Enzymes and metabolism

What happens to the structure/function of an enzyme when it is placed at a

higher temperature ?

• The enzyme increases its work rate(works faster)

• The enzyme becomes more flexible and reacts with more substrates

• The enzymes active site changes shape and the enzyme is denatured

• The enzyme adapts by changing its primary amino acid sequence

Answer explanation

In higher temperatures enzymes can lose their shape, making them stop working

properly. This process is called "denaturation" which refers to the answer C. The other

answers are wrong because they are all false.

What is an example of catabolic and anabolic reaction?

• Combustion reaction and cellular respiration

• Polymerization reaction and protein respiration

• Hydrolysis of ATP and combustion reaction

• Glycolysis (Glucose broken down) and Photosynthesis

Answer explanation

Answer D. is correct because Glycolysis is a catabolic reaction (glucose is being broken

down into smaller pieces), and PHotosynthesis is an anabolic reaction (from a smaller

molecule to a larger one)

Other answers include reactions that are neither anabolic nor catabolic such as combustion

reactions, polymerization reactions, Etc.

A characteristic of a catabolic reaction is:

• Makes bonds

• Releases energy

• Requires energy

• Condensation

What is the function of a catalyst?

• To slow down a chemical reaction

• To start a chemical reaction without changing itself

• Increase the rate of chemical reactions

• To make the reaction stop

Which of the following correctly describes the relationship between enzymes and substrates during a biochemical reaction?

• Enzymes increase the activation energy of a reaction by binding to multiple substrates non-

  specifically.

• Enzymes lower the activation energy by binding specifically to substrates at their active sites, forming

  an enzyme-substrate complex.

• Enzymes are consumed during the reaction and must be replaced after each catalytic cycle.

• Substrates bind randomly to enzymes without specificity, allowing the reaction to proceed faster.

Answer explanation

The correct answer is B Enzymes lower the activation energy by binding specifically to substrates at their active sites, forming an enzyme-substrate complex.

Which correctly links a carbohydrate type with its structural or functional characteristic?

• Glucose: a polysaccharide found in plant cell walls providing rigidity and support

• Cellulose: a polysaccharide used for energy storage in animals, composed of fructose units linked by β-

  glycosidic bonds

• Starch: a polysaccharide used for energy storage in plants, composed of glucose units linked by α-

  glycosidic bonds

• Glycogen: a monosaccharide used as the primary energy source for cellular respiration

Answer explanation

The correct answer is C Starch a polysaccharide used for energy storage in plants, composed of glucose units linked by a-glycosidic bonds.

Which of the following best describes the role of enzymes in anabolic and catabolic reactions?

• Enzymes increase the temperature for both types of reactions.

• Enzymes slow down catabolic reactions but speed up anabolic ones.

• Enzymes act as catalysts, lowering activation energy for both anabolic and catabolic reactions.

• Enzymes are only involved in catabolic reactions, not anabolic ones.

Answer explanation

Enzymes are biological catalysts that lower activation energy in both anabolic (building up)

and catabolic (breaking down) reactions.

Which statement correctly explains the effect of temperature and pH on enzyme activity?

• Enzymes function best at extreme temperatures and acidic pH levels.

• Higher temperatures always increase enzyme activity without limit.

• Each enzyme has an optimal temperature and pH, and deviation can denature it.

• Enzymes are unaffected by changes in environmental conditions.

Answer explanation

Enzymes work best at specific temperatures and pH. Too high or too low can denature the

enzyme, altering the shape of its active site.

What happens to an enzyme if the temperature gets too high?

• It works faster and faster forever

• It denatures and stops working

• It breaks down the substrate more efficiently

• It binds to more substrates

Answer explanation

Why B is correct:

Enzymes are proteins, and high temperatures can cause them to denature — meaning their shape changes, especially the active site. If the active site changes, the substrate can no longer fit, so the enzyme stops working properly.

A) It works faster and faster forever

This is not true. Enzyme activity increases only up to an optimal temperature. After that, it drops sharply because the enzyme denatures.

C) It breaks down the substrate more efficiently

This is only true up to a point (before denaturation). If the temperature is too high, the enzyme won’t break down anything because it loses its shape.

D) It binds to more substrates

This also only applies up to the optimal temperature. After that, binding becomes difficult or impossible due to the damaged active site.

Why are enzymes important in metabolism?

• They slow down chemical reactions

• They provide energy for reactions

• They speed up reactions without being used up

• They change the products of reactions

Answer explanation

Why C is correct:

Enzymes act as biological catalysts. They speed up the chemical reactions of metabolism by lowering the

activation energy needed, and they are not consumed or changed in the reaction, so they can be used

again and again.

A) They slow down chemical reactions

Completely false. Enzymes speed up reactions — that’s their main job.

B) They provide energy for reactions

Enzymes don’t provide energy. They reduce the amount of energy needed, but they don’t give energy

themselves.

D) They change the products of reactions

Enzymes only help the reaction go faster. They don’t change what the final product is — that depends on

the substrate and the type of reaction.