T1 - Enzymes

Question 1

What are enzymes

Answer 1

Biological catalysts that increase the rate of a chemcial reaction

Question 2

What is an advantage of enzymes in the body

Answer 2

Enables cellular reactions to take place at lower temperatures

Question 3

What is the active site of an enzyme

Answer 3

The region of an enzyme to which a substrate molecule binds and the reaction takes place

Question 4

How are enzymes ‘high specificity’

Answer 4

Only substrates with a specific, complementary shape can fit into an enzymes active site

Question 5

Describe the ‘lock and key model’

Answer 5

1. Substrate collides with the active site of an enzyme
2. Substrate binds, enzyme-substrate complex forms
3. Substrate converted to products
4. Products released from the active site which is now free to bind to another substrate

Question 6

What factors affect the rate of an enzyme-controlled reaction

Answer 6

Temperature
PH
Substrate concentration

Question 7

Explain how increasing temperature initially affects the rate of an enzyme-controlled reaction

Answer 7

• as temperature increases molecules have more KE
• movement of molecules increases
• probability of a succesful collison increases
• more enzyme-substrate complexes form
• rate of reaction increases

Question 8

Explain how increasing temperature above the optimum affects the rate of an enzyme controlled reaction

Answer 8

• temperature increases above optimum
• increased vibrations break bonds in enzyme’s structure
• active site changes shape, enzyme is denatured
• no more enzyme-substrate complexes can form
• rate of reaction decreases

Question 9

Explain how PH affects the rate of an enzyme-controlled reaction

Answer 9

• enzymes have an optimum PH
• ph shifts from the optimum
• bonds in the enzyme’s structure are altered
• active site changes shape, enzyme is denatured
• rate of reaction decreases

Question 10

Explain how the substrate concetration affects the rate of an enzyme-controlled reation

Answer 10

Probaility of succesful collisions increase
Rate of reaction increases
Once all active sites become full, the rate of reaction plateaus

Question 11

How can the rate of an enzyme-controlled reaction be calculated when given a value for time

Answer 11

Rate = 1/time

Question 12

What are the units for rate

Answer 12

S^-1

Question 13

Why must large organic molecules be broken down into smaller, simpler molecules in the body

Answer 13

• large molecules are too big to be absorbed across the surface of the gut wall
• large molecules are broken down into smaller molecules for absorption into the bloodstream

Question 14

What type of molecules are proteins and carbohydrates

Answer 14

Polymers

Question 15

What are the monomers of carbohydrates

Answer 15

Simple sugars

Question 16

Which group of enzymes catalyses the breakdown of carbohydrates

Answer 16

Carbohydrases

Question 17

Whcih type of carbohydrase catalyses the breakdown of starch

Answer 17

Amylase

Question 18

What are the monomers of proteins

Answer 18

Amino acids

Question 19

What typ of enzyme catalyses the breakdown o proteins

Answer 19

Proteases

Question 20

What is the function of lipases

Answer 20

Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol

Question 21

Why are small molecules synthesised into larger organic molecules in the body

Answer 21

Large molecules are used for storage (e.g. glycogen) or are used to build structures (e.g organelles)

Question 22

Which enzyme catalyses the formation of glycogen from glucose

Answer 22

Glycogen synthase

Question 23

How can the amount of energy contained in food be measured (calories)

Answer 23

Measured using calorimetry

Question 24

What is calorimetry

Answer 24

A method of measuring the heat transfer during a chemical reaction

Question 25

Describe the method used to measure the amount of energy in a sample of food

Answer 25

1. Add a set volume of water to a boiling tube, record initial temperature
2. Record the mass of a sample of food (e.g bean)
3. Stick the sample into a mounted needle
4. Using a bunsen burner light the food sample
5. Hold the sample under the boiling tube until it burns up
6. Record the maximum temperature reached by the water
7. Record the final mass of a food sample

Question 26

How can the amount of energy in the food sample be calculated

Answer 26

Energy in food (J)= mass of mater x temperature of water x 4.2

Energy (J/g) = energy in food (J)/mass of food burnt(g)

Question 27

Compare peanuts to potatoes when meauring their energy

Answer 27

The higher the fat (e.g peanuts) the higher the temperature it will cause the water to go meaning it has more energy than a potato which is high in carbohydrate