Models of Enzyme Action ㅡ Extremozymes

Question 1

The __________ is the relatively small part of an enzyme’s structure that is actually involved in catalysis.

Answer 1

active site

Question 2

A commonly observed enzyme-influenced phenomenon that occurs outside the human body is the discoloration (browning) that occurs when freshly cut fruit (apples, pears, etc.) and vegetables (potatoes) are exposed to air for a short period of time. The enzyme involved, which is present in the food, is an oxidoreductase enzyme called _________.

Answer 2

phenolase

Question 3

An ________________ is the intermediate reaction species that is formed when a substrate binds to the active site of an enzyme.

Answer 3

enzyme–substrate complex

Question 4

In the _____________, the active site in the enzyme has a fixed, rigid geometrical conformation. Only substrates with a complementary geometry can be accommodated at such a site, much as a lock accepts only certain keys.

Answer 4

lock-and-key model

Question 5

The _____________ allows for small changes in the shape or geometry of the active site of an enzyme to accommodate a substrate.

Answer 5

induced-fit model

Question 6

_______________ is the extent to which an enzyme’s activity is restricted to a specific substrate, a specific group of substrates, a specific type of chemical bond, or a specific type of chemical reaction.

Answer 6

Enzyme specificity

Question 7

_______________: the enzyme will catalyze only one reaction.

Answer 7

Absolute specificity

Question 8

____________ is an enzyme with absolute specificity. It catalyzes the conversion of hydrogen peroxide
(H2O2) to O2 and H2O. Hydrogen peroxide is the only substrate it will accept.

Answer 8

Catalase

Question 9

___________: the enzyme will act only on molecules that have a specific functional group, such as hydroxyl, amino, or phosphate groups.

Answer 9

Group specificity

Question 10

____________ is group-specific; it cleaves amino acids, one at a time, from the carboxyl end of a peptide chain.

Answer 10

Carboxypeptidase

Question 11

____________: the enzyme will act on a particular type of chemical bond, irrespective of the rest of the molecular structure.

Answer 11

Linkage specificity

Question 12

___________ hydrolyze phosphate-ester bonds in all types of phosphate esters. Linkage specificity is the most general of the common specificities.

Answer 12

Phosphatases

Question 13

_______________: the enzyme will act on a particular stereoisomer. Chirality is inherent in an enzyme active site because amino acids are chiral compounds.

Answer 13

Stereochemical specificity

Question 14

____________ is a measure of the rate at which an enzyme converts substrate to products in a biochemical reaction.

Answer 14

Enzyme activity

Question 17

Four factors affect enzyme activity:

Answer 17

temperature
pH
substrate concentration
enzyme concentration

Question 18

___________ is a measure of the kinetic energy (energy of motion) of molecules.

Answer 18

Temperature

Question 19

___________ _________ is the temperature at which an enzyme exhibits maximum activity.

Answer 19

Optimum temperature

Question 20

______________ is the pH at which an enzyme exhibits maximum activity.

Answer 20

Optimum pH

Question 21

Each enzyme has a characteristic optimum pH, which usually falls within the physiological pH range of 7.0–7.5. Notable exceptions to this generalization are
the digestive enzymes ________ and _______. _______, which is active in the stomach, functions best at a pH of 2.0. On the other hand, ________, which operates in the small intestine, functions best at a pH of 8.0.

Answer 21

pepsin
trypsin

Question 22

An enzyme’s ________________ is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of temperature, pH, and saturation.

Answer 22

turnover number

Question 23

An ______________ is a microorganism that thrives in extreme environments, environments in which humans and most other forms of life could not survive.

Answer 23

extremophile

Question 24

optimal growth at pH levels of 3.0 or below

Answer 24

acidophiles

Question 25

optimal growth at pH levels of 9.0 or above

Answer 25

alkaliphiles

Question 26

a salinity that exceeds 0.2 M NaCl needed for growth

Answer 26

halophiles

Question 27

a temperature between 80°C and 122°C needed to thrive

Answer 27

hypothermophiles

Question 28

a high hydrostatic
pressure needed for growth

Answer 28

piezophiles

Question 29

a temperature of 15°C or lower needed for growth

Answer 29

cryophiles

Question 30

An _______________ is a microbial enzyme active at conditions that would inactivate human enzymes as well as enzymes present in other types of higher organisms.

Answer 30

extremozyme