chapter 5 - enzymes

Question 1

define catalyst

Answer 1

a substance that increases the rate of a chemical reaction and is not changed by the reaction

Question 2

define enzyme

Answer 2

a protein that functions as a biological catalyst

Question 3

describe enzyme action

Answer 3

the enzyme and the substrate molecules have complementary shapes, so they fit together.
the product is released by the enzyme molecule and the enzyme is then free to repeat the reaction with more substrate molecules.

Question 4

what is an anabolic reaction?

Answer 4

reactions in which large molecules are built up from smaller molecules.

Question 5

what is a catabolic reaction?

Answer 5

reactions that split large molecules into smaller ones.

Question 6

what happens when the enzyme combines with substrate?

Answer 6

an enzyme-substrate complex is formed temporarily.

Question 7

what makes enzymes specific?

Answer 7

an enzyme that which normally acts on one substrate will not act on a different one.
enzymes have a shape called an active site, which exactly fits the substances on which it acts.
the shape of the substrate molecule and the active site are complementary.

Question 8

what do we call an enzyme that acts on proteins?

Answer 8

protease

Question 9

what do we call an enzyme that acts on carbohydrates?

Answer 9

carbohydrase

Question 10

what do we call an enzyme that acts on lipids?

Answer 10

lipase

Question 11

what do we call an enzyme that removes hydrogen from a substances?

Answer 11

dehydrogenase

Question 12

Describe the effect of temperature on enzyme activity

Answer 12

a rise in temperature increases the rate of enzyme activity up to a certain degree, above which the rate falls.

Question 13

Explain the effect of temperature on enzyme activity

Answer 13

increase in temperature increases rate of reaction, because the enzyme and substrate molecules gain more kinetic energy, move faster and there is a greater chance of collisions.
above the optimum temperature, the shapes of enzymes can be permanently changed and it can no longer combine with the substrates (active sites are deformed) —> denatured

Question 14

Describe the effect of pH on enzyme activity

Answer 14

Each enzyme works best at a particular level of acidity or alkalinity —-> optimum pH

Question 15

Explain the effect of pH on enzyme activity

Answer 15

acid or alkali conditions alter the chemical properties of proteins, including enzymes.
these changes are usually reversible, but extremes of pH may denature enzymes irreversibly.
active site is deformed —> enzyme and substrate no longer fit together.

Question 16

state how pH varies in human digestive systems

Answer 16

protease work best at an acidity of pH 2, so the stomach is acidic.
carbohydrase would not function at this pH, that is why carbohydrates are not digested in the stomach.
conditions in the duodenum (small intestine) are slightly alkaline (pH 8), which is the optimum temperature for pancreatic lipase.