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year 1 > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

which amino acid is NOT a neutral polar amino acid?

a) serine
b) glutamine
c) cysteine
d) asparagine
e) threonine

A

cysteine - contains sulphur and is NONPOLAR

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2
Q

What is an imino acid

A

An imino group is when the nitrogen forms its fourth bond is attached to another carbon atom (over all bonded to two carbons) to form a ring structure

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3
Q

Name an acidic amino acid example

A

Aspartic acid
Glutamic acid

(Contain a COOH group on their side chain)

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4
Q

Basic amino acid example

A

Arginine or lysine

They have an amine group on the side chain

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5
Q

Name an example of a non polar amino acid

A

Glycine

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6
Q

Name a sulphur containing amino acid

A

Cysteine

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7
Q

Lysozyme hydrolyses which bonds in bacterial cell walls

A

Beta 1,4 linkage between NAG and NAM

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8
Q

What is a zymogen

A

Inactive forms of enzymes

Eg pepsinogen

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9
Q

Describe the Activation of pepsinogen

A

1) chief cells produce pepsinogens
2) parietal cells produce HCl which lowers pH
3) at low pH pepsinogen autocleaves itself and becomes pepsin

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10
Q

Describe the activation of trypsinogen

A

1) enterokinase enzymes in cell wall of interstinal cells partially activate trypsinogen to trypsin
2) trypsin then activates more zymogens including chymotrypsinogen

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11
Q

Chymotrypsinogen activation

A

Chymotrypsin is a protease enzyme. Benefits of activation is that it’s faster than synthesising the enzyme from scratch.

1) trypsin converts chymotrypsinogen -> pi-chymotrypsin by breaking the peptide bond between residues 15 and 16
2) autoactivation by removal of serine and arginine (14,15) to form delta-chymotrypsin
3) residues 148,147 cut to form alpha-chymotrypsin

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12
Q

which function is NOT performed by mitochondria?

a) steroid synthesis
b) cell signalling
c) inducing apoptosis
d) produce ammonia
e) produce reactive oxygen species

A

d) produce ammonia

mitochondria in the liver have enzymes that detoxify ammonia

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13
Q

what is the cytoskeleton composed of?

A

microtubules
microfilaments
intermediate filaments

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14
Q

what are the roles of the nucleolus?

A
  • synthesis of rRNA

- synthesis of immature ribosomes

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15
Q

which one is NOT a function of smooth ER?

a) lipid synthesis
b) calcium ion storage
c) drug detoxification
d) protein synthesis
e) steroid metabolism

A

d) protein synthesis

protein synthesis occurs in Rough ER

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16
Q

what is the difference between gram positive and gram negative bacteria?

A

gram positive:

  • thick peptidoglycan wall
  • only one membrane
  • easily stained

gram negative:

  • thin peptidoglycan wall
  • two membranes, plasma and outer
  • less easily stained
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17
Q

list some structural features of bacterial cells not present in eukaryotic cells

A
  • capsule
  • cell wall (peptidoglycan)
  • mesosomes
  • plasmids
  • lack membrane bound nucleus
  • smaller ribosomes
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18
Q

what is an acid?

A

can donate a proton, gaining a negative charge

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19
Q

what is an alkali?

A

can accept a proton, gaining a positive charge

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20
Q

what are the sources of acids in the body?

A

carbonic acid - from Carbon dioxide
keto acids - from breakdown of triglycerides
lactic acid - product of anaerobic respiration
sulphuric acids - metabolism of AA containing sulphur

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21
Q

what are the main buffers in the human body?

A
  • haemoglobin
  • proteins
  • phosphate
  • bicarbonate
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22
Q

what is “buffer capacity”?

A

the extent to which it can resist pH change

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23
Q

what is the dissociation constant?

A

the equilibrium constant measuring the dissociation of a larger object into smaller objects reversibly. denoted as Kd

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24
Q

what is the relevance of the henderson-hasselbach equation? what is the pKa?

A

it predicts the behaviours of buffer solutions.
pH=pK + log ( [A-]/[HA] )

pKa= acid dissociation constant
pKa = 50% of acid is dissociated/ionised
the lower the pKa value, the stronger the acid
when pH=pKa it means there are equal concentrations of acid and conjugate base

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25
Q

what is “critical pH”?

A

when pH is low enough to cause tooth mineral to dissollve

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26
Q

what is the main buffer found in saliva?

A

bicarbonate - neutralises the acid as opposed to buffering it due to the production of CO2 in the process which is lost

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27
Q

how does the concentration of bicarbonate in the saliva change?

A
  • flow rate
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28
Q

what is the critical pH of the mouth?

A

5.2-5.5

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29
Q

what is optical isomerism?

A

two non-superimposable mirror images of each other that rotate plane polarised light in different orientations : dextro or levo

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30
Q

at which physiological pH do the amino acid exists as..?

a) cationic form (+ve)
b) zwitter ion
c) anionic form (-ve)

A

a) pH below 7.4
b) pH at 7.4
c) pH above 7.4

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31
Q

what type of Amino acids are tyrosine and phenylalanine?

A

aromatic amino acids

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32
Q

how do you work out the isoelectric point?

A

(pKa + pKb)/2

pKa = highest pH at which isoelectric point is 0
pKb = lowest pH at isoelectric point is 0
find the average

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33
Q

name an amino acid important in physiological buffering

A

histidine

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34
Q

name an amino acid that can attach to carbohydrates following post-translational modification

A

serine and threonine

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35
Q

what is glycine a precursor of?

A

heme

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36
Q

what is tyrosine or phenylalanine precursors of?

A

dopamine, adrenaline, noradrenalin

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37
Q

what are precursors of nucleotides?

A

aspartate, glycine, glutamine

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38
Q

what is tryptophan a precursor of?

A

serotonin

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39
Q

what are the bonds that determine tertiary structure of a protein?

A

ionic bonds
hydrophobic/hydrophilic interactions
van Der Waals
disulphide bonds

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40
Q

what is a quaternary structure?

A

union of more than 1 protein molecule/AA chain

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41
Q

what are the three classes of proteins?

A

globular
fibrous
membrane-associated

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42
Q

what is a prosthetic group in protein structures?

A

eg haem group = iron

non-protein components needed for function

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43
Q

what is a zymogen?

A

an inactive precursor of an enzyme

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44
Q

what is a holoenzyme?

A

an enzyme that requires a coenzyme for its activity

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45
Q

what is a apoenzyme?

A

an apoenzyme is an enzyme that doesnt require a coenzyme for its activity. it is labile to heat

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46
Q

describe the action of lysozyme in breaking down bacterial cell wall

A

hydrolyses the 1-4 beta linkages between NAG and NAM

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47
Q

which three amino acids are found at the active site of most enzymes?

A

serine
histidine
aspartate

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48
Q

which cells in the stomach produce HCL?

A

parietal cells

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49
Q

which cells in the stomach produce pepsinogen?

A

chief cells

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50
Q

how is trypsinogen activated? where is it from?

A

trypsinogen is secreted into the duodenum through the b=pancreatic enzymes.
it is activated by enterokinase cells

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51
Q

what is the role of the enzyme trypsin?

A

to activate chymotrypsinogen.

does so by converting chymotrypsinogen into pi chymotrypsin —> alpha chymotrypsin
removal of 2 dipeptides

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52
Q

what does Km stand for in michaelis-menten equation?

A

Km= substrate concentration at half Vmax

it is a constant - each enzyme has a specific Km for its substrate

a small Km = high affinity = high specificity
(less time was taken for half of the enzymes to become ES complex)

useful in comparisons of enzymes and substrates

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53
Q

glucokinase has a Km of 10mM
hexokinase has Km of 0.1mM
which enzyme has a higher affinity for glucose?

A

hexokinase

lower Km = higher affinity

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54
Q

how does a competitive inhibitor affect Vmax and Km?

A 
vmax = doesnt change
Km = increases

(because it will take greater amount of time for half of enzymes to become saturated (Km) but eventually with increasing [substrate] the substrate will outcompete the inhibitor (Vmax)

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55
Q

how does a non competitive inhibitor bind to the enzyme?

A

binds to allosteric site when free or when in ES complex

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56
Q

how does a non competitive inhibitor affect the Vmax and Km

A 
Vmax= decreases
Km= constant
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57
Q

how does uncompetitive inhibition effect Vmax and Km

A 
Vmax = decreases
Km= decreases
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58
Q

how does negative allosteric regulation of enzymes affect Vmax and Km?

A 
Vmax = decreases
Km = increases
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59
Q

what are the main types of lipids and their function?

A

triglycerides - energy storage, insulation
fatty acids - generation of ATP, triglycerides, etc
steroids - hormones, cholesterol
phospholipids - membranes

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60
Q

give a named example of a saturated and unsaturated fatty acid

A

saturated : palmitic acid

unsaturated : oleic acid

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61
Q

how are lipids in the body stored?

A

triglycerides

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62
Q

which hormones enhance lipolysis?

A

cortisol
thyroid hormone
adrenaline
noradrenaline

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63
Q

what is an “essential fatty acid”?

A

fatty acids required in the human diet that cannot be synthesised by the body

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64
Q

why is phospholipid amphipathic?

A

the two fatty acid tails are hydrophobic

phosphate head is hydrophilic

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65
Q

what are apoproteins?

A

found on lipoproteins, they interact with cellular receptors and determine fate of lipoprotein

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66
Q

what is the function of lipoproteins?

A

to transport triglycerides from liver to body cells

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67
Q

is glucose aldose or ketone ?

A

aldose

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68
Q

how does alpha glucose differ from beta glucose?

A

at the anomeric carbon,

alpha: OH on same side
beta: OH on different sides

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69
Q

what is mutarotation?

A

the equilibrium between interchanging alpha and beta anomers

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70
Q

list the types of sugar modifications that can occur

A

deoxy sugars: OH group replaced with H

sugar acids: OH oxidised to COOH

sugar alcohol: aldehyde or ketone reduced to OH

phosphorylated: alcohol group esterified with phosphoric acid

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71
Q

what type of bond exists in the disaccharide sucrose?

A

alpha 1,-2 glycosidic bond

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72
Q

which two bonds exist in glycogen?

A

alpha 1,6 linkages between branches

alpha 1,4 linkages between the monomers

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73
Q

which enzyme breaks up glycogen?

A

glycogen phosphorylase

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74
Q

what two polysaccharides make up starch?

A

amylose

amylopectin

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75
Q

glycogen is branched every ____ residues?

a) 10
b) 12
c) 15
d) 20

A

a) 10

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76
Q

how is amylopectin different from glycogen?

A

amylopectin branches less frequently

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77
Q

name the simplest GAG

A

hyaluronic acid

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78
Q

name the function of glycoproteins

A

major role in immune recognition

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79
Q

what is the difference between N-linked and O-linked glycosylation?

A

N-linked: Nitrogen of asparagine AA

O-linked: Oxygen atom of hydroxyl group of serine/threonine, hydroxyproline, hydroxylysine AA

80
Q

what is a proteoglycan and its function?

A

protein core attached to GAGs

form the ECM and have a role in regulating movement through the matrix and affecting activity and stability of proteins and signalling molecules in the matrix

81
Q

what are the components of GAGs

A

amino sugars : - glucosamine
- galactosamine

uronic acid: - glucaronic acid
- iduronic acid

82
Q

what is the name of a type of GAG that is sulphated?

A

chondroitin sulphate

heparin

83
Q

what is energy balance?

A

balance between energy intake and energy expenditure

84
Q

give an example of a anabolic and catabolic hormone

A

anabolic: insulin
catabolic: glucagon

85
Q

what are the functions of glucagon ?

A
  • glycolysis
  • lipolysis > beta-oxidation
  • proteolysis - gluconeogenesis
86
Q

which organ in the body can produce glucose by glycolysis directly?

A

liver

muscles release lactate following glycolysis which enters the cori cycle

87
Q

Pyruvate dehydrogenase is made up of which 3 enzymes?

a) Pyruvate decarboxylase, dihydrolipoyl dehydrogenase and lipoamide reductase
b) Pyruvate carbokinase, dihydrolipoyl dehydrogenase and lipoamide reductase transacetylase
c) Pyruvate decarboxylase, dihydrolipoyl dehydrogenase and lipoamide reductase transacetylase
d) Pyruvate kinase, dihydrolipoyl dehydrogenase and lipoamide reductase transacetylase
e) Lactate dehydrogenase, dihydrolipoyl dehydrogenase and lipoamide reductase transacetylase

A

c) Pyruvate decarboxylase, dihydrolipoyl dehydrogenase and lipoamide reductase transacetylase

88
Q

what are the product produced after one turn of the krebs cycle? + quantities

A

3 NADH
1 GTP
1 FADH2
2 CO2

89
Q

where does oxidative phosphorylation occur?

A

inner mitochondrial membrane

90
Q

name three inhibitors of the electron transport chain

A

rotenone

antimycin A

CN- or CO

91
Q

what is free energy? (Gibbs free energy)

A

the enrgy contained within a molecule, due to its vibrations, rotations and bond energy

A + B ———-> C + D

delta G = free energy of (C + D) - free energy of (A + B)

+ delta G = endergonic
- delta G = exergonic = spontaneous reaction

92
Q

cell metabolism is organised by….?

A

enzymes

93
Q

how do energetically unfavourable reactions (endergonic) take place in the body?

A

enzymes couple them to an energetically favourable reaction

eg with hydrolysis of ATP

94
Q

generally, which reaction is energetically favourable?

a) condensation
b) hydrolysis

A

hydrolysis

95
Q

how are polymers synthesis? and is it an energetically favourabl or unfavourable reaction?

A

condensation reactions,

energetically unfavourable - coupled with ATP hyrdolysis

96
Q

which one is NOT an activated carrier molecule?

a) ATP
b) acetyl CoA
c) uridine diphosphate glucose
d) NADP
e) carboxylated biotin
f) S-adenosylmethionine
g) FADH2

A

d) NADP

the activated form is NADPH

97
Q

where in the body is glucose actively transported?

A

intestines

98
Q

which type of Glucose transporters have a high Km? and where are they found?

A

GLUT 2 - liver and pancreatic cells

low glucose uptake

99
Q

which type of glucose transporters are insulin sensitive? and where are they found?

A

GLUT 4 - muscle and adipose tissue

100
Q

which GLUTs are found on most plasma membranes?

A

GLUT 1 + 3

101
Q

what factors increase GLUT 4 receptors on plasma membranes of muscle cells?

A

insulin

exercise

102
Q

what inhibits hexokinase activity?

A

high concentrations of glucose-6-phosphate (negative feedback mechanism)

103
Q

what two molecules are needed in the phosphorylation of glucose by hexokinase?

A

ATP

Mg2+

104
Q

what bonds exist between the phosphate molecules of an ATP?

A

phosphoanhydride bond

105
Q

why does hexokinase remove water during phosphorylation of glucose?

A

to ensure ATP is not hydrolysed

106
Q

which enzyme catalyses the production of fructose 6-P from glucose 6P?

a) aldolase
b) triose phosphate isomerase
c) phosphofructokinase
d) phosphoglucose isomerase
e) phosphoglycerate kinase

A

d) phosphoglucose isomerase

107
Q

is glucose an aldose or ketose?

A

aldose

108
Q

which enzyme is involved in the rate limiting step of glycolysis?

A

phosphofructokinase

production of fructose6P to fructose-1,6-bisphosphate

109
Q

what is the difference between phosphofructokinase I and phosphofructokinase II?

A

PFK I :
produces fructose-1,6-bisphosphate

PFK II: produces fructose-2,6-bisphosphate

110
Q

what inhibits phosphofructokinase I?

A

high ATP and citrate levels

allosteric inhibition
(when high [ATP] = binds to low affinity regulatory site)

111
Q

what activates phosphofructokinase I?

A

high fructose-2,6-bisphosphate

high AMP,ADP levels

112
Q

when is phosphofructokinase II activate?

A

when PFK I is inactive

113
Q

how does high [ATP] reduce glycolysis?

A

ATP binds to allosteric site that has a low affinity for ATP (regulatory site) on PFK I

causes conformational change to PFK I

fructose-6P unable to bind to active site of PFK I

decreased glycolysis

114
Q

which enzyme catalyses the conversion of fructose-1,6-bisphosphate into glyceraldehyde-3P?

a) aldolase
b) triose phosphate isomerase
c) phosphofructokinase
d) phosphoglucose isomerase
e) phosphoglycerate kinase

A

a) aldolase

115
Q

which enzyme catalyses the production of glyceraldehyde-3P into dihydroxyactone-P?

a) aldolase
b) triose phosphate isomerase
c) phosphofructokinase
d) phosphoglucose isomerase
e) phosphoglycerate kinase

A

b) triose phosphate isomerase

116
Q

what is the difference between kinases and mutases?

A

kinases transfer phosphate from ATP

mutases transfer phosphate from one carbon atom to the next

117
Q

which enzyme in the glycolysis pathway doesn’t require Mg2+ ?

a) hexokinase
b) phosphofructokinase
c) aldolase
d) enolase
e) phosphoglycerate kinase

A

c) aldolase

118
Q

how many ATP molecules produced from glycolysis from one glucose molecule?

A

2

119
Q

how many NADH molecules produced per glucose from glycolysis?

A

2

120
Q

why do anaerobic organisms metabolise pyruvate into ethanol?

A

to re produce NAD+

121
Q

what is the significance of the malate aspartate shuttle?

A

to transport NADH into the mitochondria

inner mitochondrial membrane impermeable to NADH

122
Q

which enzyme is involved in the conversion of galactose-1P into glucose 1P?

a) galactose-1P uridylyltransferase
b) phosphoglucomutase
c) galactokinase
d) galacto-glucose isomerase
e) phosphoglycerate kinase

A

a) galactose-1P uridylyltransferase

123
Q

what are the two main ways blood glucose levels are maintained to avoid hypoglycaemia?

A

gluconeogenesis

glycogenolysis

124
Q

where does gluconeogenesis occur?

A

liver

kidneys

125
Q

what are the precursors for gluconeogenesis?

A

lactate

alanine (amino acid)

glycerol

glutamine (kidneys) (amino acid)

126
Q

which enzyme catalyses the conversion of pyruvate into lactate?

A

lactate dehydrogenase

127
Q

what activates pyruvate carboxylase?

A

acetyl CoA

128
Q

what enzymes catalyse pyruvate back to phosphoenolpyruvate?

A

MALATE DEHYDROGENASE: malate → oxaloacetate

PYRUVATE CARBOXYLASE: pyruvate → oxaloacetate

PEP CARBOXYKINASE: oxaloacetate → phosphoenolpyruvate

129
Q

which enzyme catalyses the reverse reaction of hexokinase?

A

glucose-6-phosphatase

130
Q

which enzyme catalyses the reverse reaction of phosphofructokinase I?

A

fructose-1,6-bisphosphatase

131
Q

Which enzymes are NOT involved in glycolysis?

a) enolase, glucose-6-phosphotase, fructose-1,6-bisphosphatase, pyruvate carboxylase
b) glucose-6-phosphotase, fructose-1,6-bisphosphatase, pyruvate carboxylase, PEP carbokinase
c) glucose-6-phosphotase, fructose-1,6-bisphosphatase, pyruvate decarboxylase, PEP carbokinase
d) phosphoglycerate mutase, phosphofructokinase, pyruvate carboxylase, PEP carbokinase

A

b) glucose-6-phosphotase, fructose-1,6-bisphosphatase, pyruvate carboxylase, PEP carbokinase

132
Q

which amino acids are not glucogenic?

a) alanine and lysine
b) alanine and glutamine
c) glutamine and lysine
d) lysine and leucine
e) aspargine and lysine

A

d) lysine and leucine

133
Q

how is the enzyme glycogen synthase activated?

A

dephosphorylation

134
Q

which enzyme catalyses the rate limiting step in glycogen synthesis?

a) pyrophosphatase
b) glycogen synthase
c) glycogen phosphorylase
d) phosphoglucomutase
e) UDP-glucose pyrophosphorylase

A

glycogen synthase

135
Q

which enzyme breaks down alpha 1-4 glycosidic linkages in glycogen?

a) pyrophosphatase
b) glycogen synthase
c) glycogen phosphorylase
d) phosphoglucomutase
e) UDP-glucose pyrophosphorylase

A

c) glycogen phosphorylase

136
Q

which enzyme catalyses the reaction of glucose-1P to glucose-6P?

a) pyrophosphatase
b) glycogen synthase
c) glycogen phosphorylase
d) phosphoglucomutase
e) UDP-glucose pyrophosphorylase

A

d) phosphoglucomutase

137
Q

which two enzymes are involved in the debranching of glycogen?

A

α 1-4 transglycosylase

α 1-6 glucosidase

138
Q

which enzyme becomes inactive when undergoing phosphorylation ?

a) pyrophosphatase
b) glycogen synthase
c) glycogen phosphorylase
d) phosphoglucomutase
e) UDP-glucose pyrophosphorylase

A

b) glycogen synthase

139
Q

which enzymes of the TCA cycle are allosterically activated by Calcium ions?

a) aconitase and α ketoglutarate dehydrogenase
b) α ketoglutarate dehydrogenase and succinyl CoA synthase
c) isocitrate dehydrogenase and α ketoglutarate dehydrogenase
d) α ketoglutarate dehydrogenase and malate dehydrogenase
e) isocitrate dehydrogenase and citrate synthase

A

c) isocitrate dehydrogenase and α ketoglutarate dehydrogenase

140
Q

which molecule cannot pass through the inner mitochondrial membrane?

a) malate
b) aspartate
c) citrate
d) actetyl CoA

A

d) actetyl CoA

141
Q

what inhibits the pyruvate dehydrogenase complex?

A

acetyl CoA and NAD+ (fatty acid oxidation)

phosphorylation of PDC = inactive

142
Q

how does high glucose level suppress fatty acid oxidation?

A

high glucose = high citrate = high production of acetyl CoA and malonyl CoA

malonyl CoA inhibits fatty acid transporter (CPR-1)

143
Q

describe the phases of interphase in a cell cycle

A
  • G1 = production of organelles and cytosol
  • S = DNA replication
  • G2 = production of enzymes needed in mitosis
144
Q

which stage of the cell cycle contains the restriction point

A

G1 phase of interphase

145
Q

at which stage does cytokinesis occur?

a) late prophase
b) late metaphase
c) late anaphase
d) telophase
e) late telophase

A

c) late anaphase

146
Q

at what point does a cell enter G0 phase of the cell cycle?

A

when it has terminally differentiated

147
Q

what is positive nitrogen balance?

A

protein synthesis > protein degradation (normal)

148
Q

how does pH affect calcium binding to plasma proteins?

A

calcium binds to the protein albumin .

increase in pH = more calcium binding

149
Q

which hormone works to reduce calcium serum concentration?

a) parathyroid hormone
b) calcitonin
c) calcitriol
d) vitamin D3

A

b) calcitonin

150
Q

which hormone is the main regulator of calcium concentration in serum?

a) parathyroid hormone
b) calcitonin
c) calcitriol
d) vitamin D3

A

a) parathyroid hormone

151
Q

what is von Gierke’s disease?

A

deficiency of glucose 6 phosphatase

152
Q

what is the difference in between alkaptonuria and phenylketonuria?

A

alkaptonuria: defect in breakdown of phenylalanine and tyrosine
phenylketonuria: deficiency of phenylalanine hydroxylase

153
Q

what are is the anatomy of islet of langerhans and their functions?

A

alpha: secrete glucagon
beta: secrete insulin
delta: secrete somatostatin

F cells : pancreatic polypetides

capillaries

154
Q

what is present in Beta cells in pancrease that causes release of insulin?

A

GLUT 2 receptors allow glucose to enter cells

Gucokinase is also present

metabolism of glucose = ATP+NADH

= release of insulin

155
Q

list the locations of the different GLUT receptors

A

GLUT 1 and 3: all body tissues

GLUT 2: liver and pancreatic cells

GLUT 4: muscle cells and adipose tissue

156
Q

which compounds oppose effects of insulin?

A
  • glucagon
  • adrenaline
  • growth hormone
  • glucocorticoids
157
Q

which cell type is the most numerous in the anterior pituitary?

a) somatotroph
b) thyrotroph
c) gonadotroph
d) corticotroph
e) lactotroph

A

a) somatotroph

158
Q

which hormone secretion from anterior pituitary causes the release of cortisol from adrenal cortex?

a) LH
b) hGH
c) FSH
d) PRL
e) ACTH

A

e) ACTH - adrenocorticotropic hormone

159
Q

name an example of a glucocorticoid and mineralcorticoid

A

glucocorticoid: cortisol
mineralcorticoid: aldosterone

160
Q

which hormone is released in response to increased plasma K+ levels?

a) androgens
b) aldosterone
c) cortisol
d) adrenaline
e) thyroid hormone

A

b) aldosterone

161
Q

what causes the release of hGH from the anterior pituitary gland?

A

the hypothalamus is stimulated to secrete GHRH during hypoglycaemic conditions which causes stimulation of ant. pituitary to release hGH

162
Q

which cells secrete calcitonin? and what is its role

A

parafollicular cells of thyroid gland

regulates calcium homeostasis by inhibiting osteoclast activity and decreasing calcium serum levels

163
Q

what is myxoedema ?

A

tissue swelling caused by hypothyroidism

164
Q

what is the action of the enzyme alanine aminotranferase?

A

transfers amide group from glutamate to pyruvate to form alanine and alpha ketoglutarate

165
Q

what are the three methods amino acids can be formed?

A

transamination

amidation

from other amino acids

166
Q

which one does not have an amide group?

a) alanine
b) glutamine
c) pyruvate
d) aspargine
e) aspartate

A

c) pyruvate

167
Q

where does deamination occur?

A

in the liver mitochondria

168
Q

which molecule links the urea cycle and the krebs cycle?

A

argininosuccinate

169
Q

how many ATP molecules used up in detoxification of ammonia? 1 cycle

A

3 ATP

170
Q

which part of the urea cycle is only taken place in the mitochondria?

A

the production of carbomoyl phosphate from ammonia, co2

171
Q

which enzyme catalyses the reaction of glucose-6P to glucose 1P?

A

phosphoglucomutase

172
Q

which enzyme catalyses the conversion of glucose 1P to UDP glucose?

A

UDP-glucose pyrophosphorylase

173
Q

which enzyme catalyses the conversion of UDP glucose to glycogen?

A

glycogen synthase

174
Q

which enzyme catalyses the reaction from glycogen to glucose 1P?

A

glycogen phosphorylase

175
Q

how is glycogen synthase activated?

A

dephosphorylation

176
Q

how is glycogen synthase activated?

A

phosphorylation

(think of it as when cell is activated protein kinases are activated and so the cell needs energy, and protein kinases phosphorylate the enzyme so more glucose is available )

177
Q

how does glucagon affect glycogen breakdown?

A

glucagon causes increase cAMP production

increase protein kinase A activity.

kinases phosphorylates both glycogen synthase and glycogen phosphorylase.

glycogen synthase is inactivated

glycogen phosphorylase is activated

increased breakdown of glycogen into glucose to raise blood glucose levels

178
Q

how does insulin affect glycogen synthesis?

A

insulin receptors decrease cAMP productions, thus reduces activity of protein kinase A

this means there is dephosphorylation of the enzymes glycogen synthase and glycogen phosphorylase

glycogen synthase becomes active

glycogen phosphorylase becomes inactive

179
Q

what is the consequence in the lack of the HPRT enzyme?

A

no breakdown of the purines guanine and hypoxanthine

purines broken down to uric acid in liver

accumulation of uric acid

crystal formation in joints and kidney stones

180
Q

how many hydrogen bonds between A and T base pairs in dna?

A

2

181
Q

list some of the proteins involved in DNA replication

A

helicase: unwinds double stranded DNA

single stranded DNA binding proteins: stabilise single DNA strands to prevent them from reannealing

RNA primase: synthesis f short RNA primers reuired for initiation of DNA synthesis

RNAase H: removes the RNA primer

DNA polymerase I: follows RNAase H and replaces the RNA primer with DNA nucleotides

DNA ligase: joins the okazaki fragments on the lagging strand

182
Q

what four molecules are needed for initiation of RNA synthesis by RNA polymerase?

A

transcription factor II D
transcription binding proteins
transcription binding II A/B
ATP

183
Q

which one is not exclusive to eukaryotes?

a) pre mRNA
b) rRNA
c) snoRNA
d) snRNA
e) siRNA

A

b) rRNA

184
Q

what is the function of snoRNA?

A

snoRNA= small nucleolar RNA

involved in chemical modification of rRNA

185
Q

what is the function of miRNA?

A

micro RNA

regulation of gene expression

186
Q

which RNA type is involved in splicing of pre mRNA?

a) miRNA
b) rRNA
c) snoRNA
d) snRNA
e) siRNA

A

d) snRNA

187
Q

what are the steps involved in converting pre mRNA into mature mRNA?

A

1) end modification : addition of CAP and poly A tail
2) splicing of introns by spliceosomes and snRNA
3) cutting
4) chemical modification

188
Q

which enzyme is absent in the Von Gierke’s Disease?

A

glucose phosphatase

no gluconeogenesis

189
Q

what is the lacking enzyme in Phenylketonuria?

A

no phenylalanine hydroxylase

(build up of phenylalanine and no tyrosine production = no melanin as tyrosine needed to produce melanin)

classic symptoms: blue eyes, fair hair, mental retardation

190
Q

what causes alkaptonuria?

A

defect in breakdown of phenylalanine and tyrosine due to homogenistic acid oxidase block

191
Q

what causes fructose intolerance?

A

deficiency of fructose aldose

192
Q

which enzyme is absent in galactosemia?

A

galactose 1 phosphate uridyltransferase

193
Q

what causes type III diabetes mellitus?

A

human placental lactogen hormone interferes with insulin receptors

194
Q

in diabetes, what two things lead to dehrydration?

A

increased lipolysis = increased ketone bodies = ketoacidosis = vomiting = dehydration

decreased glucose uptake = hyperglycaemia = glycosuria = osmotic diuresis = dehydration

195
Q

Familial hypercholesterolaemia occurs in response to..

a. Malfunctioning of phenylalanine hydroxylase
b. Absence of aldolase
c. Accumulation of homegentisic acid
d. Reduced LDL receptors
e. Deficiency of glucose 6-phosphatase

A

d. Reduced LDL receptors

196
Q

what causes maple syrup disease?

A

defect in branched amino acid metabolism = accumulation of ketoacids in blood and urine

year 1 (8 decks)

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