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BIOLOGY REVISION > enzymes 2.4 > Flashcards

enzymes 2.4 Flashcards

1
Q

What are enzymes?

A

Enzymes are biological catalysts that speed up metabolic reactions in living organisms

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2
Q

What is turnover number

A

Turnover number is the number of reactions an enzyme can catalyse per second

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3
Q

Describe he active site and what is susceptible to

A

The active site has a crucial tertiary structure that is complimentary to the substrate molecule. The active site and therefore the enzymes ability to catalyse reaction sis therefore altered by changes in temperature and pH as they affect the bonds in the tertiary structure

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4
Q

Two types of enzymes

A
  • Intracellular

- extracellular

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5
Q

Describe catalase

A

Catalase is a 4 polypeptide chain enzyme, each with an iron haem group. It is found in vesicles called peroxisomes in eukaryotic cells. It breaks down hydrogen peroxide to water and oxygen. It optimum temperature is 7

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6
Q

2 extracellular enzymes

A
  • amylase

- trypsin

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7
Q

What is a cofactor and a prosthetic group?

A

Co factor is a non protein molecule helping the enzyme to work.
A prosthetic group is a co factor that is permentely attached to the enzyme by covalent bonds

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8
Q

Example of prosthetic group

A

-carbonic anhydrase has a zinc ion bound permanently to its active site

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9
Q

What are 2 things temporary cofactor can do?

A

Cofactors temporarily bind to either the substrate or the enzymes

  • Act as co substrates, binding to the substrates to together form the correct shape to bind to the active site
  • change the charge distribution on the surface of the substrate or on the active site and temporarily bond in the enzyme substrate complex to make it easier to form
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10
Q

What are coenzymes

A

Coenzymes are small organic non protein molecules which bind temporarily to the active site of enzymes ,molecules. After binding they are chemically changed so need to be recycled

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11
Q

What are sources of co enzymes

A

Some vitamins are sources of co enzymes, nictotinamide (B3) is a source of NAD or NADP

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12
Q

2 complexes that can form in active site

A
  • enzyme substrate complex (break down)

- enzyme product complex (formation of larger molecule)

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13
Q

2 theories of enzyme action

A

-lock and key hypothesis
Active site specific and complimentary to substrate
-induced fit hypothesis
presence of substrate induces a shape change to the active site, letting it mould to the molecule

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14
Q

More detail into induced fit hypothesis

A
  • Shape is complimentary but binding causes subtle changes to the shape of the R groups on the amino acids giving a more precise conformation and fit
  • ESC formed and non covalent forces hold it in place
  • EPC formed
  • product has different shape to substrate so they detach
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15
Q

Enzymes and activation energy

A

Enzymes lower the activation energy of a reaction

On a graph the jump in activation energy will be below the reaction without an enzyme

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16
Q

Discuss collisions between enzyme and substrate relating to heat

A

When mixture is heated both molecule will gain kinetic energy and move faster. This increases the rate of successful collisions. Formation of ES complexes increases so rate of reaction increases

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17
Q

What is optimum temperature

A

This is the temperature where rate of reaction is at its maximum

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18
Q

Denaturing due to heat

A

Heat energy makes molecules vibrate breaking weak hydrogen bonds holding the active site together so substrate cannot fit. Gets permanently change so reaction ceases
It does NOT affect primary structure

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19
Q

example bacteria who work best in cold temps called

A

bacteria which work best in the cold are called psychrophillic

20
Q

example bacteria which work best in hot temps

A

bacteria working best in hot temps are thermophilic bacteria

21
Q

Graph of enzymes and rate of reaction

A

One peak

22
Q

What is the temperature coefficient

A

Temperature coefficient refers to the increase in rate of progress when the temperature is increased by 10 degrees celcius

23
Q

Chemical reactions Q10 value and what it means

A

Chemical reaction sin test tubes have a Q10 of 2 meaning their rate of reaction doubles when increasing temperature by 10 degrees

24
Q

Calculate Q10

A

rate of reaction at temperature +10 degrees /

rate of reaction at temperature

25
Q

How pH affects enzymes structure

A
  • Hydrogen bonds hold the alpha helix in place
  • Lowering pH adds H+ which is attracted to the negative areas of the bonds already in place
  • H+ interfere with the bonds trying to bond themselves o the structure gets pulled apart, changing active site shape
  • H+ alters charges on active site interfering with bonding
26
Q

Small changes and reversing pH effects?

A

Small changes in pHs effects can be reversed if normal optimum pH is restored

27
Q

Discuss cyanide

A

Cyanide:

  • Potassium cyanide
  • inhibited aerobic respiration and catalase
  • digested and hydrolysed makes hydrogen cyanide which is toxic, dissociates into H+ and CN- ions
  • CN- bind to enzyme in mitochondria inhibiting the final stage of respiration
28
Q

Discuss snake venom

A

Snake venom;

  • Inhibits acetylcholinesterase which breaks down acetylcholine
  • Acetylcholine stays attached t the receptor on the muscle membrane keeping muscles contracted
  • paralysis of muscles
29
Q

Discuss aspirin

A

Aspirin:

  • Salicylic acid binds to enzymes that catalyse formation of prostaglandins
  • prevents formation of prostaglandins which are cell signalling molecules when cells are damaged or infected
  • prostaglandins make nerve cells more sensitive and tissues swell, so aspirin prevents this
30
Q

Discuss ATPase inhibitors

A

ATPase inhibitors:

  • cardiac glycosides from fox gloves treat heart failure and abnormal atria beating
  • Inhibit sodium potassium pumps in cell membranes of heart muscles cells, allowing calcium to enter the cells
  • calcium ions increase co traction strengthening heart beat
31
Q

Discuss ACE inhibitors

A

ACE inhibitors:

  • ACE operates a metabolic pathway that increases blood pressure
  • lower blood pressure in hyper tension patients who cannot take beta blockers
  • treat heart failure
  • Minimise risk of second heart attack or stroke
32
Q

protease inhibitors

A
  • Prevent replication of virus particles in host cells by inhibiting protease enzymes
  • competitive inhibition
33
Q

nucleoside reverse transcriptase inhibitors

A

Nucleoside reverse transcriptase inhibitors inhibit enzymes involved in making DNA using the viral RNA template. For HIV

34
Q

2 Metabolic poison and 5 medicinal drugs as enzyme inhibitors

A 
metabolic poisons as enzyme inhibitors
-Cyanide
-snake venom
Medicinal drugs as enzyme inhibitors 
-Aspirin
-ATPase inhibitors
-ACE inhibitors
-Protease inhibitors
-nucleoside reverse transcriptase inhibitors
35
Q

Substrate/competitive inhibitors concentration effects

A
  • Higher substrate concentration dilutes the effects of the inhibitor as inhibitor unlikely to collide with enzymes
  • Higher inhibitor concentration means more active site to inhibitor collisions so higher effect
36
Q

Effects of competitive inhibitor

A
  • Enzyme inhibitor complex
  • prevents substrate from joining preventing enzyme substrate complexes and reducing production of product-reduces number of available active sites
37
Q

irreversible competitive inhibitor

A

Irreversible competitive inhibitors are called inactivators

38
Q

Where do non competitive inhibitors bind?

A

They bind somewhere other than the active site called the allosteric site

39
Q

Effects of non competitive inhibitors

A

Non competitive inhibitors alter the tertiary structure of the active site changing its shape meaning it is no longer complimentary to the substrate molecule

40
Q

End product inhibition

A

End product inhibition is where we regulate reactions by keeping the product molecule tightly bound to the enzyme so the enzyme cannot form any more product . Negative feedback

41
Q

Graphs of non competitive and competitive enzyme inhibition

A
  • Non competitive stays low and level eve if substrate concentration increases
  • Competitive increases as substrate concentration is increased
42
Q

metabolic sequences and enzymes

A
  • product of one enzyme catalysed reaction is the substrate for the next enzyme catalysed reaction in the pathway
  • Prevent end product accumulating by end product binding non competitively to the active site of the first enzyme to stop the reaction
  • Conc of product falls causes the end product to detach from the first enzyme allowing metabolic pathway to run again
43
Q

Effect of changing substrate concentration

A
  • Increasing concentration increases rate of reaction as more enzyme substrate complexes can form
  • more product
  • Limiting factor
  • Enzymes work at maximum rate so adding more will not increase rate of reaction as all active sites are occupied so substrate cannot collide with an active site
44
Q

What 2 things in living cells does enzyme concentration /availability depend on

A
  • Enzyme synthesis~ genes switched on or off

- enzyme degradation

45
Q

Enzyme degradation

A
  • Degrading into component amino acids
  • Advantageous as it means abnormally shaped proteins which might accumulate and harm the cell are eliminated and metabolism is regulated by eliminating any superfluous enzymes
46
Q

Changing enzyme concentrations effect

A
  • Increasing mean more active sites are available
  • more enzyme substrate complexes
  • limiting factor
  • fixed substrate concentration means reaction gets to maximum rate and increasing enzyme concentration has no effect
47
Q

Initial rate of reaction

A
  • Fastest point
  • great chance of enzyme active site and substrate molecules colliding
  • substrate molecules get used up so concentration of substrate lowers so rate of reaction slows

BIOLOGY REVISION (21 decks)

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