Tanveer Saeed

Assistant Professor

AKU-SONAM

• Smallest basic unit of life.

• Body has about 100 trillion cells.

• All cells have DNA and cytoplasm.

Cell size and Shape

Human cell are microscopic in size they

are in different size and shapes.

• RBC diameter 7.5µm

• Egg cell size is 1000µm

Cell

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Cells

• Smallest living unit

• Most are microscopic

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Plasma Membrane

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• Selectively permeable membrane that

surround the cell is called plasma

membrane

• Phosphobilipidc consists of two back to

back layer made up of three types of lipid

molecules.

Phospholipid 75% Glycolipid

5% Cholesterol 20%

PM Cont’d

• Double layer of phospholipids & proteins

• The lipid bilayer arrangement occur because the lipid is

amphipathic it mean that lipid have both polar and non

polar part.

• In Phospholipid the polar part is phosphate which is

hydrophilic and the non polar part is two long fatty acid tail

hydrophobic

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1. Plasma membrane give form to the cell and separate the

cell internal structure from the extra cellular environment

2. It provides selective transportation across the membrane

3. The membrane protein serve a variety of functions i.e.

• Provide structural support

• Form tiny channels through which certain substance flow

into or out of the cell

• Act as transporter or carrier of some substances

• Some integral membrane protein are called receptors

which serve as cellular recognition sites

• Membrane glycoprotein and Glycolipid often are cell

identity marker. It give the cell its immunologic identity

Function of Plasma Membrane

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Cytoplasm Cytoplasm has 2 component

• Cytosol

• Organelles Viscous fluid containing organelles

• components of cytoplasm

– Interconnected filaments & fibers

– Fluid = cytosol

– Organelles (not nucleus) specialized structure that have characteristic shape and that perform specific function in cellular growth, maintenance and reproduction.

– storage substances

Cytoplasm

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Cytoskeleton

• cell's skeleton

• Made of 3 fiber types of fibers; – Microfilaments

– Microtubules

– Intermediate filaments

• function: – mechanical support

– anchor organelles

– help move substances

Many cell have surface extension called Microvilli, cilia and flagella

Microvilli:

• It is the extension of the cell membrane that serve as to increase the surface area.

• They are best develop in cell specialized for absorption such as epithelial cell of the intestine and kidney tubule.

– Flagella & cilia - hair-like projections from some human

cells

• cilia are relatively short & numerous (e.g., those

lining trachea)

• a flagellum is relatively long and there's typically just

one (e.g., sperm)

Cell Surface Extension

Centrioles

• Pairs of microtubular structures

• Play a role in cell division

Endoplasmic Reticulum

• Helps move substances within cells

• Network of interconnected membranes

• Two types

– Rough endoplasmic reticulum

– Smooth endoplasmic reticulum

Rough Endoplasmic Reticulum (RER)

A network of

interconnected

membranes forming

channels within the cell.

Covered with ribosomes

(causing the "rough"

appearance) which are

in the process of

synthesizing proteins for

secretion or localization

in membranes.

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Smooth Endoplasmic Reticulum

• No attached ribosomes

• Has enzymes that help build molecules

– Carbohydrates

– Lipids

• Ribosome consists of 2 sub units the

smaller and the larger subunit one about

half the size of the other

• The larger and the smaller sub units both

are made separately in side the nucleolus

after formation it exit the nucleus and

come together in the cytoplasm

• Ribosomes are concern with protein

synthesis

Ribosome

Ribosomes

– composed of rRNA (ribosomal RNA) &

protein

• may be dispersed randomly

throughout the cytoplasm or attached

to surface of rough endoplasmic

reticulum

• often linked together in chains called

polyribosomes or polysomes

• primary function is to produce proteins

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Golgi Apparatus

• Involved in synthesis of plant cell wall

• Packaging & shipping station of cell

Golgi apparatus

A series of stacked membranes. Vesicles

(small membrane surrounded bags) carry

materials from the RER to the Golgi

apparatus. Vesicles move between the

stacks while the proteins are "processed" to

a mature form. Vesicles then carry newly

formed membrane and secreted proteins to

their final destinations including secretion or

membrane localization.

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Golgi Apparatus Function

1. Molecules come in vesicles

2. Vesicles fuse with Golgi membrane

3. Molecules may be modified by Golgi4. Molecules

pinched-off in separate vesicle

5. Vesicle leaves Golgi apparatus

6. Vesicles may combine with plasma membrane to

secrete contents

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• Mitochondria • are found exclusively in eukaryotic cells.

• These organelles are often called the "power plants" of

the cell

• their main job is to make energy (ATP).

• Mitochondria are highly unusual--they contain their

own genetic material and protein-making machinery.

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Mitochondria

• They have a double-membrane: outer

membrane & highly convoluted inner

membrane.

• inner membrane has folds or shelf-like

structures called cristae that contain

elementary particles; these particles

represent an enzyme important in ATP

production

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– Centrioles -

• paired cylindrical structures located near the

nucleus

• play an important role in cell division

• Mitosis and the role of centrioles

• Lysosomes: Contain digestive enzymes

• Functions

– Aid in cell renewal

– Break down old cell parts

– Digests invaders

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Vacuoles

• Membrane bound storage sacs

• More common in plants than animals

• Contents

– Water

– Food

– wastes

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Molecule Movement & Cells

• Passive Transport

• Active Transport

• Endocytosis

(phagocytosis & pinocytosis)

• Exocytosis

Types of Passive Transport

1. Diffusion

2. Osmosis

3. Facilitated diffusion

Passive Transport

• No energy required

• Move due to gradient

– differences in concentration, pressure, charge

• Move to equalize gradient

– High moves toward low

Osmosis

• Special form of diffusion

• Fluid flows from lower solute concentration

• Often involves movement of water

– Into cell

– Out of cell