Enzymes and ATP

Question 1

What is ATP made of?

Answer 1

• Ribose sugar
• Adenine
• Three phosphate groups

Question 2

How is ATP used and restored?

Answer 2

When a covalent bond breaks during hydrolysis and a phosphate group is broken off, it releases energy that the organelles can use.
ATP can be restored by condensation

Question 3

How are the properties of ATP suitable for its function?

Answer 3

• Small - moves into and out of cells easily
• water soluble - energy-requiring process happen in aqueous environments
• Easily regenerated - can be recharged with energy
• Releases energy in small quantities - enough for cellular needs but energy isn’t lost as heat

Question 4

Why is ATP not good for long term storage?

Answer 4

P group is unstable so fats/carbs are used instead.

Question 5

Why are enzymes (catalysts) needed? (2)

Answer 5

• Conditions needed otherwise (high temp, pressure) would damage cell components
• Needed for anabolic/catabolic reactions

Question 6

How do enzymes function?

Answer 6

Helps the molecules collide successfully and reduce activation energy

Question 7

What is the lock and key hypothesis? (5)

Answer 7

• Tertiary structure of enzyme is complementary to the shape of a specific substrate molecule
• Substrate binds to active site forming enzyme-substrate complex
• R-groups within active site reacts with substrate
• Product is formed and released
• Enzyme can be reused

Question 8

What is the induced fit model? (3)

Answer 8

• Interactions between enzyme and substrate cause induce changes in tertiary structure of enzyme
• Enzyme changes slightly to become complementary to the substrate
• Enzyme can be reused after product is released

Question 9

What are intracellular and extracellular enzymes?

Answer 9

Intracellular - work inside cells (e.g. catalase)

Extracellular - work outside cells (e.g. to break down food - amylase)

Question 10

How is starch broken down in the small intestine? (2)

Answer 10

1) Amylase breaks down starch into maltose

2) Maltase breaks down maltose into glucose

Question 11

Where is amylase produced and released? (2)

Answer 11

Produced in salivary glands and pancreas.

Released in saliva in mouth and pancreatic juice in small intestine

Question 12

What is the effect of temperature on enzyme reactions? How does it work? (3)

Answer 12

• More kinetic energy means more collisions
• So higher the temperature, higher rate of reaction
• After 37ºC enzymes are denatured and cannot be used

Question 13

What is the effect of pH on a reaction? (4)

Answer 13

• Affects ionic and h-bonds, R-group interactions
• H+ ions interact (low pH) with polar R-groups
• Changes shape if not the right pH
• Large changes in pH can denature an enzyme

Question 14

What is the effect of substrate/ enzyme concentration?

Answer 14

• Substrate - higher means higher volume means more collisions. More substrate complexes. Limited by number of enzyme
• Enzyme - higher means more substrates can bind and higher r.o.r. Limited by number of substrate

Question 15

What is a serial dilution?

Answer 15

A dilution where successive concentrations increase/decrease logarithmically

Question 16

How do you make a serial dilution? (end solution= 10cm3) [4]

Answer 16

• Add 16cm3 of solution into a test tube and add 4cm3 of water to it
• Add 10cm3 of that mixture into another test tube and add 10cm3 of water to it
• Remove 10cm3 of that mixture and add it into another test tube, repeating the steps until you have made as many dilutions as you need.
• Discard the extra solution.

Question 17

How do competitive inhibitors work? (3)

Answer 17

• The molecule has a similar shape to the substrate
• Blocks the substrate by binding to the active site
• Degree of inhibition depends on conc. of inhibitor/substrate/enzymes

Question 18

How do non-competitive inhibitors work? (3)

Answer 18

• Binds at a different location (allosteric site)
• Changes the shape of the enzyme so its active site is no longer complementary to the substrate
• Enzyme-substrate complex can’t form

Question 19

Why are inhibitors needed?

Answer 19

• Inactivates enzymes
• Increased conc. inhibitor = decreased r.o.r.
• Regulates product formation

Question 20

Where are cofactors and coenzyme obtained from?

Answer 20

• Inorganic cofactor - (minerals, iron, calcium, zinc ions)

- Organic coenzyme - from vitamins

Question 21

What are permanent additions?

Answer 21

• Prosthetic groups.

- Changes cause interactions that change tertiary structure + active site

Question 22

What does ATP stand for?

Answer 22

Adenosine triphosphate