Environmental factors

Question 1

The pH at which an enzyme functions optimally is called the

Answer 1

pH optimum

Question 2

Making the solution more basic or more acidic sharply

Answer 2

decreases the rate of the reaction

Question 3

These pH changes alter the degree of ____ of amino acid R groups in the protein, as well as the extent to which they can ______

Answer 3

ionization

H bond

Question 4

This causes the enzyme to lose its biologically active configuration; it becomes ____. Less drastic changes in the R groups of an enzyme active site can also destroy the ability to form the ___________

Answer 4

denatured

enzyme-substrate complex.

Question 5

Some environments within the body must function at a pH far from

Answer 5

7

Question 6

For instance, the pH of the stomach is approximately

Answer 6

2

Question 7

why is the pH of the stomach 2

Answer 7

as a result of the secretion of hydrochloric acid by cells of the stomach lining.

Question 8

The proteolytic digestive enzyme ____ must effectively degrade proteins at this extreme pH

Answer 8

pepsin

Question 9

In the case of pepsin, the enzyme has evolved an amino acid sequence that can maintain a ___ tertiary structure at pH ___ and is most active in the hydrolysis of peptides that have been denatured by very low pH. Thus, pepsin has a pH optimum of __.

Answer 9

stable
2
2

Question 10

functions under the conditions of higher pH found in the intestine

Answer 10

trypsin

Question 11

Both pepsin and trypsin cleave peptide bonds by virtually identical mechanisms, yet their amino acid sequences have evolved so that they are stable and active in______ environments.

Answer 11

very different

Question 12

The body has used the adaptation of enzymes to different environments to protect itself against one of its

Answer 12

own destructive defense mechanisms

Question 13

Within the cytoplasm of a cell are organelles called ____. “suicide bags” because they are membrane-bound vesicles containing about fifty different kinds of ____ that degrade large biological molecules into small molecules.

Answer 13

lysosomes

hydrolases

Question 14

If the hydrolytic enzymes of the lysosome were accidentally released into the cytoplasm of the cell, the result would be the

Answer 14

destruction of cellular macromolecules and death of the cell

Question 15

Because of this danger, the cell invests a great deal of energy in maintaining the integrity of the

Answer 15

lysosomal membrane

Question 16

An additional protective mechanism relies on the fact that lysosomal enzymes function optimally at an acid pH

Answer 16

4.8

Question 17

Should some of these enzymes leak out of the lysosome or should a lysosome accidentally rupture, the cytoplasmic pH of ________

Answer 17

7-7.3

renders then inactive

Question 18

The enzymes in our cells are rapidly destroyed if the temperature of their environment rises much above ___ but they remain stable at much ____ temperatures

Answer 18

37 C

lower

Question 19

This is why enzymes used for clinical assays are stored in

Answer 19

refrigerators or freezers before use

Question 20

The rate of the uncatalyzed reaction steadily increases with _____ temperature because ____collisions occur with sufficient ____ to overcome the energy barrier for the reaction.

Answer 20

increasing
more
energy

Question 21

The rate of an enzyme-catalyzed reaction also increases with modest increases in temperature because there are increasing numbers of collisions between the ____ and the ____.

Answer 21

enzyme

substrate

Question 22

the enzyme is functioning optimally and the rate of the reaction is maximal.

Answer 22

temperature optimum

Question 23

above the temperature optimum, increasing temperature begins to increase the _____ energy of the bonds within the enzyme. Eventually, so many bonds and weak interactions are _____that the enzyme becomes _____, and the reaction _____

Answer 23

vibrational
disrupted
denatured
stops

Question 24

because heating enzymes and other proteins destroys their three-dimensional structure, and hence their activity, a cell cannot survive

Answer 24

very high temperatures

Question 25

Thus, heat is an effective means of sterilizing medical instruments and solutions for

Answer 25

transfusions or clinical test