Physio 2 Cell Physiology

7/27/2019 Physio 2 Cell Physiology

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GENERAL PHYSIOLOGY

STRUCTURE AND PHYSIOLOGY OF

CELL


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The Cell


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The cell


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Structure & Function of a Cell

Fundamental unit of life- CELL

Most cells in human being have diameters of

10-20 m Principal constituents are:

A. Cell membrane

B. Nucleus & its Chromosome C. Cytoplasm & its organelles


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BASIC PARTS OF A CELL

Cells contain a variety of Internal Structures calledORGANELLES.

An organelle is a Cell Component that PERFORMSSPECIFIC FUNCTIONS FOR THE CELL.

Just as the organs of a multicellular organism carry outthe organism's life functions, the Organelles of a cellMaintain the Life of the Cell.

All cells have an outer boundary, an interior substance,and a control region.


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The Cell And Its Functions

The Cell membrane is:

Thin (7.5 10 nms. in thickness)

Pliable elastic structure

Fluid state (MOSAIC MODEL)

Double layered Lipoprotein film

Interspersed with protein molecules

Outer coat of Glycocalyx

Selectively permeable


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The Cell membrane is composed of :

Proteins - 55%

Phospholipids - 25% Cholesterol 13%

Other lipids 4%

Carbohydrate 3%


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The

PhospholipidMolecule


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The Phospholipid Molecule


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Properties Of The Phospholipid

Molecule


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The Phospholipid Bilayer


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The Lipid Cell Membrane


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The cell membrane proteins (Glycoproteins):

Integral

Provide

ChannelsCarrier proteins

Pumps

Receptors

Peripheral

Mostly Enzymes


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Transmembrane Proteins extend thru the membrane

and serve as:

A. Channels thru which ions/ small soluble

substances diffuse.

B. Carriers actively transport materials across thelipid layer.

C. Pumps actively transport across the lipid layer.

D. Receptors which when activated initiate

intracellular reactions.


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The entire outer surface of the cell is covered by a

loose coat of Carbohydrates called Glycocalyx

The functions of the Glycocalyx :

Gives a negative charge to the surface of the cell

Adherence to the adjacent cells

Participation in immune reactions Receptor site (eg for binding of Insulin)

Cell membrane


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Glycocalyx As A Receptor


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Cytoplasm Cytoplasm is a water-like substance that fills cells.

The cytoplasm consists of cytosol and the cellularorganelles, except the cell nucleus.

The cytosol (cytoplasm, which also includes the

organelles) is the internal fluid of the cell, and a

portion of cell metabolism occurs here.

The cytosol is made up of water, salts, organic

molecules and many enzymes that catalyze

reactions. It is found within the plasma membrane of a cell and

surrounds the nucleus and envelopes the organelles


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Cell Organelles

Examples:

Endoplasmic Reticulum (smooth & granular)

Ribosomes (attached to the GER) Golgi Apparatus

Lysosomes

Secretory vesicles Mitochondria


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Endoplasmic Reticulum

A network of interconnecting tubular and flatvesicular structures (surface area is 3040times that of the cell membrane)

Lipid bilayer wall with or without attachedRibosomes

Granular/rough ER (RER) studded with

ribosomes Agranular/smooth ER (SER) without

ribosomes


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ER

The Endoplasmic Reticulum:

The inner space is continuous with the space

between the two walls of the nuclear

membrane

Acts as conduit

Machinery for Metabolic functions (proteins

and lipids)


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The Endoplasmic Reticulum


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ER

Attachment of Ribosomes to the ER gives it

the granular look.

Together, the GER & the Ribosome are the

main factories for the synthesis of proteins

destined to be secreted outside the cell or

packed in the Lysosomes.


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Ribosomes

Ribosomes are composed of a mixture of

Ribonucleic Acid (RNA) and proteins.

Free Ribosomes are the sites for the

synthesis of proteins destined to be used

inside the cell.

Ribosomes are devoid of a limiting membrane.


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The Granular Endoplasmic Reticulum


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The Agranular Endoplasmic Reticulum


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Functions Of Endoplasmic Reticulum


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Golgi Apparatus

The Golgi Apparatus is the Processing, Packaging and

Secreting Organelle of the Cell.

The Golgi Apparatus is made of 4-6 stacks of

flattened SAC like Structures called CISTERNAE. It works Closely with the ER, the Golgi Apparatus

modifies proteins for export by the cell.

Golgi apparatus is involved in the manufacture of

Lysosomes, Peroxisomes and Secretory vesicles


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The Golgi Apparatus


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The Golgi Body Complex


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The Golgi Body Complex


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Lysosomes

Lysosomes

(Contain 40 different hydrolase enzymes)

Damaged

cellularstructures

Food

particles

bacteria


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The Lysosomes


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The Lysosome


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The Lysosome


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Peroxisomes

Peroxisomes are similar to the Lysosomes

Except;

Formed by budding off from Smooth ER

Contain enzymes used in the detoxification process

They are named for the Hydrogen Peroxide, H2O2,they produce when breaking down alcohol and killingbacteria.

Peroxisomes also break down fatty acids, which the

mitochondria can then use as an energy source Peroxisomes contain oxidative enzymes, such as

catalase, D-amino acid oxidase and uric acid oxidase


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Secretory vesicles

Plenty in secretory cells

Formed by the GER Golgi Body system

Found more towards the secretory surface of

the cell


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The Secretory Granules


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The Mitochondria


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Mitochondria

Mitochondria are found scattered throughout the Cytosol,and are relatively Large Organelles.

Mitochondria are the sites of Chemical Reactions that transferEnergy from Organic Compounds to ATP.

Energy contain in food is released. Converted to ATP. ATP isthe molecule that most Cells use as their main EnergyCurrency.

THE "POWERHOUSE" OF THE CELL.

Mitochondria are Usually more numerous in Cells that have a

High Energy Requirement - muscle cells contain a largenumber of mitochondria.


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Mitochondrion

Powerhouse of the cell

All Mitochondria are maternal in origin

Are self replicative(has its own genome)

Variable in number and size

Bound by two separate membranes


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Mitochondria is surrounded by TWO Membranes.

A. The smooth outer membrane serves as a boundarybetween the mitochondria and the cytosol.

B. The inner membrane has many long folds, known asCRISTAE.

The Cristae greatly increases the surface area of the innermembrane, providing more space for the Chemical Reactionsto occur.

Mitochondria have their own DNA, and new mitochondria

arise only when existing ones Grow and divide. ATP Production is called CELLULAR RESPIRATION.


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The Structure Of The Mitochondrion

(Cristae)

(Intercristal space)


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The ATP Molecule


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Formation Of ATP


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Energy from the ATP molecule is used in three

ways:

Membrane transport

Protein synthesis

Mechanical work


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Energy For Cellular Functions


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NUCLEUS

The nucleus (The library of the cell):

Manufactures DNA (Genes) and RNA

control the characteristics of all cell proteins

control reproduction


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Structure Of The Nucleus


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Nuclear Membrane

2 separate bilayer membranes

The outer continuous with the ER

The peri-nuclear space between the 2 layers

communicates with the matrix of the ER

Punctuated with multiple coated pores


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The Nuclear Membrane


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Nucleolus

Most prominent in cells actively andvigorously involved in protein synthesis.

Not coated with a limiting membrane.

Actually a mass of recently assembled RNAand proteins.

Contributes to the formation of the

Ribosomes.


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Cytoskeleton Just as our body depends on skeleton to maintain its

shape and size, so a Cell needs structures to maintain itsshape and size.

In Animal Cells, an internal framework called

CYTOSKELETON maintains the Shape of the Cell.

THE CYTOSKELETON PARTICIPATES IN THE MOVEMENTOF ORGANELLES WITHIN THE CYTOSOL AND HELPS THECELL MOVE.

Cytoskeleton is a network of long protein strands locatedin the Cytosol, that are Not surrounded by a membrane.


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CYTOSKELETON consists of Three Types:

MICROTUBULES, MICROFILAMENTS AND

INTERMEDIATE FILAMENTS.


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MICROTUBULES

Microtubules are HALLOW TUBES, are the Largest

Strands of the Cytoskeleton. Are made of a PROTEIN called TUBULIN.

Microtubules have THREE FUNCTIONS:

A. To maintain the shape of the cell and hold

organelles in place.

B. To serve as tracks for organelles and molecules to

move along within the cell.


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C. Two short cylinders of Microtubules at right angles

known as Centrioles can be found situated in the

cytoplasm near the nuclear envelope.

Centrioles organize the microtubules of the cytoskeleton

during Cell Division in animal cells, plant cells lack

centrioles


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Microfilaments

MICROFILAMENTS are structures that resembles ROPE

made of TWO TWISTED CHAINS OF PROTEIN called

ACTIN.

MICROFILAMENTS can CONTRACT, causing movement.

Muscle Cells have many microfilaments


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Intermediate filaments

Intermediate filaments are rods that anchor the nucleusand some other organelles to their place in the cell.

They maintain the internal shape of the nucleus.

Hair-follicle (hair-root) cells produce large quantities ofintermediate filament proteins. These proteins make up

most of the hair shaft.

l & l ll


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Cilia & Flagella

Cilia and Flagella are Hairlike Organelles that extend from the surfaceof the cell, where they assist in movement.

Microtubules are sometimes bundled into structures called CILIAAND FLAGELLA.

CILIA ARE SHORT HAIRLIKE PROJECTIONS.

FLAGELLA ARE LONG WHIPLIKE PROJECTIONS.

CILIA ARE OFTEN NUMEROUS. FLAGELLA ARE OFTEN SINGULAR.

Unicellular organisms such as Paramoecium and Euglena use Cilia andFlagella to move through water.

Sperm use flagella to swim to the egg.

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Physio 2 Cell Physiology