Gastro - metabolism Flashcards
(94 cards)
1
Q
what is the efficiency of ATP in the body
A
40% - around 24kJ/mol
2
Q
describe plasma glucose
A
can be used by all tissues
available stores are very small
3
Q
describe glycogen as a store
A
- Can be rapidly mobilized
- Can supply energy aerobically
- Hydrated – weight limits size of energy store
4
Q
describe triacylglycerol as a store
A
- Highly reduced – so big energy yield
- Not hydrated – no weight penalty
- Largest energy store in the body – 10-20kg
- Cannot be metabolized anaerobically
5
Q
describe protein as an energy store
A
• Big store – muscle is 40% of body mass
• Can be converted to glucose or ketone bodies
• All protein is functional – breakdown leads to loss
of function
6
Q
describe glucose
A
- Brain metabolises mostly glucose
- Red blood cells only metabolise glucose
- Liver glycogen can be used to replenish plasma glucose but muscle glycogen can not
- Glucose cannot be made from fatty acids – adipose tissue
- Glucose can be made from some amino acids but all protein is functional – a lot of protein is needed to make protein 1.75g to 1g
7
Q
describe concentrations of fatty acids
A
low but increase when fasting
8
Q
describe concentrations of ketone bodies
A
low when feeding and increase dramatically when fasting
Very high concentrations such as in type 1 diabetes leads to metabolic acidaemia
9
Q
describe the concentrations of amino acids in the blood
A
each amino acid has a different concentration
10
Q
describe lactate in the blood
A
higher when fed than fasting – increases in anaerobic exercise
11
Q
describe creatine phosphate in the blood
A
Concentration higher than that of ATP in muscle. It is a phosphagen – has a phosphate group which can be transferred to ADP to form ATP and release the creatine
12
Q
compare slow and fast twitch muscle fibres
A
slow twitch - type I - "red" contraction rate - slow myoglobin content - high myosin ATPase activity - low creatine kinase activity - low mitochondrial oxidation rate - high glycolytic rate - low
fast twitch - type II - "white" all the opposite contraction rate - high myoglobin content - low myosin ATPase activity - high creatine kinase activity - high mitochondrial oxidation rate - low glycolytic rate - high
13
Q
what are the fuels for muscle contraction
A
• Anaerobic
o Muscle ATP
o Creatine phosphate
o Muscle glycogen
• Purely aerobic exercise
o ATP, creatine P, muscle glycogen
o Fatty acids (muscle and adipose tissue)
o Plasma glucose (from liver glycogen and gluconeogenesis)
14
Q
how many ATP in glycolysis vs full breakdown
A
2 vs ~30
15
Q
describe the pool of amino acids and NPU
A
Protein is in a constant state of flux, being resynthesized from a pool of free amino acids
Amino acid pool is replenished by diet
Net protein utilization – NPU is the weight of amino acids turned into protein divided by the weight of protein ingested and it is different for different sources of protein
16
Q
what are the essential amino acids
A
- Isoleucine
- Leucine
- Lysine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
- Methionine
Some arginine and histidine needs to be ingested as we can make it but not enough
17
Q
what is a cause of protein deficiencies in developing countries
A
monoculture crops
18
Q
what is postive nitrogen balance
A
where there is more protein synthesis than degradation and therefore less excretion than intake
19
Q
what is negative balance
A
balance can be due to protein intake being insufficient – excretion stays the same but synthesis is inhibited
This can also be caused by essential amino acid deficiency
In trauma, disease and surgery, hormonal changes cause increase in breakdown of protein
20
Q
what happens if extracellular proteins are damaged
A
they are taken up by endocytosis. Binds to receptors, they are then internalized with them and the protein inside a plasma membrane. These endosomes then fuse with lysosomes which contain caspases and a low pH.
21
Q
what happens if intracellular proteins are damaged
A
several molecules of ubiquitin bind. The degradation is carried out by a proteosome – depends on ATP.
22
Q
what do chief cells produce?
A
degradative enzymes, particularly pepsin
23
Q
what is the job of parietal (oxyntic) cells
A
cause acidification.
have gastric ATPases on the apical side (lumen) which hydrolyses ATP to ADP and Pi to take in potassium and pumping protons in to the lumen. These protons come from carbonic acid. On the basolateral side (plasma) there is an anion antiporter which exchanges bicarbonate with chloride ions.
Acidification inhibits bacterial growth and denatures enzymes to make them easier to hydrolyse.
24
Q
what are degradative enzymes released as?
A
zymogens
25
describe pepsin
released as pepsinogen which is activated by hydrogen ions
| Pepsin breaks down proteins into fairly large peptides which are then broken down further.
26
what is the role of the pancreas
releases bicarbonate to neutralize stomach pH and also proteases
27
what is trypsinogen activated by
enteropeptidase to become trypsin. Trypsin can autocatalyze the production of trypsin and also activation of other zymogens
Trypsin inhibitor deals with any accidental activation of trypsinogen by binding to trypsin
28
how are amino acids taken up
Co-transporters which recognize different amino acids take them up along with sodium into the cells in the intestine.
Any left-over peptides can be further degraded with in the cells. Most are degraded before uptake.
29
describe transamination
Catalysed by aminotransferases. The amino group from an amino acid is transferred to 2-oxoglutarate. This coverts the amino acid to an oxoacid and the 2-oxoglutarate becomes glutamate. The amino group is then removed by glutamate dehydrogenase in the mitochondria. In this process, NAD is reduced to NADH and ammonia is liberated.
So in total:
Amino acid + NAD ---------> oxo-acid + NADH + NH4
Half of ammonia reacts with CO2 and is phosphorylated to form carbamoyl phosphate.
30
describe the urea cycle
Urea cycle happens in the liver.
Carbamoyl phosphate can transfer its amino group onto ornithine to make citrulline.
Citrulline can then receive another amino group from aspartate (made when glutamate is transaminated with oxoacetate) to form arginine. Arginine is then broken down to release urea.
Because this can only be done in the liver, glutamate is transaminated with pyruvate to form alanine which travels to the liver. Alanine can then be transaminated again to form glutamate.
31
what are the properties of urea
• Very soluble in water
• Electrically neutral
• Contains 48% N by weight. (protein contains
~16%)
• Synthesised in the liver – not further metabolized
• Normal plasma concentration 2.5-7mmol/L
o Rises in renal failure (uraemia)
o Falls in liver cirrhosis
• Plasma ammonia is normally low (12-60umol/L) but rises if urea cycle is inhibited (e.g. liver cirrhosis)
• Ammonia is toxic especially to CN
32
how is glutamate transported to the liver
Glutamate can be converted to glutamine in the tissues and transported to the liver where glutaminase takes the amino group off again.
33
describe one carbon metabolism
One carbon fragments can be attached to tetrahydrofolic acid and can be then oxidised or reduced. The products this makes are useful ingredients in the synthesis of purines, thymine and methionine (B12 dependent). In B12 deficiency, the whole pathway stops and affects DNA replication
34
what is a typical western diet in terms of carbohydrate
* Starch (polysaccharide) – 160g/day
* Sucrose (disaccharide) – 120g/day
* Lactose (disaccharide) – 30g/day
* Glucose (monosaccharide) – 10g/day
* Carbohydrate meets up to 50% of energy requirement
* Free glucose and glycogen are usually unimportant
* All dietary carbohydrates are convertible to glucose
* There are no essential dietary sugars
35
what names are there for linkages between sugars
The linkage between one sugar and another is dependent on whether the OH on carbon one is above (beta) or below (alpha) the plane ring.
36
what types of starch are there
```
• Amylose
o 10-20%
o Unbranched chains
o Formed by the linking of glucose molecules between carbon 1 and 4
o The configuration of bond is alpha
o Called a(1-4) link
```
• Amylopectin
o 80-90%
o Branched
o a(1-4) and a(1-6) links
37
describe starch digestion
• amylase
o present in saliva – levels variable
o also secreted into the duodenum by the pancreas
o is an endoglycosidase: hydrolyses a(1-4) links
o products are oligosaccharides
• glucoamylase
o present on the luminal side of the intestinal wall
o exoglycosidase: hydrolyses a(1-4) links at the end of chains in oligosaccharides, trisaccharides and maltose
• isomaltase
o present on the luminal side of the intestinal wall
o hydrolyses a(1-6) links in isomaltose
a-glucosidase inhibitors prevent starch being digested
38
what hydrolyses lactose
lactase
39
what hydrolyses sucrose
sucrase
40
what is there on the basolateral side of the intestinal cells
Na/K ATPase which pump 2 K in for 3 Na out
41
what is there on the apical side of the intestinal cells
a relatively large concentration of Na which is transported in and takes in glucose via secondary active transport (symporter). Then glucose can run down its concentration gradient via a uniporter called GLUT2
42
what does insulin decrease as well as glucose
also NEFA due to inhibiting lipolysis
43
what is special about the GLUT 4 transporter
in adipose, muscle and heart is insulin responsive and is increased in response to it
44
what is glucose phosphorylated by in the liver
by hexokinase which is in all tissues and glucokinase which has a saturation curve which keeps increasing even in very high glucose levels
45
how is glucose converted to glycogen
glucose-6-phophate is isomerized to glucose-1-phophate. Then attached to UTP to form UTP-glucose. This is the precursor of glucose in glycogen.
Glycogen is a polymer of glucose with a(1-4) links and occasional a(1-6) links.
Free OH on C1 is the reducing end and all the others are on C4s which are the non reducing ends which is where glucose is hydrolysed off or added.
• Up to 12 layers of branches
• 55000 glucose units
• 2000 non-reducing ends
Insulin promotes glycogen synthesis in liver and muscle.
Adrenaline in muscle and glucagon in liver adds a phosphate which breaks off G-1-P to turn back into G-6-P.
46
describe how we get 2 ATP from glycolysis
One glucose molecule produces two 3 carbon sugars which release 2 ATP each on their way to pyruvate. An ATP is required to turn glucose into glucose-6-phosphate and another from fructose-6-P to fructose-1,6-bisphosphate. This leaves us with a net gain of 2 ATP.
47
what happens to pyruvate after glycolysis
The two pyruvates from the glucose can then be reduced to 2 lactates by the reoxidisation of the reduced NAD that was generated earlier in the reaction.
Or pyruvate can enter the mitochondria to be oxided to CO2 and produce a lot more ATP.
48
describe gluconeogenesis
* Takes place only in the liver and kidney
* Replenishes plasma glucose
* Phosphoenol pyruvate pyruvate is irreversible so two enzymes convert pyruvate to oxaloacetate and then to phosphoenol pyruvate which uses an ATP and a GTP
* The pyruvate can come from lactate (anaerobically exercising muscle) or some amino acids
* Glycerol can also help make glucose
49
describe the pentose-phosphate pathway
• Present in many types of cell but particularly active in cells where fat or cholesterol synthesis is occurring
o Liver
o Adipose tissue
o Mammary gland
• 2 molecules of NADPH are produced per glucose
• The products of this are needed for DNA and RNA synthesis but most are put into carbon shuttling reactions to regenerate 6 carbon sugars
o Transketolase can take 2 carbons off one sugar and add it to another leaving us with one C3 and one C7
o Transaldolase takes 3 carbons off one and adds it to the other to give a C6 and a C4
50
describe G6PDH deficiency
* Commonest genetic disorder in humans
* X-linked, usually affects males
* G6PDH is low, but not zero
* Leads to haemoglobin crosslinking which leads to haemolysis
* Exacerbated by anti-malarial drugs, some antibiotic and broad beans
51
describe fructose breakdown
• Comes from the hydrolysis of sucrose
• Fructokinase in the liver phosphorylates this to fructose-1-P and these are turned into 3 carbon sugars which are fed into the glycolytic pathway
• Fructose-1-P aldolase deficiency leads to fructose intolerance.
o Inhibition of glycogen breakdown
o Inhibition of gluconeogenesis
o Inhibition of oxidative phosphorylation
o Causes hypoglycaemia and lactic acidaemia
52
describe galactose breakdown
* Phosphorylated in liver by galactokinase to galactose-1-P. this is transferred to UDP and then UDP-galactose epimerase converts it to UDP-glucose.
* Deficiency of kinase or of the transferase which transfers it to UDP leads to galactosaemia and it then accumulates in the liver causing hepatomegaly and jaundice. Also affects the eyes.
53
describe alcohol breakdown
* Alcohol dehydrogenase in the liver mostly to ethanal (acetaldehyde) and then oxidized again to ethanoic acid (acetic acid) which is convertible to acetyl-CoA
* Acetyl CoA can be a precursor for fatty acids or ketones or oxidized in the tricarboxylic acid cycle.
* An aldehyde dehydrogenase deficiency leads to a build up of ethanal while its converted to ethanoic acid which leads to nausea – prevalent in the east and south America.
* A drug called Antabuse is used to inhibit aldehyde dehydrogenase for alcohol aversion therapy.
* Alcohol dehydrogenase oxidises other alcohols such as methanol or ethylene glycol which yield toxic products – can be treated by ethanol infusion as an inhibitor or a drug called fomepizole which inhibits it.
54
describe triacylglycerol
The fatty acids in triacylglycerols and phospholipids are straight chain and saturated or unsaturated
Carboxyl group (COOH) is numbered carbon 1 and then carbons are numbered away from that.
Cis double bond is like a C - always cis in the body
Trans is like an S
Most fat in diet and storage is triacylglycerol
Digestion of triacylglycerol is catalysed by pancreatic lipase – makes monoacylglycerol and 2 fatty acids and these are taken up by the intestine. The majority are then re-esterified to triacylglycerol.
Orlistat is a drug which inhibits pancreatic lipase so can be used to treat weight gain.
further broken down by bile salts – natural detergents
55
describe chylomicrons
contain triacylglycerol, phospholipids, cholesterol and esters, and vitamin A, D, E and K
degradation of chylomicrons
• Collect another lipoprotein C-II from high density lipoprotein which activates the enzyme which degrades them – lipoprotein lipase.
• Hydrolysed to glycerol and fatty acids. Fatty acids taken up, glycerol metabolized by liver
• Chylomicrons converted to chylomicron remnants which are taken up by the liver
56
describe the start of fat synthesis
• Major input is carbohydrate which is oxidized to acetyl-CoA
• First reaction catalysed by acetyl-CoA carboxylase
o Acetyl-CoA to malonyl-CoA
o CO2 from bicarbonate and requires ATP
57
how is acetyl-CoA carboxylase regulated
• The inactive form is the phosphorylated form
o Promoted by glucagon and increase of AMP in cells
o Dephosphorylation is promoted by insulin
58
describe the fatty acid synthase complex
• Multi enzyme complex
• Stages
o Priming – attaching an acetyl group from
acetyl-CoA to a cysteine side chain
o Loading – transfer of a malonyl group from
malonyl-CoA to phosphopantothein
o Condensation – acetyl group transferred onto
malonyl group, CO2 lost – left with 4 carbon
oxo-acid attached to phosphopantothein
o Two reductions, first to a hydroxyacid and
then to a 4 carbon saturated fatty acid
o Acyl transfer – 4 carbon fatty acid transferred
back to the cysteine
o Reloading – enzyme is reloaded with another
malonyl-CoA and the process repeats
• This works up to 16 carbons – all even carbon numbers
• Separate systems to elongate them further.
59
how is triacylglycerol synthesis regulated
* Acetyl-CoA which the malonyl-CoA is from is most likely from glucose whose uptake is promoted by insulin
* Insulin also promotes acetyl-CoA formation and release from mitochondria
* Glucagon inhibits glucose to pyruvate and also acetyl-CoA carboxylase
60
describe the fatty acid desaturase system
* The fatty acid synthase system makes saturated fatty acids and the double bonds need to be made after
* 2 hydrogens used to reduce O2 to water
* The other oxygen is reduced by NADH to NAD+ through an electron transport chain
* Can introduce double bonds at 4, 5, 6 and 9 and carbon 9 is the first to take place so introduction of ones beyond 9-10 is impossible and ones that have ones beyond this are ESSENTIAL fatty acids
61
how is triacylglycerol in adipose tissue hydrolysed
by hormone-sensitive lipase which is activated by adrenaline, glucagon and growth hormone and inhibited by insulin.
62
how are fatty acids transported to and kept within cells
Fatty acids are transported bound to serum albumin and enter cells through the aid of transporters.
Fatty acid activation requires ATP and esterifies it onto the sulphydryl group on coenzyme A to keep it in the cell
63
describe cholesterol
* Component of plasma membranes
* Precursor for bile and bile salts
* Precursor of hormones including sex hormones
* 2 acetyl-CoA s joined together to make acetoacetyl-CoA and then another joined on to make 6 carbon intermediate hydroxymethyl glutaryl-CoA
* This is then reduced to mevalonate (6 carbon). This forms a 5 carbon intermediate and these become a 15 carbon intermediate. 2 of these form squalene. Squalene is a 30 carbon compound which then becomes cholesterol (27 carbons)
* The reduction to mevalonate is catalysed by HMG-CoA reductase and this is targeted by statins
64
how are bile acids synthesised
* cholesterol is converted to 7a-hydroxy cholesterol by adding a hydroxyl group
* hydroxylation and sidechain cleavage leaves it with 2 or 3 hydroxyl groups and a carboxyl group at the end of the side chain.
* This makes it amphipathic (hydrophilic on one side, hydrophobic on the other)
* Primary bile acids are cholate and chenodeoxycholate
* These are conjugated with taurine or glycine – form an ester with the side chain and these are then called bile salts – 4 in total, one for each amino acid conjugated with each primary bile acid
* Bacteria tend to hydrolyse and reduce these to secondary bile acids
About 95% of bile acids are resorbed and return to the liver via the portal venous system
65
what do fibrates do
increase uptake of LDL into the liver
66
what can the concentration of free fatty acids reach in starvation
as high as 0.6mmol/L
67
what concentration is serum albumin
around 0.5-0.7mmol/L but albumin can bind many proteins so can easily deal with any concentration of free fatty acids
68
can acyl-CoA get through mitochondria membranes
can easily pass through the outer membranes of mitochondria due to porins.
Cannot get through inner membrane so acyl group transferred to carnitine to form acyl-carnitine (this is catalysed by CPT-1 which in inhibited by malonyl-CoA). This can be transported through the inner membrane in exchange for free carnitine and then transferred back to coenzyme A.
69
describe beta oxidation of fatty acids
* First a double bond is introduced, reducing electron-transferring flavoprotein which in turn reduces ubiquinone.
* This double bond is then hydrated to form a hydroxy-acid attached to CoA
* This is then oxidized to an oxo-acid by NAD
* Then acetyl CoA is split off to form a shortened long chain fatty acid which can reenter the cycle
70
what are the products of the beta oxidation of fatty acids
Most fatty acids have even numbers of carbons in which case the only product is acetyl-CoA
Some which have uneven will have propanyl-CoA
these come mainly from plants and the metabolism of isoleucine, methionine and valine.
Propanyl-CoA is carboxylated and then isomerised which produces succinyl-CoA which is an intermediate in the tricarboxylic acid cycle.
71
describe pyruvate dehydrogenase
• In the mitochondria – so pyruvate has to enter the mitochondria
• 30 copies of one subunit (vitamin B1 prosthetic group), 60 of another (lipoic acid prosthetic group), 12 of another (vitamin B2 prosthetic group) – very large
• Overall reaction is pyruvate to coenzyme A with the reduction of NAD to NADH and the loss of CO2
• Regulation is by a phosphorylation/dephosphorylation cycle
o PDH kinase activated by ATP, NADH and acetyl-CoA (its own products inhibit it)
o PDH phosphorylase activated by Ca and insulin
72
describe vitamin A deficiency
beri beri but also common in alcholics as alcohol inhibits the uptakeof vitamin B1 and its processing in to the coenzyme thiamine pyrophosphate. – tremor and paralysis
73
describe the tricarboxylic acid cycle
* Acetyl-CoA enters with reaction with oxaloacetate to form citrate which is irreversible
* Three NAD-reducing dehydrogenases in the cycle
* Conversion of succinyl-CoA to succinate is linked with the formation of GTP – this is called substrate level phosphorylation
* Other intermediates can join on the way round
* Around 10.6 ATP per turn of the cycle
74
describe why ketone bodies are made
The precursor for gluconeogenesis is oxaloacetate
• Acetyl-CoA cannot be converted to glucose so therefore:
o Fat, ethanol and ketogenic amino acids cannot be converted to glucose
o They are instead converted to ketone bodies
o Ketone bodies build up in starvation when there is a lot of fat breakdown
o Acetyl-CoA converted to HMG-CoA which is then broken down to the first ketone body, acetoacetate
o This is reduced or carboxylated to form the other two
o Reduced to 3-hydroxybutyrate which, along with acetoacetate can be taken up by tissues including the brain for fuel
o The carboxylated one is acetone which you can smell on the breath when there is a lot of circulating ketone bodies
o In type 1 diabetes, we have unregulated fat breakdown and concentration of circulating ketones occur and these can cause metabolic acidaemia
75
what are cristae
Inner membrane infoldings of mitochondria
76
what is the inside of a mitochondria called
the matrix
77
what are electrons in the electron transport chain transferred to?
to carriers with higher affinity for electrons (more positive redox potential)
78
describe prosthetic groups on proteins
Prosthetic groups attached to proteins via covalent or strong non-covalent bonds
• Flavoproteins (flavin prosthetic groups)
o Riboflavin is vitamin B2 – flavin derived from this
o Can accept 2 hydrogens
• Iron-sulphur proteins
o Clusters of iron and sulphur and cysteine side
chains
o Iron from ferric to ferrous form
• Ubiquinone (coenzyme Q)
o Very hydrophobic
o Carries hydrogen
• Cytochromes
o Have haem which can be covalently or non-
covalently bonded to proteins
79
describe the mitochondrial electron transport chain
```
has 5 complexes which each have many proteins
There are inhibitors of the complexes
• Rotenone – complex 1
• Atovaquone – complex 2
• Antimycin-A – complex 3
• Cyanide, Carbon dioxide – complex 4
• Oligomycin – complex 5
```
Complexes 1, 3 and 4 pump hydrogen ions out
Complex 5 is ATP synthase
80
what is the theoretical P/O ratio
* P/O = mols ATP produced/ atoms of O reduced
* For NADH oxidation P/O is about 2.5 – textbooks say 3
* For succinate oxidation P/O is about 1.5 – textbooks say 2
81
what is respiratory control
A reduction in ATP/ADP ratio stimulates ATP synthase which takes in more H+
This lowers the electrochemical gradient which stimulates the electron transport chain
This increases NAD/NADH ratio which activates TCA cycle
82
compare fatty acid degradation and synthesis
------------------degradation ---------------- synthesis
location - mitochondria ------ cytoplasm
reactions - oxidative ----------- reductive
coenzymes - NAD, ubiquinone -------- NADPH
enzymes - seperate ------------- multienzyme complexes
intermediates - CoA esters -------------- esterified to
------------------------------------------------enzyme complex
83
what are energy requirements for babies, adults and athletes
* Baby 2.5MJ per day (has highest need per KG body weight)
* Adult 10-12MJ per day
* Manual worker/athlete 17-21MJ per day
84
what are the macro nutrients
* Protein 30-40g per day
* Essential amino acids ~12g per day
* Essential fatty acids ~20g per day
85
what electrolytes do we need
* Na+, K+, Cl-, PO43-
* Ca, Fe, Mg
* Trace elements: Cu, Mn, Mo, I, Se, Cr, Zn
86
what does the brain run on when fasting
In fasting, glycogen is broken down to glucose for brain fuel and when these start to run low, ketones are produced
87
what is the difference between liver and muscle glycogen
Muscle doesn’t release glucose into the plasma but liver does
100g liver
400g muscle
88
what is metaformin
an activator of AMP-activated protein kinase is used for the treatment of type 2 diabetes
89
describe the role of insulin in healthy people
liver - increase glycogen synthesis
- decrease glycogenolysis and gluconeogenesis
muscle - increase glucose uptake, glycogen
synthesis and protein synthesis
- decrease glycogenolysis
adipose tissue - increase glucose uptake and TAG
synthesis
- decrease lipolysis
90
describe the role of insulin in type 1 diabetes
liver - opposite to healthy so leads to hyperglycaemia
muscle - reduced protein synthesis and glucose uptake so weight loss
adipose - reduced glucose uptake and increases lipolysis so ketoacidemia
91
describe the role of insulin in type 2 diabetes
reduced uptake of glucose but lipolysis and protein synthesis remain so all just lead to hyperglycaemia
92
what happens in starvation compared to fed state
reduced basal metabolic rate
blood glucose normal
increased fatty acids in blood
increased ketone body production, gluconeogenesis, muscle proteolysis and urea synthesis
nitrogen balance down
93
what happens in trauma compared to fed state
increased basal metabolic rate, blood glucose and fatty acids, gluconeogenesis, muscle proteolysis and urea synthesis
decreased nitrogen balance
94
describe what happens in exercise
Phosphorylase breaks down glycogen to glucose by using a phosphate to create glucose-1-P
Phosphorylase is allosterically activated by AMP whose concentration rises in exercise
Glycogen phosphorylase is also activated by phosphorylation which is catalysed by phosphorylase kinase
Phosphorylase kinase is activated by calcium ions (cytoplasmic Ca concentration rises when the muscle is working) or protein kinase A which is indirectly activated by adrenaline
During anaerobic exercise, triacylglycerol isn’t used as breakdown requires oxygen
In aerobic exercise, triacylglycerol can be broken down to free fatty acids and broken down all the way to CO2
Initially in exercise, muscle glycogen is mainly used along with muscle triacylglycerol
As the duration of exercise goes on, NEFA becomes the largest source of energy (ceiling of about 70-80%) and plasma glucose also increases
