Lecture 21

Question 1

What does Oligomeric mean?

Answer 1

Multi subunit

Question 2

Can enzyme activity be cooperative?

Answer 2

Enzyme activity may be cooperative

Question 3

What does the graph of a relationship between a substrate and reaction velocity look like if the enzyme activity is cooperative?

Answer 3

There is a sigmoidal relationship between substrate and reaction velocity

Question 4

What is the activity like with allosteric enzymes?

Answer 4

The activity is cooperative

Question 5

What is the sigmoidal relationship in allosteric enzymes a consequence of?

Answer 5

The equilibrium that exists between the low activity and high activity state of the enzyme

Question 6

What compounds may affect the equilibrium between the T and R states with enzymes?

Answer 6

Compounds besides the substrate can affect equilibrium between the T and R states

Question 7

What is an activator of an enzyme?

Answer 7

Something that binds to and stabilizes the R state/high activity state

Question 8

What does something that stabilizes the R state do?

Answer 8

It makes the enzyme better at taking the substrate and turning it into product

Question 9

What does something that stabilizes the T state do?

Answer 9

It makes the enzyme less able to convert the substrate into product

Question 10

What does an inhibitor do?

Answer 10

It binds to an enzyme and stabilizes the T state making it less able to convert the substrate into product

Question 11

What do the graphs of allosteric enzymes look like on reaction velocity substrate concentration curve?

Answer 11

The show a sigmoidal relationship

Question 12

What does the binding curve of a non-allosteric enzyme look like?

Answer 12

It will have a hyperbolic binding curve

Question 13

What does the sigmoidal curve of allosteric enzyme reflect?

Answer 13

• Increasing substrate results in increasing production of product
• substrate is a homoallosteric activator

Question 14

What is an allosteric enzyme’s catalytic activity is modulated by?

Answer 14

The noncovalent binding of specific molecules at a site other than the active site

Question 15

What does a negative heteroallosteric inhibitor do?

Answer 15

Binds to a regulatory site and changes the shape at the 4º and 3º level

Question 16

What levels of structure do both homoallostery and heteroallostery change proteins?

Answer 16

3º and 4º structure

Question 17

How does binding of an inhibitor affect an enzyme?

Answer 17

It changes the binding site of the enzyme making it unable to effectively bind the substrate

Question 18

What are the two states of allosteric enzymes?

Answer 18

T (tense, low activity)

R (relaxed, high activity)

Question 19

What state do allosteric activators favor?

Answer 19

They favor the R state

Question 20

What state do allosteric inhibitors favor?

Answer 20

They favor the T state

Question 21

What determines how much of the protein is in the T state and how much of the protein is in the R state at any given moment?

Answer 21

The balance of the substrate, any activators, any inhibitors and the protein

Question 22

What does a sigmoidal relationship on a reaction velocity vs substrate concentration graph indicate?

Answer 22

That a substrate is a positive homoallosteric activator

Question 23

What direction will a substance that decreases binding affinity shift the curve?

Answer 23

To the right

Question 24

What will shift a reaction velocity vs substrate concentration curve to the left?

Answer 24

A positive heteroallosteric activator

Question 25

How many curves required to determine if a substrate is a positive homoallosteric effector?

Answer 25

Only one curve, because we just need to see if its sigmoidal

Question 26

How many curves are required to see if something is a hetero allosteric effector?

Answer 26

Two curves to see if it shifts left or right

Question 27

What level of structure does covalent modification of an amino acid change?

Answer 27

3º structure

Question 28

What is the most common type of reversible covalent modification?

Answer 28

Phosphorylation

Question 29

Which amino acids can be phosphorylates?

Answer 29

• Serine
• Threonine
• Tyrosine

Question 30

How does phosphorylation affect amino acids?

Answer 30

It increases size, polarity and makes it negatively charged

Question 31

How may phosphorylation affect the activity of a target enzyme?

Answer 31

They may increase or decrease activity of the target enzyme by changing the active site

Question 32

What do protein kinases do?

Answer 32

Catalyze the phosphorylation of proteins by taking a phosphate from ATP

Question 33

What do Protein phosphatases do?

Answer 33

Catalyze the dephosphorylation of proteins by hydrolyzing the phosphoester bond

Question 34

What are the characteristics of lipids?

Answer 34

Compounds that are primarily insoluble in water, hydrophobic, and non-polar

Question 35

What are some types of fatty acids?

Answer 35

• Fatty acids
• Triacylglycerol
• Membrane lipids
• Cholesterol

Question 36

What is triacylglycerol?

Answer 36

Three acid group attached to a glycerol molecule

Question 37

What are fatty acids?

Answer 37

Long chain hydrocarbon structures containing carboxylic acids or carboxylates

Question 38

Up to how many carbons long can Fatty Acids be?

Answer 38

Up to 24 but 16 and 18 are the most common

Question 39

Why do fatty acids tend to have an even number of carbons?

Answer 39

Because they are assembled from two carbon units

Question 40

What is the general formula for Fatty Acids?

Answer 40

CH3(CH2)NCOO-

Question 41

What is the polarity of fatty acids?

Answer 41

They are Amphipathic

Question 42

What does a saturated fatty acid lack?

Answer 42

Double bonds

Question 43

What does an unsaturated fatty acid have?

Answer 43

Double bonds