biology chapter 5

Question 1

what is a catalyst

Answer 1

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

Question 2

what is an enzyme

Answer 2

biological catalysts that can increase the rate of a chemical reaction, without being chemically changed by the reaction. They are made up of proteins and are involved in all metabolic reactions

Question 3

what reactions do enzymes catalyse

Answer 3

• reactions in digestion ( some food molecules are large and insoluble in water. these molecules cannot diffuse through the cell membrane. )
• reactions that build up or break down complex substances ( besides digestion, other biological reactions also require one or more enzymes as catalysts)

Question 4

what does it mean by digestion

Answer 4

the process of breaking down food molecules into smaller substances is known as digestion

Question 5

what are food digested by

Answer 5

foods are digested by digestive enzymes

Question 6

what are some of the digestive enzymes

Answer 6

amylase, maltase, protease, lipase

Question 7

what is the function of an amylase

Answer 7

digest starch into maltose

Question 8

what is the function of a maltase

Answer 8

digest maltose to glucose

Question 9

what is the function of a lipase

Answer 9

digest fats to fatty acids and glycerol

Question 9

what is the function of a protease

Answer 9

digest proteins to amino acids

Question 10

how are enzymes named

Answer 10

enzymes are names according to a scientific system. the name of each enzymes shows the substance on which the enzyme reacts and end in ‘ase’

Question 11

how are enzymes classified

Answer 11

enzymes are classified according to the substances they act. for example:

• carbohydrates digest carbohydrates
• proteases digest proteins
• lipase digest into fats (lipids)

Question 12

how does an enzyme work

Answer 12

the substances on which enzymes act are called substrates. each enzyme has a groove on its surface called the active site. only a substance with a complementary shape can fit into the active site

Question 13

what happens when substrates bind to the active site of the enzyme

Answer 13

when the substrate binds to the active site of an enzyme, an enzyme- substrate complex is formed.

Question 14

what are the characteristics of enzymes

Answer 14

• enzymes catalyse reversible reactions
• every enzyme has an optimum pH at which is most active
• enzymes are required in minute amounts
• enzymes are specific in action
• every enzyme has an optimum temperature at which is most active

Question 15

describe the structure of the enzymes

Answer 15

enzymes are proteins that contain a highly specific active site that fits into a specific substrate

Question 16

why are enzymes necessary to biological systems

Answer 16

they speed up reactions so that less energy is required for the reaction to occur

Question 17

describe the enzyme action

Answer 17

a substrate that fits the specific active site of the enzyme binds to create an enzyme substrate complex, a reaction occurs and then the products are released

Question 18

what does the statement “enzymes are highly specific” mean

Answer 18

the active site of the enzyme must bind with the substrate that has a complementary shape so that specific actions can be catalysed

Question 19

state the four factors that affect the rate of an enzyme controlled reaction

Answer 19

temperature, pH level, substrate concentration, enzyme concentration

Question 20

describe the effect of temperature on the rate of an enzyme controlled reaction

Answer 20

as the temperature increases, the rate of the reaction increases. once the temperature exceeds the optimum temperature, the enzyme becomes denatured and the rate of the reaction decreases

Question 21

why does the rate of an enzyme controlled reaction increase when the temperature increases

Answer 21

as the temperature increases, the particles gain more kinetic energy. this increases the collisions between molecules and later leading to a reaction

Question 22

if the temperature increases above the optimum, how does this affect the enzyme function

Answer 22

the active site will be distorted as the enzyme denatures and so it will no longer fit the substrate

Question 23

describe the effect of the pH on the rate of an enzyme controlled reaction

Answer 23

the rate of an enzyme catalysed reaction is the fastest at the optimum pH. If the pH is too high or low, the enzyme will work less efficiently and the active site may be denatured at extremes of pH

Question 24

how does a pH that is different to the optimum affect the enzyme activity

Answer 24

the change in pH will distort the enzyme’s active site, denaturing it so that it can no longer fit the specific substrate