Protein Function and Enzymes Flashcards Preview

MGD > Protein Function and Enzymes > Flashcards

Flashcards in Protein Function and Enzymes Deck (52):
0

Which two complexes transport oxygen in the body?

Haemoglobin and myoglobin

1

What type of curve does oxygen binding to myoglobin show?

Hyperbolic

2

Describe the features of haemoglobin structure

2 polypeptide chains - 2 alpha and 2 beta
Each chain contains a haem prosthetic group

3

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

A sigmoidal curve

4

What gives haemoglobin its shape of binding curve?

It can move between the T state and the R state

5

What does the binding of oxygen in haemoglobin promote?

The R state

6

What is meant by 'cooperative binding' of haemoglobin?

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

7

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

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

8

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

Decrease its affinity - the Bohr effect

9

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

It has a higher affinity

10

What is the mutation in sickle cell anaemia?

Glutamate (negative hydrophilic) to valine (neutral hydrophobic)

11

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

Increases. This promotes oxygen release at tissues from haemoglobin

12

What type of inheritance is sickle cell anaemia?

Autosomal recessive

13

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

A sticky hydrophobic pocket forms allowin deoxygenated haemoglobin to polymerise.

14

Why are sickle cells bad?

More prone to lysis and leading to anaemia
More rigid so block microvasculature

15

What are thalassaemias?

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

16

What is beta-thalassaemia?

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

17

When do symptoms occur in beta-thalassaemia?

After birth

18

When do symptoms occur in alpha-thalassaemia?

Before birth

19

What is alpha-thalassaemia?

Decreased/absent alpha-chain production.

20

What is the activation enthalpy?

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

21

What is the transition state?

The high energy intermediate between substrate and product

22

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

Increases the number of molecules with the activation enthalpy.

23

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

Increases the chance of molecular collisions

24

What is an enzyme?

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

25

What does Vmax mean?

Maximal rate when all active sites are saturated with substrate

26

What is Km?

The substrate concentration that gives half of the maximal velocity

27

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

High affinity

28

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

-1/Km

29

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

Km/Vmax

30

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

1/Vmax

31

What is an enzyme inhibitor?

Molecules that slow down or prevent an enzyme reaction

32

What type of bonds do irreversible inhibitors form?

Covalent bonds

33

Do competitive inhibitors affect Vmax or Km?

Km

34

Do non-competitive inhibitors affect Vmax or Km?

Vmax

35

What is product inhibition?

The build of a product inhibits an enzyme reaction

36

What is an allosteric enzyme?

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

37

What do allosteric activators do?

Increase the proportion of enzymes in the R state

38

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

To the right

39

Name two allosteric activators

AMP
Fructose-2,6-bis phosphate

40

Name two allosteric inhibitors

ATP, citrate, H+

41

What type of enzyme is phosphorylation catalysed by?

A kinase

42

What is phosphorylation?

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

43

What is a zymogen?

The inactive precursor of a proteolytic enzyme

44

Give examples of enzymes which have zymogens

Digestive enzymes eg pepsin, chymotrypsin, trypsin
Some protein hormones eg insulin

45

What activates the intrinsic pathway for the clotting cascade?

Membrane damage

46

What is a zymogen?

An inactive precursor of an enzyme

47

What initiates the intrinsic pathway of the clotting cascade?

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

48

What initiates the extrinsic pathway

Trauma to tissue. This releases factor 3.

49

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

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

50

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

Hexokinase in glycolysis.
Inhibited when glucose 6-P concentration increases.

51

Give two examples of zymogens and their active enzymes

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