Transport Across Cell Membranes

Question 1

what is the model used to describe the arrangement of molecules in the membrane?

Answer 1

fluid mosaic model

Question 2

what are the membrane components?

Answer 2

• phospholipids
• choloesterol
• proteins
• glycoproteins
• glycolipids

Question 3

what does the cholesterol do?

Answer 3

gives the membrane stability

Question 4

where is the cholesterol in the cell surface membrane?

Answer 4

between phospholipids, binds to hydrophobic tails

Question 5

what is simple diffusion?

Answer 5

net movement of particles from an area of higher concentration to an area of lower concentration

Question 6

what is facilitated diffusion?

Answer 6

diffusion of particles that are large, polar and hydrophilic

Question 7

what are the two proteins involved in facilitated diffusion?

Answer 7

carrier and channel proteins

Question 8

what do carrier proteins help to diffuse?

Answer 8

large particles

Question 9

what do channel proteins help to diffuse?

Answer 9

charged particles, they form pores in the cell membrane

Question 10

what is osmosis?

Answer 10

net movement of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential

Question 11

what type of particles can be transported by simple diffusion?

Answer 11

• small
• non-polar
• hydrophobic

Question 12

what is active transport?

Answer 12

movement of molecules from an area of lower concentration to an area of higher concentration, using ATP and carrier proteins

Question 13

what is co transport?

Answer 13

movement of 2 different substances using a carrier protein

Question 14

explain how sodium ions and glucose are absorbed by cell lining the mammalian ileum.

Answer 14

• sodium ions are actively transported out the epithelial cells in the ileum into the blood by the sodium-potassium pump
• this creates a concentration gradient, so there is a higher concentration of sodium ions in the lumen of the ileum than inside the cell
• this causes sodium ions to diffuse from lumen of ileum into epithelial cells down the concentration gradient (done via the sodium-glucose co-transporter proteins)
• co transporter carries glucose into the cell with the sodium, so concentration of glucose inside the cell increases
• glucose diffuses out of the cell into the blood, down the concentration gradient through a channel protein by facilitated diffusion