Enzymes pt. 3 (Quiz 1)

Question 1

1. In the Enzyme and substrate concentrations, the rate of reaction ________ as
   substrate concentration _________ (at constant enzyme concentration).

note: same answer

2. _______ activity occurs when the
   enzyme is saturated.

Answer 1

1. increases
2. Maximum

Question 2

The relationship between reaction rate and substrate concentration is _________, and ___________ (levels off) when the enzyme is saturated

Answer 2

exponential
asymptotes

Question 2

The Effect of [E] on velocity:

The _______of an enzyme-catalyzed reaction is always proportionate to the concentration of enzyme

This property of enzyme is made use in determining the ________ for the diagnosis of diseases.

Answer 2

initial rate
serum enzyme

Question 3

In the Enzyme Concentration and Reaction Rate:

1. The rate of reaction ______as enzyme concentration _______(at constant substrate concentration)
2. At ____________, more enzymes are available to catalyze the reaction (more reactions at once)
3. There is a _________ relationship between reaction rate and enzyme concentration (at constant substrate concentration)

Answer 3

1. increases
2. higher enzyme concentrations
3. linear

Question 3

The effect of temperature on velocity:

1. Enzymes are most active at an __________ (usually 37°C in humans)
2. Show little activity at _______ temperatures.
3. Lose activity at ________ temperatures as __________ occurs.

Answer 3

1. Optimum Temperature
2. low
3. high, denaturation

Question 3

Effects of Temperature:

__________ of reaction increases until an Optimum temperature is reached

Answer 3

Speed

Question 4

Effects of Temperature::

1. ____________ is the temperature at which the enzyme works best
2. After this point the rate of reaction decreases until there is _________
3. At this point enzyme is said to be _________ - active site destroyed

Answer 4

1. Optimum temperature
2. no reaction
3. DENATURED

Question 5

A reaction rate will generally increase with increasing Temperature due to ____________ in the system until a maximal velocity is reached.

Above this maximum, the kinetic energy of the system exceeds the energy barrier for breaking weak
H-bonds and hydrophobic interactions, thus leading to _____________ of the enzyme and a decrease in reaction rate.

Answer 5

increased kinetic energy
unfolding and denaturation

Question 6

Increasing the temperature denature (destroys) the shape of the __________.

Answer 6

protein

Question 7

Effect on rates of enzyme activity

o At __________ greatest number of collisions between enzyme & substrate

o ________________
❖ 35°-40°C (body temp = 37°C)

o Raise temperature (boiling)
❖ denature protein = ?______________

o Lower temperature T
❖ molecules move ________
❖ fewer _________ between enzyme & substrate

Answer 7

Optimum temperature
human enzymes
denature protein = unfold = lose shape
slower
collision

Question 8

In the effect of temperature: (See image from notes)

Q10 (the temperature coefficient) = the increase in reaction rate with a 10°C rise in temperature.

• For chemical reactions the Q10 = 2 to 3 (the rate of the reaction ________ with every 10°C rise in temperature
• ___________ reactions follow this rule as they are chemical reactions
• The optimum temperature for an enzyme controlled reaction will be a balance between the ___________.

Answer 8

• doubles or triples
• Enzyme-controlled
• Q10 and denaturation

Question 9

• For most enzymes (outside the human body) the optimum temperature is about _______ . Many are a lot lower, cold water fish will die at this temperature because their enzymes denature
• A few bacteria have enzymes that can withstand very high temperatures up to ________
• Most enzymes however are fully denatured at _____

Answer 9

• 30°C
• 100°C
• 70°C

Question 10

Effect of pH value on velocity:

• Each enzyme has an optimal pH or pH range (where the enzyme has __________ activity).
• Requirements for the catalytic groups in the active site in appropriate _______ is a common reason for this phenomenon.

Answer 10

• maximal
• ionization state

Question 11

The pH optimum for different enzymes. Most enzyme’s is in neutral pH ranging ________

Answer 11

6-8

Question 12

Variations in pH can affect a particular enzyme in many ways, especially if __________ side chains are involved in binding of the substrate and/or catalysis.

Answer 12

ionizable amino acid

Question 13

________ can also lead to denaturation of an enzyme if the ionization state of amino acid(s) critical to correct folding are altered.

Answer 13

Extremes of pH

Question 14

Extreme pH levels will produce ________

The structure of the enzyme is ______

The _______ is distorted and the substrate molecules will no longer fit in it

Answer 14

denaturation
changed
active site

Question 15

At pH values slightly different-from the enzyme’s optimum value, small changes in the charges of the enzyme and it’s ___________will occur

This change in ionization will affect the ________ of the substrate with the active site

Answer 15

substrate molecules
binding

Question 16

Effect on rates of enzyme activity

• changes in pH changes protein _______
• most human enzymes = ______(pH level)
  o depends on where in body
  o pepsin (________) = pH ___
  o trypsin (________) = pH ___

Answer 16

shape
pH 6-8
stomach, pH 3
small intestines, pH 8

Question 17

In pH and Enzyme Activity:

• Enzymes are most active at __________
• Amino acids with acidic or basic side-chains have the proper charges when the _______

Note: first two ques. have the same answer.

• Activity is lost at ______or______ as tertiary structure is disrupted

Answer 17

optimum pH
pH is optimum
low or high pH

Question 18

Most enzymes of the body have an optimum pH of about ____. However, in certain organs, enzymes operate at lower and higher optimum pH values

Answer 18

7.4

Question 19

___________ are molecules that bind to enzymes and increase their activity.

Answer 19

Enzyme activators

Question 20

Enzyme activators:

i. Inorganic ions
o __________, such as Na+, K+, Mg2+, Ca2+, Cu2+, Zn2+, Fe2+ et al
o ________: such as Cl-, Br-, I-, CN- et al

ii. Organic
o _______, such as Cys, GSH

iii. Proteins

Answer 20

Metal ions
Anions
Reducing agents

Question 21

Any molecule which acts directly on an enzyme to lower its catalytic rate (not denaturation)

Answer 21

Inhibitor

Question 22

Some _________ are normal body metabolites.

Other may be foreign substances, such as ________

Answer 22

enzyme inhibitors
drugs or toxins

Question 23

Other means to affect or Regulate ENZYME ACTIVITY (5)

Answer 23

1. Allosteric binding sites
2. By Covalent Modification
3. Induction and repression of enzyme synthesis
4. Zymogen Cleavage
5. Location within the cell

Question 24

_________ enzymes are regulated by molecules called _______ (modifiers) that binds nonconvalently at a site other than the active site.

Answer 24

Allosteric
effectors

Question 25

Many enzymes are regulated by ____________ , most frequently by the addition or removal of ‘phosphate’ group to serine, threonine or tyrosine residue of the enzyme by _______. (enzyme)

Answer 25

covalent modification
kinases (a.k.a phosphorylation)

Question 26

In_________ of enzyme synthesis, cells can also regulate the amount of enzymes present by altering the rate of enzyme synthesis

Answer 26

Induction and repression

Question 27

Some enzyme are synthesized as Inactive precursor, called __________, that are activated by proteolysis (e.g., digestive enzyme, pepsinogen is inactive and cleaved to pepsin which is active chymotrypsin)

Answer 27

zymogens

Question 28

Many enzymes are ________ in specific organelles within the cell. This, ________ helps in the regulation of the metabolic pathway.

Answer 28

localized
compartmentation