Biochem Chapter 6

Question 1

Enzymes are also called

Answer 1

Biological Catalysts

Question 2

Enzymes bind to ____ on a specific spot called the ______ _____

Answer 2

Substrates, Active Site

Question 3

What is Activation Energy? What do Enzymes do to them?

Answer 3

The amount of energy chemical reactions need to move forward. Enzymes decrease the activation energy so that it does not take as much energy for the reaction to occur and therefore the reaction goes faster.

Question 4

Describe the ways enzymes prepare substrates for reaction.

Answer 4

1. The active site contains amino acid R groups that end up close to chemical bonds in the substrate, which makes the bonds easier to break
2. Brings substrates together in the correct position
3. Transfers electrons to or from the substrate to oxidize it, destabilising it, making it more likely to react
4. Add or remove hydrogen ions to or from the substrate, destabilising it and making it more likely to react

Question 5

What is the Induced Fit Hypothesis

Answer 5

Just prior to the substrate binding, the enzyme changes its shape or conformation, so that the active site becomes even more precise in its ability to bind to its substrate

Question 6

What is a co-factor vs a co-enzyme

Answer 6

Cofactor - a non-protein group that binds very precisely to an enzyme (iron, copper)

Co-enzyme - water-soluble vitamins that bind to an enzyme. They shuttle molecules from one enzyme to another

Question 7

List the factors that affect enzyme activity

Answer 7

Substrate Concentration, Enzyme Concentration, pH, Temperature

Question 8

What happens when the concentration of a substrate is constant and at a high level?

Answer 8

the rate of reaction will be proportional to the enzyme concentration because the amount of enzyme limits the rate

Question 9

When the amount of Enzyme is constant and the substrate is increasing

Answer 9

the rate of reaction will be increased up to the saturation level. At this maximum rate, they will combine with the substrate

Question 10

pH indicates…

Answer 10

the concentration of hydrogen ions in a particular solution

Question 11

An increase or decrease in the pH changes the ion concentration of the solution and these ions alter the structure of the enzymes either due to…

Answer 11

the formation of additional bonds or breakage of already existing bonds. Ultimately the chemical makeup of the enzyme and substrate are changed so the substrate can no longer identify the enzyme

Question 12

What is the optimal pH for pepsin? What does it do? Where is it found? What happens to enzyme activity as the pH deviates from the optimal pH?

Answer 12

2, breaks down proteins in the stomach, at 6 it denatures

Question 13

What is the optimal pH for trypsin? What is it and where is it found? How does this relate to the optimal pH

Answer 13

8, breaks down proteins in the duodenum, chyme is very acidic but the sodium bicarbonate neutralizes it bringing it up to a pH of 8

Question 14

The temperature has an effect on enzyme activity in two distinct processes

Answer 14

1. General effect on all chemical reactions - as the temp rises so does kinetic motion, more frequent collisions
2. Effect on all proteins - as the temp rises, the kinetic motion of amino acid chains of enzymes increase, at the same time the strength and frequency of collisions between the enzyme molecules and any surrounding molecules also increases

Question 15

Describe Competitive Inhibitors

Answer 15

the competitive inhibitor binds to the active site blocking access to the normal substrate and slowing the rate or reaction.

Question 16

Describe Non-competitive inhibition

Answer 16

a non-competitive inhibitor binds to an enzyme at a location other than the active site which changes the shape of the enzyme reducing the ability of the substrate to bind efficiently

Question 17

what is reversible inhibition

Answer 17

when the binding of the inhibitor is weak and readily irreversible.

Question 18

what is irreversible inhibition

Answer 18

when they bind so strongly through the formation of covalent bonds that they completely disable the enzyme

Question 19

Why are enzymes of extreme medical interest?

Answer 19

Most drugs prescribed are inhibitors.

Question 20

Cyanide

Answer 20

a potent poison that bonds strongly to and inhibits cytochrome oxidase (key step in cellular respiration)

Question 21

Penicillin

Answer 21

inhibits the synthesis of peptidoglycan, a key component of bacterial cell walls. Penicillin mimics the structure of the two amino acids that are normally brought together by the active site. This bond is irreversible, effectively destroying the molecule.

Question 22

Allosteric Activation

Answer 22

Stimulates enzyme activity. It causes the active site to have a high affinity for its substrate.

Question 23

Feedback Inhibition

Answer 23

If the product is in excess, it will slow or stop the enzymatic reaction that produces it.

If the product is scarce, inhibition is reduced therefore it increases the rate of reaction

Question 24

What is lactose intolerance

Answer 24

Lactase digests lactose. People with lactose intolerance do not produce enough lactase therefore lactose is not digested or absorbed properly. The lactose is then consumed by bacteria in the gut which leads to symptoms including nausea, cramping, and bloating.

Question 25

Chymosin

Answer 25

Cheese production. Bacteria is added to milk to aid in the curdling process. Lactic acid is produced as a waste product. This lowers the pH of milk and it starts to denature. Chymosin is then added to hydrolyze the milk protein (casein).

Question 26

Starch to glucose

Answer 26

enzymes break down starch into glucose syrup

Question 27

Laundry Detergent

Answer 27

Enzymes improve stain removal making it more effective at lower temperatures.

Question 28

Brewing

Answer 28

Removes carbohydrates in beer

Question 29

Animal Feed

Answer 29

degradation of the components in the feed to improve digestion

Question 30

Leather

Answer 30

unhalving, batting, and defatting, soaking to soften hides and skins

Question 31

Wine and Juice

Answer 31

degradation of the protein pectin for clarification and increase juice yield.