carbohydrate metabolism Flashcards
1
Q
what is metabolism
A
the process by which energy is derived from raw materials from food and used for growth and repair
2
Q
explain the pathway of food
A
enters GI tract, is broken down and absorbed into blood where it can either be excreted or transferred to tissues where it is used for synthesis
3
Q
what is a catabolic reaction
A
break down of larger molecules into smaller ones. this is an oxidative reaction where loss of H atoms occurs providing reducing power
4
Q
what is an anabolic reaction
A
synthesis of larger molecules from building blocks using energy released from catabolic reactions. this is a reductive reaction because uses ATP and reductive poor from H atoms
5
Q
what is required for the synthesis of new molecules
A
reducing power and energy
6
Q
what is required for cellular process’ / cell function
A
energy
7
Q
name the waste products of metabolism
A
CO2, H2O and (NH2)2CO (urea)
8
Q
name the fuel molecules used during metabolism
A
building blocks used in biosynthesis e.g amino acids and these are used for growth and repair
organic precursors which allow interconversion of building blocks (acetyl coA)
biosynthetic reducing power (NADH)
energy(ATP)
9
Q
types of work in the body which require ATP
A
biosynthetic
transport- ion gradients and transport of nutrients
specialised- e.g mechanical, electrical or osmotic
10
Q
energy intake and energy consumption ratio of a healthy person
A
they are both equal
11
Q
how much is 1kcal in kj
A
4.184KJ
12
Q
which food sources contain the most and least energy
A
fat has most, then alcohol, then carbs and then protein has the least
13
Q
what is energy used for
A
BMR- basal metabolic rate which is energy used each day is not moving = 1,400-1,700 kcal
activity- depends on how strenuous but = 1,000-3,000 kcal
specific dynamic action of food- this is the energy used to digest the food = 150kcal
some energy is also lost as heat
14
Q
what happens when energy intake>use of energy
A
then synthesis or production of adipose tissue occurs
15
Q
what happens when energy intake
A
then tissue will be lost
16
Q
how long can you survive without food
A
20-70 days if average man or woman 70/58kg
17
Q
what type of energy do cells use and why can’t they use heat energy
A
they use chemical bond energy. can’t use heat energy because man is isothermic and using heat would upset homeostasis
18
Q
what is an exergonic and an endergonic reaction
A
exergonic= releases energy. delta G is less than 0 and occurs spontaneously endergonic= requires energy and delta G is more than 0. does not occur spontaneously
19
Q
what is delta G
A
free standard energy change. is specific to a certain pH, temp and conc
20
Q
what are the 2 redox reactions
A
oxidation = loss of e- or H atoms
OIL RIG
21
Q
name the oxidised and reduced H carrier molecules
A
oxidised= NAD+, NADP+ and FAD reduced=NADH, NADPH and D=FADH2 - act as carriers for reducing power N= nicotinamide F= flavin A= adenine D= dinucleotide
22
Q
what type of reaction is the break down of food
A
exergonic, this is the release of energy and an oxidation reaction. energy goes to NAD+ or NADP+ or FAD and energy is transferred for other uses e.g biosynthesis or ATP synthesis
23
Q
NADH=
NADPH=
A
NADH= synthesis of ATP NADPH= biosynthesis
24
Q
how is energy released from ATP
A
phosphate bond is broken releasing energy = exergonic
25
why is ATP a good energy molecule
it has high energy bona, it acts as a carrier and it is stable
26
name the high energy signals and what they do
ATP, NADH, NADPH and FADH2 they activate anabolic pathways
27
name the low energy signals and what they do
AMP, ADP, NAD+, NADP+ and FAD. - they activate catabolic reactions
28
what is creatine phosphate, how is it made and why do we need it
it is needed for when high energy needed quickly by some skeletal muscles. when lots of ATP is available then its used to make phosphocreatine and when there is low supply then its converted back releasing ATP simultaneously. the enzyme used is creatine kinase.
29
what is the enzyme ck used as a marker for
used as a marker for MI. it is released by myocardiocytes in blood after few hours
30
product of break down of creatine or phosphocreatine
creatinine
31
what is creatinine a marker of
used for measurement of muscle mass and measure hormones during pregnancy
32
what are the 4 main stages of catabolism
1) large molecules broken down in the gut and absorbed into the blood stream
2) metabolites are converted to acetyl coA and small amount of energy and reducing power are produced
3) Krebs cycle where more energy is released
4) ETC and oxidative phosphorylation where ATP is synthesised and lots of energy is released
33
what is a carbohydrates general formula and the types of carbohydrate
```
(CH2O)n
mono- glucose, galactose and fructose
di- maltose, lactose and sucrose
olgi- dextrins
poly - starch and glycogen
```
34
for which cells is glucose a necessity
red blood cells, neutrophils, kidney medulla and lens of eye. also brain prefers glucose but will use ketone bodies in an emergency
35
stage 1 - break down in gut. give the details of the enzymes used
saliva- amylase which breaks down starch to olgisacherides
pancreas- amylase which breaks down starch/dextrins to mono
small intestine- lactase, sucrase and pancreatic amylase.
all broken down to monosacherides
36
why can't cellulose be digested
because it has beta1,4 glycosidic bonds which we do not have an enzyme for to break it down
37
types of lactose intolerance
primary deficiency- absence of persistent allele meaning become lactose intolerance as get older. (when adult)
secondary deficiency- caused by injury to small intestine by disease e.g churns or coeliac. can be reversible
congenital- very rare. recessive deficient lactose gene where never have the correct lactase enzyme. can never digest milk even as baby
38
how are monosaccharides absorbed into the blood stream
1st absorbed from GI tract into intestinal epithelium by active transport by use of sodium pump
2nd absorbed from epithelial cell into blood stream by facilitated diffusion via the GLUT transporter
39
describe stage 2 in detail
this is the break down to produce acetyl coA and for carbohydrates this is called glycolysis. draw this out
40
enzymes and in the order they are used in in glycolysis
hexokinase.
phophofructokinase
pyruvate kinase
41
features of glycolysis
2 net ATP produced by substrate level phosphorylation, NADH produced and glucose is oxidised (exergonic). this occurs in all tissues and is cytosolic
42
why are there so many steps in glycolysis
easier, efficient energy consumption, allows fine control and interconnections between different pathways
43
why are the steps using enzymes irreversible
because the delta G for the reverse reaction is not spontaneous
44
what is the committing step
step 3. after this it is committed to glycolysis . before this can also be used for tother pathways
45
clinical use of glucose
used in PET scan to diagnose cancer because cancer cells use lots of glucose yo because they have very high metabolism
46
how is glycerol phosphate produced and what is it used for
it is produced from DHP in glycolysis and is catalysed by the enzyme G3P dehydrogenase and is used for the synthesis of triglycerides and phospholipids. production also results in production of NADH
47
how is 2,3 bisphosphoglycerate produced and what is it used for
from 1,3 bisphosphoglycerate in glycolysis and is catalysed by the cyme bisphophosphate mutase. used in RBC for regulation of the release of O2 from haemoglobin
48
what is lactate dehydrogenase and why do we need it
its an enzyme which catalyses the regeneration of NAD+ from NADH. in RBC (because no mitochondria for steps 3 and 4) and exercising skeletal muscles (incld brain GI and skin) NAD+ can not be regenerated and therefore glycolysis stops. lactase dehydrogenase catalyses pyruvate, NADH and H+ to form lactate and NAD+.
49
how and where is lactate broken down
in heart and liver the reverse reaction is catalysed. in liver pyruvate is used for glucageneisis for more glycolysis and in heart its used for energy. done here because both these places are well oxygenated
50
what is hyperlacteamia
high lactate. up to 5mM of lactate in blood but pH not yet raised because being buffered by proteins
51
what is lactic acidosis
when enough lactate to reduce pH
52
why does high lactate occur
either lots being produced or poor removal of it
53
how is fructose metabolised
catalysed by fructokinase and aldose to produce 2 gylceraldheydes which are then able to join glycolysis
54
what is essential fructosuria
fructokinase is missing which means there is fructose in urine but no clinical signs
55
what is fructose intolerance
when aldose is missing meaning build up fructose1-P which can cause damage to liver meaning fructose. must be cut out of diet
56
how is galactose metabolised
metabolised by galactokinase, G1P uridyl transferase and UDP galactose epimerase to form glucose which then joins glycolysis
57
what is galactosaemia and what does it cause
when any 3 of the enzymes are deficient but if you are deficient G1P uridyl transferase or UDP galactose epimerase this results in the build up of galactose 1 P which then enters other pathways
58
which other pathway does galactose 1 P enter and what happens
is converted to galacticol using up NADPH which is used in proper synthesis of sulphide bonds. if not present results in cataracs in lens or haemolysis from heinz bodies
59
what is the pentose phosphate pathway
when glucose 6P is converted to ribulose which can still rejoin glycolysis and then ribose which is used in the synthesis of DNA, RNA and coenzymes. catalysed by enzyme G6P dehydrogenase.
60
features of the pentose phosphate pathway
1) no ATP is produced
2) loss of CO2 means it is irreversible
3) production of NDAPH and therefore it is controlled by the ratios of NADP+ and NADPH
this means if this reaction is low then there will also be low NAPH and same problem as with galactosaemia
61
types of allostery
1) binding to allosteric site to either inhibit or activate the enzyme
2) covalent activation whereby a phosphate group is added to enzyme altering the structure and causing either activation of inhibition of the enzyme
62
why can irreversible steps be regulated and reversible ones cannot
because reversible means it will reach equilibrium and therefore not alter the amount of product. irreversible reaction cannot equilibrate
63
explain allosteric regulation by the product
the product reduces the entry of the substrate and therefore the build up of intermediates. this is called feedback inhibition
64
what is the committing step and why is it a good target for regulation
committing step means substrate can no longer be directed to other pathways. this means by inhibiting this pathway the substrate will be sent to other pathways
65
which molecules inhibit or activate enzymes
high energy will inhibit enzymes and low energy will activate enzymes
66
explain hormonal regulation
hormone will bind to the receptor and activate a signalling pathway and this will activate a protein kinase or protein phosphatase which will either phosphorylate or dephosphorylate an enzyme altering the activity of the enzyme
67
what is feedforward regulation
early pathway substrate provides signal to stimulate later enzyme to activate a pathway
68
adrenaline as an example of phosphoregulation
adrenaline activates protein kinase A which activates a kinase activity an enzyme which promotes glycogen break down
69
insulin an an example of phosphoregulation
dephosphorylation of an enzyme will stimulate glucose use and of another enzyme will inhibit glycogen break down
70
how is hexokinase in glycolysis regulated
regulated by product inhibition by G6P
71
how is PFK regulated in glycolysis
high [ATP] inhibits PFK and high [AMP] will stimulate PFK. also high insulin concentrations stimulated PFK in order to make use of the glucose
72
how is step 6 (the NADH one) regulated in glycolysis
is regulated by conc ratios of NADH/NAD+. when [NADH] is high then there is inhibition of step 6
73
how is pyruvate kinase regulated
it is stimulated by high insulin
74
what happens before pyruvate enters the Krebs cycle
pyruvate is converted to acetyl coA by pyruvate dehydrogenase. CO2 is produced and is therefore an irreversible reaction meaning is a key regulatory step
75
equation for the conversion of pyruvate to acetyl coA
pyruvate + coA + NAD+ = acetylcoA + CO2 + NADH +NAD+
76
how is the pyruvate dehydrogenase regulated
it is activated by NAD+, ADP and insulin and inhibited by NADH, ATP citrate and acetyl co A
77
key features of the Krebs cycle
it occurs in the mitochondria , require fad and nad+, produces some energy and biosynthesis precursors e.g amino acids, fatty acids and heat groups as well as glucose DRAW IT OUT
78
hw many FADH2, NADH and GTP per molecule of glucose produced by the TCA cycle
2 FADH2, 6NADH and 2 GTP
79
during the TCA cycle which bonds are broken and what conditions are required
requires O2 for function. all c-c bonds and c-h bonds are broken during the Krebs cycle. c atoms are also oxidised to form co2. all H atoms are transferred to H carrier moelcules
80
how many total ATP produced at end of Krebs and where is the rest of the energy
4 ATP rest of ATP synthesis occurs in mitochondria by the ETC. lots of energy is produced ad needs O2 to function as it acts as the final electron acceptor. draw structure of mitochondria
81
explain the ETC and how it works
NADH and FADH2 are oxidised by enzymes and the electrons are transferred along the electron transport chain each time releasing energy which is used to pump H+ ions out of the inner membrane space into the mitochondria
82
relative electron energy between FADH2 and NADH
NADH electrons have more energy. 2.5 ATP per NADH and 1.5 ATP per FADH2
83
how is ATP synthesised
H+ move back into intermembrane space down their electrochemical gradient and ATP is synthesised by the enzyme ATP synthase
84
how is the ETC regulated
when [ATP] is high [ADP] is low and therefore there is no substrate for ATP synthase meaning H+ stops flowing into mitochondria and H+ conc in inter membrane space increases preventing H+ being pumped out. NO MORE ATP
85
how is the TCA cycle regulated
isocitrate dehydrogenase which catalyses isocitrate is activated by ADP and inhibited by NADH and ATP
alpha ketogluterate dehydrog is inhibited by NADH and ATP and succinylcholine coA which is the product. (this is from c5 to c4)
86
inhibitors of the ETC
e.g cyanide prevents oxygen from accepting the electrons therefore preventing the ETC from continuing and therefore stop ATP synthesis
87
what are uncouplers
uncouplers increase the permeability of the innermemrbane to protons reducing proton gradient (p.m.f). an example of an uncoupler in fatty acids
88
diseases that affect ATP synthesis
if issue with mtDNA then no ETC and no ATP synthesis
89
what is energy coupling and how is this controlled in brown adipose tissue
it is how efficiently the energy from the ETC is converted for ATP synthesis. rest is lost as heat. more tightly bound = more energy. in brown adipose tissue uncouplers (fatty acids) callow extra heat to be released by the enzyme thermogenin
90
explain how thermogenin works
fatty acids activate thermogenin and make it transport H+ back into mitochondria. ETC is uncoupled fro ATP synthesis and energy from p.m.f is relased as heat
91
where is brown adipose found and why is it needed
extra heat needed in new horns and hibernating animals
92
oxidative phosphorylation vs substrate level phosphorylation
OP- occurs in mitochondria, requires O2, los of ATP produced, energy coupling is indirect via ETC and ATP synthesis (p.m.f)
SLP- occurs in mitochondria and in cytoplasm, no O2, barely any ATP produced, energy coupling via P group transfer onto ATP.
93
how many ATP molecules are produced from 1 glucose molecule
32 ATP
94
what is marasmus
occurs due to insufficient energy intake due to multiple nutritional deficiencies. This is due to protein being used for energy in the brain and therefore loss of muscle protein
95
appearance of marasmus
very thin limbs and very underweight.
96
side effects of marasmus
unable to replace and repair tissues therefore GI tract is affected, anaemia develops, hormones affects and the cardiovascular system is impaired. the brain is also affected in severe forms
97
what is kwashiorkor
calorie intake is normal but have very low protein intake. need essential amino acids from the diet for synthesis of some essential proteins. liver therefore cannot use proteins to make lipoproteins and fatty acids will build up in liver causing septic disfunction and oedema occurs due to reduced onctoic pressure of plasma causing fluid to move out of plasma
98
appearance of kwashiorkor
swelled legs and pot belly. thin muscles but fat present
99
what is re feeding syndrome
ammonia toxicity due to down regulation of enzymes in urea cycle meaning can't digest proteins. must reintroduce very slowly.
