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ESA1 > MGD 1- Proteins > Flashcards

MGD 1- Proteins Flashcards

1
Q

In what part of the cell does rRNA synthesis occur?

A

Nucleus / nucleolus

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2
Q

Why do mitochondria contain ‘cristae’?

A

To maximise the surface area of the inner mitochondrial membrane, for maximum ATP synthesis.

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3
Q

What are ribosomes made up of?

A

Proteins and rRNA molecules

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4
Q

What type of ribosomes do bacteria and archaea have?

A

70S = 30S + 50S

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5
Q

What type of ribosomes do eukaryotes have?

A

80S = 40S + 60S

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6
Q

Which organelle performs glycosylation of proteins and lipids?

A

Golgi

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7
Q

Which Golgi cisternae faces the rER?

A

Cis

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8
Q

Which Golgi cisternae faces the plasma membrane?

A

Trans

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9
Q

Why is glucose a ‘polar’, soluble molecule?

A

Contains -OH (hydroxyl) groups which can form bonds with water molecules

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10
Q

Why is palmitate a ‘non-polar’, insoluble molecule?

A

Does not contain any -OH (hydroxyl) groups, so cannot interact with water molecules

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11
Q

Which molecules are more soluble: polar or non-polar? Why?

A

Polar, as they contain -OH (hydroxyl) groups which can interact with water molecules

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12
Q

What is an amphipathic molecule?

A

A molecule with both polar and non-polar regions

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13
Q

Which protein isomer is found naturally?

A

L-isomer

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14
Q

Is a strongly acidic protein is likely to have a high pK or low pK value?

A

Low pK

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15
Q

What is physiological pH?

A

7.4

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16
Q

What is the ‘Isoelectric point’ of a protein?

A

The pH at which there is no net charge on the protein.

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17
Q

Do acidic or basic amino acids become positively charged?

A

Basic amino acids become positively charged

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18
Q

Do acidic or basic amino acids become negatively charged?

A

Acidic amino acids become negatively charged

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19
Q

Which protein terminal is synthesised first?

A

N-terminal

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20
Q

What are the 2 secondary structures of a protein?

A

1- alpha helix

2- beta sheet

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21
Q

How many amino acids are required for 1 turn of an alpha helix?

A

3.6 AA

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22
Q

What is the height (nm) of 1 turn of an alpha helix?

A

0.54 nm

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23
Q

Which 2 amino acids are ‘alpha helix breakers’?

A

Proline and Glycine

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24
Q

What is the distance (nm) between amino acid residues in a beta-sheet?

A

0.35 nm

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25
Q

What are the 4 main ways to denature a protein?

A

1- Heat
2- pH
3- Detergent
4- Reducing agent

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26
Q

How does heat often denature proteins?

A

Heat increases the kinetic energy of the molecules, breaking weak hydrogen and ionic bonds, unfolding the protein.

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27
Q

How does a change in pH often denature proteins?

A

This will alter the ionisation states of the amino acids, breaking ionic and hydrogen bonds, unfolding the protein

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28
Q

How do detergents denature proteins?

A

They disrupt the hydrophobic interactions within a protein

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29
Q

Give an example of a reducing agent:

A

Beta-mercaptoethanol

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30
Q

How do reducing agents denature proteins?

A

They break covalent disulphide bonds

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31
Q

What is a ‘transmissable spongiform encephalopathy’?

A

A prion disease which affects the brain and nervous system

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32
Q

Give 3 examples of transmissable spongiform encephalopathies:

A

1- Bovine spongiform encephalopathy (BSE)
2- Creutzfeld-Jakob Disease (CJD)
3- Kuru

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33
Q

Define amyloid fibrils:

A

Misfolded insoluble form of a normally soluble protein, which aggregates and is resistant to degradation.

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34
Q

What type of protein assists the folding of other proteins?

A

Chaperone proteins

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35
Q

What is the small conformational change caused when oxygen binds to haem in haemoglobin?

A

The Fe atom is pulled into the plane of the porphyrin ring

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36
Q

How many haem groups are in haemoglobin?

A

4

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37
Q

How many haem groups are in myoglobin?

A

1

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38
Q

What is the function of myoglobin?

A

To store O2 in muscle

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39
Q

What is the shape of a Myoglobin O2-binding curve?

A

Hyperbolic

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40
Q

What is the shape of a Haemoglobin O2-binding curve?

A

Sigmoidal

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41
Q

Why does Haemoglobin have a sigmoidal O2-binding curve?

A

As it exhibits co-operative binding of O2 (Must change from low-affinty T state, to high-affinity R state)

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42
Q

What is the T state of Haemoglobin?

A

The tense state of Haemoglobin is deoxyhaemoglobin, when it has low affinity for oxygen.

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43
Q

What is the R state of Haemoglobin?

A

The relaxed state of Haemoglobin is oxyhaemoglobin, when it has high affinity for oxygen.

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44
Q

Name 3 molecules which affect O2 binding to Haemoglobin:

A

1- H+
2-CO2
3- 2,3-BPG

45
Q

What is the full name of 2,3-BPG?

A

2,3-Bisphosphoglycerate

46
Q

Why does 2,3-BPG promote O2 release from Haemoglobin?

A

2,3-BPG binds to Haemoglobin where O2 usually binds

47
Q

Why does the amount of 2,3-BPG present increase at higher altitudes?

A

To promote O2 release at tissues, as ppO2 drops exponentially with increased altitude.

48
Q

How does adult haemoglobin differ from foetal haemoglobin, in BPG binding?

A

Foetal haemoglobin binds 2,3-BPG much less tightly than adult haemoglobin, allowing O2 to be readily passed from adult maternal Hb to foetal Hb.

49
Q

What is meant by the Bohr effect?

A

An increase of H+ / CO2 causes a decrease in pH, which lowers the affinity of Hb for O2, promoting deoxyhaemoglobin.

50
Q

How does the Bohr effect alter the Haemoglobin O2-binding curve?

A

It causes it to shift to the right

51
Q

How does an increase in pH alter the Haemoglobin O2-binding curve?

A

It causes it to shift to the left

52
Q

How does an increase in temperature alter the Haemoglobin O2-binding curve?

A

It causes it to shift to the right

53
Q

How does a decreased pH alter the Haemoglobin O2-binding curve?

A

It causes it to shift to the right

54
Q

How is the Bohr effect related to metabolically active tissues?

A

Metabolically active tissues produce more CO2, which causes an increased [H+] in the area, which produces the Bohr effect, promoting the dissociation of O2 from haemoglobin.

55
Q

At what point is CO poisoning usually fatal?

A

When COHb > 50%

56
Q

Why is CO poisoning often fatal?

A

CO binds to Hb much more readily than O2, so prevents O2 transport.

57
Q

What and where does the mutation occur which causes Sickle Cell Anaemia?

A

A>T, Glu6>Val in beta Hb chain

58
Q

What happens to HbS when in deoxygenated T state?

A

Forms hydrophobic interactions with adjacent chains, creating sticky hydrophobic pockets. These polymerise, distorting the RBC into a ‘sickle’ shape.

59
Q

Why is anaemia a common symptom of Sickle cell disease?

A

The constant sickling and un-sickling of RBCs reduce their life-span, increasing haemolysis, reducing the number of RBC’s in circulation

60
Q

What is the inheritance pattern of Sickle Cell Anaemia?

A

Autosomal recessive

61
Q

Why hasn’t Sickle Cell Anaemia been eradicated by natural selection?

A

Provides resistance against Malaria.

62
Q

Why is the amino acid change caused by Sickle cell disease so important?

A

The amino acid change from Glu to Val changes the polarity of the protein, as Glu is negatively charged, whereas Val is non-polar.

63
Q

What is alpha thalassaemia?

A

Decreased or absent alpha globin chain production

64
Q

How many genes are involved in the production of the alpha haemoglobin chain?

A

4 genes

65
Q

How many genes are involved in the production of the beta haemoglobin chain?

A

2 genes

66
Q

How many genes must be affected to cause chronic anaemia due to alpha thalassaemia?

A

3 genes

67
Q

How many genes must be affected in alpha thalassaemia to cause a miscarriage/stillbirth?

A

4 genes

68
Q

Why does alpha thalassaemia cause miscarriage, but beta thalassaemia does not?

A

Foetus’ require alpha chains to form their haemoglobin, they do not require beta chains until after birth.

69
Q

If only 1 alpha globin gene is affected in alpha thalassaemia, what are the symptoms?

A

No / little effect, as 3 normal genes

70
Q

If both genes are affected by beta thalassaemia, what treatment is required?

A

Lifelong blood transfusions.

71
Q

At what age does beta thalassaemia present?

A

~ 6 months after birth

72
Q

Which chains make up foetal haemoglobin?

A

alpha and gamma chains

73
Q

Sickle cell disease reduces the life span of a RBC from 120 days to what?

A

20 days

74
Q

What are the 3 main ways to increase the rate of a reaction?

A

1- Increase amount of enzyme present
2- Increase the concentration of reactants present
3- Increase the temperature

75
Q

When plotting Rate vs [Substrate], what kind of curve do MOST enzymes give?

A

Hyperbolic

76
Q

What is Km?

A

The substrate concentration at half the maximum rate of reaction.

77
Q

What is Vmax?

A

The maximum rate of reaction, when all enzyme active sites are saturated with substrate.

78
Q

Describe the affinity of an enzyme for its substrate if it has a high Km:

A

Low affinity - requires a higher substrate concentration to reach Vmax

79
Q

Describe the affinity of an enzyme for its substrate if it has a low Km:

A

High affinity - requires ow substrate concentration to reach Vmax.

80
Q

Name the 2 enzymes which can phosphorylate Glucose into Glucose 6-phosphate:

A

1- Hexokinase

2- Glucokinase

81
Q

Which enzyme is necessary for the 1st step in glycolysis, present in most tissues in the body?

A

Hexokinase

82
Q

Which enzyme is necessary for the 1st step of glycolysis to occur in the Liver?

A

Glucokinase

83
Q

Which has higher affinity for glucose: Hexokinase or Glucokinase?

A

Hexokinase

84
Q

What initiates the activity of Glucokinase (in the Liver)?

A

Feeding, causing an increase in blood glucose levels.

85
Q

What kind of curve is produced by the Lineweaver-Burk plot?

A

Linear line

86
Q

What value is given at the point where a Lineweaver-Burk plot crosses the x-axis?

A

-1/Km

87
Q

What value is given at the point where a Lineweaver-Burk plot crosses the y-axis?

A

1/Vmax

88
Q

What are the 2 types of reversible enzyme inhibitors?

A

1- Competitive

2- Non-competitive

89
Q

How does a competitive inhibitor affect the Km and Vmax of an enzyme?

A

Km increases

Vmax unaffected

90
Q

How does a non-competitive inhibitor affect the Km and Vmax of an enzyme?

A

Km unaffected

Vmax decreases

91
Q

What are the 4 short-term ways to regulate an enzymes activity?

A

1- Change substrate/product concentration
2- Allosteric regulation
3- Covalent modification
4- Proteolytic activation

92
Q

What is allosteric regulation?

A

The binding of an activator/inhibitor not at the active site, to stabilise either the T or the R state, affecting the enzymes conformation. They exhibit positive co-operativity, as multiple subunits can be allosterically regulated, producing a sigmoidal curve.

93
Q

Phosphofructokinase can be allosterically regulated. Name an activator and an inhibitor found in the human body:

A

Activator: AMP, F-2,6-B
Inhibitor: ATP, Citrate, H+

94
Q

Does phosphorylation activate or inhibit glycogen breakdown?

A

Activate

95
Q

What is a kinase?

A

An enzyme which adds a phosphate group

96
Q

What is a phosphatase?

A

An enzyme which removes a phosphate group

97
Q

Define zymogen:

A

Inactive enzyme precursor

98
Q

What are the 2 long-term ways to regulate an enzymes activity?

A

1- Change rate of protein production

2- Change rate of protein degradation

99
Q

What is meant by ‘enzyme cascade’?

A

Succession of activation reactions following an initial stimulus

100
Q

Damage to endothelial blood vessel walls causes them to release…?

A
  • ADP
  • Endothelins
  • Factor III
101
Q

What is the role of endothelins in the clotting cascade?

A

Stimulate vasoconstriction and cell division

102
Q

What is the role of Factor III in the clotting cascade?

A

Involved in the production of Thrombin from Prothrombin

103
Q

What is the role of Thrombin in the clotting cascade?

A
  • Cleave Fibrinogen into Fibrin

- Activate co-factors

104
Q

Why is Ca2+ necessary for clot formation?

A
  • Required to allow Factor with Gla domains to interact with damaged site
  • Attracts -vely charged clotting factors out of the blood
105
Q

What 3 processes cause termination of clotting?

A

1- Digestion of clotting factors by proteases
2- Dilution of clotting factors y blood flow and removal by Liver
3- Specific inhibitors

106
Q

What is required to breakdown the fibrin clot?

A

Plasmin

107
Q

What is the zymogen of Plasmin?

A

Plasminogen

108
Q

Defective Factor VIII causes which type of Haemophilia?

A

Haemophilia A

ESA1 (22 decks)

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