Enzyme Regulation (Quiz 2)

Question 1

What are enzymes?

Answer 1

-proteins
-biological catalysts
-they accelerate specific chemical reactions
-some enzymes require molecules other than proteins for the enzymatic activity

Question 2

What is a holoenzyme/haloenzyme?

Answer 2

-the active enzyme
-enzyme with nonprotein
-usually vitamins or minerals
-they’re essential for enzymatic activity
-ex: dehydrogenase with NAD

Question 3

What is an apoenzyme?

Answer 3

-inactive enzyme
-its inactive bc it doesn’t have its nonprotein component, so if it gets its nonprotein component then it becomes activated and is now called a holoenzyme
-ex: dehydrogenase

Question 4

What are cofactors?

Answer 4

-component of holoenzyme
-non-protein metal ion such as Cu, Mg, Zn

Question 5

What are coenzymes?

Answer 5

-holoenzyme
-non-protein component is a vitamin (organic molecules)
-active form of vitamin

Question 6

What are cosubstrates?

Answer 6

coenzymes that only transiently associate with the enzyme

Question 7

What are prosthetic groups?

Answer 7

coenzyme (made of vitamin + protein) that is permanently associated with the enzyme

Question 8

An active compound formed by a carboxylase + biocytin =

Answer 8

a holoenzyme

Question 9

Which vitamin is associated with the coenzyme flavin adenine dinucleotide (FAD)?

Answer 9

riboflavin (vitamin B2)

Question 10

Which vitamin is associated with the coenzyme nicotinamide adenine dinucleotide (NAD)?

Answer 10

nicotinic acid (also known as niacin or vitamin B3)

Question 11

Which vitamin is associated with the coenzyme, Coenzyme A?

Answer 11

pantothenic acid, also known as pantothenate or vitamin B5

Question 12

Which vitamin is associated with the coenzyme pyridoxal phosphate (PLP)?

Answer 12

pyridoxine (vitamin B6)

Question 13

Which vitamin is associated with the coenzyme thiamine pyrophosphate (TPP)?

Answer 13

thiamin (vitamin B1)

Question 14

Which vitamin is associated with the coenzyme biocytin?

Answer 14

biotin (vitamin B7)

Question 15

Which vitamin is associated with the coenzyme tetrahydrofolate?

Answer 15

folic acid (vitamin B9)

Question 16

Which enzymes are regulated?

Answer 16

only rate limiting enzymes

Question 17

What are the 4 types of enzyme regulation mechanisms (cells don’t want to waste time and energy, so the enzyme needs to be regulated)?

Answer 17

1) allosteric regulation
2) covalent modification
3) activation by proteolytic cleavage
4) isozymes

Question 18

In many pathways, the end product is an allosteric inhibitor of the first enzyme. This is called _________________ regulation

Answer 18

negative feedback

Question 19

What is allosteric regulation?

Answer 19

-allosteric regulation binds to a site other than the active site and changes enzyme confirmation, which results in an apparent change in binding affinity
-the allosteric site that bonded will cause change in the active site so that the substrate cant bind to the active site
-its reversible binding of modulators to sites other than the active site

Question 20

______ shape curve indicates a regulated enzyme

Answer 20

S

Question 21

Does allosteric regulation have Km and Vmax?

Answer 21

no

Question 22

Increased 2,3 BPG is an example of an allosteric __________

Answer 22

inhibitor

Question 23

Presence of CO is an example of an allosteric _____________

Answer 23

activator

Question 24

What is covalent modification?

Answer 24

-most common form of covalent modification is phosphorylation
-ser, thr, and tyr all have OH in their R group, so they can be phosphorylated (OH is replaced with phosphate)
-this is reversible and phosphate can go back to OH when needed
-hormones frequently do this, like insulin and glucagon to turn on and off enzymes

Question 25

What is activation by proteolytic cleavage?

Answer 25

Question 26

What are some examples of zymogens (type of inactive form of enzyme)?

Answer 26

Question 27

What are isozymes?

Answer 27

-used for enzyme regulation -groups of enzymes catalyze the same reaction but differ in AA sequence and enzyme properties -example: Glut 1 and 2 are isozymes

Question 28

What are the 6 classes of enzymes?

Answer 28

1) oxidoreductase 2) transferase 3) hydrolase 4) lyase 5) isomerase 6) ligase

Question 29

Which enzymes are a part of the oxidoreductase enzyme class?

Answer 29

-oxidase (removes H/electrons) -reductase (adds H/electrons) -dehydrogenase (removes or adds H)

Question 30

What type of reaction is catalyzed with oxidoreductase?

Answer 30

transfer of electrons or H atoms

Question 31

Which enzymes are a part of the transferases enzyme class?

Answer 31

-kinase (adds phosphate) -phosphorylase (breaks polymer and adds phosphate to one of the monomers) -transferase

Question 32

What type of reaction is catalyzed with transferases?

Answer 32

group transfer reactions

Question 33

What 2 groups of enzymes are a part of the hydrolase enzyme class?

Answer 33

1) digestive enzymes 2) phosphatase (removes phosphate) note: both use water in hydrolysis reaction to break bond

Question 34

What type of reaction is catalyzed with hydrolases?

Answer 34

hydrolysis reactions (use water to break polymer into monomers)

Question 35

Which enzymes are a part of the lyases enzyme class?

Answer 35

-decarboxylase (removes carbon) -lyases

Question 36

What type of reaction is catalyzed with lyases?

Answer 36

breaking of various chemical bonds by means other than hydrolysis and oxidation

Question 37

Which enzymes are a part of the isomerases enzyme class?

Answer 37

-mutase (name is same) -isomerase (isomers are molecules with the same formula but different structure)

Question 38

What type of reaction is catalyzed by isomerases?

Answer 38

isomerization

Question 39

Which enzymes are a part of the ligase enzyme class?

Answer 39

-synthase (ATP not seen directly in rxn) -synthetase (ATP seen directly) -carboxylase (adds carbon)

Question 40

What do ligases do?

Answer 40

join 2 molecules with covalent bonds usually coupled with ATP hydrolysis

Question 41

What does oxidase do?

Answer 41

removes H or electrons

Question 42

What does reductase do?

Answer 42

adds H or electrons

Question 43

What does dehydrogenase do?

Answer 43

removes or adds hydrogen

Question 44

What do kinases do?

Answer 44

add phosphate

Question 45

What does phosphorylase do?

Answer 45

breaks polymer and adds phosphate to one of the monomers

Question 46

What does phosphatase do?

Answer 46

removes phosphate and uses water for hydrolysis reaction

Question 47

What does decarboxylase do?

Answer 47

remove carbon

Question 48

What do synthases do?

Answer 48

used in reactions without ATP directly present to glue molecules together

Question 49

What do synthetases do?

Answer 49

used in reactions with ATP directly present to glue molecules together

Question 50

The enzyme trypsin is classified as which of the following? A) oxidoreductase B) lyase C) hydrolase D) ligase

Answer 50

C) hydrolase

Question 51

What does the inhibitor bind to during feedback inhibition?

Answer 51

allosteric site of the enzyme being inhibited