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Revision lectures (Year 1) > MCGB Revision Lecture 1b > Flashcards

MCGB Revision Lecture 1b Flashcards

1
Q

DNA replication is

A

sem-conservative

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2
Q

DNA replication is a 3 stage process

A
  • initiation
  • elongation
  • termination
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3
Q

in DNA replication the chain grows in a

A

5’ to 3’ direction

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4
Q

what drives DNA replication

A

pyrophosphate hydrolysis

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5
Q

outline DNA replication

A

1) Topoisomerase unwinds the DNA and Helicase breaks the hydrogen bonds between the parental double helix
2) DNA primase synthesises RNA primers, which allow DNA polymerase to bind to single strand
3) Leading strands is read in the 3’ to 5’ direction and synthesised continuously in the 5’ to 3’ direction by DNA polymerase
4) Lagging trans is synthesised discontinuously- primase synthesises numerous short primers which are extended by polymerase to form Okazaki fragments
5) After the primer is replaced by DNA, DNA ligase joins the Okazaki fragments

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6
Q

termination of DNA replication occurs when

A

two facing repclication forks meet and DNA ligase joins the final frgaments

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7
Q

telomeres

A

repetitive DNA sequences that protect the integrity of chromsosmes

  • prevents degradation of coding material
  • ensure genomic stability
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8
Q

telomerase

A

prevents telomeres shortening

  • -> when there is not enough DNA for primers (oligonucleotides) to bind to = uneven length of both strand s of DNA= degradation of longer strand
  • -> telomerase lengthens the DNA so primers can bind- preventing loss of DNA
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9
Q

Hayflicks constant

A

maximum number of times a cell can divide without telomerase = 61.3 in human cells

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10
Q

mitosis order

A 
prophase
prometaphase
metaphase
anaphase
telophase
cytokinesis
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11
Q

mitosis: prophase

A
  • Nuclear envelop disintegrates
  • Chromosomes condense
  • Mitotic spindle starts to forms
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12
Q

mitosis: prometaphase

A

spindles form from centrioles and connect with kinetochore of chromosomes

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13
Q

mitosis: metaphase

A

chromosomes randomly line up at the metaphase plate

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14
Q

mitosis: anaphase

A
  • Kinetochore microtubules pull chromatids towards the poles

- Go to different poles (now become chromosomes (not called chromatids anymore)

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15
Q

mitosis: telophase

A
  • Spindle disappears
  • Nuclear membrane reforms
  • Nucleolus reappears
  • Chromosomes decondense
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16
Q

mitosis: cytokinesis

A

cleavage of daughter cells with equal number of chromosomes

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17
Q

mitosis overview

A

cell division for somatic cells
–> Production of two identical daughter cells
o Same number of chromosomes content as parental cell
- Important during development (~50 mitotic rounds) and mitotic growth (epidermis, mucosae, bone marrow, spermatogenesis)

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18
Q

in humans the haploid cells created by meiosis are

A

sperms and eggs

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19
Q

meiosis is

A

division for germ line cells

  • Oogenesis
  • Spermatogenesis
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20
Q

meiosis produces

A

4 non-identical cells - half chromosome content of parental cell (2n–> n)

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21
Q

how many rounds of replication and division in meiosis

A
  • one round of replication

- two rounds of division- to separate sister chromatids

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22
Q

outline meiosis I

A

1) Prophase I: 1) Chromosomes begins to condense and pair up (homologous chromosomes (from mums and dad) will look for each other)

2) Metaphase I: spindle begins to capture chromosomes and move them towards the centre of the cell- metaphase plate
- Each chromosome attaches to microtubule from just one pole of the spindle
- Homologous pairs not individual chromosomes line up for separation.

3) Anaphase I: homologues are pulled apart and move apart to opposite neds of the cell
- Sister chromatids of each chromosome remain attached to one another and
don’t come apart

4) Telophase I: chromosomes arrive at opposite poles of the cell
- Cytokinesis occurs at the same time as telophase I
- Cleavage- formation of two haploid non-identical daughter cells

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23
Q

when does homologous recombination occur and how

A

during Prophase I via crossing over

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24
Q

explain crossing over

A

o DNA is broken at the same spot on each homologue and exchange part of their DNA
o Crossing over occurs as chiasmata- cross shaped structures where homologues are linked together
o Chiasmata keep homologues connected
o Can have multiple cross overs

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25
Q

meiosis II

A

Cells move from meiosis I to II without copying their DNA. Meiosis II is a shorter and simpler process than meiosis I basically ‘mitosis for haploid cells’.

  • Cells that enter meiosis II are made in meiosis I
  • Cells are haploid and have one chromosome from each homologues pair
  • But chromosomes still consists of two sister chromatics
  • In MII sister chromatids separate, making haploid cells with nonduplicated chromosomes
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26
Q

outlines meiosis II

A

1) Prophase II: Chromosome condense and nuclear envelop breaks down- if needed
- Centrosomes move apart
- Spindle forms between them
- Spindle microtubules begin to capture chromosomes
- Two sister chromatids are captures by microtubules from opposite spindle poles

2) Metaphase II: the chromosomes line up individually along the metaphase plate.
3) Anaphase II: sister chromatids separates and are pulled towards opposite poles of the cell

4) Telophase II: nuclear envelopes form around each set of chromosomes and the chromosomes decondense.
- Cytokinesis splits the chromosome set into new cells
- Forming 4 haploid cells in which each chromosomes has just

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27
Q

describe oogenesis

A

1) Primary oocyte (2n) divides to form 1 secondary oocyte (1) and 1 polar body
2) The secondary oocyte (n) divides to form ovum (n)

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28
Q

polar bodies in oogenesis

A

4 polar bodies in total produced (2 from original polar body and one from secondary oocyte

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29
Q

describe spermatogenesis

A

1) Primary spermatocyte (2n) divides to form 2 secondary spermatocyte (n)
2) Secondary spermatocytes divide to form 4 spermatids
3) 4 spermatids mature into sperm

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30
Q

importance of meiosis

A

introduces variation

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31
Q

meiosis introduces variation via

A
  • random segregation
  • independent assortment
  • crossing over
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32
Q

non-disjunction

A

results in variations in chromosome number, which can occur in both meiosis I and II
- e.g. aneuploidy

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33
Q

which meiosis is non-disjunction most harmful in

A

meiosis I

- non of the cells face a correct number of chromsomes

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34
Q

sources of DNA damage

A

endogenous

exogenous

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35
Q

endogenous sources

A
  • replication stress
  • reactive oxygen species
  • intrinsic instability of DNA (hydrolysis, oxidation, methylation)
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36
Q

exogenous DNA damage

A
  • chemical radical
  • ionising irradiation
  • UV light
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37
Q

name some types fo DNA damage

A 
ss break
mismatch
damaged base
ds break
intrastrand cross link
interstrand crossline
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38
Q

DNA damage response (3)

A
  • senesence
  • proliferation
  • apoptosis
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39
Q

replication stress defined as

A

‘Inefficient replication that leads to replication fork slowing, stalling and/ breakage.’

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40
Q

Replication stress can be caused by:

A

1) Replication machinery defects

2) Replication fork hindrance
• Forward and backward slippage
• e.g. Trinucleotide repeats

3) Defects in response pathway

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41
Q

1) Replication machinery defects

A
  • Misincorporation by DNA polymerase

* Proofreading error by DNA polymerase

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42
Q

2) Replication fork hindrance

A

Repetitive DNA can lead to fork slippage

Forward slippage (deletion mutation)
• New strand has an extra nucleotide (A)
• Newly synthesised strand loops out

Backward slippage (insertion mutation)
• New strand is missing a nucleotide (A)
• Template strand loops out

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43
Q

example of a disease caused by replication fork progression hindrance

A

Fork slippage leads to trinucleotide expansion
e.g. Huntington’s (backward slippage)

  • HTT gene
  • Trinucleotide CAG repeats- polyglutamine repeats
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44
Q

increased CAG repeats in Huntington’s causes

A

neurone degeneration

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45
Q

replication machinery defects

A

DNA polymerase has a 3’ to 5’ DNA exonuclease domain and proofreads leading to the right nucleotide in its place. However, sometimes mismatches occur. Other enzymes involved in the replication can also be faulty such as topoisomerase or helicase.

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46
Q

defects in response pathway

A

repair doesn’t occur at the checkpoints

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47
Q

DNA repair techniques

A

1) Base excision repair

2) Nucleotide excision repair

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48
Q

Double strand break repair mechanisms (high energy radiation)

A
  • non-homologous end joining

- homologous recombination (better)

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49
Q

what can proteins act as

A

RITE

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50
Q

R

A

receptors

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51
Q

I

A

ion channels

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52
Q

T

A

transporters

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53
Q

E

A

enzymes

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54
Q

structural unit of proteins

A

amino acids

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55
Q

what joins amino acids

A

peptide bonds

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56
Q

properties of peptide bond

A

planar

rigid

stereosiosmerism

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57
Q

amino acids are classified according to their

A

R groups properties

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58
Q

pKa is a

A

pKa value is one method used to indicate the strength of an acid. pKa is the negative log of the acid dissociation constant or Ka value. A lower pKa value indicates a stronger acid. That is, the lower value indicates the acid more fully dissociates in water.

59
Q

if there is a negatively charged froup

A

loss of hydrogen has occured

60
Q

if an R group can donate hydrogen

A

it is acidic

61
Q

lower pKa

A

more acidic

62
Q

if pH

A

R group is protonated

63
Q

if pH> pKa

A

R group is deprontonated

64
Q

pKa equation

A

pKa = -log (Ka)

65
Q

pI

A

isoelectric point

66
Q

isoelectric point

A

pH at which there is no overall net charge

67
Q

if pH

A

protein protonated

68
Q

if pH>pI

A

protein is deprotonated

69
Q

protein folding

A
  • primary
  • secondary
  • tertiary
  • quaternary
70
Q

primary structure

A

linear amino acid sequence

71
Q

secondary structure

A

local spatial arrangement of polypeptide backbone to for an alpha helix or beta pleated sheet

72
Q

tertiary structure

A

3D configuration with further folding

73
Q

quaternary structure

A

different polypeptides join, sometimes with a prosthetic group

74
Q

bonds in primary structure

A

Covalent

  • peptide
  • disulphide (between cysteine)
75
Q

bonds in secondary structure

A
  • hyrogen
  • peptide
  • disulphide
76
Q

bonds in tertiary structure

A
  • hydrophobic bonds
  • hydrogen bonds
  • ionic bonds
  • van der waal forces
  • disulphide
77
Q

bonds in quaternary structure

A
  • hydrophobic
  • hydrogen
  • ionic
  • van der waals
  • disulphide
78
Q

fibrous proteins

A

Long and anrrow- role in providing structural support

79
Q

fibrous protein solubility

A

mostly insoluble

80
Q

sequence of amino acids in fibrous proteins

A

repetitive

81
Q

stability of fibrous proteins

A

less sensitive to changes in heat and pH

82
Q

examples of fibrous proteins

A

collagen and keratin

83
Q

globular proteins

A

rounded/spherical- role is functional (catalysts and transport)

84
Q

solubility of globular proteins

A

soluble

85
Q

sequence of amino acids in globular proteins

A

irregular

86
Q

stability of globular proteins

A

more sensitive to changes in heat and pH

87
Q

examples of globular proteins

A

hb, insulin and catalse

88
Q

enzyme models

A
  • lock and key

- induced fit

89
Q

enzymes

A

lower the activation energy required for a reaction to occur

90
Q

which equations can be used to predict the Vmax and Km of an enzyme

A

Michaelis- menten and Lineweaver Burk Plot

91
Q

how to recognise Michaelis menton

A

hyperbole shape

- Velocity vs [substrate]

92
Q

how to recognise Lineweaver Burk plot

A

straight lines

93
Q

Vmax

A

rate of reaction when the enzyme is fully saturated by substrate, indicating that all the binding sites are constantly reoccupied

94
Q

Km is the

A

substrate concentration that give gives half Vmax

95
Q

the lower the Km

A

the higher the affinity for the substrate

96
Q

types of enzyme inhibition

A

competitive

non-competitive

97
Q

competitive

A

inhibitor binds to active site - directly blocking the active site for the substrate

98
Q

non-competitive

A

changes the shape of the active site by bnidnign to allosteric site

99
Q

inhibitors are molecules which

A

slow down of prevent enzyme reaction. they can be irreversible or reversible

100
Q

reversible competitive inhibitors

A

adding more substrate can override the effect on the enzyme

- as a result the Vmax is unaffacted but the Km will increase

101
Q

reversible non-competitive inhibitor

A

the Vmax decreases but Km is unaffected

102
Q

what can cause irreversible damage to enzymes

A

denaturation, pH and temp

103
Q

energy is the capacity to

A

do work and exists in may forms

104
Q

food has stored

A

chemical enegry

105
Q

humans require energy for

A
  • biosynthesis work
  • transport work
  • mechanical worj
  • electrical work
106
Q

what is the official SI unit of food enegry

A

Kj

107
Q

what do doctors usually use to explain energy in food

A

calories

108
Q

1kcal is equal to how many KJ

A

4.2KJ

109
Q

catabolism

A

catabolism breaks large molecules into smaller ones

110
Q

anabolism

A

anabolism builds complex molecules from simpler ones

111
Q

what are essential components of the diet

A
  • carbohydrates
  • proteins
  • fats
  • mineral
  • vitamins
  • fibre
112
Q

examples of carbohydrates

A

starch, sucrose, fructose, glucose, maltose, glycogen

113
Q

monosaccharides

A

glucose
fructose
galactose

114
Q

disaccharides

A

maltose
lactose
sucrose

115
Q

maltose

A

glucose-glucose

116
Q

lactose

A

galactose-glucose

117
Q

sucrose

A

glucose-fructose

118
Q

list the 9 essential amino acids (pneumonic)

A 
If 
Learned
This 
Helpful
List
May
Prove
Truly
Valuable 
Isoleucine
Leucine
Threonine
Histidine
Lysine
Methionine
Phenylalanine
Tryptophan
Valine
119
Q

why may children and pregnant women require amino acids added to their diet

A

high rate of protein synthesis

e.g. need extra arginine, tyrosine and cysteine

120
Q

fat contains less

A

oxygen compared to hydrogen than carbohydrates or proteins

121
Q

fat has less oxygen and this means

A

it becomes more reduced and yields more oxygen when oxidised

122
Q

fats provide a source of

A

essential fatty acids ( linoleum and linolenic) which can’t be synthesised in the body

123
Q

minearls

A

required to maintain ion gradients, calcium and phosphorus for structure, signalling, enzyme cofactors (iron, magnesium, copper, zinc, manganese) and haemoglobin

124
Q

vitamins

A

e.g. A, D, K, C, folate, B6

essential for life and can lead to deficiency diseases

125
Q

Vitamin A deficiency

A

xerophthalmia

126
Q

Vitamin D deficiency

A

rickets

127
Q

Vitamin K deficiency

A

defective blood clotting

128
Q

Vitamin C deficiency

A

scurvy

129
Q

folate deficiency

A

neural tube defects and anaemia

130
Q

B6 deficiency

A

dermatitis

131
Q

BMI calculation

A

weight (kg)/ height (m^2)

132
Q

obesity is due to

A

excessive energy intake which is stored in adipose tissue

133
Q

when does obesity occur

A

when energy intake> energy expenditure

134
Q

what can obesity cause?

A

T2D
CHD
Osteoarthritis
Cancers

135
Q

underweight BMI

A

<18.5

136
Q

normal BMI

A

18.5- 24.9

137
Q

overweight BM

A

> 25

138
Q

obese BMI

A

> 30

139
Q

severely obese BMI

A

> 40

140
Q

main two conditions which occur in malnutrioned children

A
  • Marasmus

- Kwashiorkor

141
Q

Marasumus characterised by

A

not having too low protein (non oedema)

142
Q

outline marasmus

A
  • calorific deficiency and protein deficiency
  • children under the age of 5
  • muscle wasting
  • emaciated
  • loss of body fat
  • thin hair
  • diarrhoea
  • anaemia
143
Q

outline kwashiorkor

A
  • protein deficiency
  • children displaced from breastfeeding
  • ascites and oedema (starling forces`)
  • hepatomegaly (fat deposition- causes abdominal distension)
  • thin limbs

Revision lectures (Year 1) (17 decks)

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