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enzymes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are enzymes?

A

biological catalysts, speed up metabolic reactions, remain unchanged and can be used again.

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2
Q

no. of reactions an enzyme can catalyse per min. is called…?

A

turnover number

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3
Q

three ways enzymes better than chemical catalysts

A

lower temperature, lower pressure than chemical catalysts and neutral pH; more specific, no unwanted by-products and mistakes rare; cells can regulate production and activity

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4
Q

how can enzyme tertiary structure be affected genetically?

A

mutation in genetic code change amino acid sequence

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5
Q

what component can help enzymes function?

A

cofactors

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6
Q

what is the result of deficient enzymes in an organism?

A

metabolic disorder; enzymes catalyse formation of structural components and can cause malfunctions of connective tissue.

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7
Q

what is the active site?

A

specific indentation on surface which fits substrate

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8
Q

how can tertiary structure of active site be altered?

A

by changes in pH or temperature

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9
Q

two types of enzyme catalysed reaction?

A

intracellular and extracellular

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10
Q

what is an intracellular reaction?

A

enzyme controlled reaction which occurs within the cell

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11
Q

what is a metabolic pathway?

A

series of consecutive enzyme controlled reactions

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12
Q

what is a catabolic metabolic pathway?

A

pathway where metabolites broken down to smaller molecules, release energy.

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13
Q

what is an anabolic metabolic pathway?

A

pathway where energy used to synthesise larger molecules from smaller ones

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14
Q

two examples of complex metabolic pathways?

A

photosynthesis and respiration

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15
Q

what is the role of catalase?

A

quickly breaks down hydrogen peroxide to prevent damage to cell by reactive oxygen. used in wbcs to kill pathogens

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16
Q

structure of catalase?

A

four polypeptide chains and a haem group with iron

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17
Q

where catalase found?

A

in small vesicles called peroxisomes

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18
Q

describe action of extracellular enzymes

A

secreted from cells where made and act on substrates outside of cells

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19
Q

example of how fungi uses extracellular enzymes

A

e.g. bread mould mucor, release hydrolytic enzymes from hyphae, digests carbs, proteins, lipids in bread, products absorbed for respiration and growth

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20
Q

how are extracellular enzymes used in the gut?

A

secreted from cells lining alimentary canal into gut lumen, digest carbs, lipids, proteins, nucleic acids in foods. products absorbed via epithelial cells of the gut into bloodstream for respiration, growth and tissue repair

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21
Q

two examples of extracellular enzymes

A

trypsin and amylase

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22
Q

how does amylase work?

A

digest polysaccharide starch to disaccharide maltose

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23
Q

Where does amylase work?

A

secreted from salivary glands into the mouth, and from pancreas into small intestine

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24
Q

how does trypsin work?

A

digest proteins into smaller peptides by hydrolysing peptide bonds

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25
Q

Where does trypsin work?

A

from pancreas, works in the small intestine

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26
Q

What is the optimum pH of trypsin?

A

pH 7.5-8.5

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27
Q

Where does trypsin work?

A

from pancreas, works in the small intestine

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28
Q

Three types of cofactors

A

prosthetic groups, coenzymes, ions which do not permanently bind to enzyme.
prosthetic groups

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29
Q

How do prosthetic groups work?

A

cofactor permanently bound to enzyme by covalent bonds

30
Q

What is the cofactor used by carbonic anhydrase?

A

zinc ion permanently bound to active site

31
Q

What reaction does carbonic anhydrase catalyse?

A

turns carbon dioxide and water to carbonic acid, then to hydrogen carbonate ions and protons for transport of carbon dioxide

32
Q

effect of temporary ion cofactor

A

ease formation of enzyme-substrate complex, increase rate of catalysed reaction

33
Q

state two ways temporary cofactors work

A

co-substrates bind to substrate to better fit the active site; some change charge distribution on active site or substrate and make temporary es bonds easier to form

34
Q

example of temporary cofactor

A

enzyme amylase digests starch to maltose only if chloride ions are present

35
Q

Which temporary cofactor is used by amylase?

A

chloride ions help digest starch to maltose

36
Q

what are coenzymes?

A

organic non-proteins bind temporarily to the active site with substrate. chemically changed during reaction, need to be recycled sometimes by different enzyme

37
Q

why are vitamins important?

A

many coenzymes derived from vitamins, some act as coenzymes, deficient vitamins may cause certain diseases

38
Q

describe the lock and key model

A

enzyme and substrate have specific complementary shapes, successful collision between the two, the substrate fits the active site, temporary hydrogen bonds form es complex, product molecule(s) leave active site

39
Q

describe the induced fit model

A

enzyme and substrate have complementary shapes, active site R-groups mould to fit the substrate perfectly, temporary hydrogen, ionic, hydrophobic etc. bonds form, enzyme-product complex forms, shape changes so product detaches from active site and leaves enzyme

40
Q

what is activation energy?

A

energy needed to start a chemical reaction

41
Q

effect of enzymes on activation energy

A

lowers activation energy by bringing substrate close enough to react without need of excessive heat

42
Q

effect of heat on a substance

A

ncreases kinetic energy of molecules, move faster and collide more, and collide with more force

43
Q

effect of heat on enzyme catalysed reaction

A

substrate and enzyme gain kinetic energy and move faster, more successful collisions, rate formation of es complexes increases and therefore ep complexes, rate max at optimum temperature.

44
Q

how does heat damage enzymes?

A

causes vibrations, can break weaker bonds like ionic and hydrogen in the enzyme. Changes shape, substrate doesn’t fit and rate decreases. continue heating, shape change irreversibly, enzyme is denatured. primary structure is not altered

45
Q

what is optimum temperature of an enzyme?

A

the temperature at which the enzyme works fastest, and the rate of reaction is highest

46
Q

what is a buffer?

A

substance which resists change in pH by accepting or donating hydrogen ions, some proteins like haemoglobin can also do this

47
Q

How can you maintain pH in lab investigation?

A

Use a buffer solution

48
Q

How does change in pH affect enzymes?

A

H+ interfere with hydrogen and ionic bonds in enzyme, altering tertiary structure, alters charges of R-groups at active site, interfere with formation of es complex. Extreme pH active site can change permanently and is denatured

49
Q

How does substrate concentration affect the rate of reaction?

A

as increases, rate increases, more successful collisions forming es complexes. eventually will reach max as enzymes working at highest rate, substrate no longer a limiting factor

50
Q

what is enzyme degradation?

A

enzymes broken down to their amino acids and rebuilt to make new enzymes

51
Q

Why is enzyme degradation important?

A

to prevent the build up of abnormal proteins and control the amount of enzymes to regulate metabolism

52
Q

effect of enzyme concentration on rate of reaction

A

increase means more active sites available and more successful collisions, more es complexes and increased rate until no longer limiting factor as surplus of active sites.

53
Q

when is a reaction at its highest rate?

A

intial rate is always highest as there is the most substrate and highest chance of successful collisions, substrate runs out and more product forms, less likely to collide with substrate

54
Q

what is an inhibitor?

A

slows rate of reaction by binding of the substrate to the enzyme
- preventing formation of enzyme substrate complex
- could be reversible or irreversible

55
Q

how does a competitive inhibitor work?

A

competitive inhibitors fit the active site, and prevent substrate from entering. depends on concentration of substrate/inhibitor

56
Q

How can the effect of a competitive inhibitor be reversed?

A

increase concentration of substrate, more likely to bind with substrate, rate increases

57
Q

if competitive inhibitor binds permanently it is called an…?

A

inactivator

58
Q

how do non-competitive inhibitors work?

A

bind elsewhere on enzyme, change tertiary structure and substrate can no longer fit. reduces max rate of reaction. some bind reversibly, some irreversibly.

59
Q

what is end-product inhibition?

A

method of regulating reaction - product remains in active site, ensuring no more can be formed by the enzyme. fits cells needs

60
Q

how are metabolic sequences regulated?

A

end product in chain of enzyme controlled reactions can act as non-competitive inhibitor to first enzyme in the chain. slows the formation of the final product.

61
Q

how do metabolic poisons/toxins work?

A

many inhibit or inactivate enzymes

62
Q

How does potassium cyanide work as a toxin?

A

KCN ingested and hydrolysed to hydrogen cyanide, dissociates to H+ CN- and negative ions bind irreversibly to enzyme in mitochondria, inhibit final stage aerobic respiration, and sequence stops.

63
Q

How does snake venom work?

A

contains chemical which inhibits enzyme acetylcholinesterase (AChE). At neuromuscular synapses, cannot break down neurotransmitter, which remains attached to receptors and keeps muscles contracted, causing paralysis.

64
Q

How does aspirin work by inhibition?

A

salicylic acid binds to enzymes that form prostaglandins, cell-signallers which make nerve cells more sensitive to pain and increase swelling during inflammation. aspirin also reduces risk blood clots in vessels.

65
Q

What are ATPase inhibitors?

A

from purple foxglove, treat heart failure and atrial arrhythmia, chemicals are digitalis, digitoxin, digitalin, digoxin.

66
Q

How do ATPase inhibitors work?

A

inhibit sodium potassium pump in membrane of heart muscle cells allowing more calcium ions in, which increase contraction and strengthen heartbeat.

67
Q

What are ACE inhibitors?

A

medical, inhibit enzyme which increases blood pressure.

68
Q

what are ACE inhibitors used for?

A

lower blood pressure in patients with hypertension who cant take beta-blockers, to treat heart failure, to minimise risk of second heart attack or stroke in patients who suffered myocardial infarction.

69
Q

What are Protease inhibitors?

A

treat viral infections, prevent replication in host cells by inhibiting protease enzymes so viral coats cant be made, often competitive inhibition.

70
Q

What are nucleoside reverse transcriptase inhibitors

A

antiviral, inhibit enzymes involved in making DNA using viral RNA.

Biology (18 decks)

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