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Biology a level - ocr a > Chapter 4 - Enzymes > Flashcards

Chapter 4 - Enzymes Flashcards

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1
Q

What are enzymes?

A

Biological catalysts that interact with substrate molecules to facilitate chemical reactions, without being used up

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2
Q

What are anabolic reactions?

A

Chemical reactions required for growth (building up) -catalysed by enzymes - energy is required

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3
Q

What are catabolic reactions?

A

Chemical reactions that involve the breaking down of large organic molecules - this process releases energy

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4
Q

Metabolism

A

The sum of all the different reactions and reaction pathways happening in a cell or an organism

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5
Q

What is Vmax?

A

Is the maximum initial velocity or rate at which the enzyme catalysed a reaction

Happens when all active sites are saturated by substrates

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6
Q

What is the specificity of an enzyme ?

A

The ability of an enzyme to bind with a specific substrate or catalyse a specific set of chemical reactions

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7
Q

Activation energy

A

The minimum amount of energy required to start a reaction

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8
Q

The two enzyme hypothesis :

A

The lock and key hypothesis

Induced fit hypothesis

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9
Q

Lock and key hypothesis

A
  • an area within the tertiary structure of the enzyme has a complementary shape to the substrate which is called the active site
  • the enzyme and substrate bind to form an enzyme-substrate complex
  • the substrate is held so that the right atom groups are close enough to react
  • r groups in the active site interact with the substrate forming temporary bonds
  • these put strain on the bonds within the substrate - helps réaction along
  • enzyme-product complex is formed
  • products released
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10
Q

Induced fit hypothesis

A
  • active site slightly changes shape as substrate enters it
  • initial reaction between the enzyme and substrate is weak, however these interactions cause changes in the enzymes tertiary structure that strengthen binding , putting strain on the substrates molecule
  • this can weaken bonds in the substrate - lowering the activation energy
  • forms enzyme-product complex
  • products leave the active site
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11
Q

What are intracellulaire enzymes?

A

Enzymes that act within cells

E.g catalase - breaks down hydrogen peroxide which is a toxic product of many metabolic pathways

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12
Q

What are extracellular enzymes ?

A

Enzymes that work outside the cell that made them

  • enzymes are released to break down polymer nutrients into smaller molecules in the process of digestion, so they can become able to pass through the cell surface membrane (can be absorbed in bloodstream) to provide cells with components necessary for survival and growth

Amylase , trypsin

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13
Q

Why is amylase and maltase needed to digest starch

A
  • Amylase partially breaks down starch polymers into maltose
    Amylase is produced by salivary glands and pancreas - released as salivai and pancreatic juice (in small intestine)
  • maltase is then used to break down maltose into glucose
  • maltase is present in the small intestine
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14
Q

What is protease

A

Type of enzyme that catalysés the digestion of proteins into smaller peptides, further broken down into amino acids

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15
Q

The digestion of protein

A
  • trypsin is produces in the pancreas and released with pancreatic into small intestine juice
  • it acts on proteins , breaking it down
  • amino acids are absorbed by cells lining the digestive system
  • then absorbed into bloodstream
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16
Q

Temperature affecting the enzyme rate of reaction

A 
- increase temperature 
= more kinetic energy 
= more frequent collisions 
= more successful collisions 
- increase in rate of reaction
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17
Q

Température coefficient q10

A

Measure of how much the ror increases with a 10C rise in temperature

Is usually 2

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18
Q

Dénaturation from temperature

A
  • bonds holding the protein together vibrate
  • vibrations increase until the bonds strain and then break
  • results in a change in the tertiary structure
  • changes shape of active site - no longer function as a catalyst
  • no longer complementary
  • denatured
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19
Q

Optimum temperature

A

Temperature at which enzymes has the highest rate of activity

40c in human body

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20
Q

Temperature extremes

Cold environments
Thermophiles

A

Cold

  • enzymes have more flexible structures
  • less stable
  • smaller temperature changes will denature

Thermophiles
- more stable
because of hydrogen bonds and sulphur bridges in tertiary structure
- more resistance to change as the temperature rises

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21
Q

How does ph affect enzymes

A
  • hydrogen ions interact with polar and charged rgroups, changing ph changes this interaction.
  • affects hydrogen and ionic bonds causing bonds to break and the shape of the enzyme to change
  • alters active site
  • RENATURATION = ph returns to optimum and resumes its normal shape
  • DENATURED = ph changes significantly
22
Q

Substrate and enzyme concentration

A

When substrate / enzyme concentration is increased

  • higher collision rate with active site
  • formation of more enzyme-substrate complexes
  • reaction increases until Vmax
  • at this point all of the active sites are occupied by substrate particles
  • no more enzyme-substrate particles can be formed until products are release from active site

The concentration of … becomes the limiting factor

23
Q

Denatured

A

R group interactions are interrupted

Change in tertiary structure

Change in 3D shape of active site

No longer complementary

24
Q

What are inhibitors

A

Molecules that prevent enzymes from carrying out their function of catalysis - slow them down

25
Q

Competitive inhibition

A
  • molecule with a similar shape to the substrate fits into the active site
  • this prevents the enzyme from binding to a substrate and forming an enzyme substrate complex
  • the enzyme can not carry out its function
  • molecule and substrate will compete to bind to the active site , and catalyse the reaction
  • reduces the number of enzyme substrate complexes at any given time, therefore slows down the rate of reaction
26
Q

Effects on rate of reaction - competitive inhibitors

A

Reduces the rate of reaction

Does not change the Vmax

27
Q

Examples of competitive inhibitors

A

Statins
Used to help people reduce blood cholesterol concentration

Aspirin
Irreversibly inhibits the active site of COX, preventing the synthesis of chemicals responsible for pain and fever

28
Q

Non competitive inhibitors

A
  • the inhibitor binds to the enzyme at the ALLOSTERIC site
  • the binding causes a change in the tertiary structure of the enzyme , causing active site to change
  • active site is no longer complementary
  • can’t carry out its function
29
Q

Effect of rates or reaction - non competitive

A

Increasing enzyme concentration will not overcome the effect

Adding more inhibitor will further decreases the active sites

30
Q

WHAt is End product inhibition

A

final Product of the metabolic pathway acts as the inhibitor to an enzyme that acts previously in the pathway - negative feedback

31
Q

Example of end product inhibition

A

In the breakdown of glucose, ATP regulates its own production.
This is because the two phosphate groups that results in initial breakdown of glucose is catalysed by the enzyme PFK, which is competitively inhibited by ATP

  • When ATP levels are high, more ATP binds to the PFK, preventing the addition of the second phosphate
  • Glucose is not broken down, and ATP is neither made

-ATP is used, PFK catalyses the addition of the second phosphate leading to more production of ATP

32
Q

What are cofactors

A

Non protein components necessary for the effective functioning of an enzyme , help transfer atoms and molecules between the reaction pathway and can form part of the active site to help bind together enzyme and substrate

33
Q

What is the role of cofactors

A

They work by helping the enzyme and substrate bind together

They don’t directly participate

34
Q

What is the role of coenzymes

A

They participate in the reaction and are changed by it

Carriers that move chemical groups between different enzymes

35
Q

what is a Prosthetic group

A

Prosthetic groups are cofactors that are tightly bound to and enzyme to form a permanent feature of the protein

36
Q

What is precursor activation used for

A

Enzymes are synthesised as inactive precursors to prevent them from causing damage to cells / whose actions need to be controlled and only activated under certain conditions - protease

To be activated they need to undergo a chemical change
Achieved by an additions of a cofactors

37
Q

Adding a cofactors to a precursor protein

A

Apoenzyme inactive + cofactors activator —> haloenzyme active

38
Q

Other ways precursor enzymes can be activated

A

A change in the tertiary structure brought about by the action of another enzyme, which breaks bonds

Change in conditions (ph and temperature)
E.g
Pepsinogen is released and activated in stomach by ph levels

39
Q

How do enzymes affect activation energy

A

Help molecules collide successfully

And reduce activation energy

40
Q

What are serial dilutions

And when are they useful

A

Repeated stepwise dilution of a solution

Even when solution is unknown
Gives relative concentrations

41
Q

How to make serial solutions

A

Add 1ml of stock solution to 9ml of distilled water

Take 1ml of that made solution and add 9ml of water

42
Q

Why do enzymes at low temperatures have flexible structures

A 
Low kinetic energy 
Enzymes move slower 
Less frequent collisions 
Collisions have less energy 
Flexible active sites needed to 
Increase the number of successful collisions
43
Q

How do drugs act as enzyme inhibitors

Penicillin

Drugs that stop hiv

A

Antibiotics
Inhibits enzyme that catalyses formation of protein in cell wall
- can’t regulate osmotic pressures
- bacteria bursts and dies

Antivirals
Inhibits enzyme that catalyses replication of viral DNA
- prevents virus from replicating

44
Q

How do metabolic poissons interfere with metabolic reactions

Cyanide
Arsenic
Malonate

A

Inhibits enzyme that catalyses respiration

Cells die

45
Q

What is the bonding in inhibitors that makes them non reversible

A

Covalent bonds

Can’t be removed easily

46
Q

What is the bonding in inhibitors that makes them reversible

A

Weaker hydrogen bonds or ionic bonds

Inhibitor can be removed

47
Q

What does end product inhibition do

A

Regulates the pathway

Controls the amount of product made

48
Q

What is a coenzyme

A

Organic cofactors

49
Q

Example of cofactor

A

Cl-

50
Q

Example of coenzyme

A

Vitamin

51
Q

Example of prosthetic group for carbonic anhydrase

A

Zn2+

Biology a level - ocr a (11 decks)

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