Membrane Structure and Function

Question 1

explain the Fluid Mosaic
Membrane model of
biological membrane
structure

(The roles of phospholipids, cholesterol, glycolipids, protein and
glycoproteins. Diagrams are required)

Answer 1

The Fluid Mosaic Model is a conceptual framework that describes the structure and function of biological membranes, including cell membranes. It was proposed by S.J. Singer and G.L. Nicolson in 1972. According to this model, biological membranes are dynamic structures composed of various components arranged in a fluid, mosaic-like fashion. Here’s a breakdown of the components and their roles in the Fluid Mosaic Model:

Phospholipids:

Phospholipids are the primary structural components of biological membranes.
They consist of a hydrophilic (water-attracting) phosphate head and two hydrophobic (water-repelling) fatty acid tails.
In the membrane, phospholipids arrange themselves into a lipid bilayer with the hydrophilic heads facing outward towards the aqueous environment and the hydrophobic tails facing inward, shielded from water.
Cholesterol:

Cholesterol is a lipid molecule that is interspersed within the phospholipid bilayer of cell membranes.
Cholesterol helps maintain membrane fluidity and stability by preventing the phospholipid tails from packing too closely together.
It regulates the fluidity of the membrane, making it more resistant to changes in temperature.
Glycolipids and Glycoproteins:

Glycolipids and glycoproteins are molecules embedded in the outer leaflet of the cell membrane.
They consist of carbohydrate chains attached to lipid or protein molecules, respectively.
These molecules play roles in cell-cell recognition, cell signaling, and immune responses.
Glycolipids and glycoproteins often serve as receptors for signaling molecules or as antigens for the immune system.
Proteins:

Proteins are another major component of the cell membrane.
They are embedded within the lipid bilayer, with some spanning the entire membrane (integral proteins) and others attached to the inner or outer surface (peripheral proteins).
Membrane proteins have diverse functions, including transport of molecules across the membrane, cell signaling, cell adhesion, and enzymatic activity.
Integral proteins often serve as channels or carriers for specific molecules, while peripheral proteins can act as enzymes or linkers between the membrane and the cell’s internal cytoskeleton.
Fluidity and Mosaic Structure:

The term “fluid” in the Fluid Mosaic Model refers to the dynamic nature of the membrane, where lipids and proteins can move laterally within the bilayer.
This lateral movement allows for flexibility and adaptation of the membrane to changing environmental conditions.
The “mosaic” aspect of the model refers to the mosaic-like arrangement of proteins, lipids, and carbohydrates within the membrane, with various components distributed asymmetrically and heterogeneously.

Question 2

explain the processes of
diffusion, facilitated
diffusion, osmosis, active
transport, endocytosis
and exocytosis.

(Emphasis on the distinction between diffusion and osmosis; and active and passive processes. Diagrams are required. No calculations will be set on water
potential.)