Proteins and Enzymes

Question 1

bond that occurs between two oppositely charged amino acids

Answer 1

salt bridge

Question 2

which bond helps protect a protein from denaturation during changes in blood pH or salt concentrations?

Answer 2

disulfide bonds - strong bonds

Question 3

what is an example of an extracellular protein that is held together by disulphide bonds?

Answer 3

insulin

Question 4

a protein composed of two subunits

Answer 4

dimer

Question 5

a protein composed of several subunits

Answer 5

oligomer

Question 6

a protein composed of many subunits is called a

Answer 6

multimer

Question 7

what are proteins that help other proteins get into their correct shape and correct cellular locations?

Answer 7

chaperones

Question 8

how are chaperone proteins released?

Answer 8

ATP hydrolysis

Question 9

___ are common chaperone proteins that bind and stabilize portions of proteins not yet folded

Answer 9

heat shock proteins

• get induced in cells during various stress conditions produced by cellular insult, environmental changes, temperature, infections, tumors etc

Question 10

a ___ is any repeating structural unit within a multimeric protein

Answer 10

protomer

Question 11

enzymes are an example of a type of ____ protein

Answer 11

globular

Question 12

enzymes are protein ____ that speed up specific reactions and remain ______ by the reaction

Answer 12

protein catalysts that speed up specific reactions and remain unchanged by the reaction

Question 13

the minimal amount of energy needed to make/break the bonds necessary for a reaction to occur

Answer 13

activation energy

Question 14

Enzyme molecules contain a special cleft called the

Answer 14

active site

Question 15

The active site forms by precise _____ structure of the protein

Answer 15

quaternary

Question 16

Amino acids in the active site participate in substrate binding and catalysis

Question 17

Binding of substrate is thought to induce a conformational change in shape of the enzyme is called

Answer 17

the Induced fit model

Question 18

the addition or removal of a proton can make a substrate more reactive

Answer 18

acid-base effect

Question 19

Which amino acid side chain do you think can function easily as an acid or a base?

Answer 19

positively or negatively charged amino acids

Question 20

A nucleophilic side group in the enzyme active site forms a temporary covalent bond with the substrate

Answer 20

Covalent catalysis

Question 21

Common nucleophilic side groups include:

Answer 21

• Asp and Glu (R-COO-)
• Ser (R-OH) and Cys (R-SH)

Serine and Cystein are only weakly nucleophilic, but their nucleophilicity is enhanced by the presence of other amino acids that can remove the H

Question 22

molecules that aid in substrate recruitment

Answer 22

cofactors and coenzymes

Question 23

Cofactors are typically metal cations

Answer 23

Mg and Zn

Question 24

We have already discussed the role of Mg2+ in several glycolytic enzymes involving ATP. What was the role of magnesium?

Answer 24

• Magnesium helped to position the ATP in the enzyme active site
• Helped to stabilize the negative changes on the ATP

Question 25

examples of coenzymes?

Answer 25

Typically derived from vitamins B3: NAD+ <>NADH + H+ Can accept or donate elections in redox reactions

Question 26

3 ways coenzymes and cofactors can help enzymes speed up reactions

Answer 26

1. help position the substrate in the active site 2. stabilize negative charges on the substrate or the TS to make it easier for a nucleophilic attack to occur 3. can accept/donate electrons in redox reactions

Question 27

what is the optimal temperature for enzymes

Answer 27

the temperature of the organism

Question 28

Do you think a fevers are good or bad?

Answer 28

There are benefits to a certain point - Enzyme activity can be increased, metabolism can be increased (to fight infection) and bacteria can no longer function BUT temps that are too high can cause enzymes to not function = fatality

Question 29

Changing the pH can change the ______ state of the enzyme and/or the substrate

Answer 29

protonation

Question 30

What types of bonds between Enzyme and Substrate would potentially be disrupted by a change in pH?

Answer 30

H-bonds – for example: - If an H is removed, no H-bond can be formed - If an H is added, an H-bond might form that is not usually formed. Electrostatic interactions - for example: - Adding an H can turn COO- into COOH - Removing an H can turn NH3+ into NH2

Question 31

Main site of intracellular enzymatic degradation for a wide range of molecules. They have proteolytic enzymes that break unwanted material in the cell.

Answer 31

function of lysosome

Question 32

enzymes can be controlled in four main ways

Answer 32

1. genetic 2. covalent modification 3. allosteric regulation 4. compartmentalization

Question 33

Enzymes transcription can be induced or repressed based on the needs of the cell

Answer 33

genetic modification

Question 34

Involves altering the structure of an enzyme (or “proenzyme”) by making or breaking covalent bonds

Answer 34

covalent modification

Question 35

Involves the addition or removal of a group to the enzyme that causes it to convert to its active or inactive form

Answer 35

reversible covalent modifcation

Question 36

* Other common groups that can be added to or removed enzymes include ____ and ______ groups

Answer 36

methyl and acetyl

Question 37

The main regulated enzyme in glycogenesis is ________ by phosphorylation

Answer 37

deactivated

Question 38

while the main enzyme in glycogenolysis is _______ by phosphorylation.

Answer 38

activated

Question 39

what enzyme in glycogenolysis is activated by phosphorylation

Answer 39

Glycogen phosphorylase kinase and Glycogen phosphorylase

Question 40

what enzyme in glycogenesis is deactivated by phosphorylation

Answer 40

glycogen synthase

Question 41

Involves cleavage of peptide bonds in proenzymes or zymogens. Make sure the enzyme is not used until it is in the correct location and until it is needed.

Answer 41

Irreversible covalent modification

Question 42

Binding to enzyme’s allosteric site changes the conformation and activity of the enzyme. Changes the binding affinity of the substrate at the active site

Answer 42

Allosteric modification

Question 43

Increase binding of the substrate to the enzyme

Answer 43

Effector = activator

Question 44

Decrease binding of the substrate to the enzyme

Answer 44

Effector = inhibitor

Question 45

Separation of enzymes from opposing pathways into different cellular compartments, and selective transportation of substrates

Answer 45

1. Compartmentalization

Question 46

Creation of unique microenvironments

Answer 46

2.Compartmentalization