Cell membraneThe transport and modification of

the cell

Present by Saad Sami Almuhanna

Learning objective

• What are the different Mechanisms responsible of transport?

• How the large molecules transport out from and into the cell ?

• What are the Modifications, their functions, examples ?

Mechanism of transport

• Passive transport• Active transport

Passive transport

1.Diffusion

2. Facilitated diffusion

3. Osmosis

Diffusion

Movement from high concentration to low concentration.

Facilitated diffusion• Channel proteins Provide corridors that allow a specific molecule or ion to cross the membrane.• Carrier proteins Undergo a subtle change in shape that translocate the salute-binding site across the membrane.

Osmosis• The movement of water across a semi permeable

membrane. • Osmosis is the movement of water (red dots) through a

semipermeable membrane to a higher concentration of solutes (blue dots).

Active transport

Process that moves materials across the plasma membrane

Requires energy from the cell in the form of ATP

Materials move against the concentration gradient:

low concentration high concentration

3 Kinds:Pumps, Endocytosis, and Exocytosis

Active Transport Pumps

1. An ATP molecule breaks down into ADP, releasing a phosphate group and a whole lot of energy.

2. The phosphate group attaches to a protein pump, causing it to change its shape so that it can move a small molecule or ion across the plasma membrane.

3. The protein changes shape again so that the molecule can be released on the other side.

There are many types of carrier proteins and they only carry specific molecules across the plasma membrane.

large molecules transportLarger molecules cannot fit. Because they are too big so they enter the cell by endocytosis and go out by exocytosis

Larger materials transport into the cell it is includes three slightly different processes:

Endocytosis:-

1. Phagocytosis: cell eating2. Pinocytosis: cell drinking3. Receptor mediated endocytosis

1. Phagocytosis:-endocytosis of solid particles.- cell engulfs particle with pseudopodia and pinches off a food vacuole- vacuole fuses with a lysosome containing hydrolytic enzymes that will

digest the particle2. pinocytosis:-fluid droplets of extracellular fluid are incorporated into small vesiclesthe process is not discriminating. the cell takes in all solutes dissolved in the droplet3. receptor-mediated endocytosis:- - cells have receptors for certain molecules on their surface. when these receptors encounter t molecule, they bind tightly to it. the complex of the molecule and its receptor is then engulfed by endocytosis. - a molecule that binds to specific receptor site of another molecule is called a ligand.

Exocytosis:-

The movement of material out of the cell via membranous vesicles

The modification and their function

Modification

apical lateral basal

1. Apical surface

its tissue of cell membrane on toward the lumen, there are many examples of apical

- stereocilia

- cilia

- flagella

- microvilli

stereocilia

Its function is

increase the cells surface area, facilitating the movement of molecules into and out to the cell

Its can be found in

the lining of the epididymis

Its function is

Its can be found in

cilia

trapping the materials to protect them

the lining of the trachea ( windpipe)

Its function is

Its can be found in

microvilli

reflecting cytoplasmic movement that will increase the total surface area of cells

kidney and intestines

Its function is

Its can be found in

flagella

it concerned with movement

in some certain eukaryotesEX. sperms in humans

2.lateral

it is a kind of protein which joins between adjacent cells within epithelium

these proteins have four types of junction:• tight junction• gap junction• adherens junction• desmosome

to form seal that prevents the flow of materials between epithelial cells in either direction.- help prevent the integral membrane proteins of the apical surface from being transferred

Tight junction

epithelial cells in general, brain cells

Function:

Examples

permit the rapid exchange between cells of molecules with small diameters

Function:

Examples

they are relevant in signal transfers in the brain

Gap junction

unction provide strong mechanical attachments between adjacent cells (provide for firm adhesion of one cell to its neighbors )

Function:

Examples

Adhering junction

present in narrow bands connecting adjacent cells or discrete patches holding the cells together

Desmosome

desmosome provide firm adhesion among the cells

Function:

Examples

Skin cells

3- Basal

its a friction of the plasma membrane at the basal side, which faces the underlying connective tissue

Example of Basal

polarity

Basal lamina

polarity

in cells, polarity refers to the asymmetric organization of different aspects of the cell including the cell surface, intracellular organelles and the cytoskeleton

Basal Lamina

Basal Lamina acts as base where the cells in the body can grow. It links cells together and underlies connective tissue.

Thanks for lessening