35 Flashcards
To carry out activities for one day, an adult person weighing 70 kg uses ATP equivalent to about
A 4.18 kilojoules of energy
B 30 kilojoules of energy
C 30 g of ATP
D 70 kg of ATP
Oxidising about 500 g of fuel (carbohydrate, fat and protein) generates about 70 kg of ATP; 10,000 kJ
If your heart is beating faster in an exam because of stress, it can obtain extra ATP from your leg muscles, which don’t need much because you are sitting down.
TRUE or FALSE
ATP is not transferred between tissues; it is made in the tissue that needs it
ATP is NOT an energy store
Fuels are stored: glycogen and fat
We need fuel stores
We can’t carry around our body weight in
ATP…
To address this, we take 2 to 3 meals a day, So:
• How do we get energy between meals?
• E.g., How do we get energy during the night?
• We must store fuel from meals and then access the stored energy as we need it
Why do we need fuels stores?
Because the body cannot store ATP
ATP must be made in the cell
• at the time it is needed
• at the rate it is needed
• by oxidising fuels
ATP must be made in the cell ….
• at the time it is needed
• at the rate it is needed
• by oxidising fuels
What we physiologically need fuel stores for:
• to maintain a supply of glucose between meals
• to provide immediate fuel for increased activity
• for long periods when food intake may be inadequate
Fuel reserves for a normal 70kg subject
- only reason there is glycogen in the blood is for transport
What are Tryglycerides stored as ?
stored as fat droplets in adipose tissue
What happens to excess dat and carbs form diet?
excess fat and carbohydrate from diet can be
converted to stored fat
Humans have ______ fat stores
unlimited fat stores
Tri-acyl-glycerol structure
thr ee - fatty acids - glycerol
- attached through ester linkage to glycerol back bone
Glycerol as an hydroxyl group that can easily be etifled to form a
Triclyglycerol (between acidic fatty acid end and glycerol)
- fatty acid chains are hydrophobic
- in this example there is a kink caused by the double bond
- the kink prevents the lipids form packing together
Palmo(toleic) tells us…
There is a double bond
Scanning micrograph of white adipose tissue
Electron micrograph of white adipose tissue
In adipose tissue cells Triaglycerol pushes cell organelles to the side
Synthesis of triacylglycerols
• fatty acids from chylomicrons
• glycerol backbone from glucose
• activation of fatty acids to acyl-CoA
• esterification of acyl groups to glycerol 3-phosphate
• stimulated by insulin
Synthesis of triacylglycerols is stimulated by
Insulin
Fatty acids getting into adipose tissue from chylomicrons
- chylomicrons arrive at the capillaries of the adipose tissue and then lipase (membrane bound) cleaves the fatty acid off the glycerol back bone
- lipase is also activated by insulin
- cleaved fatty acids are then deposited inside the adipose tissue
- remenants of chylomicrons go back into the circulation (liver) where they are degraded and recycled
- (fatty acid then put back into TG for storage)
Chylomicrons are essential for
Moving Fattty acids in the form tryclyglycerol to the adipose
Lipoprotein lipase found in in _______ of ______
Capillaries
Adipose tissue
L ipoprotein lipase in capillaries of adipose tissue is stimulated by
Insulin
Fatty acids are _____ so they ______ flow through the membrane
Hydrophobic
Freely
Schematic diagram of the insulin receptor
- insulin binds to alpha subunit and causes a conformational change which is relayed through the beta subunits to activate kinase activity
- kinase takes a phosphate from ATP and attaches it to a hydroxyl Group on the tyrosine amino acid (phosphorylation of hydroxyl group
- the left tyrosine phosportlyates the tyrosine on the right, right tyrosine phosphorylates the tyrosine on the left
Insulin helps activate tyrosine kinase which then does what …. For fatty acids inside the cell and lipase in the membrane
- stimulates reactivating of the fatty acids inside the adipose tissue
- (also helps activate the lipase in the membrane to cleave the carry acids off the chylomicron)
What bond attaches between glycerol and fatty acid
Ester bond
What’s funky about the glycerol back bone that’s used to make the triclyglyerol?
It’s not staging glucerol - its glycerol phosphate
Where does the glycerol phosphate come from in forming triclyglycerols?
- it is diverted from glycolysis
Formation of glycerol from glycolysis
In glycolysis DHAP can be snatched away
DHAP converted to glycerol-P by glycerol-3-phosphate dehydrogenase
glycerol-P to glycerol to triacylglycerol requires several steps
glycerol-3-phosphate acyltransferase (attaches 3 of the fatty acids) and phosphatidate phosphatase (removes the phosphate) followed by diacylglycerol acyltransferase (adds the last fatty acid)
Tiacly glycerols respond to …
Activeted hormone-sensitive lipase
Hormone sensitive lipase cleaves off..
Fatty acids
After fatty acids have been cleaved by hormone - sensitive lipase what happens
- leaves cell and attached to acid-albumin complexes where it is taken to do b-oxidation and obtain ATP
What does a fatty acod need to move in blood?
Albumin
- but not much Albany in in blood hence why fatty acid is low in blood
- amount of fatty acod in blood is controlled by how much albamin in blood
Two diff ent senarios where hormone - sensitive lipase is activated
- adrenaline - sacred - fast
- glucagon - normal regulation
Mobilisation of triacylglycerols
• hydrolysis of TAGs
• catalysed by hormone-sensitive lipase
• stimulated by hormones: adrenaline glucagon
• release of free fatty acids
• release of glycerol
G-protein coupled receptors?
- breakdown of triclyglycerols ?
Structure of glycogen
• branched polysaccharide
• a,1-4 and a,1-6 glycosidic bonds
Where is glycogen stored ? What’s in the cytoplasm?
• stored in liver and muscle
• granules in cytoplasm (of liver and muscle)
Glucose is stored as
Glycogen
Structure of glycogen showing the a-linkages
Size of a glycogen granule compared to a mitochondria
Granules ~0.1 micrometer
Mitochondrial ~ 10 mincrometer
Where does glycogen synthesis mainly occur?
Mainly in liver and muscle immediately after a meal
Glycogen syntheses requires…
Energy inputs (ATP and UTP)
UTP in glycogen synthesis makes …
An activated high-energy precursor, UDP-glucose
Enzymes needed for glycogen synthesis
glycogen synthase and branching enzyme
Glycogen synthesis is stimulated by…
Insulin (all that second messenger pathway shit from that diagram)
What makes the a-1,4 linkages ?
glycogen synthase
What makes the 1,6 linkages
Branching enzyme
Are the ends of glucose reducing?
No
How to get from glucose to glycogen
- Glucose comes into the cell and made into glucose-6-P, if we need ATP it will go down glycosidic pathway to pyruvate, if we have sufficient ATP, glucose-6-P will bound up and an enzyme called mutate moves the phosphate group onto carbon 1 instead of carbon 6 getting, glucose 1-P
- Once it becomes glucose-1-P the enzymes of glycolysis can no longer recognise it
- Glucose 1-P is activated by forming a new ester bond using UTP to make a UDP-glucose molecule (UDP-glucose bond very high energy)
- We can then hydrolyse the high energy bond and use the energy to attach the glucose to the growing glycogen chain
Once glucose has been phosphorlated it can no longer…
Cross back over the membrane
Glucose 1-phosphate + UTP —-> UDP-glucose
Hydrolyses of the UDP-glucose bond by _____ _____ is stimulated by _____
Hydrolysis of this bond by glycogen synthase activity is stimulated by insulin
UPP glucose —-> glycogen (glycogen synthase steps)
- branching enzyme is able to cleave branches and add it to another 1-6 linkage
- they are all about the same size - enzymes can only work to a certain size
What happens when all full of glycogen
Only so much space for glycogen; excess glucose is converted to acetyl-CoA and then into fatty acids by the FA synthase complex in liver cytosol
Mobilisation of glycogen
• degraded by glycogenolysis
• liver glycogen - released as glucose into blood (for brain)
• muscle glycogen releases fuel for glycolysis within muscle cells
• Can you get fat directly from glucose?
Yes - when glycogen store is full and we have sufficient ATP
• Can you get fat from just eating carbohydrate?
Yes
Glucose → fatty acids
• excess glucose carbon converted to fatty acids
• occurs mainly in liver
• complex, energy-requiring process
• exported as TAGs in VLDL
• fatty acids stored as TAGs in adipose tissue
• stimulated by insulin
Glucose → fatty acids diagram
- energy rich, lots of ATP, made all our glycogen
- glucose enters liver, converted into Acetyl CoA then stitched together in two units by FA synthase complex (7 activities in one enzyme)
- tuned into palmatic acid (FA) which is then attached to glycerol back bone
- TG packaged onto VLDL lipoproteins and sent to the adipose tissue and processes to release fatty acid into tissue occur- stimulated by insulin
- we then store the TG - as there is no limit to its storage
THIS PROCCES NEED NADPH - NOT SURE WHERE THO???
Fuels for different tissues
Brain: glucose (cannot use fatty acids)
Red blood cells: glucose
Liver, Heart, Muscle: mostly fatty acids mostly fatty acids resting - mostly fatty acids marathon - mix of fatty acids and glucose
