown of molecules involves lysosomes, vacuoles, and peroxisomes

– Breakdown of an internalized bacterium by a phagocytic cell would involve all of these


Digestiveenzymes

LysosomePlasmamembrane

Food vacuole

Digestion

4.12 Vacuoles function in the general maintenance of the cell

Vacuoles are membranous sacs that are found in a variety of cells and possess an assortment of functions

– Examples are the central vacuole in plants with hydrolytic functions, pigment vacuoles in plants to provide color to flowers, and contractile vacuoles in some protists to expel water from the cell


Nucleus

Chloroplast

Centralvacuole


Energy processing involves mitochondria in animal cells and chloroplasts in plant cells

– Generation of energy-containing molecules, such as adenosine triphosphate, occurs in mitochondria and chloroplasts


Mitochondrion

Intermembranespace

Innermembrane

Cristae

Matrix

Outermembrane

Chloroplast

Stroma

Inner and outermembranes

Granum

Intermembranespace


Structural support, movement, and communication involve the cytoskeleton, plasma membrane, and cell wall

– An example of the importance of these is the response and movement of phagocytic cells to an infected area


Microfilament

Actin subunit

7 nm

Intermediate filament

Fibrous subunits

10 nm

Microtubule

Tubulin subunit

25 nm

Nucleus

Nucleus

Centralmicrotubules

Outer microtubuledoublet

Radial spoke

Dynein arms

Plasmamembrane

Triplet

Cross sections:

Flagellum

Basal body

Basal body


There are four life processes in eukaryotic cells that depend upon structures and organelles

– Manufacturing

– Breakdown of molecules

– Energy processing

– Structural support, movement, and communication


Nucleus Golgi apparatus

Smooth ERRough ERRibosome

LysosomesVacuoles

Perixisomes

ChloroplastMitochondria

a.

b.

c.

d.

e.

f.

g.

h.

i.

j.

k.

l.

Quiz 3


1. Which organelle is involved in manufacture of protein?

2. Which organelles acts as a kind of recycling center for the cell and breaks down old molecules so they can be used again?

3. Which organelle acts as an energy transformer?

4. A cell that’s primary function is to produce protein would have a lot of_____________.

a. Mitchondria

b. Vacuole

c. Ribosome

d. Lysosome

Matching: can be used more than once

Quiz 3


5. Name one difference between plant and animal cells.

6. What is the most important macromolecule found the nucleus of a cell?

7. T/F One function of the cytoskeleton is to give support to the cell.

8. T/F Vesicles are similar to little circular bubbles that can carry proteins around in the cell.

9. T/F The Golgi apparatus stores, modifies, and packages proteins.

10. Would you like to get a point for answering this question?

Hydrophilic heads

Hydrophobic tails

Proteins

Hydrophobic region ofprotein

Inside cell Hydrophilic region ofprotein

Outside cell

4.5 The structure of membranes correlates with their functions

The plasma membrane controls the movement of molecules into and out of the cell, a trait called selective permeability

– The structure of the membrane with its component molecules is responsible for this characteristic

– Membranes are made of lipids, proteins, and some carbohydrate, but the most abundant lipids are phospholipids


Hydrophilic head

Hydrophobic tails

Symbol

Phosphategroup

4.20 The extracellular matrix of animal cells functions in support, movement, and regulation

Cells synthesize and secrete the extracellular matrix (ECM) that is essential to cell function

– The ECM is composed of strong fibers of collagen, which holds cells together and protects the plasma membrane


EXTRACELLULAR FLUID

Microfilaments

Collagen fiber

Connectingglycoprotein

Integrin

Plasmamembrane

Glycoproteincomplex with longpolysaccharide

CYTOPLASM

4.21 Three types of cell junctions are found in animal tissues

Adjacent cells communicate, interact, and adhere through specialized junctions between them

– Tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells

– Anchoring junctions fasten cells together into sheets

– Gap junctions are channels that allow molecules to flow between cells


Animation: Desmosomes

Animation: Gap Junctions

Animation: Tight Junctions

4.21 Cell junctions are found in plant tissues

Plasmodesmata

Cytoplasmic streaming


Tight junctions

Anchoring junction

Gap junctions

Plasma membranesof adjacent cells

Extracellular matrix

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