Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Molecules and Cells > Enzymes > Flashcards

Enzymes Flashcards

1
Q

what are catalysts

A

catalysts speed up chemical reactions without themselves being changed as a result of it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are enzymes

A

catalysts in living cells, that accelerate specific reactions in biological systems millions of times faster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how do enzymes relate to the equlibrium of reactions

A

they do not alter the actual equilibrium, but rather they accelerate the time to reach the equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

why are enzymes important

A

they are vital for life, they catalyse chemical reactions such as our metabolism in cells that keep us alive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the roles of the enzymes in living organisms

A

aiding:
- respiration
- digestion
- muscle and nerve function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are examples of enzymes found in the oral environment

A
  • alkaline phosphatase
  • amylase
  • maltase
  • lysozyme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are examples of enzymes found elsewhere in the body from the mouth

A
  • pepsin
  • trypsin
  • acetylcholinesterase
  • dna polymerase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is alkaline phosphatase

A

enzyme found throughout the body that is involved in mineralisation of tissue and bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is amylase

A

enzyme found in saliva that converts starch into sugars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is maltase

A

enzyme found in saliva, breaks the sugar maltose into glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is lysozyme

A

antimicrobial enzyme that is an innate part of the immune system that breaks down the peptidoglycan layer in cell walls of bacteria, and is found in many secretions including saliva, tears, human milk, mucous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is pepsin

A

digestive enzyme of the stomach that breaks down the proteins into smaller peptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is trypsin

A

enzyme found in the small intestine that breaks down proteins into amino acids. produced by the pancreas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is acetylcholinesterase

A

enzyme that breaks down the neurotransmitter acetylcholine in nerves and muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is dna polymerase

A

synthesises DNA from deoxyribonucleotides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the different models that enzymes can work by

A

lock and key model, induced fit model

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the lock and key model of enzymes

A

the enzyme active site is complementary in shape to that of the substrate. the active site precisely shaped to hold specific substrates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the induced fit of enzymes

A

the active site and substrate do not fit together exactly. instead, the enzyme changes shape when the substrate binds, and the active site has a shape complementary to the substrate only after the substrate has bound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

are all enzymes proteins

A

no only most are

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the exceptions to enzymes that are not proteins

A

ribozymes (the catalytic rna molecules)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the enzymic activity of proteins dependent on

A

the maintenance of their three dimensional structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is enzyme activity affected by

A

temperature and pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what can occur to enzymes at extremes of pH and temperature

A

the enzyme may lose its 3D structure (denature) and become totally inactive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the standard free energy change

A

the difference between energies of the reactants and the products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does reaction rate depend on

A

the activation energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is activation energy

A

the energy input required to initiate reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

is activation energy for a catalysed reaction higher or lower than an uncatalysed reaction

A

lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

can enzymes alter the free energy change

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what factors affect the rate of an enzyme reaction

A

temperature
pH
enzyme concentration
substrate concentration
inhibitors and activators
covalent modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is thermodynamic activation

A

increase in free energy

12
Q

what is thermodynamic inactivation

A

the protein is denatured

13
Q

what is the relationship between enzyme concentration and reaction rate

A

an increase in enzyme concentration will increase the reaction rate

13
Q

what happens to the concentrations of product and substrates once equilibrium is reached

A

they will no longer change

14
Q

what is [E]

A

enzyme concentration

15
Q

what is [S]

A

substrate concentration

15
Q

what is [V]

A

reaction rate

16
Q

when is reaction rate linearly proportional to substrate concentration

A

when substrate concentration is small

16
Q

describe the effect of substrate concentration on reaction rate when the concentration of substrate is low

A
  • an increased substrate concentration gives a steep increase in reaction rate
  • not all the enzyme active sites are occupied, as they are waiting for the substrate to bind for much of the time
  • the rate of the product formation is limited by the amount of available substrate
17
Q

explain the effect of substrate concentration on reaction rate when the substrate concentration is high

A
  • the enzyme is working at maximum rate due to being saturated with substrate
  • all the active sites are occupied
  • the rate of product formation now depends on the activity of the enzyme itself, adding more substrate will not significantly affect the reaction rate and maximum reaction rate will be achieved
18
Q

what is Vmax

A

the maximum rate of reaction

19
Q

when does Vmax occur

A

when the enzyme is saturated with substrate

19
Q

what is Km

A

the substrate concentration at which V = 0.5 Vmax and is a measure of the affinity of the enzyme for its subsrate: the lower the Km, the higher the affinity

19
Q

what does the relationship between the reaction rate and substrate concentration depend on

A

the affinity of an enzyme for its substrate

19
Q

what does the Km of an enzyme relative to the concentration of its substrate determine

A

if the rate of product formation will be affected by substrate availability

20
Q

if there is a low Km, is the enzyme more or less saturated with substrate

A

the enzyme will normally be saturated with the substrate at a low Km - it will also be fairly constant rate regardless of the variations in substrate concentration

20
Q

if there is a high Km, is the affinity of the enzyme for the substrate higher or lower, and how does this affect its activity

A

the enzyme will not normally be saturated with the substrate, and its activity will vary as substrate concentration varies.

21
Q

what does the rate of product formation depend on when the Km is high

A

substrate availability

22
Q

how does the concentration of an unbound enzyme change with time

A

decreases in the pre steady state when the bound ES is forming, after this it slowly increases again

23
Q

how does the concentration of the bound enzyme and substrate change over time

A

increases initially, then levels off, then starts to gradually decrease

23
Q

how does the concentration of unbound substrate change with time

A

gradually decreases

24
Q

how does the total concentration of enzyme change with time

A

remains constant

25
Q

how does the concentration of product change with time

A

slowly increases

26
Q

what is the michaelis menten equation

A

V = Vmax[S]/(Km+[S])

27
Q

what is one of the main components of dental plaque

A

the polysaccharide dextran - a polymer of glucose. the enzyme that makes it is dextran sucrase, and the substrate is sucrose.

28
Q

what does plaque formation depend on

A

how long you have sweet things in your mouth

29
Q

what is the lineweavr burk plot

A

a more accurate estimate of Vmax and Km - is obtained by plotting 1/V against 1/[S]. gives a straight line for most enzymes

30
Q

give a brief explanation of irreversible inhibitors

A

these inhibitors damage enzymes beyond repair, and generally cause covalent modification of the enzyme

31
Q

give a brief explanation of reversible inhibitors

A

most natural enzyme inhibitors fall into this category, and the enzyme will regain full activity once the inhibitor has been removed

32
Q

what does control of metabolic pathways usually occur by

A

feedback inhibition

33
Q

give a summary of feedback inhibition

A
  • when the product of a metabolic pathway builds up in the cell, inhibition of the pathway often occurs.
  • this is often done by the product of the pathway acting as an inhibitor of an earlier step in the pathway
  • an example of this is the pathway that forms isoleucine from threonine
34
Q

what is an example of feedback inhibition

A

the feedback inhibition of threonine deaminase by the end product isoleucine. if isoleucine is not metabolised by the cell it accumulates and switches off further synthesis

35
Q

give a brief summary on competitive inhibitors

A
  • substrate and inhibitor compete for the same active binding site. they are structural analogues that prevent the substrate from binding
  • inhibition can be overcome with large quantities of substrate - the substrate will ultimately occupy all binding sites, and the enzyme will be fully operative
36
Q

give a brief summary of non competitive inhibition

A
  • binds to an allosteric site on the enzyme, is structurally unrelated to the substrate, but it cannot be reversed by adding large quantities of substrate
37
Q

how does competitive inhibition affect Vmax

A

it is unaltered - a large quantity of sustrate can compete out the inhibitor

38
Q

how does competitive inhibition affect Km

A

it is increase - as the inhibitor competes with the substrate for binding to the active site, the affinity of the substrate will appear to decrease. the Km is an inverse measure of affinity

39
Q

how does non competitive inhibition affect Vmax

A

the Vmax will be decreased, as a proportion of enzyme molecules will be inactive at any time due to binding by the inhibitor

40
Q

how does non competitive inhibition affect Km

A

it is unchanged, as the binding of the substrate can still occur

41
Q

give a brief summary of allosteric enzymes

A
  • they possess multiple subunits
  • in addition to active sites they possess allosteric sites where non substrate modulators bind, which creators a conformational change in the subunits
  • many important regulator enzymes are allosteric
42
Q

how do the subunits on the allosteric enzymes interact

A

such that the binding site of a substrate, inhibitor, or activator to one subunit alters the conformation of all the subunits

43
Q

what are positive modulators

A

these increase the affinity for substrates at an active site

44
Q

what are negative modulators

A

these decrease the affinity for substrates at active sites

45
Q

do allosteric enzymes conform to the michaelis menten kinetics

A

no

46
Q

give a brief summary of the control of enzyme activity by covalent modification of enzyme molecules

A
  • many enzymes can be covalently modified
  • common modification is the addition of a phosphate group to serine, threonine or tyrosine hydroxyl
  • glycogen phosphorylase, which breaks down glycogen to provide glucose, is activated by phosphorylation
  • phosphorylase kinase is the enzyme which brings this about, and is in turn activated indirectly by adrenaline and glucagon
  • reversed by phosphorylase phosphatase

Molecules and Cells (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions