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MODULE 2 - Natural Defences > BIOCHEMISTRY - Blood and Proteins > Flashcards

BIOCHEMISTRY - Blood and Proteins Flashcards

1
Q

What are the two main functions of albumin?

A

Non-specific transporter
Maintains oncotic pressure

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2
Q

What is the role of transferrin?

A

Binds to and transports Fe3+ in the blood

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3
Q

What is the role of ceruloplasmin?

A

Binds to and transports Cu2+ in the blood

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4
Q

What is the difference between plasma and serum?

A

Plasma is in vivo (in the body)
Serum is in vitro (in a test tube left to clot)

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5
Q

Which three lipids make up the erythrocyte membrane?

A

Phospholipids
Sphingolipids
Cholesterol

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6
Q

List the peripheral proteins of the erythrocyte membrane

A

Spectrin
Ankryn
Actin
Protein 4.1

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7
Q

What is the function of the erythrocyte peripheral membrane proteins?

A

Provide strength and structure

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8
Q

What can occur when there is a defect in protein 4.1?

A

Elliptical erythrocytes that a more susceptible to lysis

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9
Q

List the integral membrane proteins of the erythrocyte membrane

A

Glycophorin A
GLUT 1
Sodium potassium ATPase pump
Anion exchanger

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10
Q

What are the function of Glycophorin A ?

A
  • Prevents aggregation of the erythrocytes to one another and to the blood vessel walls
  • Determines blood types
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11
Q

What property in Glycophorin A determines blood types?

A

Carbohydrate bound to the glycophorin A protein

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12
Q

What is the function of GLUT 1?

A

Brings glucose into the cell for glycolysis and the pentose phosphate pathway

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13
Q

What is the function of the anion exchanger?

A

Exchanges bicarbonate produced from dissociation of carbonic acid with chloride to maintain the pH

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14
Q

What type of metabolism occurs in erythrocytes?

A

Anaerobic (no mitochondria)

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15
Q

How is ATP generated in erythrocytes?

A

Glycolysis

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16
Q

How does glycolysis differ in erythrocytes?

A

2,3 BiPglycerate forms which is a negative allosteric effector of haemoglobin/O2 affinity, allowing for more O2 to reach the tissues

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17
Q

How is NADPH produced in erythrocytes?

A

Pentose phosphate pathway

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18
Q

Why is NADPH important in erythrocytes?

A

NADPH maintains glutathione in its reduced state

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19
Q

What is methaemoglobin?

A

Oxidised haemoglobin

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20
Q

What are the three consequences of methaemoglobin formation?

A

Doesn’t bind to/transport O2
Heinz body formation
Cell death

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21
Q

What is the function of glutathione in erythrocytes?

A

Glutathione is readily oxidised to prevent the oxidation of the iron found in haemoglobin, preventing the formation of methaemoglobin

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22
Q

Which substances ensure the regeneration of glutathione in erythrocytes?

A

NADPH
Glutathione reductase enzyme

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23
Q

List the clinical signs of methaemoglobinaemia

A

Cyanosis (purple mucous membranes) due to lack of O2
Exercise intolerance
Vomiting
Chocolate brown blood
Anaemia (occasionally)

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24
Q

What is the function of proximal histidine in regards to haem?

A

Proximal histidine anchors the Fe2+ in place

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25
Q

What is the function of distal histidine in regards to haem?

A

Distal histidine protects the O2 binding site through preventing oxidation of the Fe2+ and preventing carbon monoxide poisoning by lowering haem affinity for carbon monoxide

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26
Q

Describe myoglobin structure

A

Myoglobin has one polypeptide chain, one haem group and one O2 binding site

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27
Q

Describe haemoglobin structure

A

Haemoglobin is an allosteric enzyme with four polypeptide chains, four haem groups and four O2 binding sites

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28
Q

What is the function of myoglobin?

A

O2 storage in the tissues

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29
Q

What is the function of haemoglobin?

A

Transport of O2 to the tissues

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30
Q

Why do the functions of myoglobin and haemoglobin differ?

A

Myoglobin isn’t allosteric so has a much higher O2 affinity than haemoglobin so does not release O2 under normal physiological conditions and thus is more useful for O2 storage rather than transport

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31
Q

What are the differences between the structure of adult haemoglobin and foetal haemoglobin?

A

Adult haemoglobin is made up of 2 alpha and 2 beta chains whereas foetal haemoglobin is made up of 2 alpha and 2 gamma chains (has a higher O2 affinity)

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32
Q

How is oxygen transferred in the maternal/foetal circulation?

A

Adult haemoglobin has less O2 affinity compared to foetal haemoglobin, so more O2 is released from the adult haemoglobin and bound to the higher affinity foetal haemoglobin

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33
Q

List the negative allosteric effectors of haemoglobin/O2 affinity

A

CO2
H+
2,3 BiPglycerate (2,3-BPG)

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34
Q

What is the function of the negative allosteric effectors of haemoglobin/O2 affinity?

A

Negative allosteric effectors bind to the haemoglobin, lowering the haemoglobin affinity for O2, increasing the O2 release into the tissues

moves the oxygen dissociation curve to the right

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35
Q

Where does 2,3 BiPglycerate bind to the haemoglobin?

A

The 2,3-BPG binds to the central compartment of haemoglobin

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36
Q

What are the three places where haem is synthesised?

A

Liver
Erythroblasts
Reticulocytes

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37
Q

What is congenital erythropoietic porphyria?

A

Defect in the formation of the pyrrole structure of haem causing severe skin photosensitivity

38
Q

In which species is congenital erythropoietic porphyria seen most often?

A

Holstein Friesian calves

39
Q

What determines amino acid properties?

A

R-groups

40
Q

List the different R-groups

A

Hydrophobic (methyl group)
Aromatic hydrophobic (benzene group)
Hydrophilic

41
Q

Which amino acid is always the first amino acid found in a protein sequence?

A

Methionine

42
Q

Why is methionine always the first amino acid found in protein sequences?

A

Due to the ATG start codon

43
Q

Which amino acid is very commonly involved in disulphide bonding and why?

A

Cysteine has an SH group on its R-group so is often involved in di-sulphide bonding

44
Q

Which amino acids are commonly used in protein assays and why?

A

Aromatic hydrophobic amino acids (tryptophan, tyrosine, phenylalanine) have a benzene ring within their R-group so have to ability to absorb UV light at 280nm - useful for protein assays

45
Q

Which amino acids have an OH at the end of their R-group?

A

Serine
Threonine

46
Q

Which post-translational modification can involve serine and threonine?

A

O-linked glycosilation to produce glycoproteins

47
Q

Which amino acid has an NH2 at the end of it’s R-group?

A

Asparagine

48
Q

Which amino acid has a ring structure which forces bends within protein structures?

A

Proline

49
Q

How can proteins be measured?

A

Proteins can be measured with mean molecular mass
1 amino acid = 100 daltons

50
Q

What is primary protein structure?

A

The amino acid sequence joined by peptide bonds

51
Q

What is secondary protein structure?

A

Amino acids folded in alpha helices or beta sheets through hydrogen bonding

52
Q

What is tertiary protein structure?

A

The overall folding of a protein through R-group interactions. When in tertiary structure the protein will be biologically active

53
Q

What is quaternary protein structure?

A

Protein complexes consisting of 2 or more polypeptide subunits

54
Q

What is protein denaturation?

A

Denaturation is the disruption of R-group interactions and hydrogens bond, causing proteins to unfold

55
Q

List four different factors which can cause proteins to denature

A

Heat
pH
Detergents and organic solvents
Chaotropic agents

56
Q

What are chaotropic agents?

A

Ions or small molecules which form hydrogens bonds with proteins, disrupting the existing hydrogen bonds, causing the protein to unfold

57
Q

List two methods that can be used for predicting protein structure

A

Molecular modelling
X-ray crystallography

58
Q

Why is the primary structure of proteins so important?

A

If the primary structure of a protein is maintained, then proteins that are denatured can still be refolded

59
Q

Which proteins are essential for protein refolding?

A

Chaperone proteins

60
Q

What can cause a change in the primary protein structure?

A

Genetic mutations

61
Q

List the two classifications of substitution mutations

A

Conservative substitutions
Radical substitutions

62
Q

Describe the effects of conservative substitution mutations

A

Conservative substitutions are when the same type of amino acid is substituted which has very little/no effect

63
Q

Describe the effects of radical substitution mutations

A

Radical substitutions are when a different type of amino acid is substituted which can alter ligand binding and enzyme activity

64
Q

Describe the effects of insertion and deletion mutations

A

Insertion and deletion mutations are the gain or loss of an amino acid which can alter protein function, have no effect if a non-essential amino acid is removed, cause new protein function

65
Q

What is the structure of collagen?

A

Collagen triple helix

66
Q

Which amino acid occupies every third position in the collagen triple helix? Why is this?

A

Glyceine is the only amino acid small enough to fit into the interior of the collagen triple helix

67
Q

List all three amino acids found in the collagen triple helix structure

A

Glyceine
Prolene
Hydroxyprolene

68
Q

What stabilises the collagen triple helix?

A

Hydrogen bonds between the hydroxyprolene amino acids

69
Q

List two examples of diseases caused by defects in the collagen structure

A

Scurvy
Osteogenesis imperfecta (brittle bone disease)

70
Q

Describe the cause of scurvy

A

Scurvy is caused by a vitamin C deficiency as vitamin C is a co-enzyme for the enzyme prolyhydroxylase which catalyses the conversion of prolene to hydroxyprolene. Insufficient hydroxyprolene leads to insufficient hydrogen bonds causing the collage triple helix to become unstable

71
Q

Describe the cause of osteogenesis imperfecta (brittle bone disease)

A

A mutation in the glyceine codon

72
Q

What are prion proteins?

A

Globular proteins found mainly in the brain and the spinal cord (central nervous system)

73
Q

What are prion diseases?

A

Diseases that arise due to the globular form of prion proteins converting to the fibrous form (scrapie form)

74
Q

How does the fibrous (scrapie) form of prion proteins cause disease?

A

The fibrous (scrapie) prion proteins aggregate within cells, causing tissue damage mainly within the central nervous system (brain and spinal cord) leading to interference in brain transmission

75
Q

Give two examples of prion protein diseases

A

Scrapies
Bovine spongiform encephalitis (mad cow disease)

76
Q

What are the main functions of enzymes?

A

Catalyse biological functions
Decreases activation energy
Stabilise the transition state

77
Q

How do enzymes speed up the rate of biological reactions?

A

Enzymes form an intermediate complex (enzyme-substrate complex) which lowers the activation energy and stabilises the transition state through bringing substrates close together in the correct orientation to interact

78
Q

What can alter enzyme activity?

A

pH
Temperature

79
Q

What are co-enzymes?

A

Organic molecules derived from vitamin ingestion which bind to enzyme active sites to assist in the catalysis of the reaction

80
Q

What are enzyme co-factors?

A

Usually metal ions which stabilise the substrate binding to the enzyme active site

81
Q

What shape is a enzyme reaction when plotted on a graph?

A

Hyperbolic curve

82
Q

What is the maximum velocity (Vmax) of an enzyme catalysed reaction?

A

Vmax is the point during an enzyme catalysed reaction where the enzyme is fully saturated with substrate so there can no longer be any increase in the rate of reaction

83
Q

What is Km?

A

Km is the substrate concentration required to reach half the maximum velocity (Vmax)

84
Q

What does a low Km value indicate?

A

Low Km indicates that there is a high substrate-enzyme affinity as a low substrate concentration is required for a reaction to reach Vmax

85
Q

What does a high Km value indicate?

A

High Km indicates that there is a low substrate-enzyme affinity as a high substrate concentration is requires for a reaction to reach Vmax

86
Q

What is the Line Weaver-Bulk plot?

A

The Line Weaver-Burk plot is the double reciprocal graph of the Michaelis-Menten equation
- i.e. the linear form of the hyperbolic curve

87
Q

What are reversible enzyme inhibitors?

A

Competitive or non-competitive inhibitors which bind to enzymes and rapidly dissociate

88
Q

What are irreversible enzyme inhibitors?

A

Inhibitors which bind to enzymes and have such a slow dissociation time that these inhibitors are described as irreversible

89
Q

What is the difference between competitive and non-competitive reversible enzyme inhibitors?

A
  • Competitive inhibitors bind to the active site of the enzyme and the effects of competitive inhibitors can be reversed by increasing substrate concentrations
  • Non-competitive inhibitors don’t bind to the enzyme active site and instead change the shape of the enzyme protein
    • non-competitive inhibitors prevent reactions from reaching Vmax
90
Q

What shape is an allosteric enzyme reaction when plotted on a graph?

A

Sigmoid curve

MODULE 2 - Natural Defences (10 decks)

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