Transport in membranes

Question 1

What is the plasma cell membrane ?

Answer 1

• All cells and organelles are surrounded by a partially permeable membrane composed of a lots of phospholipids with protein molecules between the phospholipid molecules.
• The main function of the membrane is controlling the movement of substances in and out of the cell/organelle. However, it also contains receptors for other molecules such as hormones and 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

What is diffusion ?

Answer 2

• Diffusion is the passive movement of small, non-polar lipid soluble molecules such as
  carbon dioxide and oxygen from an area of high concentration to an area of low
  concentration. The molecules move directly through the phospholipid bilayer.

Question 3

What is Osmosis ?

Answer 3

Osmosis is the diffusion of water molecules from an area of high water potential to an
area of low water potential through a partially permeable membrane.

Question 4

What is facilitated diffusion ?

Answer 4

Facilitated diffusion requires a channel protein in the cell membrane to transport
polar molecules, charged and water soluble molecules across the membrane.

Question 5

What is active transport ?

Answer 5

Active transport can transport all types of molecules through carrier proteins from an
area of low concentration to an area of high concentration. However, this process
requires energy in the form of ATP.

Question 6

What is endocytosis and exocytosis ?

Answer 6

Exocytosis and endocytosis transport large particles and bulk transport . The particles
are enclosed in vesicles made from the cell surface membrane and transported into the
cell in endocytosis. In exocytosis, vesicles containing large particles are fused with
the cell surface membrane.

Question 7

What substances does the membrane allow in it ?

Answer 7

• Non polar
• Hydrophobic
• Uncharged

Question 8

What are the three lipids that are in the cell membrane ?

Answer 8

• Phospholipids
• Cholesterol
• Glycolipids

Question 9

What is the function of Phospholipids ?

Answer 9

• Control the movement of substances
• Only allows
• Non polar
• Hydrophobic
• Uncharged

Question 10

What is the function of cholestrol ?

Answer 10

• Regulates the membrane fluidity
• It restricts movement of phospholipids and proteins
• Prevents water and ions from leaking out

Question 11

What is the function of glycolipids?

Answer 11

• Phospholipids attached to a carbohydrate
• Act as cell markers or antigens allowing cells to attach to one another to form tissues.

Question 12

What else are found on the cell membrane ?

Answer 12

• Proteins

Question 13

What are the three types of proteins ?

Answer 13

• Surface proteins
• Glycoproteins
• Transport proteins

Question 14

What is the function of surface proteins ?

Answer 14

• Provide mechanical support for cell

Question 15

What is the function of Glycoproteins ?

Answer 15

• Have a carbohydrate attached to it
• ## Act as recognition to foreign cells or for chemicals

Question 16

What affects the membrane ?

Answer 16

• Temperature
• Solvent

Question 17

How does temperature affect the membrane ?

Answer 17

• An increase in temperature causes an increase in kinetic energy of phospholipds
• causes membrane to lose its structure and even cause the channel proteins to denature
• As a result membrane permeability increases and can even break down completely