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Biology > Chapter 4 - Enzymes > Flashcards

Chapter 4 - Enzymes Flashcards

globular proteins, specificity, enzyme-substrate complex

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1
Q

what are enzymes?

A

enzymes are biological catalysts.

GLOBULAR proteins that interact with substrate molecules to lower reactions activation energy.

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2
Q

which reactions do enzymes catalyse in cells?

A

metabolic reactions

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3
Q

what is metabolism?

A

the sum of all reactions occurring within an organism or cell.

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4
Q

types of metabolic reactions?

A

ANABOLIC- chemical reactions needed for growth (smaller to bigger), energy required
CATABOLIC- breaking down reactions, release energy

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5
Q

what is Vmax?

A

the maximum initial velocity or rate of the enzyme-catalysed reaction

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6
Q

what is the specificity of an enzyme?

A

a molecular recognition system which allows an enzyme to choose one specific substrate between many.

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7
Q

what is activation energy?

A

minimum energy needed for a reaction to start

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8
Q

what are the two hypotheses for how enzymes work?

A

lock and key

induced-fit

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9
Q

what is the active site?

A

the small region of the enzyme’s tertiary structure that is COMPLEMENTARY to the shape of the specific substrate molecule

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10
Q

describe the lock and key hypothesis

A

when the specific substrate fits exactly into the enzyme

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11
Q

what forms when an enzyme and substrate bind? what forms when the substrates react to form the product?

A

an enzyme-substrate complex

an enzyme-product complex

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12
Q

what changes and what remains unchanged during catalysis?

A 
substrate changes (to form product)
enzyme remains unchanged and can cary on forming ESC’s
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13
Q

enzyme + substrate —> enzyme substrate complex —> enzyme product complex

A

yes

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14
Q

which model has more recently been more accepted than the lock and key model? why?

A

induced fit

- more evidence to prove

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15
Q

describe the induced fit model of enzyme action

A

the enzymes active site changes shape slightly as the substrate enters

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16
Q

describe how the induced fit model lowers activation energy of a reaction

A

interactions between the enzymes active site and substrate are weak but then cause the tertiary structure to change, strengthen binding IN THE ACTIVE SITE and put strain on the substrate and weaken bonds IN THE SUBSTRATE.

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17
Q

describe how lock and key model lowers activation energy of a reaction

A

the R groups within the active site react with the substrate forming temporary binds and put strain in bonds within the substrate.

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18
Q

why are extracellular enzymes needed?

A

to break down larger molecules to smaller ones to be transported inside cells

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19
Q

where are intracellular enzymes made?

A

in the cell, ribosome (site of protein synthesis)

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20
Q

give examples of extracellular enzymes and state what they are involved in?

A

amylase, trypsin - digestion

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21
Q

give examples of intracellular enzymes and state what they are involved in?

A

DNA polymerase, DNA ligase, ATP synthetase - DNA replication

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22
Q

process of digestion of starch step 1

starch first broken down into maltose by _____ which is released into the _____ and ______

A

amylase, salivary glands and pancreatic juice in small intestine

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23
Q

process of digestion of starch step 2

maltose is broken down into _____ which is a ______ by _______ which is present in the ______

A

glucose, monosaccharide, maltase, small intestine

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24
Q

process of digestion of proteins
the protease enzyme that breaks down proteins into ______ in the small intestine is called _____. this enzyme is produced in the ______ and carried to the small intensities via _____ _____. amino acids which are produced by digestion if proteins are _____ into the ________ by the cells lining the _____ _____

A

smaller peptides, trypsin, pancreas, pancreatic juice, absorbed, bloodstream, digestive system

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25
Q

What is an enzyme?

A

A biological catalyst that speeds up the rate of a biochemical reaction by lowering the activation energy.

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26
Q

Structure of enzymes?

A

Globular protein with a helical secondary structure

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27
Q

What are the two types of enzymes?

A

Intracellular and extracellular

28
Q

What are intracellular enzymes?

A

Function/have effect within the cell

29
Q

What are extracellular enzymes?

A

Function/ have effect outside the cell

30
Q

What factors affect the rate of reaction/action of enzyme-assisted reactions?

A

enzyme concentration, substrate concentration, temperature, pH

31
Q

What is the substrate?

A

The substance on which the enzyme acts.

32
Q

what is a cofactor

A
  • a component necessary for the function of the enzyme,
  • inorganic
  • not permanently attached
  • e.g. chloride ions for amylase function
33
Q

what is a coenzyme

A
  • a component necessary for the function of a specific enzyme
  • organic
  • TEMPORARILY attached
34
Q

what is a prosthetic group

A
  • a non protein component necessary for the function of an enzyme
  • PERMAMENTLY attached
35
Q

what is precursor activation

A

some enzymes produced in an inactive form, must have e.g. cofactor added to them to work

36
Q

what is an enzyme called before the cofactor is added

A

apoenzyme

37
Q

what is an enzyme called after the cofactor is added

A

holoenzyme

38
Q

what is a enzyme which needs an environment change to work called?

A

a zymogen or proenzyme

39
Q

what does the change in temperature/pH do in precursor activation?

A

changes the tertiary structure so enzyme can function

40
Q

give and example of a zymogen activation

A

inactivated pepsinogen becomes activated by the acidic conditions in the stomach

41
Q

what is the turnover number?

A

the number of reactions an enzyme can catalyze per second

42
Q

what happens if the enzyme that catalyses a reaction is deficient?

A

metabolic disorder results

43
Q

example of an intracellular enzyme? where is it found?

A

catalase breaks down hydrogen peroxide, found in vesicles called peroxisomes

44
Q

example of an extracellular enzyme? where is it found?

A

amylase digests starch, produced in salivary glands

45
Q

example of prosthetic group?

A
  • e.g. Zinc ions for carbonic anhydrase

found in erythrocytes, catalyses conversion of CO2 to water and carbonic acid

46
Q

example of coenzyme?

A
  • e.g. Vitamin B5 for Coenzyme A
47
Q

what is Q10?

A

the increase in the rate when the temp. increases by 10 degrees
= rate of reaction at T + 10
————————————–
rate of reaction at T

48
Q

what does a Q10 of 2 mean? what is the Q10 for most reations in a test tube?

A

for every 10 degrees increase, the rate is DOUBLED.

it is 2

49
Q

how can u find the rate from just one point? (as there is no gradient)

A

1
—————–
time/value

50
Q

how does heat denature an enzyme?

A

molecules vibrate faster, weaker bonds like ionic and hydrogen bonds break, tertiary structure breaks, the active site DENATURED.

51
Q

why doesn’t heat change the primary structure?

A

peptide bonds are covalent and so very strong

52
Q

how does temperature increase rate of reaction?

A
  • enzyme and substrate have more KE
  • collide more often and more successfully
  • more enzyme-substrate complexes formed
  • more enzyme-product complexes formed
53
Q

what does the rate of reaction against pH graph look like?

A

bell-shaped

54
Q

how does pH increase rate of reaction? then lower it?

A

excess DO

55
Q

explain how enzymes lower the activation energy of reactions

A

Because they bring the substrate molecules close together, as the substrate molecules fit into the enzyme’s active site, and form S–E complexes, and stay there long enough to react.

56
Q

how do the enzymes of organisms that live in extreme conditions vary from others, that allow them to withstand

A

These proteins may have many disulfide bridges as these bonds are heat stable.

57
Q

why do enzymes only work within narrow ranges of pH?

A

Because changes in pH change the balance of hydrogen ions/protons, and these interfere with the hydrogen bonds that hold the shape of the enzyme’s active site. If the shape of the active site changes slightly, the substrate molecules do not fit in so well.

58
Q

why is the enzyme added last during an experiment?

A

so the reaction doesn’t start before we start timing

59
Q

why are some enzymes produced in an inactive form?

A

so they don’t digest/harm cells or tissue where they were made and only work where needed

60
Q

(imagine a graph of substrate conc. to rate of reaction)
(increases, then plateaus)
explain the shape of the graph

A

Between A and B, the concentration of SUBSTRATE is the LIMITING FACTOR. As substrate concentration increases, rate of reaction increases. At point B the maximum rate of reaction is reached, because there are NO MORE ACTICE SITES available for substrate molecules to form ES complexes. Between B and C, the substrate concentration is no longer the limiting factor. Something else is limiting the reaction – the availability of enzyme active sites, in other words the enzyme concentration. Adding more substrate molecules does not increase the rate of reaction as the number of enzyme active sites is limited.

61
Q

e. g. why do some plants have the enzyme urease?

- how would u tackle this question?

A
  • urease … UREA
  • breaks down urea
  • why would u break down urea
  • to make ammonia which is a source of nitrogen so can be absorbed by soil and make new proteins
62
Q

explain how competitive inhibitors reduce enzyme activity

A

Competitive inhibitors have a similar shape to those of the enzyme’s substrate, so they may attach to the active site when enzyme and inhibitor molecules collide; they form enzyme–inhibitor complexes; they compete with the substrate for the enzyme’s active site; because the active site is occupied, the substrate molecules cannot fit into it, so there are fewer ES complexes, fewer catalysed reactions, and fewer product molecules are made.

63
Q

explain how non-competitive inhibitors reduce enzyme activity

A

They attach to a part of the enzyme molecule, other than the active site ALLOSTERIC SITE, and cause the enzyme to change shape. This distorts the shape of the active site, so it is no longer complementary to the substrate; substrate cannot fit into the active site and fewer ES complexes form.

64
Q

explain how end-product inhibition may regulate metabolic pathways

A

The product molecules may remain bound to the enzyme/regulatory subunits of enzyme, keeping the enzyme in
its inactive form (the active site may not be exposed). Many metabolic pathways are regulated by different
enzymes that form a large multi-enzyme complex. The end product may bind to an enzyme early in the pathway.

65
Q

graph for competitive inhibition?

compared to no inhibitor

A

lower gradient, reaches same max initial rate as no competitor

66
Q

graph for non-competitive inhibition?

compared to no inhibitor

A

max initial rate much lower than with no competitor

Biology (25 decks)

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