The cell for medical school

THE CELL

V.S.RAVIKIRAN, MSc.

V.S.RAVIKIRAN, MSc., Department of Biochemistry,

ASRAM Medical college, Eluru-534005.AP, [email protected]

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V.S.RAVIKIRAN

CELLS

Two generations of membrane models

Fatty acids (FAs) form the basic structures of

phospholipids

1.2.1 Simplified structure of lipid bilayer and phospholipids

Polar group

PhosphateGlycerol

Fatty acid-(unsaturated)

Phospholipid molecule

Fatty acid (saturated)

Hydrophilic head

Hydrophobic fatty acid tails

Hyd

rop

hob

ic

core

of

lip

id

bilayer

Hydrophilic head to cytoplasm

Hydrophilic head on surface

1.4.1 Lipid composition of different plasma membranes: note cholesterol contents

Cell Membrane

• Ion channel• Transporter• Receptor• Enzyme• Cell Identity marker• Linker

Endocytosis

Phagocytosis

Pinocytosis

Cytoskeleton

The Cytoskeleton

• Made of filamentous proteins

• Helps give the cell its shape

• Coordinates cellular movements.

• Three categories:– microfilaments– intermediate filaments – microtubules

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22

Centrosome

Non-membranous Organelles

• Centrioles and the centrosome– Centrosome

• Area close to the nucleus• Organization site for microtubules

– Centrioles (exist as a pair)• In the centrosome• Perpendicular to each other• 9 sets of microtubule triplets• Important in cell division (spindle)

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35

Microvilli, Cilia and Flagella

• Appendages extending from the surface of some cells. – Microvilli:

• short, cytoplasmic extensions• For absorption

– Cilia:• usually occur in large numbers• work together to move materials or fluids along the surface of a cell.

– Flagella:• longer than cilia, and usually occur as single appendages.• Move the cell

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37

CiliaFlagella

Ribosome

EndoplasmicReticulum

(smooth and rough)

Golgi Complex

Protein Export by Golgi Complex

Lysosome

Peroxisomes

• Modify molecules through redox reactions (fatty acid)

• Produce peroxide as a result (H2O2)

• Split into two as they grow

Mitochondria

Nucleus

Interactions between nucleus and cytoplasm

86 Copyright Cmassengale

Isolating Organelles by Cell Fractionation

• Cell fractionation– Takes cells apart and separates the major

organelles from one another

• The centrifuge– Is used to fractionate cells into their component

parts

Cell fractionation is used to isolate(fractionate) cell components, based on size and density.

First, cells are homogenized in a blender tobreak them up. The resulting mixture (cell homogenate) is thencentrifuged at various speeds and durations to fractionate the cellcomponents, forming a series of pellets.

• The process of cell fractionation

APPLICATION

TECHNIQUE

Figure 6.5

Tissuecells

Homogenization

Homogenate1000 g(1000 times theforce of gravity)

10 min Differential centrifugation

Supernatant pouredinto next tube

20,000 g20 min

Pellet rich innuclei andcellular debris

Pellet rich inmitochondria(and chloro-plasts if cellsare from a plant) Pellet rich in

“microsomes”(pieces of plasma mem-branes andcells’ internalmembranes)

Pellet rich inribosomes

150,000 g3 hr

80,000 g60 min

Figure 6.5

In the original experiments, the researchers

used microscopy to identify the organelles in each pellet,

establishing a baseline for further experiments. In the next series of

experiments, researchers used biochemical methods to determine

the metabolic functions associated with each type of organelle.

Researchers currently use cell fractionation to isolate particular

organelles in order to study further details of their function.

RESULTS

Figure 6.5

DNA to mRNA to Ribosometo make Proteins

Transcription

Translation

Replicationof DNA

Mitosis and Meiosis

Aging and Cells

Geriatrics

Telomeres

Free radicals

Cancer Terms

• Neoplasia• Benign• Malignant• Metastases• Carcinoma• Sarcoma• Angiogenesis• Mutation

Terms to Know• Anaplasia

• Atrophy

• Dysplasia

• Hyperplasia

• Hypertrophy

• Progeny

• Progeria

THANKS FOR YOUR ATTENTION