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MGD > Protein Function and Enzymes > Flashcards

Protein Function and Enzymes Flashcards

0
Q

What type of curve does oxygen binding to myoglobin show?

A

Hyperbolic

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1
Q

Which two complexes transport oxygen in the body?

A

Haemoglobin and myoglobin

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2
Q

Describe the features of haemoglobin structure

A

2 polypeptide chains - 2 alpha and 2 beta

Each chain contains a haem prosthetic group

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3
Q

What type of curve does haemoglobin show on binding to oxygen?

A

A sigmoidal curve

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4
Q

What gives haemoglobin its shape of binding curve?

A

It can move between the T state and the R state

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5
Q

What does the binding of oxygen in haemoglobin promote?

A

The R state

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6
Q

What is meant by ‘cooperative binding’ of haemoglobin?

A

The binding of one oxygen molecule promotes the binding of subsequent oxygen molecules

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7
Q

What effect does 2,3-BPG have on the affinity of haemoglobin for oxygen?

A

2,3-BPG decreases its affinity by stabilising the T state

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8
Q

How do H+ and carbon dioxide affect haemoglobin’s affinity for oxygen?

A

Decrease its affinity - the Bohr effect

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9
Q

How does foetal haemoglobin differ to the mother’s haemoglobin (affinity)

A

It has a higher affinity

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10
Q

What is the mutation in sickle cell anaemia?

A

Glutamate (negative hydrophilic) to valine (neutral hydrophobic)

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11
Q

What happens to BPG concentrations at high altitudes and what effect does this have?

A

Increases. This promotes oxygen release at tissues from haemoglobin

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12
Q

What type of inheritance is sickle cell anaemia?

A

Autosomal recessive

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13
Q

In sickle cell anaemia, what is the result of the mutation?

A

A sticky hydrophobic pocket forms allowin deoxygenated haemoglobin to polymerise.

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14
Q

Why are sickle cells bad?

A

More prone to lysis and leading to anaemia

More rigid so block microvasculature

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15
Q

What are thalassaemias?

A

A group of genetic disorders where there is an imbalance in the alpha and beta sub-units in haemoglobin.

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16
Q

What is beta-thalassaemia?

A

Decreased/absent beta chain production so alpha chains are unstable to form tetramers

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17
Q

When do symptoms occur in beta-thalassaemia?

A

After birth

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18
Q

When do symptoms occur in alpha-thalassaemia?

A

Before birth

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19
Q

What is alpha-thalassaemia?

A

Decreased/absent alpha-chain production.

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20
Q

What is the activation enthalpy?

A

The minimum energy a substrate must have for the reaction to occur

21
Q

What is the transition state?

A

The high energy intermediate between substrate and product

22
Q

How does increasing the temperature increase the rate of an enzyme reaction?

A

Increases the number of molecules with the activation enthalpy.

23
Q

How does increasing the concentration increase the rate of an enzyme reaction?

A

Increases the chance of molecular collisions

24
Q

What is an enzyme?

A

A biological catalyst that increases the rate of a reaction by lowering the activation enthalpy

25
Q

What does Vmax mean?

A

Maximal rate when all active sites are saturated with substrate

26
Q

What is Km?

A

The substrate concentration that gives half of the maximal velocity

27
Q

Does a low Km mean an enzyme has a high or low affinity for its substrate?

A

High affinity

28
Q

In a Lineweaver-Burk plot, what does the intercept at the x-axis mean?

A

-1/Km

29
Q

In a Lineweaver-Burk plot, what does the gradient of a line mean?

A

Km/Vmax

30
Q

In a Lineweaver-Burk plot, what does the intercept at the y axis mean?

A

1/Vmax

31
Q

What is an enzyme inhibitor?

A

Molecules that slow down or prevent an enzyme reaction

32
Q

What type of bonds do irreversible inhibitors form?

A

Covalent bonds

33
Q

Do competitive inhibitors affect Vmax or Km?

A

Km

34
Q

Do non-competitive inhibitors affect Vmax or Km?

A

Vmax

35
Q

What is product inhibition?

A

The build of a product inhibits an enzyme reaction

36
Q

What is an allosteric enzyme?

A

A multi-subunit enzyme with more than one active site for the substrate

37
Q

What do allosteric activators do?

A

Increase the proportion of enzymes in the R state

38
Q

Which way do allosteric inhibitors shift the sigmoid curve for the rate of an enzyme reaction?

A

To the right

39
Q

Name two allosteric activators

A

AMP

Fructose-2,6-bis phosphate

40
Q

Name two allosteric inhibitors

A

ATP, citrate, H+

41
Q

What type of enzyme is phosphorylation catalysed by?

A

A kinase

42
Q

What is phosphorylation?

A

The addition of a phosphate group to an -OH group on an amino acid

43
Q

What is a zymogen?

A

The inactive precursor of a proteolytic enzyme

44
Q

Give examples of enzymes which have zymogens

A

Digestive enzymes eg pepsin, chymotrypsin, trypsin

Some protein hormones eg insulin

45
Q

What activates the intrinsic pathway for the clotting cascade?

A

Membrane damage

46
Q

What is a zymogen?

A

An inactive precursor of an enzyme

47
Q

What initiates the intrinsic pathway of the clotting cascade?

A

Damage to endothelial lining of blood cells. This releases factor 12.

48
Q

What initiates the extrinsic pathway

A

Trauma to tissue. This releases factor 3.

49
Q

Give an example of an enzyme which is controlled allosterically and name it’s inhibitors and activators.

A

Phosphofructokinase
Activators: AMP, fructose 2,6-bisphosphate
Inhibitors: ATP, citrate, H+

50
Q

Give an example of an enzyme inhibited by substrate/product concentration

A

Hexokinase in glycolysis.

Inhibited when glucose 6-P concentration increases.

51
Q

Give two examples of zymogens and their active enzymes

A

Trypsinogen ➡️ trypsin
Pepsinogen ➡️ pepsin
Prothrombin ➡️ thrombin
Fibrinogen ➡️ fibrin

MGD (10 decks)

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