Biological Membranes

Question 1

Function of membrane

Answer 1

Function of membrane
- Responsible for controlling the movement of substances in and out of the cell
- Contains receptors for molecules such as hormones
- Enables adjacent cells to stick together

The fluidity of the membrane and the mosaic arrangement of the protein give the structure of the membrane its name – fluid mosaic model.

Question 2

Types of movements through cell membrane

Answer 2

Types of movements through cell membranes

Diffusion, movement of small, non-polar, lipid soluble molecules (hydrophobic) such as carbon dioxide and oxygen from area of high concentration to an area of low concentration

Facilitated Diffusion, requires a channel protein to support polar, charged and water soluble molecules across the membrane

Osmosis, diffusion of water molecules from an area of low solute (high water potential) concentration to an area of high solute (low water potential) concentration through a partially permeable membrane

Active Transport, can transport all types of molecules through carrier proteins from an area of low concentration to an area of high concentration (requires ATP)

Exocytosis, transport large particles. In endocytosis Particles are enclosed in vesicles made from cell surface membranes and transported into cell by endocytosis. In exocytosis, vesicles containing large particles are are fused with cell membrane, particles can then enter cell

Question 3

Rate of gas exchange by diffusion

Answer 3

Rate of gas exchange by diffusion
- becomes more rapid as surface area increases
- becomes more rapid as diffusion distance decreases
- becomes more rapid as diffusion gradient becomes more steep