Biological membranes - Active Transport

Question 1

define active transport

Answer 1

the movement of molecules or ions through carrier proteins across membranes against their concentration gradient using energy from ATP

Question 2

how does active transport work

Answer 2

• the molecule or ion binds to receptors on the carrier protein
• ATP binds to the carrier protein and is hydrolysed into ADP and phosphate
• this causes the carrier protein to change shape and the molecule or ion is released on the other side of the membrane

Question 3

give six examples of active transport

Answer 3

root - magnesium ions taken in for chlorophyll
intestine - removal of glucose from gut into blood
kidney - useful molecules reabsorbed
phloem - sucrose loaded into phloem
nerve impulses - sodium potassium pump
muscles - special form of ER stores calcium ions

Question 4

what organelle will cells involved in active transport contain large numbers of and why

Answer 4

lots of mitochondria for the production of ATP in aerobic respiration

Question 5

what are the five factors affecting the rate of active transport in cells

Answer 5

oxygen concentration
glucose concentration
temperature
poisons
number of carrier proteins

Question 6

how does oxygen concentration affect the rate of active transport

Answer 6

oxygen required for aerobic respiration which results in more ATP - greater rate

Question 7

how does glucose concentration affect the rate of active transport

Answer 7

glucose is a substrate for respiration and so will provide ATP - greater rate

Question 8

how does temperature affect the rate of active transport

Answer 8

increased temperature increases enzyme activity in respiration providing more ATP - greater rate
too high a temperature will denature proteins preventing active transport

Question 9

how do poisons affect the rate of active transport

Answer 9

e.g cyanide
attaches to an enzyme in mitochondria preventing aerobic respiration, decreasing the rate of active transport

Question 10

how does the number of carrier proteins affect the rate of active transport

Answer 10

more carrier proteins means more molecules can move at the same time - greater rate

Question 11

state the similarities between active transport and facilitated diffusion

Answer 11

both use carrier proteins
bind + carrier proteins change shape

Question 12

state the differences between active transport and facilitated diffusion

Answer 12

AT requires energy by FD does not
AT against concentration gradient but FD down concentration gradient
AT only uses carrier proteins but FD uses carrier and channel proteins