Maintaining a Balance

Question 1

What are enzymes?

Answer 1

Organic catalysts – substance that speeds up or brings about a chemical change without itself being used up in the reaction.

Question 2

What do enzymes do?

Answer 2

• control all chemical reactions that constitute the body’s metabolism
• reduce the activation energy required in metabolic reactions
• enable reactions to occur at lower temperatures

Question 3

What is the anabolic metabolic reaction?

Answer 3

build-up of large organic compounds from simpler molecules (requires energy)

Question 4

What is the catabolic metabolic reaction?

Answer 4

breakdown of complex organic compounds into simpler molecules

Question 5

What is the chemical composition of enzymes?

Answer 5

PPAP. Most enzymes are proteins. 3D protein structures consist of one or more polypeptide chains – composed of long chains of amino acids joined together by peptide bonds.

Question 6

What is the active site of an enzyme?

Answer 6

The area where the enzyme binds to the substrate – composed of a folded group of polypeptide chains which form a recessed groove into which the substrate molecule/s fit.

Question 7

What does the lock and key model suggest?

Answer 7

Enzymes are specific in their action - their structure only allows specific substrates to form an enzyme-substrate complex. Active site.

Question 8

When and by who was the lock and key analogy first described?

Answer 8

Emile Fisher in 1894.

Question 9

What does specificity mean?

Answer 9

Only one compound (or a few) can react with a particular enzyme. Each enzymes catalyse a distinct chemical reaction, in which the substrates are changed into other compounds.

Question 10

What is reaction rate?

Answer 10

Measuring time taken for a reaction. A reaction that occurs quickly will take less time but have a higher reaction rate.

Question 11

What effect does temperature have on enzyme activity?

Answer 11

As temperature increase, the rate increases because the molecules move faster and are more likely to collide and react.
Beyond a certain peak temperature, the enzymes intricate shape begins to distort, and the reaction slows. If the temp was lowered again, RR could be restored.

Question 12

What happens to the enzyme if temperature reaches an extreme level?

Answer 12

The distortion of the enzymes shape may result in total shut-down of the reaction, permanently. The enzyme has been DENATURED.

Question 13

Describe the graph of temperature affecting enzyme activity.

Answer 13

Not usually symmetrical. It tends to rise gradually at temperatures below the optimum, but often falls more steeply at temperatures above optimum because the denaturation of the enzyme can lead to rapid decline in activity.

Question 14

Describe the graph of an enzyme tested at different pH levels.

Answer 14

Symmetrical on either side of the peak.

At optimum

Question 15

What happens at optimum pH of an enzyme?

Answer 15

At optimum pH the enzymes 3-D shape is ideal for attracting the substrate so reaction rate is maximum.

Question 16

What happens at pH lower or higher the optimum pH of an enzyme?

Answer 16

At any pH higher or lower than optimum, the enzyme’s shape begins to distort, and reaction rate declines as the substrate no longer fits so perfectly.

Question 17

What happens at extremes of pH of an enzyme?

Answer 17

The enzyme can be irreversibly denatured and show no activity at all.

Question 18

Describe the graph of substrate concentrate affecting enzyme activity.

Answer 18

Initially the rate of reaction increases as the substrate concentration goes up. Soon after, the graph begins to flatten out and level off because the enzyme molecules are “saturated” with substrate and cannot work any faster.