Question

question 9
what might be the outcome if membrane cholesterol molecules were not present?
a the membrane would become too rigid, losing proper flexibility
b the membrane would become completely waterproof and stop all transport
c the membrane would permanently open all protein channels, and lose selective permeability
d the membrane would grow thicker and form extra phospholipid layers around the cell

question 10
what is the fluid mosaic model?
a proteins and lipids can leave the membrane and come back to it
b water cannot interact with the membrane
c membrane components move like fluid and are made of many parts
d the membrane is solid and fixed in place, not moveable

Explanation:

• Question 9: Cholesterol in the membrane helps in maintaining fluidity. Without it, at lower temperatures, the membrane would be too rigid (as phospholipids pack closely). Option a is correct. Option b is wrong as membranes are already semi - permeable and cholesterol doesn't make them completely waterproof. Option c is incorrect as cholesterol doesn't control protein channels in that way. Option d is wrong as cholesterol doesn't prevent extra phospholipid layers.
• Question 10: The fluid mosaic model describes the plasma membrane as a mosaic of components (lipids, proteins, carbohydrates) where membrane components move like a fluid. Option c is correct. Option a is an incorrect description of the model. Option b is wrong as water can interact with the membrane (e.g., through aquaporins). Option d is incorrect as the membrane is fluid, not solid and fixed.

Answer:

Question 9: a. The membrane would become too rigid, losing proper flexibility
Question 10: c. Membrane components move like fluid and are made of many parts