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
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
3
Q
Name an acidic amino acid example
A
Aspartic acid
Glutamic acid
(Contain a COOH group on their side chain)
4
Q
Basic amino acid example
A
Arginine or lysine
They have an amine group on the side chain
5
Q
Name an example of a non polar amino acid
A
Glycine
6
Q
Name a sulphur containing amino acid
A
Cysteine
7
Q
Lysozyme hydrolyses which bonds in bacterial cell walls
A
Beta 1,4 linkage between NAG and NAM
8
Q
What is a zymogen
A
Inactive forms of enzymes
Eg pepsinogen
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
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
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
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
13
Q
what is the cytoskeleton composed of?
A
microtubules
microfilaments
intermediate filaments
14
Q
what are the roles of the nucleolus?
A
- synthesis of rRNA
- synthesis of immature ribosomes
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
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
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
18
Q
what is an acid?
A
can donate a proton, gaining a negative charge
19
Q
what is an alkali?
A
can accept a proton, gaining a positive charge
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
21
Q
what are the main buffers in the human body?
A
- haemoglobin
- proteins
- phosphate
- bicarbonate
22
Q
what is “buffer capacity”?
A
the extent to which it can resist pH change
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
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
25
what is "critical pH"?
when pH is low enough to cause tooth mineral to dissollve
26
what is the main buffer found in saliva?
bicarbonate - neutralises the acid as opposed to buffering it due to the production of CO2 in the process which is lost
27
how does the concentration of bicarbonate in the saliva change?
- flow rate
28
what is the critical pH of the mouth?
5.2-5.5
29
what is optical isomerism?
two non-superimposable mirror images of each other that rotate plane polarised light in different orientations : dextro or levo
30
at which physiological pH do the amino acid exists as..?
a) cationic form (+ve)
b) zwitter ion
c) anionic form (-ve)
a) pH below 7.4
b) pH at 7.4
c) pH above 7.4
31
what type of Amino acids are tyrosine and phenylalanine?
aromatic amino acids
32
how do you work out the isoelectric point?
(pKa + pKb)/2
pKa = highest pH at which isoelectric point is 0
pKb = lowest pH at isoelectric point is 0
find the average
33
name an amino acid important in physiological buffering
histidine
34
name an amino acid that can attach to carbohydrates following post-translational modification
serine and threonine
35
what is glycine a precursor of?
heme
36
what is tyrosine or phenylalanine precursors of?
dopamine, adrenaline, noradrenalin
37
what are precursors of nucleotides?
aspartate, glycine, glutamine
38
what is tryptophan a precursor of?
serotonin
39
what are the bonds that determine tertiary structure of a protein?
ionic bonds
hydrophobic/hydrophilic interactions
van Der Waals
disulphide bonds
40
what is a quaternary structure?
union of more than 1 protein molecule/AA chain
41
what are the three classes of proteins?
globular
fibrous
membrane-associated
42
what is a prosthetic group in protein structures?
eg haem group = iron
| non-protein components needed for function
43
what is a zymogen?
an inactive precursor of an enzyme
44
what is a holoenzyme?
an enzyme that requires a coenzyme for its activity
45
what is a apoenzyme?
an apoenzyme is an enzyme that doesnt require a coenzyme for its activity. it is labile to heat
46
describe the action of lysozyme in breaking down bacterial cell wall
hydrolyses the 1-4 beta linkages between NAG and NAM
47
which three amino acids are found at the active site of most enzymes?
serine
histidine
aspartate
48
which cells in the stomach produce HCL?
parietal cells
49
which cells in the stomach produce pepsinogen?
chief cells
50
how is trypsinogen activated? where is it from?
trypsinogen is secreted into the duodenum through the b=pancreatic enzymes.
it is activated by enterokinase cells
51
what is the role of the enzyme trypsin?
to activate chymotrypsinogen.
| does so by converting chymotrypsinogen into pi chymotrypsin ---> alpha chymotrypsin
removal of 2 dipeptides
52
what does Km stand for in michaelis-menten equation?
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
53
glucokinase has a Km of 10mM
hexokinase has Km of 0.1mM
which enzyme has a higher affinity for glucose?
hexokinase
lower Km = higher affinity
54
how does a competitive inhibitor affect Vmax and Km?
```
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)
55
how does a non competitive inhibitor bind to the enzyme?
binds to allosteric site when free or when in ES complex
56
how does a non competitive inhibitor affect the Vmax and Km
```
Vmax= decreases
Km= constant
```
57
how does uncompetitive inhibition effect Vmax and Km
```
Vmax = decreases
Km= decreases
```
58
how does negative allosteric regulation of enzymes affect Vmax and Km?
```
Vmax = decreases
Km = increases
```
59
what are the main types of lipids and their function?
triglycerides - energy storage, insulation
fatty acids - generation of ATP, triglycerides, etc
steroids - hormones, cholesterol
phospholipids - membranes
60
give a named example of a saturated and unsaturated fatty acid
saturated : palmitic acid
| unsaturated : oleic acid
61
how are lipids in the body stored?
triglycerides
62
which hormones enhance lipolysis?
cortisol
thyroid hormone
adrenaline
noradrenaline
63
what is an "essential fatty acid"?
fatty acids required in the human diet that cannot be synthesised by the body
64
why is phospholipid amphipathic?
the two fatty acid tails are hydrophobic
| phosphate head is hydrophilic
65
what are apoproteins?
found on lipoproteins, they interact with cellular receptors and determine fate of lipoprotein
66
what is the function of lipoproteins?
to transport triglycerides from liver to body cells
67
is glucose aldose or ketone ?
aldose
68
how does alpha glucose differ from beta glucose?
at the anomeric carbon,
alpha: OH on same side
beta: OH on different sides
69
what is mutarotation?
the equilibrium between interchanging alpha and beta anomers
70
list the types of sugar modifications that can occur
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
71
what type of bond exists in the disaccharide sucrose?
alpha 1,-2 glycosidic bond
72
which two bonds exist in glycogen?
alpha 1,6 linkages between branches
| alpha 1,4 linkages between the monomers
73
which enzyme breaks up glycogen?
glycogen phosphorylase
74
what two polysaccharides make up starch?
amylose
| amylopectin
75
glycogen is branched every ____ residues?
a) 10
b) 12
c) 15
d) 20
a) 10
76
how is amylopectin different from glycogen?
amylopectin branches less frequently
77
name the simplest GAG
hyaluronic acid
78
name the function of glycoproteins
major role in immune recognition
79
what is the difference between N-linked and O-linked glycosylation?
N-linked: Nitrogen of asparagine AA
O-linked: Oxygen atom of hydroxyl group of serine/threonine, hydroxyproline, hydroxylysine AA
80
what is a proteoglycan and its function?
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
what are the components of GAGs
amino sugars : - glucosamine
- galactosamine
uronic acid: - glucaronic acid
- iduronic acid
82
what is the name of a type of GAG that is sulphated?
chondroitin sulphate
| heparin
83
what is energy balance?
balance between energy intake and energy expenditure
84
give an example of a anabolic and catabolic hormone
anabolic: insulin
catabolic: glucagon
85
what are the functions of glucagon ?
- glycolysis
- lipolysis > beta-oxidation
- proteolysis - gluconeogenesis
86
which organ in the body can produce glucose by glycolysis directly?
liver
muscles release lactate following glycolysis which enters the cori cycle
87
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
c) Pyruvate decarboxylase, dihydrolipoyl dehydrogenase and lipoamide reductase transacetylase
88
what are the product produced after one turn of the krebs cycle? + quantities
3 NADH
1 GTP
1 FADH2
2 CO2
89
where does oxidative phosphorylation occur?
inner mitochondrial membrane
90
name three inhibitors of the electron transport chain
rotenone
antimycin A
CN- or CO
91
what is free energy? (Gibbs free energy)
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
cell metabolism is organised by....?
enzymes
93
how do energetically unfavourable reactions (endergonic) take place in the body?
enzymes couple them to an energetically favourable reaction
| eg with hydrolysis of ATP
94
generally, which reaction is energetically favourable?
a) condensation
b) hydrolysis
hydrolysis
95
how are polymers synthesis? and is it an energetically favourabl or unfavourable reaction?
condensation reactions,
| energetically unfavourable - coupled with ATP hyrdolysis
96
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
d) NADP
the activated form is NADPH
97
where in the body is glucose actively transported?
intestines
98
which type of Glucose transporters have a high Km? and where are they found?
GLUT 2 - liver and pancreatic cells
| low glucose uptake
99
which type of glucose transporters are insulin sensitive? and where are they found?
GLUT 4 - muscle and adipose tissue
100
which GLUTs are found on most plasma membranes?
GLUT 1 + 3
101
what factors increase GLUT 4 receptors on plasma membranes of muscle cells?
insulin
| exercise
102
what inhibits hexokinase activity?
high concentrations of glucose-6-phosphate (negative feedback mechanism)
103
what two molecules are needed in the phosphorylation of glucose by hexokinase?
ATP
| Mg2+
104
what bonds exist between the phosphate molecules of an ATP?
phosphoanhydride bond
105
why does hexokinase remove water during phosphorylation of glucose?
to ensure ATP is not hydrolysed
106
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
d) phosphoglucose isomerase
107
is glucose an aldose or ketose?
aldose
108
which enzyme is involved in the rate limiting step of glycolysis?
phosphofructokinase
| production of fructose6P to fructose-1,6-bisphosphate
109
what is the difference between phosphofructokinase I and phosphofructokinase II?
PFK I :
produces fructose-1,6-bisphosphate
PFK II: produces fructose-2,6-bisphosphate
110
what inhibits phosphofructokinase I?
high ATP and citrate levels
| allosteric inhibition
(when high [ATP] = binds to low affinity regulatory site)
111
what activates phosphofructokinase I?
high fructose-2,6-bisphosphate
| high AMP,ADP levels
112
when is phosphofructokinase II activate?
when PFK I is inactive
113
how does high [ATP] reduce glycolysis?
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
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) aldolase
115
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
b) triose phosphate isomerase
116
what is the difference between kinases and mutases?
kinases transfer phosphate from ATP
mutases transfer phosphate from one carbon atom to the next
117
which enzyme in the glycolysis pathway doesn't require Mg2+ ?
a) hexokinase
b) phosphofructokinase
c) aldolase
d) enolase
e) phosphoglycerate kinase
c) aldolase
118
how many ATP molecules produced from glycolysis from one glucose molecule?
2
119
how many NADH molecules produced per glucose from glycolysis?
2
120
why do anaerobic organisms metabolise pyruvate into ethanol?
to re produce NAD+
121
what is the significance of the malate aspartate shuttle?
to transport NADH into the mitochondria
inner mitochondrial membrane impermeable to NADH
122
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) galactose-1P uridylyltransferase
123
what are the two main ways blood glucose levels are maintained to avoid hypoglycaemia?
gluconeogenesis
| glycogenolysis
124
where does gluconeogenesis occur?
liver
| kidneys
125
what are the precursors for gluconeogenesis?
lactate
alanine (amino acid)
glycerol
glutamine (kidneys) (amino acid)
126
which enzyme catalyses the conversion of pyruvate into lactate?
lactate dehydrogenase
127
what activates pyruvate carboxylase?
acetyl CoA
128
what enzymes catalyse pyruvate back to phosphoenolpyruvate?
MALATE DEHYDROGENASE: malate → oxaloacetate
PYRUVATE CARBOXYLASE: pyruvate → oxaloacetate
PEP CARBOXYKINASE: oxaloacetate → phosphoenolpyruvate
129
which enzyme catalyses the reverse reaction of hexokinase?
glucose-6-phosphatase
130
which enzyme catalyses the reverse reaction of phosphofructokinase I?
fructose-1,6-bisphosphatase
131
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
b) glucose-6-phosphotase, fructose-1,6-bisphosphatase, pyruvate carboxylase, PEP carbokinase
132
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
d) lysine and leucine
133
how is the enzyme glycogen synthase activated?
dephosphorylation
134
which enzyme catalyses the rate limiting step in glycogen synthesis?
a) pyrophosphatase
b) glycogen synthase
c) glycogen phosphorylase
d) phosphoglucomutase
e) UDP-glucose pyrophosphorylase
glycogen synthase
135
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
c) glycogen phosphorylase
136
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
d) phosphoglucomutase
137
which two enzymes are involved in the debranching of glycogen?
α 1-4 transglycosylase
| α 1-6 glucosidase
138
which enzyme becomes inactive when undergoing phosphorylation ?
a) pyrophosphatase
b) glycogen synthase
c) glycogen phosphorylase
d) phosphoglucomutase
e) UDP-glucose pyrophosphorylase
b) glycogen synthase
139
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
c) isocitrate dehydrogenase and α ketoglutarate dehydrogenase
140
which molecule cannot pass through the inner mitochondrial membrane?
a) malate
b) aspartate
c) citrate
d) actetyl CoA
d) actetyl CoA
141
what inhibits the pyruvate dehydrogenase complex?
acetyl CoA and NAD+ (fatty acid oxidation)
phosphorylation of PDC = inactive
142
how does high glucose level suppress fatty acid oxidation?
high glucose = high citrate = high production of acetyl CoA and malonyl CoA
malonyl CoA inhibits fatty acid transporter (CPR-1)
143
describe the phases of interphase in a cell cycle
- G1 = production of organelles and cytosol
- S = DNA replication
- G2 = production of enzymes needed in mitosis
144
which stage of the cell cycle contains the restriction point
G1 phase of interphase
145
at which stage does cytokinesis occur?
a) late prophase
b) late metaphase
c) late anaphase
d) telophase
e) late telophase
c) late anaphase
146
at what point does a cell enter G0 phase of the cell cycle?
when it has terminally differentiated
147
what is positive nitrogen balance?
protein synthesis > protein degradation (normal)
148
how does pH affect calcium binding to plasma proteins?
calcium binds to the protein albumin .
increase in pH = more calcium binding
149
which hormone works to reduce calcium serum concentration?
a) parathyroid hormone
b) calcitonin
c) calcitriol
d) vitamin D3
b) calcitonin
150
which hormone is the main regulator of calcium concentration in serum?
a) parathyroid hormone
b) calcitonin
c) calcitriol
d) vitamin D3
a) parathyroid hormone
151
what is von Gierke's disease?
deficiency of glucose 6 phosphatase
152
what is the difference in between alkaptonuria and phenylketonuria?
alkaptonuria: defect in breakdown of phenylalanine and tyrosine
phenylketonuria: deficiency of phenylalanine hydroxylase
153
what are is the anatomy of islet of langerhans and their functions?
alpha: secrete glucagon
beta: secrete insulin
delta: secrete somatostatin
F cells : pancreatic polypetides
capillaries
154
what is present in Beta cells in pancrease that causes release of insulin?
GLUT 2 receptors allow glucose to enter cells
Gucokinase is also present
metabolism of glucose = ATP+NADH
= release of insulin
155
list the locations of the different GLUT receptors
GLUT 1 and 3: all body tissues
GLUT 2: liver and pancreatic cells
GLUT 4: muscle cells and adipose tissue
156
which compounds oppose effects of insulin?
- glucagon
- adrenaline
- growth hormone
- glucocorticoids
157
which cell type is the most numerous in the anterior pituitary?
a) somatotroph
b) thyrotroph
c) gonadotroph
d) corticotroph
e) lactotroph
a) somatotroph
158
which hormone secretion from anterior pituitary causes the release of cortisol from adrenal cortex?
a) LH
b) hGH
c) FSH
d) PRL
e) ACTH
e) ACTH - adrenocorticotropic hormone
159
name an example of a glucocorticoid and mineralcorticoid
glucocorticoid: cortisol
mineralcorticoid: aldosterone
160
which hormone is released in response to increased plasma K+ levels?
a) androgens
b) aldosterone
c) cortisol
d) adrenaline
e) thyroid hormone
b) aldosterone
161
what causes the release of hGH from the anterior pituitary gland?
the hypothalamus is stimulated to secrete GHRH during hypoglycaemic conditions which causes stimulation of ant. pituitary to release hGH
162
which cells secrete calcitonin? and what is its role
parafollicular cells of thyroid gland
regulates calcium homeostasis by inhibiting osteoclast activity and decreasing calcium serum levels
163
what is myxoedema ?
tissue swelling caused by hypothyroidism
164
what is the action of the enzyme alanine aminotranferase?
transfers amide group from glutamate to pyruvate to form alanine and alpha ketoglutarate
165
what are the three methods amino acids can be formed?
transamination
amidation
from other amino acids
166
which one does not have an amide group?
a) alanine
b) glutamine
c) pyruvate
d) aspargine
e) aspartate
c) pyruvate
167
where does deamination occur?
in the liver mitochondria
168
which molecule links the urea cycle and the krebs cycle?
argininosuccinate
169
how many ATP molecules used up in detoxification of ammonia? 1 cycle
3 ATP
170
which part of the urea cycle is only taken place in the mitochondria?
the production of carbomoyl phosphate from ammonia, co2
171
which enzyme catalyses the reaction of glucose-6P to glucose 1P?
phosphoglucomutase
172
which enzyme catalyses the conversion of glucose 1P to UDP glucose?
UDP-glucose pyrophosphorylase
173
which enzyme catalyses the conversion of UDP glucose to glycogen?
glycogen synthase
174
which enzyme catalyses the reaction from glycogen to glucose 1P?
glycogen phosphorylase
175
how is glycogen synthase activated?
dephosphorylation
176
how is glycogen synthase activated?
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
how does glucagon affect glycogen breakdown?
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
how does insulin affect glycogen synthesis?
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
what is the consequence in the lack of the HPRT enzyme?
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
how many hydrogen bonds between A and T base pairs in dna?
2
181
list some of the proteins involved in DNA replication
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
what four molecules are needed for initiation of RNA synthesis by RNA polymerase?
transcription factor II D
transcription binding proteins
transcription binding II A/B
ATP
183
which one is not exclusive to eukaryotes?
a) pre mRNA
b) rRNA
c) snoRNA
d) snRNA
e) siRNA
b) rRNA
184
what is the function of snoRNA?
snoRNA= small nucleolar RNA
involved in chemical modification of rRNA
185
what is the function of miRNA?
micro RNA
regulation of gene expression
186
which RNA type is involved in splicing of pre mRNA?
a) miRNA
b) rRNA
c) snoRNA
d) snRNA
e) siRNA
d) snRNA
187
what are the steps involved in converting pre mRNA into mature mRNA?
1) end modification : addition of CAP and poly A tail
2) splicing of introns by spliceosomes and snRNA
3) cutting
4) chemical modification
188
which enzyme is absent in the Von Gierke's Disease?
glucose phosphatase
| no gluconeogenesis
189
what is the lacking enzyme in Phenylketonuria?
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
what causes alkaptonuria?
defect in breakdown of phenylalanine and tyrosine due to homogenistic acid oxidase block
191
what causes fructose intolerance?
deficiency of fructose aldose
192
which enzyme is absent in galactosemia?
galactose 1 phosphate uridyltransferase
193
what causes type III diabetes mellitus?
human placental lactogen hormone interferes with insulin receptors
194
in diabetes, what two things lead to dehrydration?
increased lipolysis = increased ketone bodies = ketoacidosis = vomiting = dehydration
decreased glucose uptake = hyperglycaemia = glycosuria = osmotic diuresis = dehydration
195
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
d. Reduced LDL receptors
196
what causes maple syrup disease?
defect in branched amino acid metabolism = accumulation of ketoacids in blood and urine
