2.3 - Cell transport

Question 1

Define simple diffusion

Answer 1

movement of molecules from an area of higher concentration to an area of lower concentration through a partially permeable membrane (phospholipid bilayer)

Question 2

Define facilitated diffusion

Answer 2

movement of molecules from an area of higher concentration to an area of lower concentration through channel or carrier proteins

Question 3

Define osmosis

Answer 3

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

Question 4

Define active transport

Answer 4

movement of molecules from an area of lower concentration to an area of higher concentration using energy released from hydrolysis of ATP and carrier proteins

Question 5

Define co-transport

Answer 5

movement of 2 substances simultaneously from an area of lower concentration to an area of higher concentration using energy released from hydrolysis of ATP and carrier proteins

Question 6

Explain how channel proteins function and the molecules they transport

Answer 6

transport charged molecules (ions) which are dissolved as the channel contains water

Question 7

Explain how carrier proteins function and the molecules they transport

Answer 7

transport large molecules by the binding of an inorganic phosphate to large molecule which enables it to bind to carrier protein

Question 8

Describe the absorption of sodium ions and glucose in the ileum in terms of cell transport

Answer 8

• Na+ ions actively transported out of epithelial cell into blood
• establishes a Na+ concentration gradient between the ileum lumen and epithelial cell
• Na+ ions then diffuse from lumen down their concentration gradient into epithelial cell
• glucose/amino acids attach to co-transporter protein with Na+ ions and are transported into epithelial cell against their concentration gradient
• glucose moves by facilitated diffusion from the epithelial cell into the blood

Question 9

How can cells be adapted for rapid transport across internal or external membranes?

Answer 9

• large surface area
• lots of protein channels
• lots of carrier proteins

Question 10

How do differences in water potential/concentration gradients affect the rate of movement?

Answer 10

larger gradient = faster rate of movement across the membrane

Question 11

Why is membrane called fluid mosaic?

Answer 11

mixture and movement of lots of substances it’s made up of e.g phospholipids, glycoproteins, glycolipids, cholesterol, carbohydrates

Question 12

Purpose of cholesterol

Answer 12

• keeps membrane rigid
• prevents leakage of water and dissolved ions from cell

Question 13

Purpose of glycolipids

Answer 13

• act as cell surface receptors
• allow cells to adhere to each other causing tissue formation

Question 14

Purpose of glycoproteins

Answer 14

• cell recognition
• tissue formation

Question 15

Define endocytosis

Answer 15

large particles enclosed in vesicles transported into a cell

Question 16

Define exocytosis

Answer 16

large particles in vesicles fuse with cell-surface membrane and are released from cell