METABOLIC PATHWAYS

Question 1

metabolic pathways

Answer 1

metabolic pathways are integrated and controlled pathways of enzyme catalysed reactions within a cell

Question 2

routes

Answer 2

metabolic pathways can have:
- reversible
- irreversible
- alternative
routes

Question 3

catabolic reactions

Answer 3

• one reaction within metabolic pathways can be catabolic.
• breakdown of large molecules into smaller molecules and release energy

Question 4

anabolic reactions

Answer 4

build up large molecules from small molecules and require energy

Question 5

membranes

Answer 5

protein pores, pumps and enzymes are embedded in membranes

Question 6

protein pores

Answer 6

allow specific molecules and ions to pass through membrane

Question 7

protein pumps

Answer 7

allows molecules to pass through the membrane, however requires energy - so molecule is actively pumped inside or outside the cell

Question 8

enzymes

Answer 8

catalyse chemical reactions

Question 9

alternative routes

Answer 9

MB may also contain alternative routes that allow steps in the pathway to be bypassed

Question 10

control and regulation of metabolic pathways

Answer 10

• controlled by presence or absence of particular enzymes
• regulation of the rate of reaction of key enzymes

Question 11

induced fit

Answer 11

occurs when the active site changes shape to better fit the substrate after the substrate binds

Question 12

affinity

Answer 12

• substrate molecules have high affinity for the active site
• subsequent products have a low affinity allowing them to leave active site

Question 13

presence of substrate

Answer 13

Some metabolic pathways are reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction.

Question 14

competitive inhibitors

Answer 14

• bind at the active site preventing the substrate from binding.
• Competitive inhibition can be reversed by increasing substrate concentration.

Question 15

non-competitive inhibitors

Answer 15

• Non-competitive inhibitors bind away from the active site but change the shape of the active site preventing the substrate from binding.
• Non-competitive inhibition cannot be reversed by increasing substrate concentration.

Question 16

feedback inhibitors

Answer 16

• occurs when the end product in the metabolic pathway reaches a critical concentration.
• The end-product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product.