Lesson 12 - Enzymes

Question 1

Why do biological reactions need enzymes?

Answer 1

The high pressures and temperatures needed to increase the speed of chemical reactions can not be attained in cells. This could damage organelles.

Question 2

Anabolic reactions

Answer 2

Building up / growth

Question 3

Catabolic

Answer 3

Breaking down releasing energy in metabolic reactions

Question 4

Where are substrates attained for catabolic reactions?

Answer 4

• Large organic molecules attained from the digestion of food.

Question 5

Metabolism definition

Answer 5

Sum of all chemical reactions

Question 6

Enzyme definition

Answer 6

Biological catalyst made of protein

Question 7

Enzymes can only increase the rate of reaction to a certain point. What is this?

Answer 7

V max

(maximum initial velocity or rate of the enzyme-catalysed reaction)

Question 8

Phosphorylases

Answer 8

Catalyse the addition of phosphate groups to molecules

Question 9

Lactate dehydrogenase

Answer 9

Catalyses the transfer of a H+ ion to and from a lactate.

Question 10

Pepsins catalyse

Answer 10

The breakdown of proteins (peptides) in the stomach

Question 11

ATPase

Answer 11

Uses ATP as its substrate

Question 12

When does a chemical reaction occur?

Answer 12

• When molecules collide in the right orientation.

Question 13

Effect of increasing the temperature and pressure in chemical reactions?

Answer 13

The speed of the molecules will increase, therefore so will the number of successful collisions and the overall rate of reaction.

Question 14

Specificity of an enzyme

Answer 14

• Living organisms produce thousands of enzymes.
• There are thousands of chemical reactions.
• One enzyme catalyses each chemical reaction.

Question 15

What is activation energy?

Answer 15

The energy supplied to start a chemical reaction.

Question 16

How do enzymes reduce the activation energy?

Answer 16

They help the enzymes collide sucessfully

Question 17

What are the two hypothesis for how enzymes work:

Answer 17

• Lock and Key hypothesis
• Induced fit hypothesis

Question 18

Lock and key hypothesis:

Answer 18

• An area of the enzymes tertiary structure is complementary to the shape of a specific substrate (the active site).
• When the substrate is bound to the active site and enzyme-substrate complex is formed.
• Reaction occurs and leaves an enzyme-product complex.
• Products are released leaving the enzymes unchanged.

Question 19

Lock and Key theory: how does the reaction take place?

Answer 19

Enzyme holds substrate in such a way that the right atom-groups are close enough to react.

R-groups within the active site of the enzyme interact with the substrate, forming temporary bonds. These put strain on the bonds in the substrate, helps reaction.

Question 20

Induced-fit hypothesis:

Answer 20

the active site of the enzyme changes shape to fit the substrate.
- Initial reaction between enzyme and substrate is relatively weak.
- Weak interactions rapidly induce changes in the enzyme’s tertiary structure that strengthen binding, putting strain on the substrate molecule.
- This lowers activation energy for the reaction.

(Modified version of lock and key)

Question 21

Name of enzymes that act within cells:

Answer 21

Intracellular enzymes

Question 22

What is hydrogen peroxide?

Answer 22

A toxic product of many metabolic pathways

Question 23

Which enzyme breaks down hydrogen peroxide? What into?

Answer 23

• Catalyse
• Oxygen and water

Completes the action quickly to prevent the accumulation of hydrogen peroxide.

Question 24

Where is hydrogen peroxide and catalyse found?

Answer 24

• Plant cells
• Animal cells

Question 25

What is the first step of all extracellular enzymes?

Answer 25

Released from cells

Question 26

Purpose of extracellular enzymes?

Answer 26

Break down large nutrient molecules into smaller molecules in the process of digestion. This means that smaller molecules can enter cells directly through the cell surface membrane.

Question 27

Where do extracellular enzymes work in fungi?

Answer 27

Outside the body.

Question 28

Who uses extracellular enzymes?

Answer 28

Both single celled organisms and multicellular

Question 29

Example of single celled organisms use of extracellular enzymes?

Answer 29

Bacteria and yeast Eg. - Extracellular enzymes break down proteins into amino acids and glucose. These can be absorbed by cells.

Question 30

Two enzymes involved in the digestion of starch?

Answer 30

- Amylase and Maltase

Question 31

- Starch Role of amylase

Answer 31

Produced by the salivary glands and the pancreas. It is released in saliva into the mouth and pancreatic juice into the small intestine. Breaks down starch polymers into maltose (disaccharide)

Question 32

- Starch Role of maltase

Answer 32

Maltase is in the small intestine. It breaks down maltose into glucose molecules (monosaccharide)

Question 33

Starch - Role of glucose

Answer 33

Small enough to be absorbed by the cells lining in the digestive system and subsequently absorbed into the bloodstream.

Question 34

What protease is used in the digestion of proteins?

Answer 34

Trypsin

Question 35

Proteins Role of trypsin

Answer 35

Produced by pancreas and secreted into the small intestine in the pancreatic juice. Breaks down proteins into smaller peptides

Question 36

how are other protease used in digestion of proteins

Answer 36

Other protease break down peptides into amino acids.

Question 37

Amino acids in digestion?

Answer 37

Small enough to be absorbed into the cells lining in the digestive system and subsequently absorbed into the blood stream.