in this slides we are talking about fluid mosaic model transport active passive diffusion and bilayer

2. COMPOSITION OF CELL MEMBRANE
1. Lipids
I. Phosopholipids
II. Sterols
2. Proteins
i. Integral
ii. Peripheral
3. Carbohydrates
i. Glycolipids
ii. Glycoproteins
Globuler
protein
CarbohydrateGlycoprotein
Glyco
lipid
Integral
protein
Channel
Protein
Cholestrol
Peripheral
protein

3. Phospholipids
There are two important parts of a phospholipid: the head and the two tails.
The head is a phosphate molecule that is attracted to water (hydrophilic). The
two tails are made up of fatty acids (chains of carbon atoms) that aren’t
compatible with, or repel, water (hydrophobic). The cell membrane is exposed
to water mixed with electrolytes and other materials on the outside and the
inside of the cell. When cellular membranes form, phospholipids assemble into
two layers because of these hydrophilic and hydrophobic properties. The
phosphate heads in each layer face the aqueous or watery environment on
either side, and the tails hide away from the water between the layers of heads,
because they are hydrophobic
Cholesterol
Cholesterol is a type of steroid which is helpful in regulating molecules
entering and exiting the cell. The cholesterol molecules are randomly
distributed across the phospholipid bilayer, helping the bilayer stay fluid in
different environmental conditions. The cholesterol holds the phospholipids
together so that they don’t separate too far, letting unwanted substances in, or
compact too tightly, restricting movement across the membrane. Without
cholesterol, the phospholipids in your cells will start to get closer together
when exposed to cold, making it more difficult for small molecules, like gases
to squeeze in between the phospholipids like they normally do. Without
cholesterol, the phospholipids start to separate from each other, leaving large
gaps.
Hydrophilic
head
Hydrophobic
Tail

4. 3) Proteins
The cell is made up of two different
types, or “classes”, of proteins. Integral
proteins are nestled into the
phospholipid bilayer and stick out on
either end. Integral proteins are helpful
for transporting larger molecules, like
glucose, across the cell membrane.
They have regions, called “polar” and
“nonpolar” regions, that correspond with
the polarity of the phospholipid bilayer.

5. Transport through cell
membrane Classification
based on function
Membrane transport
Passive transport Active transport
Simple diffusion Facilitated
Via Ion channels
Via various
transporters

6. Different types of transport

7. Simple diffusion

8. Facilitated diffusion
• Carrier mediated and involves transporter protein.
• A transporter protein reduces the ∆G€ for transmembrane diffusion of the solute.
• It does this by forming noncovalent interactions with the dehydrated solute to replace the H-bonding with
water and by providing hydrophilic transmembrane passageway.
• Example – Glucose transporters.

9. Endocytosis, exocytosis and membrane fluidity
•Large molecules, such as neurotransmitters and hormones, are transported into and out of the cell in fluid-
filled sacs called vesicles.
•Endocytosis is the intake of extracellular material through vesicles. Endocytotic vesicles are formed when the
plasma membrane is pulled inwards, enclosing a bit of extracellular material. The materials are transported
within the vesicle to different locations in the cell.
•Exocytosis is the removal of cell products through vesicles. These vesicles originated at different locations and
travel to the plasma membrane, where they fuse to release contents.
•Both endo- and exocytosis require energy in the form of ATP, so they can be considered forms of active
transport.
•The fluidity and dynamic properties of the plasma membrane mean that vesicles can form and reform
indefinitely. Flip-Flop movement is restricted and is catalysed by an enzyme “Flippase”- important during
membrane lipid synthesis