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BIO 241 [Exam #1] > Chapter 4 - Enzymes and Energy > Flashcards

Chapter 4 - Enzymes and Energy Flashcards

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1
Q

Enzymes are considered what type of organic molecule? Be specific

A

protein; quaternary structure of protein

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2
Q

Label this reaction (substrate and products)
What does the enzyme react with?

C <- A + B

A

A + B: substrate
C: product

Enzyme reacts with the substrate

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3
Q

A chemical reaction can still occur without an enzyme present. How would this reacion be different in comparison to a chemical reaction with an enzyme present?

A

with enzyme: rate of rxn would proceed faster
without enzyme: rate of rxn would still proceed, but much slower

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4
Q

What are the building blocks of enzymes?

A

amino acids

enzymes are considered a protein; therefore, they must be composed of amino acids

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5
Q

What do enzymes do?

A
  • enzymes catalyze (speed up) chemical reactions by increasing the reaction rate throusands of times faster
  • enzymes are NOT changed or used up by the reaction (so can be used again)
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6
Q

How do enzymes speed up/catalyze chemical reactions?

A

enzymes lower the activation energy (Ea) of the rxn

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7
Q

Define activation energy (Ea)

A

the “initial energy” that a chemical reaction has to overcome for reaction to occur

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8
Q

The lower the Ea, the ____ it is to overcome it -> chemical reaction will occur ____

A

easier
faster

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9
Q

Define an active site

A

a region of an enzyme that binds to a substrate during a reaction

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10
Q

The function of an enzyme is dictated by its ______

A

structure

protein structure -> protein function

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11
Q

Describe the appearance of an enzyme

A
  • 3-D shape
  • pockets that serve as active sites (substrates bind to active site)
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12
Q

What happens when a substrate binds to the active site of an enzyme?

A

the original bonds of the substrate become weak and allows them to break easily

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13
Q

Compare the shape/structure of an enzyme before and after the chemical reaction

A

the shape/structure of the enzyme remains the same before and after the chemical reaction

only the substrates change shape

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14
Q

How would you identify an enzyme?
Give examples of some enzymes

A

usually ends in suffix “-ase”

the first part of the name applies to function of enzyme

ex: catalase, amalase, carbonic anhydrase

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15
Q

What are the functions of the different types of enzymes?

A

DIKP

  • dehydrogenases: remove hydrogen atoms
  • isomerases: rearrange the atoms
  • kinases: add phosphate group
  • phosphatases: remove phosphate group

kinases and phosphatases are antagonistic
isomerases - “-iso” means “the same”

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16
Q

What factor do you look at to determine enzyme activity?

A

enzyme activity is measured by the rate at which a substrate is converted to a product

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17
Q

What factors can influence enzyme activity?

A

TP CoCes Si

  • temperature
  • pH
  • concentration of cofactors and coenzymes
  • concentration of enzyme and substrate
  • stimulatory/inhibitory effects of products on enzyme function
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18
Q

Describe the effects temperature has on enzyme activity

A

an increase of temperature will increase the rate of reactions (until the temperature reaches a few degrees above body temperature)

after reaching max activity, denaturation occurs

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19
Q

All enzymes operate best at an optimum/preferred temperature. What will likely happen to the enzyme past the optimum temperature? What will likely happen to the enzyme below the optimum temperature?

A

past optimum temperature: denaturation

below optimum temperature: slow rate of enzyme activity -> slower chemical reaction

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20
Q

True or false: All human enzymes have the same optimum pH. Explain why true or false.

A

False, the ideal pH depends on the pH of the fluid the enzyme is found in

stomach (acidic: 1-2)
saliva (neutral: 7)
small intestine (alkaline: 9-10)

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21
Q

Enzymes exhibit peak activity within a ________ pH range

A

narrow

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22
Q

What will happen if the pH changes away from the optimal pH?

A
  • rxn will proceed slower bc enzyme activeity is slowed
  • enzyme can also denature and lose its shape ->loss of function
23
Q

What are co-factors?

A
  • non-protein molecules
  • include metal ions (Ca2+, Mg2+, Cu2+, Zn2+) or coenzymes (small organic molecules, usually vitamins)
24
Q

Where do cofactors and coenzymes attach?

A

cofactors attach away from the active site (allosteric site)

coenzymes attach at the active site

25
Q

What is the function of cofactors/coenzymes in relation to enzyme activity?

A

help to maintain shape of enzyme and active site so enzyme can bind to substrate

almost all enzymes require cofactors

26
Q

Compare the different types of enzymes in regards to cofactors

A

apoenzyme - enzyme without a cofactor
holoenzyme - enzyme with a cofactor
zymogen (proenzyme) - inactive form (precursor) of an enzyme; needs to be modified to become active form of enzyme

zymogen is an inactive and immature protein and must be modified into its useful form

27
Q

Where is zymogen found?
How do you identify it?
Give an example of a proenzyme that is found in the body

A
  • zymogen is usually found in the digestive system
  • end in “ogen”
  • ex. pepsinogen -> pepsin

pepsinogen is the immature/inactive form; pepsin is the enzyme and is mature and active

28
Q

Explain phosphorylation vs. dephosphorylation

A

enzymes can be activated or inhibited either by adding a phosphate group (phosphorylation) or removal of phosphate group (dephosphorylation)

kinases will add a phosphate group, while phosphatases remove a phosphate group

a phosphorylated enzyme and dephosphorylated enzyme can either be active or inactive

29
Q

True/False: Phosphorylate enzymes are activated enzymes (enzymes that are turns “on”)

A

False; phosphorylated enzymes can either by active or inactive

30
Q

Sometimes a single enzyme can drive a reaction in ___ directions depending on the ______ of substrate or product

A

two
concentration

31
Q

This is a reversible reaction. The enzyme is carbonic anhydrase. Explain which way the reactions will proceed if the concentration of CO2 + H20 are high. Which way will it go if the concentration of carbonic acid is high?

CO2 + H2O - H2CO3

A

if the concentration of CO2 + H2O are high, rxn proceeds right

if the concentration of H2CO3 is high, rxn proceeds left

32
Q

True/False: Most chemical reactions in the body occur by a series of chemical reactions

A

true; one chemical reaction leads to a series of other chemical reactions

33
Q

What are metabolic pathways?

A

a series of enzyme-catalyzed reactions

begin with initial substrate, and end with a final product, with many enzymatic steps along the way

34
Q

What are the different types of metabolic pathways?

A

linear metabolic pathway

branched metabolic pathway (most common); includes branches where several products can be produced

35
Q

Describe end product inhibition

A

a final product inhibits the branch point enzymes and shifts the chemical reaction toward an alternate path (negative feedback)

36
Q

In end product inhibition, how does the final product(s) inhibit an enzyme? How does this effect the pathway?

What is this process known as?

A

the product binds to the enzyme away from active site (allosteric site) -> 3D shape of enzyme changes -> substrate cannot bind due to active site change

one pathway will become favored

allosteric inhibition

37
Q

Define “inborn errors of metabolism.” What will happen within the chemical reaction?

A

inborn errors of metabolism: occur when an abnormal gene (DNA) makes a defective enzyme (protein)

substrate will not be able to bind to the enzyme, and there is no chemcal reaction: leads to a loss of one end-product, and lead to the accumulation of a different end product (can be lethal or non-lethal)

38
Q

Describe Tay-Sachs Disease (what is it, what causes it, effects)

GM2 ————————-> GM3
hexosaminidase A

A
  • inherited, neurological disorder (fatal)
  • caused by a mutation in gene that codes for hexosaminidase A (is a required enzyme, deficient in it)
  • accumulation of GM2 (fatty material) and decrease in GM3 -> bulging lysosomes -> damaged neuron
39
Q

What is Tay-Sachs Disease also known as?
Why is it known as this?

A

lysosomal storage disease

known as this because lysosomes become bulged due to increase in fatty substance (GM2)

40
Q

How to identify Tay-Sachs disease

A
  • symptoms around 6 months
  • exaggerated startling response to noise
  • progressive blindness; cherry red spots in macula
  • narrow eye blood vessels
41
Q

Define enzyme kinetics

A

study of the rates of enzyme-catalyzed chemical reactions

42
Q

What is labeled on the x and y axis of a substrate concentration graph?

What are the effects of substrate concentration on reaction rates? Does this mean the graph will have a plateau? Why/why not

A

x-axis: substrate concentration
y-axis: reaction rate

as substrate concentration increases -> reaction rate increase initially -> stops increasing after certain substrate concentration

will have a plateau because there is a limited supply of enzyme concentration, meaning it will plateau when all active sites are occupied

43
Q

What is labeled on the x and y axis of an enzyme concentration graph

What are the effects of enzyme concentration on reaction rate? Does this mean the graph will have a plateau? Why/why not?

A

x-axis: enzyme concentration
y-axis: rate of reaction (speed)

as enzyme concentration increases, the reaction rate increases

no plateau because there is unlimited supply of substrate and enzyme, meaning rxn rate increases indefinitely

44
Q

The Michaelis-Menten Enzyme Kinetics is a mechanism that explains the _______ of enzyme-catalyzed reactions

A

velocity

45
Q

What is Km

A

is the substrate concentration (on x-axis) at 1/2 vmax

it measures the enzyme “affinity” for a substance (bond strength with substrate)

46
Q

Km indicated how “_________” the enzyme is

A

potent

47
Q

Describe the relationship between km and affinity.

A

inverse relationship

lower km -> higher affinity (strong bond, enzyme is effective in catalyzing rxn)

higher km -> lower affinity (weak bond, enzyme NOT effective in catalyzing rxn)

48
Q

How does the lineweaver-burk plot different from a michaelis-menten enzyme kinetics graph?

A
  • it is straightens curves of m-m graph
  • double reciprocal plot (1/[S] x-axis, 1/V for y-axis)
49
Q

What is the main purpose of the lineweaver-burk plot?

A

helps to visualize the effects of different types of enzyme inhibitors on an enzyme-catalyzed reaction

  1. competitive enzyme inhibitor
  2. noncompetitive enzyme inhibitor
50
Q

Compare the different types of enzyme inhibition

A

competitive inhibition

  • binds at active site -> blocks substrate
  • mimics substrate (imposter)
  • enzyme shape not changed

non-competitive inhibition

  • binds at allosteric site -> changes enzyme shape -> enzyme is non-functional
  • substrate will never be able to bind to enzyme
  • AKA allosteric inhibitor
51
Q

What does a competitive inhibitor do?
Can this reach Vmax? Why/why not?

A

competes with substrate for the active site -> reduces rate of rxn

competitive inhibitors can be overcome at a higher substrate concentration (vmax can be reached)

52
Q

What does a noncompetitive inhibitor do?
Can this reach Vmax? Why/why not?

A
  • does NOT use active site of enzyme
  • changed conformational shape of enzym e
  • substrate will NEVER be able to bind to enzyme

noncompetitive inhibitors cannot be overcome.

increasing the [substrate] will still increase the reaction rate, but because the enzyme is permanently altered, further increasing the [substrate] will never allow for the same Vmax to be reached

53
Q

Why can we overcome the effects of a competitive inhibitory, but not the effects of a non-competitive inhibitor? What must be done to overcome the effects of a competitive inhibitor?

A

NCI cannot be overcome because they permanently alter the shape of the active site of an enzyme, meaning the substrate will never be able to bind to it. Competitive inhibitors do not change the shape of the enzyme, but instead, they compete with the normal substrates for the active site.

To overcome the effects of the competitive inhibitor, increasing [S] will increase the likelihood of substrate binding to active site as normal.

BIO 241 [Exam #1] (5 decks)

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