Lecture 14

Question 1

Metabolic enzymes are regulated by what 4 factors?

Answer 1

1. Compartmentalization: different locations
2. Enzyme Concentration: on/off switch
3. Enzyme Activity: Volume control
4. Hormone signals and second messengers: master regulators

Question 2

Compare substrate level control with feedback control

Answer 2

Substrate level control: when the amount of product acts on a single reaction

Feedback control: when the amount of a produce targets a different step in a reaction pathway

Question 3

Compare what activators and inhibitors promote

Answer 3

activators promote more products

inhibitors promote less products

Question 4

Define Isozymes

Answer 4

Isozyme: a “mix and match” subunit that catalyzes the same reaction but with different efficiencies

Question 5

Explain how tissue specificity is determined and how development is carried out

Answer 5

Tissue specificity is determined via compartmentalized isozymes

Development is carried out via temporal expression of isozymes

Question 6

What can you test in a pt’s blood in order to try to determine if they have or have not had a heart attack?

Answer 6

you can test for the H4 isozyme of LDH

Question 7

_____-_____ modifications create non proteinogenic AA’s

Answer 7

post-translational

Question 8

State the function of reversible covalent modifications when they are affecting enzyme activity

Answer 8

they add 1 “functional group” to activate/inactivate an enzyme

Question 9

what molecular group is the greatest source of diversity to the proteome?

Answer 9

carbohydrates

Question 10

Myristic acid and farnesyl formation is an example of what kind of reversible covalent modification?

Answer 10

myristic acid and farnesyl are formed by performing reversible covalent modifications on lipids

Question 11

ADP-ribose is an example of what kind of reversible covalent modification?

Answer 11

ADP-ribose is formed by performing reversible covalent modifications on nucleic acids

Question 12

Ubiquitin is an example of what kind of reversible covalent modification?

Answer 12

ubiquitin is formed by performing reversible covalent modifications on proteins

Question 13

State the 4 categories of reversible covalent modifications that can occur to carbohydrates

Answer 13

1. O- vs N-linkages
2. Composition of Sugars
3. Branched vs Unbranched
4. Length of an oligosaccharide

Question 14

State and describe the 4 mechanisms that occur and describe why phosphorylation via kinases is activating

Answer 14

1. Thermodynamics: ATP hydrolysis can drive unfavorable reactions
2. Kinetics: physiologic processes dictate reaction rate
3. Cell processes: ATP amounts dictated by metabolism (energy charge) signal transduction amplification (catalytic turnover)
4. Shape and charge complementary: each phosphate adds (2-) charge and (3+) H-bonds

Question 15

what is the significance of the name of a kinase?

Answer 15

the name of a kinase indicates on which AA the phosphate will be added

Question 16

True or False:

Allosteric binding occurs in the active site of an enzyme. explain.

Answer 16

False

Allosteric binding DOES NOT occur at the active site

Question 17

Compare Heteroallostery and Homoallostery

Answer 17

Heteroallostery: The effector binds at the allosteric site

Homoallostery: cooperativity

Question 18

Describe the mechanism by which the generic regulation of ACTase is conducted

Answer 18

ACTase when CTP is present prefers the T (inactive state)

ACTase when ATP is present prefers the R (active state)

Question 19

Describe what it means when one says “enzyme amount is the ON/OFF switch”.

Answer 19

since enzyme levels control the rate of protein synthesis, their level directly controls whether that protein is considered to be be “ON/OFF”

Question 20

State the 2 levels of control that are possible via enzyme

Answer 20

Transcription regulation @ promoters

Translation regulation @ UTRs

Question 21

Compare what histone acetylation promotes, what histone phosphorylation promotes, and what histone methylation promotes.

Answer 21

Histone acetylation promotes transcription

Histone phosphorylation prevents transcription

Histone methylation either promotes OR prevents Transcription

Question 22

True or false:

mRNA levels do not correlate to protein levels. explain

Answer 22

true

miRNA’s and UTRs are what control translation. not mRNA levels.

Question 23

What type of chromatin promotes transcription and what type discourages transcription?

Answer 23

euchromatin turns transcription on

heterochromatin turns transcription off

Question 24

Name the 4 types of important enzymes that begin as zymogens

Answer 24

1. proteases (digestive enzymes, Collagenase (development), and Caspases (apoptosis))
2. Collagen
3. Blood clotting factors
4. Insulin/Hormones

Question 25

Explain the activation of chymotrypsin from it’s inactive form

Answer 25

The inactive form of chymotrypsin is chymotrypsinogen which has it’s A, B, and C chains still linked

The active form is an A, B, and C chain of chymotrypsin that forms the (active) alpha-chymotrypsin

Trypsin conducts the first cleavage, between the A and B chains, to form Pie-chymotrypsin

Pie-Chymotrypsin conducts the second cleavage, between the B and C chains, to form Alpha-chymotrypsin

Question 26

Define Zymogen

Answer 26

Zymogen: an inactive substance which is converted into an enzyme when activated by another enzyme.