3.3 Environmental Impacts on Enzyme Function

Question 1

Denaturation

Answer 1

proteins become denatured because the Quaternary structure of the protein unfolds to the breaking of R-group bonds

Question 2

4 R-group bonds

Answer 2

Hydrogen bond polar
Disulfide bonds
ionic bonds
hydrophobic bonds

Question 3

Define optimum temperature range

Answer 3

range in which reactions occur the fastest- 37* C (98.6 * F)

Question 4

What happens to the enzyme if the environmental temperature increases?

Answer 4

Initially increases reaction rate;
increased speed of molecular movement & frequency of collisions however if it increases outside of range then it will denature by 50*

Question 5

What happens if enzyme temperature decreases?

Answer 5

Slows down reaction rate ; no denature
decreased frequency of collision

Question 6

What is the optimum pH for most enzymes?

Answer 6

7

Question 7

What is the optimum pH for pepsin?

Answer 7

2; found in the stomach

Question 8

What is the optimum pH for trypsin?

Answer 8

9; found in the small intestine

Question 9

Why would the enzyme be denatured by a change in a single pH value?

Answer 9

measure the concentration of H+ ions in solution on a logarithmic scale
-pH 6 has 10x more H+ than pH7

Question 10

How can change in H+ concentrations cause enzyme denaturation?

Answer 10

Can disrupt H+ bonds that help maintain enzyme structure (quaternary level)

Question 11

Relationship between substrate concentration and reaction rate?

Answer 11

Increased susbtrate conc.=increased reaction rate

Question 12

Relationship between concentration of products and substrates

Answer 12

Increased concentration fo products- decreased opportunity for addition of substrates
matter takes up space- more product=less collisions - slow reaction rate

Question 13

Define substrate saturation

Answer 13

when there are more enzymes than substrates- substrates are saturated- limit on reaction rate

Question 14

define enzyme saturation

Answer 14

when there are more substrates than enzymes- enzymes are saturated- had a limit on reaction rate

Question 15

define competitive inhibitors

Answer 15

molecules can bind reversibly or irreversibly to the activation site of the enzyme; competes for the enzyme’s activation site
-reversible: enzyme regain function once it detaches
-irreversible- enzyme function will be prevented- covalent bonds

Question 16

Effects of competitive inhibitors on rate of reaction

Answer 16

concentration> substrate- reactions are slowed
inhibitor< substrate- reactions proceed normally

Question 17

selective inhibition

Answer 17

regulate enzyme by acting as inhibitors; essential for cellular metabolism

Question 18

Allosteric site

Answer 18

another place where enzymes can bind to other than the active site; remote to the active site

Question 19

Define Noncompetitive inhibitors

Answer 19

Inhibitors that bind to the allosteric site, not the active site= causes conformational shape changes & prevents enzyme function- active site not available

Question 20

Noncompetitive inhibitors effect on reaction rate

Answer 20

decreases
(increasing substrate does not prevent effects of binding)

Question 21

What are the 4 ways that enzyme lowers the activation energy & is a catalyst?

Answer 21

1.active orients reactants in a way that a reaction would occur
2.enzyme stretches the substrates so the bonds that need to be broken for the reaction is stressed
3. active site acts as an micro environment that the reaction would normally take place
4. Direct participation of the active site in the reaction

Question 22

Define cofactors

Answer 22

nonprotein helpers for enzymes during catalytic activity- usually metal such as magnesium or zinc
-bind loosely or tightly to the enzyme (reversible or irreversible)

Question 23

Define coenzymes

Answer 23

organic(carbon) cofactors; vitamins can be coenzymes or they can be raw enzymes for coenzymes
-performs crucial chemical function

Question 24

Define Allosteric Regulation

Answer 24

ny form of regulation where the regulatory molecule (an activator or inhibitor) binds to an enzyme someplace other than the active site

Question 25

Define Allosteric activator

Answer 25

stabilizes the shape

Question 26

define Allosteric inhibitor

Answer 26

stabilizes the inactive form of the enzyme

Question 27

Define cooperativity

Answer 27

allosteric activation in which a substrate attaches to one of the sub units active site triggering a conformational change- the active state- due to the change it is likely for the enzyme to stay in its active state

Question 28

Explain cooperativity in hemoglobin

Answer 28

binding oxygen to one site- higher affinity to bind in other sites

Question 29

Define feedback inhibition

Answer 29

when ATP allosterically inhibits enzyme in ATP generating pathway- common mode of metabolic control
- prevents cell from wasting chemical reactionnss

Question 30

What activates feedback activation?

Answer 30

ADP

Question 31

Define Km

Answer 31

the substrate concentration at 1/2 max
Km=[substrate] at 1/2vmax

Question 32

Define enzyme substrate-affinity

Answer 32

how quickly the substrate gets to its active site & enzyme makes the product

Question 33

low km

Answer 33

means high enzyme substrate affinity; only needs a small amount of substrate to reach vmax

Question 34

High Km

Answer 34

lower E-S affinity; takes longer for the reaction to take place

Question 35

Define Vmax

Answer 35

maximum rate the enzyme can sue the substrate and make it into a product

Question 36

How do you find Km on a graph?

Answer 36

first find Vmax. Go to the ½ Vmax point and horizontally follow that point until it reaches the reaction rate (blue) line.