Cell Without Images

7/27/2019 Cell Without Images

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Contents

Introduction to cell

History

Number and cell size

Cell type

Structure of cell

Cell membrane

Cytoplasm

Organelle in cytoplasm

Nucleus

Cell surface contact

Molecule movement

Endocytosis and Exocytosis

References


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Cell (fig-1,2)

Cell-Structural and functional unit of the living body.

Smallest living unit

Most of cells are microscopic

Discovery of Cells (fig-3,4)

Robert Hooke (Mid 1600)

Coined term cell

First seen cork plant cell

(1889) Rudolf Virchow all cells come from cells

Number (fig-5,6)

Unicellular(consist of a single cell)

-Bacteria, Virus

Multicellular Human (Around 100 trillion cells)

-Other animal

Cell size

Most of cell are between 5-50m in diameter


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Ex,RBC-7.5 m

Columnar epithelial cells 20 m tall

and 10 m wide

Larger cells

Skeletal muscle cell

Neurons

Cell Types

Prokaryotic

Eukaryotic

Prokaryotic cell (fig-7)

First cell type on earth

Cell type of Bacteria and Archaea

No membrane bound nucleus

Nucleoid = region of DNA concentration

Eukaryotic cell

Organelles not bound by membranes

Nucleus bound by membrane

Fungi, Protists, Plant, and Animal cells

Possess many organelles

Animal cell (fig-8)


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Plant cell (fig-9)

Structure of cell(fig-10)

Each cell is formed by cell body and membrane

Cell membrane Separate cell body from

the surrounding cell

Cell body -Cytoplasm

Nucleus

Cell membrane (fig-11)

Protective sheath enveloping the cell body

Separate intracellular and extracellular fluid

Permits exchange of some substance

Thickness- 75A to111A

Double layer of

Phospholipids & Proteins

lipid layer (fig-12)

Cell membrane-Bilayered component

Lipids are cholesterols and phospholipids

Phospholipids = Phosphrous and fatty acid

(Amino Phospholipid, Phosphetidyle Glycerol

Phosphetidyle Inositol)


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Outer part- Hydrophilic

(soluble in water)

Inner part- Hydrophobic

(soluble in fat)

Significance of lipid layer (fig-13)

Forms semi-permeable membrane

Fat soluble substance can pass through it.

-O2, CO2 and alcohols

Barrier to water soluble materials

-Glucose, Urea, Electrolytes

Protein layer (fig-14)

Glycoprotein

Two type

Integral protein and peripheral protein

Significance of protein layer (fig-15)

Integral proteins- Structural Integrity

Channels(formed by integral protein)

Diffusion of water soluble substance

Glucose, Electrolytes

Receptors protein


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Receptor for hormones and neurotransmitter

Recognize certain chemicals

Carrier protein

-Transport of substance(active or passive)

Act as antigen

-act as antigen and provide antibody formation

Carbohydrate(fig-16)

Attached to protein or lipid

Significance- Negatively charged

-Glucocalyx of neighboring cell

help in tight fixation.

-Receptor for some hormone

-Contain specific antigen(RBC-blood group antigen)

Cytoplasm(fig-17)

Viscous fluid containing organelles

Interconnected filaments & fibers

Organelles

Fluid= Cytosol

Various particles

(Different shape and size)

-Proteins, Carbohydrate,


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lipids and Electrolytes.

200mg/ml of protein

High K+

low Ca+2 low Na+

Cytoskeleton (fig-18)

Filaments & Fibers

Made of 3 fiber types

Microfilaments

Microtubules

Intermediate filaments

3 functions:

Mechanical support

Anchor organelles

Help move substances

Organelle in Cytoplasm

Organelle caries out various functions

Two type-

Bound by limiting membrane

Endoplasmic reticulum

Golgi apparatus


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lysome, Peroxisome

Mitochondria

Not bounded by limiting membrane

Chromosome, Ribosome

Microfilaments, Microtubules

Endoplasmic Reticulum

Network of tubular and micrsomal vesicular structure

Outer side-Limiting Membrane

Inner side- Endoplasmic Matrix(lumen)

Helps to move substances within cells

Two types

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Rough endoplasmic reticulum (fig-19)

Ribosomes are attached to surface

Manufacture proteins

Not all ribosomes attached to rough ER

May modify proteins from ribosome

Protein pass through membrane and accumulate in cisternae.

Smooth Endoplasmic Reticulum (fig-20)


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No attached ribosomes

Various enzymes are present on outer surface

Enzymes- Metabolic process of cell

Significance of Smooth Endoplasmic Reticulum

Carbohydrate metabolism

Synthesis of non protein substance

Cholesterol

Steroid hormones

Sebum

Catabolism of toxic substance

Cooperate with rough endoplasmic reticulum and Golgi apparatus to

synthesize new cell membrane.

Specialized type

In skeletal muscle-sarcoplasmic reticulum (store calcium)

Golgi Apparatus or Golgi Body(fig-21)

Present in all cell except Red Blood Cell

Situated near nucleus

Consist of 5 to 8 membranous sac

The Sacs are flattened and called as Cisternae

Function of Golgi Body

Processing and delivering the protein


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molecule to different parts of the cell.

Protein synthesized from endoplasmic reticulum

Transported in the form of Reticular Vesicle

To Golgi Body where it is processed and sorted out

Packed in the form of Secretory Granules, Secretory Vesicles

Vesicles delivered by golgi body leave the cell by exocytosis.

Lysosomes(fig-22)

Vesicular organelle

80 to 800nm in diameter

Have thickest covering membrane

Many small granules present in lysosomes

Contain digestive enzymes(hydrolytic enzyme)

More than 40 different type of hydroxylases

All enzyme- lysozymes

Vesicular organelle

80 to 800nm in diameter

Have thickest covering membrane

Many small granules present in lysosomes

Contain digestive enzymes(hydrolytic enzyme)

More than 40 different type of hydroxylases


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All enzyme- lysozymes

Lysosomal storage disease

Enzymes are defective because of gene

Materials that they normally degrade will accumulate within late

endosomes and lysosomes.

e.g. Tay-Sachs disease

Hurler's Syndrome: Failure to metabolize certain

mucopolysaccharides causes the accumulation of large amounts ofmatrix within connective tissue, which distorts the growth of many

parts of the body.

Peroxisome(fig-23)

Membrane limited vesicle

Derived from endoplasmic reticulum

Contain oxidative enzymes

(Urate oxidase and D- aminoacid oxidase)

Function of peroxisome

Hydrogen peroxide is produced by poisons or alcohol

(ethanol and formaldehyde)

Peroxisome ruptures when hydrogen peroxide is formed in cell.

Oxidases destroys hydrogen peroxide

Also destroy other enzymes necessary for its production

Gluconeogenesis from fats and degradation of purine and fat.


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Zellweger syndrome

Genetic abnormality in peroxisome

biogenesis

Mitochondria(fig-24)

Rod shaped, oval shaped structure

Diameter - 0.5 to 1 m

Bilayered membranous organelle

Outer layer- Smooth

Inner layer- Series of shelf like projection

-Cristae

(provide large surface area)

Contain RNA and DNA

Principle source of chemical energy in most of the cells

Enzymes are located in mitochondrial matrix and inner

mitochondrial matrix.

Function

Break down fuel molecules (cellular respiration)

Glucose

Fatty acids

Production of energy by catabolism of digested food particles

Stored in the form of ATP molecules


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So It is power house of cell

Energy released by breakdown of ATP molecule

When needed

Mitochondria contain enzymes for citric acid cycle, oxidative

phosphorylation

Mitochondria are distributed within a cell according to regional

energy requirements

-Near the base of cilia

-Near basal domain of cells of proximal convulated tubules

-Proximal end of flagellum

Genetic diseases of mitochondria affect perticular tissues

Ex. Mitochondrial myopathies

Mitochondrial neuropathies

Ribosomes(fig-24,25)

It is granular structure

Diameter of 15 to 20 nm

Contain 65%RNA and 35% Protein

Some ribosomes remain free in cytoplasm

Function of free ribosome

Synthesis of protein from amino acid

Synthesis of protein part of hemoglobin


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Protein molecules of peroxisome

Protein present in mitochondria

Nucleus (fig-26)

Control center of cell

3 to 10 m in diameter

Double membrane

(Nuclear membrane)

Contains

Nucleoplasm

Nucleolus

Nuclear membrane

Double layered, porous in nature

Communicate with cytoplasm

Outer layer continuous as endoplasmic reticulum

Inner space forms lumen of endoplasmic reticulum

Pores- Guarded by protein

- Diameter 80nm to 100nm

Nucleoplasm

Gel like substance

Contain DNA


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Called as

chromatin

One or more in each nucleus

Contain RNA and some proteins

RNA synthesized by 5 pairs of chromosome

Condensed to form subunit of ribosome

Subunit travel to cytoplasm through pore

Fusion of subunits lead to formation of Ribosome

Function of Nucleus

Control center for all activity of cell

It sends genetic information in the form of DNA to cytoplasm for

synthesis of specific enzymes

Enzymes are responsible for various metabolic reactions.

Genes present in the nucleus controls cell division.

The hereditary information is stored in the nucleus and transferred

from

one generation to next.

Cell surface contact Two type

-General adhesive contact

calcium dependent

calcium independent


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-Specialized contact

General adhesive contact

Calcium dependent adhesion molecule

Cadherins

selectins

Integrins

Calcium independent adhesion molecule

Most are transmembrane proteins

N-CAMs

I-CAMs

Specialized Adhesive Contacts

Occluding Junction( Tight junction )

-Tight junction is made up of ridges

-Ridges have two halves which are in

close contact

- provide strength and stability

-prevent movement of ions and protein

Desmosomes

Hemidesmosomes

Communicating junction(gap junction)(fig-27)


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Cytoplasm of two cells is connected by channels

Diameter of channel 3 nm

Passage of Ions, Glucose, Amino acid

Rapid propagation of action potential

Molecule Movement & Cells

Passive Transport

Active Transport

Endocytosis

(phagocytosis & pinocytosis)

Exocytosis

Passive Transport

No energy required

Move due to gradient

differences in concentration, pressure, charge

Move to equalize gradient

High concentration moves toward low concentration.

Types of Passive Transport

1. Diffusion

2. Osmosis

3. Facilitated diffusion


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Diffusion

Molecules move to

equalize concentration

Osmosis

Special form of diffusion

Fluid flows from lower solute concentration

Often involves movement of water

Into cell

Out of cell

Solution Differences & Cells (fig-28)

Solvent + Solute = Solution

Hypotonic

Solutes in cell more than outside

Outside solvent will flow into cell

Isotonic

Solutes equal inside & out of cell

Hypertonic

Solutes greater outside cell

Fluid will flow out of cell

Facilitated Diffusion


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Differentially permeable membrane

Channels (are specific) help molecule or ions enter or leave the cell

Channels usually are transport proteins

(aquaporins facilitate the movement of water)

No energy is used

Process of Facilitated Transport

Protein binds with molecule

Shape of protein changes

Molecule moves across membrane

Active Transport

Molecular movement

Requires energy (against gradient)

Example is sodium-potassium pump

Endocytosis

Movement of large material

Particles

Organisms

Large molecules

Movement is into the cells Types of


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Endocytosis

Bulk-phase (nonspecific)

Receptor-mediated (specific)

Process of Endocytosis

Plasma membrane surrounds material

Edges of membrane meet together

Membranes fuse to form vesicle

Exocytosis

Reverse of endocytosis

Cell discharges material


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References

Greys textbook of human anatomy

40th edition

Guyton and Hall textbook of medical physiology 12th edition

Ganongs textbook of medical physiology 21st edition

Human physiology volume-1,Dr. C.C Chatterjee

Text book of human histology, Inderbir singh

http://www.biologymad.com/resources

http://biology.about.com/od/molecularbiology

http://rarediseases.about.com/od/rarediseasesz/a/030505.htm


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