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MGD Flashcards

0
Q

Functions of cytoplasm

A

Metabolism of carbohydrates, amino acids and nucleotides

Fatty acid synthesis

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1
Q

Functions of Golgi body

A

Export of proteins

Detoxification reactions

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2
Q

Functions of lysosomes

A

Cellular digestion

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3
Q

Functions of mitochondria

A

ATP synthesis

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4
Q

Functions of endoplasmic reticulum

A

Export of proteins
Membrane synthesis
Lipid and steroid synthesis
Detoxification reactions

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5
Q

Functions of nucleus

A

DNA synthesis and repair

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6
Q

Functions of nucleolus

A

RNA processing and ribosome assembly

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7
Q

Functions of plasma membrane

A

Cell morphology and movement

Transport of ions and small molecules

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8
Q

Functions of ribosomes

A

Protein synthesis

free in cytoplasm or RER

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9
Q

Key differences between

prokaryotic and eukaryotic cells

A

Organism (E-PAF) (P-B)
Chromosomes (many vs one circular strand of DNA/RNA)
Ribosomes larger in E
Cytoskeleton in E vs flagella only in P
P- cell wall
E - nucleus, ER, lysosomes, Golgi complex, mitochondria, vacuoles (small/ none in animals)
OCCCRNELGMV

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10
Q

Name organisms with mammalian eukaryotic cells

A

Plants
Animals
Fungi

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11
Q

Name organisms with prokaryotic cells

A

Bacteria

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12
Q

Do eukaryotic cells have a cell wall?

A

No

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13
Q

Do eukaryotic cells have a nucleus?

A

Yes

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14
Q

Do eukaryotic cells have chromosomes?

A

Many (23 pairs in humans)

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15
Q

Do eukaryotic cells have an endoplasmic reticulum?

A

Yes

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16
Q

Do eukaryotic cells have ribosomes?

A

Yes (large)

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17
Q

Do eukaryotic cells have lysosome?

A

Yes

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18
Q

Do eukaryotic cells have a Golgi complex?

A

Yes

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19
Q

Do eukaryotic cells have vacuoles?

A

Ys (small/ none in animals)

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20
Q

Do eukaryotic cells have mitochondria?

A

Yes

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21
Q

Do eukaryotic cells have a cytoskeleton ?

A

Yes

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22
Q

Do prokaryotic cells have a cell wall?

A

Yes

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23
Q

Do prokaryotic cells have a nucleus?

A

No

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24
Q

Do prokaryotic cells have chromosomes?

A

One circular strand of DNA/RNA

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25
Q

Do prokaryotic cells have an endoplasmic reticulum?

A

No

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26
Q

Do prokaryotic cells have ribosomes?

A

No

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27
Q

Do prokaryotic cells have lysosomes?

A

No

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28
Q

Do prokaryotic cells have a Golgi complex?

A

No

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29
Q

Do prokaryotic cells have vacuoles?

A

No

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30
Q

Do prokaryotic cells have mitochondria?

A

No

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31
Q

Do prokaryotic cells have a cytoskeleton?

A

Flagella only

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32
Q

Describe macromolecular structure

A

Monomeric units

Joined by covalent bonds

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33
Q

Describe macromolecular interaction

A

Non-covalent interactions

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34
Q

Types of non-covalent (weak) interactions in macromolecules

A

Hydrogen bonds
Ionic interactions
Hydrophobic interactions
Van der waals interactions

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35
Q

What are ionic interactions ?

A

Can be attraction or repulsion of charged ions

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36
Q

What are hydrophobic interactions?

What is a hydrophobic molecule?

A

Non polar molecules
Unable to interact with water
E.g. Lipids
Storage without water and can pass through bilayer

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37
Q

What are van der waals interactions ?

A

Any two atoms in close proximity

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38
Q

What are hydrophilic molecules?

A

Polar molecule
Interact with water
Reduces storage ability (e.g. Glycogen)
Cannot pass through bilayer unassisted

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39
Q

What is pH?

A

Measurement of conc of H+ ions in a sol
Strong acids and bases completely dissociate in sol
Weak acids and bases barely dissociate

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40
Q

What is pK?

A

Stronger the tendency of an acid to dissociate

the lower the pKa value

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41
Q

What are buffers?

A

Weak acid + conjugate base

Resist changes in pH

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42
Q

If pH> pK

A

Deprotonated form dominates

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43
Q

If pH<pK

A

Protonated form dominates

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44
Q

If pH =pK

A

Amount of acid and conjugate base is equal

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45
Q

If deprotonated form dominates

A

pH>pK

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46
Q

Protonated form dominates

A

pH<pK

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47
Q

Amounts of acid and conjugate base are equal

A

pH=pK

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48
Q

Amino acid with benzene rings

A

Aromatic

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49
Q

Amino acid without benzene rings

A

Aliphatic

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50
Q

What is a zwitterion?

A

Neutral molecule

Has both positive and negative charge

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51
Q

What is pI?

A

Isoelectric point

pH at which the protein has no overall net charge

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52
Q

What is the pI of acidic protein?

A

Low pH
Many neg charged aa
Low pI
Many pos H+ ions needed to become neutral

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53
Q

What is the pI of basic protein?

A

High pH
Many pos charged aa
High pI
Few pos H+ ions needed to become neutral

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54
Q

Key features of peptide bond

A

All atoms of the bond are in the same plane
No rotation about peptide bind due to double bond characteristics
Carbonyl oxygen and amide hydrogen in trans orientation

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55
Q

Define alpha helix

A

Type of regular protein secondary structure
Right handed helix
3.6 aa residues per turn
Pitch of 0.54 nm

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56
Q

Define amino acid

A

Building blocks of proteins
Composed of central carbon attached to 4 other chemical groups:
Amino group (-NH2), carboxyl group (-COOH), hydrogen atom and variable group (R)

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57
Q

Define amphipathic

A

Molecule that has both a polar (hydrophilic) and non-polar (hydrophobic) end

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58
Q

Define beta sheet

A

Type of regular secondary structure
Polypeptide chains are on extended conformation
Parallel or anti parallel

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59
Q

Define denaturation

A

Disrupting the normal folded conformation of a protein to produce an unfolded polypeptide chain

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60
Q

Define domain

A

Region of a protein that folds into a distinct globular unit
Will often have a specific functional role within the protein
E.g. Ligand binding, interaction with other proteins

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61
Q

Define disulphide bond

A

Covalent bond
formed between two sulphur atoms
of cysteine residues in a protein

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62
Q

Define fibrous protein

A 
Insoluble class of proteins
Elongated structure 
Repeating elements
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63
Q

Define globular protein

A 
Water soluble class of proteins 
Compact highly folded structure
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64
Q

Define hydrogen bond

A

Weak electrostatic interaction

between a hydrogen atom bound to an electronegative atom (N,O) and another electronegative atom

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65
Q

What is a protein?

A

Polymer composed of aa monomers joined by peptide bonds

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66
Q

How many different types of aa are there?

A

20

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67
Q

In which aa is the carbon not a chiral centre?

A

Glycine

Variable group of hydrogen

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68
Q

Two types of spatial arrangements of aa

A

Chiral centre - shows stereoisomerism

D- and L- form

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69
Q

Naturally found spatial arrangement in proteins

A

L-form

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70
Q

Aromatic R groups

A

Phenylalanine
Tyrosine
Tryptophan
PTT

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71
Q

Polar, uncharged R groups

A 
Cysteine
Asparagine
Threonine
Serine 
CATS
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72
Q

Non polar, aliphatic R groups

A

Glycine, alanine, methionine, proline
Lucine, isoleucine, valine
GAMPLIV

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73
Q

Negatively charged R groups

A

Glutamate
Aspartate
GA

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74
Q

Positively charged R groups

A

Histidine
Arginine
Losing
HAL

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75
Q

Define peptide bond

A

Type of covalent bond
Joins amino acids in proteins
Forms between carboxyl group of one and amino group of 2nd
Peptide bond formation is a condensation reaction (release H2O)

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76
Q

Define primary structure

A

Linear amino acid sequence of polypeptide chain

Determines the overall structure and function of protein

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77
Q

Define secondary structure

A

Local spatial arrangement of polypeptide backbone

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78
Q

Define tertiary structure

A

Overall 3-dimensional arrangement of all atoms in a polypeptide
Involves folding secondary structure
So far apart aa on primary sequence can interact
Larger proteins have distinct domains- serve particular roles

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79
Q

Define quarternary structure

A

3-dimensional arrangement of multi-subunit proteins

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80
Q

Bonds in primary structure

A

Covalent (peptide) bonds

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81
Q

Common secondary structures of polypeptides

A

Alpha helix

Beta sheet

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82
Q

Bonds involved in secondary structure

A

Hydrogen bonds

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83
Q

Bonds involved in tertiary structure

A 
Hydrogen bonds
Van der waals
Hydrophobic interactions
Covalent disulphide bonds
Ionic interactions
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84
Q

Bonds involved in quaternary structure

A 
Hydrogen bonds
Van der waals
Hydrophobic interactions
Covalent disulphide bonds
Ionic interactions
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85
Q

What is a homomeric protein?

A

Protein where quaternary structure consists of identical polypeptide chain subunits

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86
Q

What is a heteromeric protein?

A

Protein where polypeptide subunits in quaternary structure are different

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87
Q

Role of globular proteins

A

Enzymes

Regulatory proteins

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88
Q

Role of fibrous proteins

A

Structure
Support
Protection

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89
Q

What can assist some proteins with folding?

A

Molecular chaperones

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90
Q

What are molecular chaperones?

A

Assist some proteins with folding

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91
Q

Define allosterism

A

The binding of a ligand/ substrate
At one site in a multi subunit protein that influences the subsequent binding of other ligand/substrates to other subunits

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92
Q

Define competitive inhibition

A 
Enzyme inhibition
Inhibitor competes with substrate 
For binding at the active site
Increase in the Km for the substrate
Vmax remains unchanged
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93
Q

Define Bohr effect

A

Decrease in oxygen binding affinity of haemoglobin

caused by decrease in pH

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94
Q

Define enzyme

A

Biological catalyst
Increases rate of reaction
Lowering the activation energy

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95
Q

Define haem

A

Poryphyrin derivative
Found in haemoglobin and myoglobin
Central iron atom
Site of reversible oxygen binding

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96
Q

Define Km

A

Substrate concentration that will give
Half the maximal rate (Vmax)
Michaelis constant

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97
Q

Define non-competitive inhibition

A

Enzyme inhibition
Inhibitor binds at a site other than the active site
Decreased vmax
Km for substrate remains the same

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98
Q

Define sickle cell anaemia

A

Haemoglobinopathy
Glu-to-Val mutation in B-haemoglobin molecules
resulting in deformed red blood cells

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99
Q

Define thalassaemia

A

Group of haemoglobinopathies
caused by mutations in globin genes
resulting in an imbalance between the globin proteins

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100
Q

Define Vmax

A

Maximal velocity of an enzyme catalysed reaction

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101
Q

Role of myoglobin and haemoglobin

A

Oxygen transporting proteins

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102
Q

Name two oxygen transporting proteins

A

Myoglobin (Mb)

Haemoglobin (Hb)

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103
Q

What part of haemoglobin do oxygen atoms bind to?

A

Haem group

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104
Q

How many oxygen molecules can myoglobin carry?

A

One

Single subunit protein

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105
Q

How many oxygen molecules can Hb bind to?

A

Four

Tetrameric molecule

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106
Q

Describe oxygen binding curve for Mb

A

Hyperbolic oxygen binding curve

No cooperativity

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107
Q

Describe the oxygen binding curve for Hb

A

Sigmoidal oxygen binding kinetics

Cooperativitiy

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108
Q

What does 2,3-BPG stand for?

A

2,3-bisphosphoglycerate

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109
Q

How does 2,3-BPG affect oxygen binding curve?

A

Increasing amount of BPG
Decreases affinity of Hb for oxygen
Curve shifts to the right

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110
Q

How does CO2 and H+ affect oxygen binding curve?

A

Decreases affinity of Hb for oxygen

Curve shifts to the right

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111
Q

How does CO affect oxygen binding curve?

A

Carbon monoxide binds tightly to Hb

Prevents oxygen binding

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112
Q

What catalyzes nearly all chemical reactions in the body?

A

Enzymes

Protein catalysts

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113
Q

What does lactase do?

A

Hydrolysed lactose into glucose and galactose

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114
Q

What does DNA polymerase do?

A

Polymerises nucleotides to form DNA

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115
Q

Name 6 classes of enzymes

A 
Transferases
Hydrolases
Oxidoreductases
Lyases
Isomerases
Ligases
THOLIL
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116
Q

Role of oxidoreductase enzymes

A

Oxidation-reduction reactions

Transfer of electrons

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117
Q

Role of transferase enzymes

A

Transfer C-,N- or P- containing groups

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118
Q

Role of hydrolases

A

Catalyse cleavage of bonds by the addition of water

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119
Q

Role of lyase enzymes

A

Addition or removal of groups to form double bonds

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120
Q

Role of isomerases

A

Transfer of groups within molecules to form isomers

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121
Q

Role of ligase enzymes

A

Formation of bonds between C and O, S and N, at the expense of ATP

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122
Q

What is a cofactor?

A

Prosthetic group
Inorganic ion
E.g. Fe2+, Mn2+

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123
Q

What are coenzymes?

A

Prosthetic group
Organic compounds
Act as temporary carriers of groups in reaction
E.g. NAD, CoA

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124
Q

What is NAD?

A

Nicotinamide Adenine Dinucletide

Coenzyme

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125
Q

What is CoA?

A

Coenzyme A

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126
Q

Examples of prosthetic groups

A

Coenzymes

Cofactors

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127
Q

What are prosthetic groups?

A

Tightly or covalently linked to enzyme protein

Additional chemical components to catalyse reactions

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128
Q

Properties of enzymes

A

Highly specific
Increase rate of reaction
Left unchanged after reaction has occurred

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129
Q

Explain specifity of enzymes

A

Interact with one or only a few substrates

Catalyse one type of reaction

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130
Q

How do enzymes affect equilibrium of a reaction?

A

They don’t.

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131
Q

How do enzymes work?

A

Lower activation energy for reaction to occur
Substrate bind to active site on enzyme
Increase local concentration of reactants
Stabilised formation of high energy transition state

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132
Q

What is an active site?

A

Site of reaction on enzyme
Coded by few aa of the long polypeptide chain
Usually clefts or crevices in protein

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133
Q

Why is active site usually crevice/cleft?

A

Allow substrate to bind

Exclude water from reaction

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134
Q

What is the lock and key hypothesis?

A

Only molecules that have a complementary shape to the active site will be able to bind
Specificity of enzyme

135
Q

What is the induced fit hypothesis?

A

Binding of substrate results in changes in shape of enzyme

To enhance binding

136
Q

How is substrate held in active site?

A

Multiple weak bonds with aa in this part of enzyme

137
Q

What does the Michaelis Menten equation show?

A

How the reaction velocity v0 varies with the substrate concentration

138
Q

What is v0?

A

Initial reaction velocity

139
Q

What is the intercept at y-axis of a Lineweaver-Burk plot?

A

1/vmax

140
Q

What is the slope of a Lineweaver-Burk plot?

A

Km/Vmax

141
Q

What is the intercept at x-axis of a Lineweaver-Burk plot?

A

-1/Km

142
Q

What are the axis of a Lineweaver-Burk plot?

A

X-axis 1/[S]

Y-axis 1/V

143
Q

How do irreversible enzyme inhibitors work?

A

Bind covalently to the enzyme molecule to destroy enzyme function

144
Q

Types of reversible enzyme inhibitors?

A

Competitive and non-competitive inhibitors

145
Q

How do competitive enzyme inhibitors work?

A

Binds at active site
Affects Km not Vmax
Can be overcome by increasing substrate concentration

146
Q

How do non-competitive inhibitors work?

A

Bind at site other than the active site
Affects Vmax not Km
Cannot be overcome by increasing the substrate concentration

147
Q

Define base

A

Nitrogenous base
Component of nucleic acid involved in base pairing
I.e. guanine (G), adenine (A), thymine (T), cytosine (C), uracil (U)

148
Q

Define base pair (BP)

A

A pair of nitrogenous bases held together by hydrogen bonds
I.e. G-Cbase pair with 3 hydrogen bonds
And A-T base pair (or A-U base pair ) with 2 hydrogen bonds

149
Q

Define chromatin

A

DNA, proteins and RNA needed to package DNA into the cell nucleus
‘Loose’ chromatin is ‘bead on a string DNA’
Highly condensed chromatin is a chromosome

150
Q

Define chromosome

A

Structure in the cell nucleus containing DNA wrapped around histones in a highly folded structured fashion

(1 double stranded DNA molecule or 2 identical double stranded molecules after DNA replication)

151
Q

Define covalent modification

A

Addition of a chemical group to a protein

Reversible covalent modification is often used as means of regulating the activity of enzymes and other proteins

152
Q

Define DNA

A

Deoxyribonucleic acid

Polymer of deoxyribonucleotides

153
Q

Define genome

A

Total genetic content (DNA sequence) of an organism

In case of diploid organisms the DNA sequence of one set of chromosomes

154
Q

Define isoenzymes

A

Enzymes that catalyse the same reaction but have a different amino acid sequence

155
Q

Define nucleoside

A

Nitrogenous base

And a pentose sugar

156
Q

Define nucleotide

A

Nitrogenous base
Pentose sugar
And a phosphate

157
Q

Define nucleosome

A

Basic repeat unit of eukaryotic chromatin

Bead-like structure formed by DNA wrapped around histones

158
Q

Define phosphorylation

A

Addition of a phosphate group

159
Q

Define protein kinase

A

Enzyme that can catalyse addition of a phosphate group from ATP to Ser/Thr/Tyr residues in a protein

160
Q

Define protein phosphatase

A

Enzyme that catalyses removal of a phosphate group from Ser/Thr/Tyr residues in a protein

161
Q

Define purine

A

Two-ring nitrogenous base

E.g. Guanine (G) and Adenine (A)

162
Q

Define pyrimidine

A

One-ring nitrogenous base

E.g. Cytosine (C), thymine (T) and uracil (U)

163
Q

Define RNA

A

Ribonucleic acid

Polymer of ribonucleotides

164
Q

Define zymogen

A

Inactive precursor of a proteolytic enzyme

165
Q

What are the main forms of enzyme regulation?

A

Substrate and product concentration
Changes in enzyme conformation
Changes in the amount of enzyme

166
Q

Ways to change enzyme conformation

A

Allosteric control
Covalent modification
Proteolytic activation

167
Q

What is an allosteric enzyme?

A

Multi subunit enzymes that contain more than 1 active site for the substrate

168
Q

What is positive cooperativity?

A

Binding of substrate to one active site enhances subsets binding to other active sites

169
Q

What does an allosteric activator do to the Michaelis Menten curve?

A

Increases activity of enzyme
Curve shifted to the left
Shifts the R to T conformational equilibrium toward R

170
Q

What does an allosteric inhibitor do to the Michaelis Menten curve?

A

Decreases activity of enzyme
Curve shifted to the right
Shifts the R to T conformational equilibrium toward T

171
Q

Which enzyme catalyses attachment of a phosphate group?

A

Kinase

172
Q

Which enzyme catalyses removal of phosphate groups?

A

Phosphatase

173
Q

What is the an enzyme’s inactive protein precursor known as?

A

Zymogen

174
Q

How are zymogen a activated?

A

Removal of part of the polypeptide chain

Many proteases produced in this form

175
Q

What is a protease?

A

Enzyme that can break peptide bonds

176
Q

How is premature proteolytic cleavage prevented?

A

Many proteases are produced in inactive zymogen form
Transported safely to sites of action
Then activated
E.g. Blood clotting factors

177
Q

Ways to change amount of enzyme for regulation purposes?

A

Regulation of enzyme synthesis

Regulated protein degradation

178
Q

How is enzyme synthesis regulated?

A

Increasing or decreasing rate of transcription of mRNA

179
Q

How is protein degradation regulated?

A

Proteins can be tagged for destruction by the addition of a small protein molecule known as ubiquitin

180
Q

Ways to regulate metabolic pathways

A

Feedback inhibition
Feed forward activation
Counter regulation

181
Q

What is feedback inhibition in metabolic pathway regulation?

A

End product of a pathway inhibits its own rate of synthesis by inhibiting enzymes earlier in the pathway
E.g. High [ATP] inhibit catabolic pathways

182
Q

What is feed forward activation?

A

Increased amounts of initial substrate increases first step in pathway
E.g. High concentration of ethanol induce microsomal ethanol oxidising enzymes

183
Q

How does counter regulation of metabolic pathways work?

A

If a catabolic pathway breaking down compound A is activated
Then the opposing anabolic pathway making compound A will be inactivated
E.g. Glycogenolysis and glycogenesis

184
Q

Main mechanisms which regulate the blood clotting cascade

A

Inactive zymogens present at low concentration
Amplification of an initial signal
Localisation of clotting factors to the site of damage
Feedback activation by thrombin
Termination of clotting by multiple processes

185
Q

How are clotting factors localised to site if damage?

A

Factor with Gla domains bind to damaged endothelial cell lining
Allow rapid activation of downstream effector molecules

186
Q

Explain feedback activation by thrombin

A

Activated thrombin enhances conversion of

Factor V, VII and XI to activated forms

187
Q

Ways to terminate clotting

A

Removal of activated proteins
Proteolytic digestion
Binding of inhibitor molecules

188
Q

Factors of extrinsic pathway

A

Factor VII

Factor X

189
Q

Factors of intrinsic pathway

A 
Factor XI
Factor IX
VIII
V
Factor X
190
Q

What is prothrombin converted to?

A

Thrombin

By factor Xa

191
Q

What is fibrinogen converted to?

A

Fibrin

By thrombin

192
Q

Which factor is necessary to form cross linked fibrin?

A

Factor XIIIa (activated by thrombin)

193
Q

How many chromosomes do humans have?

A

23 pairs

194
Q

Examples of polynucleotides

A

DNA

RNA

195
Q

What links nucleotides?

A

Covalent phosphodiester bonds

196
Q

Molecule at 5’ end?

A

Free phosphate

197
Q

Molecule at 3’ end

A

Free OH- group

198
Q

Conventionally, which way is DNA strand written?

A

5’ to 3’

199
Q

Mutation in CF

A

3bp deletion (

200
Q

Mutation in SCA

A

A>T
Glu>Val
In human beta haemoglobin protein

201
Q

What is achondroplasia ?

A

Form of short limbed dwarfism

202
Q

Mutation in achondroplasia

A

G>A
GLY>Arg
In cDNA of fibroblast growth factor gene

203
Q

Mutation in PKU

A

G>A
Premature stop codon
Unstable mRNA transcript
Of human phenylalanine hydroxylase gene

204
Q

Define allele

A

Alternative form of a gene
Each individual has two alleles for every gene
which can either be the same or different

205
Q

Define autosome

A

Chromosome other than the sex chromosomes

I.e. human chromosome 1-22

206
Q

Define centromere

A

Region of a duplicated chromosome where two sister chromatids touch
Region of a chromosome to which the micro tubule spindle attach during cell division

207
Q

Define chiasmata (pl chiasmata)

A

Point where two chromatids exchange genetic information during crossing-over in meiosis
Only when 2 non-sister chromatids (chromatids from different homologous chromosomes within a chromosome pair) exchange information will there be a genetic consequence

208
Q

Define chromatid

A

One of two identical components of a duplicated chromosome

Each containing a single (identical) double stranded DNA molecule

209
Q

Define dominant

A

Phenotypic trait is dominant when it occurs in both homozygotes and heterzygotes

210
Q

Define gene

A

Unit of heredity
Transcription unit
Length of DNA on a chromosome that contains the code for a protein (or RNA)
And sequences necessary for its expression e.g. Promoter and terminator sequences and introns

211
Q

Define genotype

A

Genetic make-up of an individual

Either as a whole or for one specific genetic locus

212
Q

Define heterozygous

A

Having two different alleles for a specific genetic locus

213
Q

Define homozygous

A

Having two identical alleles for a specific genetic locus

214
Q 
Define locus (pl loci)
Or genetic locus or gene locus
A

Specific position on a chromosome

215
Q

Define meiosis

A

Process of cell division by which gametes are produced

216
Q

Define mitosis

A

Process of cell division for somatic cells

217
Q

Define phenotype

A

All observable characteristics of an individual

The observable trait as a result of genetic make-up of one (or more) specific gene locus (loci)

218
Q

Define recessive

A

Phenotypic trait is recessive when it occurs in homozygotes only

219
Q

Define somatic cell

A

Cell other than the gametes

220
Q

Stages in the cell cycle

A

G1
S
G2
M

221
Q

What happens in G1?

A

Cell prepares for DNA replication

Cellular contents, excluding the chromosomes are duplicated

222
Q

What happens in the S phase?

A

Semi-conservative DNA replication

Each of the 46 chromosomes is duplicated by the cell

223
Q

What happens in G2 phase?

A

Cell prepares for cell division

The cell ‘double checks’ the duplicated chromosomes for error making any needed repairs

224
Q

What happens in M phase?

A

Cell division (mitosis)

225
Q

What substrates are used by the enzyme DNA polymerase?

A

Deoxyribonucleoside triphosphate (dNTP)

226
Q

What reaction is catalysed by DNA polymerase?

A

(dNMP)n + dNTP -> (dNMP)n+1 + PPi

5’ to 3’ chain growth

227
Q

What is semi-conservative DNA replication?

A

Each strand of the parent molecule is maintained in the two daughter molecules

228
Q

What does DNA helicase do?

A

Unravels the DNA double helix

229
Q

What are Okazaki fragments?

A

DNA fragments of the lagging strand which is made discontinuously

230
Q

What does DNA ligase do?

A

Joins the Okazaki fragments

231
Q

Which strand is synthesised continuously in DNA replication?

A

Leading strand

232
Q

Composition of human somatic cells

A

Diploid
23 pairs of chromosomes
(22 pairs of autosomes and 1 pair of sex chromosomes XX/XY)

233
Q

Composition of human gametes and examples

A

Sperm and egg
Haploid
One set of 23 chromosomes

234
Q

Chromosome properties after replication

A

Classical X-shape

Two identical sister chromatids joined by centromere

235
Q

What is the centromere?

A

Region of a chromosome that joins two identical sister chromatids

236
Q

How many daughter cells produced after mitosis?

A

2 diploid cells

Each have same chromosomal content as parent cell

237
Q

How many daughter cells produced after meiosis

A

4 haploid cells

Each has half the number of chromosomes as the parental cell

238
Q

What happens during meiosis?

A

Diploid cell undergoes
One round of replication
Two rounds of division (meiosis I and meiosis II)

239
Q

Why does mitosis take place?

A

Growth

Maintenance

240
Q

What is the M phase?

A

Mitosis

241
Q

Steps of mitosis

A 
Prophase 
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
242
Q

What happens in prophase?

A

Break down of nuclear membrane
Spindle fibres appear
Chromosomes condense

243
Q

What happens in prometaphase?

A

Spindle fibres attach to chromosomes

Chromosomes condense

244
Q

What happens in metaphase?

A

Chromosomes align

245
Q

What happens in anaphase?

A

Centromeres divide

Sister chromatids move to opposite poles

246
Q

What happens in telophase?

A

Nuclear membrane reforms

Chromosomes decondense

247
Q

What happens in cytokinesis?

A

Cytoplasm divides

Parent cell become 2 daughter cells with identical genetic information

248
Q

What do all people in a horizontal line in a pedigree have in common?

A

Same generation

249
Q

What are the main patterns of inheritance?

A 
✔Autosomal recessive
✔Autosomal dominant
Sex-linked inheritance
✔X-linked recessive/dominant
Y-linked
250
Q

What is autosomal inheritance?

A

When the gene in question is located on an autosome

251
Q

What is sex-linked inheritance?

A

When the gene in question is loaded on a sex chromosome

252
Q

What is X-linked inheritance?

A

When gene in question is located on the X-chromosome

Sex-linked inheritance

253
Q

What is Y-linked inheritance?

A

When gene in question is located on the Y-chromosome
Inherited directly from father to son
Sex-linked inheritance

254
Q

Unaffected Male

In pedigree

A

White Square

255
Q

Unaffected female

In pedigree

A

White circle

256
Q

Affected individual

In pedigree

A

Black

257
Q

Carrier

In pedigree

A

Half black shading

Or black dot in centre

258
Q

Deceased individual

In pedigree

A

/

Through symbol

259
Q

Unknown sex

In pedigree

A

Diamond

260
Q

What are linked genes?

A

2 genes close together on the same chromosome
Don’t show independent assortment during meiosis
They co-segregate

261
Q

How can linked alleles separate during meiosis?

A

Crossing-over

Recombination

262
Q

Define anticodon

A

Three nucleotides on tRNA molecule that are complimentary to a codon on the mRNA template

263
Q

Define codon

A

Three nucleotides on mRNA molecules that code for a specific amino acid in the protein sequence
(Except stop codon)

264
Q

What is a stop codon?

A

Does not code for an amino acid

Signals termination of polypeptide chain growth

265
Q

Define genetic code

A

Universal ‘conversion table’ from DNA information into amino acid information
I.e. how sets of three nucleotides (codons) encode the information for the different amino acids

266
Q

Define mature mRNA

A

End product of transcription
I.e. after capping, polyadenylation and splicing has occurred
Serves as template in translation

267
Q

Define ORF

A

Open reading frame

A area of gene that holds code for all amino acid residues of the gene product (the protein)

268
Q

Define promoter

A

Area of gene upstream of the ORF which regulates transcription
And therefore gene expression
Include sequences for binding of transcription factors and FNA polymerase and many regulatory factors (activators and repressors)

269
Q

Define ribosome

A

Two-unit particle composed of many protein and ribosomal RNAs
Site of protein synthesis

270
Q

mRNA

A

Messenger RNA

271
Q

rRNA

A

Ribosomal RNA

272
Q

tRNA

A

Transfer RNA

273
Q

Define transcription

A

Process by which the DNA ‘transcribed’ (‘copied’) into RNA message

274
Q

Define transcription initiation

A

Start of mRNA production

Dependent on RNA polymerase binding

275
Q

Define transcription termination

A

End of mRNA production

Which is sequence dependent

276
Q

Define translation

A

Process by which RNA message is ‘translated’ into an amino acid code (protein)

277
Q

Define translation initiation

A

Start of protein production

I.e. at the AUG codon

278
Q

Define translation termination

A

End of protein production

I.e. at a stop codon (UAA, UAG, UGA)

279
Q

Where is mRNA made, what is this process called?

A

Nucleus
Transcription
DNA to mRNA

280
Q

Where is protein made?

A

Cytoplasm
Translation
mRNA to protein

281
Q

What are the three phases in transcription process?

A

Initiation
Elongation
Termination

282
Q

What happens in initiation of transcription process?

A

Promoter recognition

And binding

283
Q

What happens in elongation of transcription process?

A

Actual process of ‘transcribing’ by RNA polymerase

284
Q

What happens in termination of transcription process?

A

Sequence-dependent termination of RNA chain growth

285
Q

Post-transcriptional processes

A

Transform pre-mRNA into mature mRNA
Capping
Tailing
Splicing

286
Q

What is capping?

A

Addition of 5’ cap

287
Q

What is tailing?

A

Polyadenylation

Addition of 3’ polyA tail

288
Q

What is splicing?

A

Removal of introns

Exons ‘spliced together’

289
Q

What are the types of RNA?

A

rRNA ribosomal 80+%
mRNA messenger
tRNA transfer

290
Q

What codon is AUG?

A

Methionine

291
Q

What is the initiation codon?

A

AUG

Methionine

292
Q

What are the stop codons?

A

UAA
UAG
UGA

293
Q

What are the three phases in the translation process?

A

Initiation
Elongation
Termination

294
Q

What happens in the initiation process of translation?

A

AUG codon recognition and binding

And formation of functional ribosome

295
Q

What happens in the elongation process of translation?

A

Actual process of ‘translating’ the RNA message into protein
mRNA read codon by codon from 5’ to 3’
While polypeptide chain growth is from amino to carboxyl terminus

296
Q

What happens in the termination process of translation?

A

Stop codon recognition and dissociation of ribosome

297
Q

Define glycosylation

A

Attachment of carbohydrate groups (oligosaccharide) to protein (side chain of certain aa residues) via glycosidic linkages
Can be N-linked (via amino side chains of Asn residues)
Can be O-linked (via hydroxyl side cabins of Ser/Thr residues)

298
Q

Define preproprotein

A

Protein containing both a signal peptide and a propeptide

299
Q

Define proprotein

A

Inactive precursor of a protein

To become fully active the protein must undergo limited proteolytic to remove the propeptide

300
Q

Define protein targeting

A

Mechanisms involved in directing proteins to their correct site of action inside (or outside) the cell

301
Q

Define scurvy

A

Disease caused by vitamin C (ascorbic acid) deficiency that results in inadequate formation of hydroxyproline residues in collagen, reducing the stability of the collagen fibres

302
Q

Define signal peptidase

A

Enzyme that removes the signal peptide from secretory proteins after entry into the ER

303
Q

Define signal peptide

A

Short N-terminal peptide sequence that directs a newly formed secretory or membrane protein into the ER

304
Q

Define signal recognition particle

A

Complex containing protein and RNA that binds the signal peptide of newly synthesised secretory proteins and escorts it to the ER for translocation

305
Q

Define tropocollagen

A

Collagen triple helices formed extracellularly where the N- and C-terminal regions have been removed

306
Q

Which proteins are more likely to be made on ribosomes on the ER?

A

Proteins destined for insertion into the plasma membrane, lysosomes, Golgi/ER or secretion

307
Q

What addition do secreted proteins have?

A

Signal sequence at the N-terminus that targets them to the ER

308
Q

What do signal sequences contain?

A

10-15 hydrophobic residues
1+ positively charged residues near amino terminus before hydrophobic sequence
Few polar amino acids in the C-terminal region

309
Q

Protein secretion pathway part 1 - signal sequence

A

1 Protein synthesis initiated on free ribosomes
2 N-terminal signal sequence produced
3 Signal sequence of newly formed protein is recognised by the signal recognition particle (SRP)

310
Q

Protein secretion pathway part 2 - SRP

A

4 GTP-bound SRP directs the ribosome synthesising the secretly protein to SRP receptors on the cystolic face of the ER
5 SRP dissociates

311
Q

Protein secretion pathway part 3

A

6 Protein synthesis continues and the newly formed polypeptide is fed into the ER via a pore in the membrane (peptide translocation complex)
7 Signal sequence removed by a signal peptidase
8 Ribosome dissociates and is recycled

312
Q

Modification to proteins in lumen of ER

A

Disulphide bond formation

Glycosylation

313
Q

N-linked glycosylation

A

Carbohydrate added via N-glycosyl link to amide nitrogen of Asn
Occurs in ER

314
Q

O-linked glycosylation

A

Carbohydrate added via glycosidic link to hydroxyl of Ser or Thr
Occurs mainly in Golgi

315
Q

Types of secretion

A

Constitutive secretion

Regulated secretion

316
Q

What is constitutive secretion?

A

Continuous process
Not regulated
Proteins packaged into vesicles and release continuously by exocytosis
E.g. Serum, albumin, collagen

317
Q

What is regulated secretion?

A

Proteins released in response to a signal/ stimulus e.g.hormone
Proteins packaged into vesicles but not released until stimulus received e.g. Insulin

320
Q

What cuts pro insulin into 3 peptides?

A

Proteases

321
Q

Biosynthesis of collagen part 1

A

1 Synthesis and entry of chain into lumen of rough ER
2 Cleavage of signal peptide
3 Hydroxylation of selected proline and lysine residues
4 Addition of N-linked oligosaccharides
5 Addition of galactose to hydroxylysine residues

322
Q

Biosynthesis of collagen part 2

A

6 Chain alignment, formation of disulphide bonds
7 Formation of triple helical pro collagen from C- to N- terminus
8 Completion of O-linked oligosaccharide chains by addition of glucose

323
Q

Biosynthesis of collagen part 3

A

9 Transport vesicle
10 Exocytosis
11 Removal of N- and C- terminal peptides

324
Q

Biosynthesis of collagen part 4

A

12 Lateral association of collagen molecules followed by covalent cross-linking
13 Aggregation of fibrils

325
Q

Define antibody

A

Protein which is produced by the body in response to a foreign compound (antigen) usually a protein.
Antibodies can be used diagnostically to detect specific proteins.

326
Q

Define cloning

A

Production of exact copies of a piece of DNA

327
Q

Define cloning vector

A

DNA molecule such as a plasmid, virus or artificial chromosome into which a piece of foreign DNA can be added for cloning

328
Q

Define ELISA

A

Enzyme-linked immunoabsorbent assay
Technique using an antibody linked to an enzyme used to quantify the amount of a molecule
Used in diagnostic tests to measure the concentration of biological molecules in solution

329
Q

Define gel electrophoresis

A

Technique which separates macromolecules (proteins/DNA/RNA) on the basis of their size or charge
Molecules are separated in gel and migrate due to the presence of an electric charge played across the gel

330
Q

Define PCR

A

Polymerase chain reaction
Very powerful and sensitive technique whereby small fragments of DNA are amplified using a DNA (or RNA) template
Amount of template needed is minute
Amount of amplified DNA end-product is enormous
Enough for further experimental procedures
E.g. Gene cloning, restriction analysis and DNA sequencing

331
Q

Define primer

A

Short oligonucleotide (10-25nt)
Can be 3’-extended by DNA polymerase
Primers of specific sequence used in molecular techniques like PCR and DNA sequencing

332
Q

Define restriction endonuclease (restriction enzyme)

A

Enzyme that recognises and cuts double stranded DNA at a specific sequence (the restriction site)

333
Q

Define restriction site

A

Sequence of DNA that can be recognised by a restriction endonuclease
Enzyme can then specifically cut the double stranded DNA molecule within (or adjacent to ) the recognition sequence

334
Q

Define SDS-PAGE

A

Sodium dodecyl sulphate polyacrylamide gel electrophoresis
Gel electrophoresis of proteins in the presence of the detergent SDS
Proteins are separated on the basis of their size

335
Q

Define western blotting

A

Technique where a protein separated by electrophoresis is transferred to a membrane filter and is detected by the binding of an antibody directed against it

336
Q

Techniques for DNA analysis at gene level

A

Restriction analysis/ gene cloning
Gel electrophoresis
Polymerase chain reaction

353
Q

How many disulphide bonds does insulin have?

A

3 disulphide bonds
Formed in pro insulin
Eer sent in mature insulin too

357
Q

Proteolytic processing of insulin

A

Preproinsulin
= pro insulin + signal sequence
= mature insulin + C peptide

ESA1 (6 decks)

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