Using And Replenishing Metabolic Stores Flashcards
What is carbohydrate stored as in the body? And in which cells of the body?
Glycogen
In liver and muscle cells
What is the structure of glycogen?
Glycogen is a branched polymer of 3 and 6-7 units using a-1,4 linkages for length of 6-7 units and a-1,6 linkages for branching of 3 glucose units
What is glycogen broken down into?
90% broken down with phosphate into glucose-6-phosphate
10% broken down using H20 into glucose
(Conversion from glucose to glucose-6-phosphate uses 1ATP)
Why is glycogen broken down into glucose-6-phosphate rather than glucose?
G6P can’t pass through the cell membrane easily so is only for use in that particular cell
Direct conversation of glycogen to G6P saves the cell one ATP molecule per glucose
How many ATP gained when glycogen converted to G6P directly?
31-33 ATP (5 direct ATP)
Rather than 30-32 ATP (4 direct ATP)
What is the limited supply time of stored glucose?
3-5 hours
What is an alternative to glucose that weight for weight yields more energy?
How much more energy does it yield?
Lipids is an alternative
Weight for weight triglycerides produce 6x as much more energy
There are 135,000 kcal of energy stored as triglycerides in adipose tissue whereas there is only 1200 kcal of energy stored as glucose or glycogen in the muscle.
What is a triglyceride made up of
A glycerol unit and 3 fatty acid chains
What is the difference between triglycerides and omega 3
Triglycerides have double bond oxygens where as omega 3 has double bond between carbons in centre
What is fat stored as
Triglycerides which are esters of glycerol and fatty acid chains
How are triglycerides stored in body broken down?
Lipase breaks down triglycerides into glycerol and 3 fatty acids
Glycerol changed to Peruvate to acetyl coA and enters citric acid cycle
3 fatty acids are beta-oxidised where 2C Acyls are broken off and with addition of Coenzyme A are turned into acetyl coA and used in citric acid cycle
How does breakdown of fats produce atp?
Doesn’t directly
Hydrogens and electrons removed during fatty acid oxidation are used to generate atp and addition of acetyl coA from fatty acids and glycerol into Krebs
Where are fatty acids and glycerol metabolised
In liver
During starvation, what happens to citric acid cycle and how is it rectified by the body?
Oxaloacetate (binds with acetyl coA in Krebs) is depleted as liver uses it to make pyruvate to make glucose via gluconeogenesis
Acetyl coA builds up and is eventually changed into ketone bodies which is an alternative fuel for the brain
Examples of ketone bodies
Acetoacetate
3-hydroxybutrate
Acetone
Breakdown of proteins during metabolism?
amino acids formed by breakdown of protein can be
Incorporated into new proteins
Those not needed can’t be stored so used as metabolic fuel - can be
Deaminated (yields NH4+) a keto acid which can be used in citric acid or Krebs - only glutamic acid
Trans animated - can’t release NH4+ so passes amino group to keto acid such as alpha-ketoglutamate Keto acid then fed into Krebs as pyruvate, acetyl coA , a-ketoglutarate or oxaloacetate
What’s anabolism
Synthesis of complex molecules
What’s gluconeogenesis
Formation of glucose from non-carbohydrate sources
How does gluconeogenesis occur?
Pyruvate > g6p > glucose
Amino acids and lactate feed into pyruvate
Glycerol and AAs feed into pathway also
What is NH4+ and what is it converted to and where does it come from
Breakdown of proteins
Ammonium
Discarded in urea
How does lipid synthesis occur
Glycerol made during glycolysis
2C acyl units from Acetyl coA linked together by fatty acid synthase to form fatty acids
One glycerol plus 3 FA makes a triglyceride
Carbohydrates broken down into what and by which metabolic pathway
Glucose via glycolysis
Fats are broken down into what and by which metabolic pathway
Fatty acids and glycerol by beta-oxidation
Proteins broken down into what and by which metabolic pathway
Amino acids via transanimation
What happens to digested protein
Broken down to Amino acids which are transamination where amino acid is passed to keto acids
Can also be incorporated into new proteins
Or can be stored in muscle
Where is most protein stored and how much is stored there
In muscle 24,000kcal
Transamination example during muscle breakdown
Amino acid pass amino group to pyruvate via transamination to form alanine which is transferred in the blood to the liver converted back to pyruvate and used to synthesis glucose so liver takes burden from muscle
How much glucose does brain use
60%
Why can’t brain use fatty acids as fuel
Can’t pass blood brain barrier
What can fuel the skeletalmuscle
Glucose fatty acids and ketone bodies
What does testing muscle use as fuel
Fatty acids
What stores are used by skeletal muscle and the brain
The brain has no stores
The muscle stores glucose as glycogen (G6P)
Rate of glycolysis and Krebs when muscle active? Lactic acid?
Rate of glycolysis outpaces rate of citric acid cycle so pyruvate is turned into lactate which is transferred to liver via blood where it can be converted back to glucose
What is the function of adipocytes
Synthesis and store triglycerides
Release fatty acid and glycerol in times of need
What does VLDL do?
Transports triglycerides proteins etc around the body
VLDL has high vol of triglyceride
What ensures body / liver has access to nutrients absorbed by gut
Hepatic portal system
What’s the role of the liver
Store and release glucose or make new glucose via glconeogenosus from constituents which aren’t from carbs
Synthesis fatty acids, esterifies and secrets into blood as VLDL
Fasting liver generates ketone bodies
Where is glucagon from
Alpha cells
Where is insulin from
Beta cells
As well as amylin
Where is somatostatin from
D-cells
What type of function is pancreas
Exocrine- to other tissues of the body via ducts etc
What happens to the glucose (percentages)
30% absorbed via HPV
30% metabolised in liver
70% distributed to other tissues
Fed state explained
Absorptive state
Shortly after meal when nutrients are available
Metabolism here is ANABOLIC
nutrient molecules used to provide energy stores of for growth and maintenance of cells and tissues and can provide energy for use immediately
Fasted state explained
Postabsoprtive state
Body needs to draw upon reserves
Metabolism is CATABOLIC
Calls on stores and they become depleted
How are metabolic pathways regulated?
Metabolic pathways are self regulated via the conc of substrates and products or via the rate of activity of enzymes (which can be affected by hormones such as insulin, glucoagon, adrenaline and noradrenaline)
Insulin release explained
High conc of blood glucose and parasympathetic nervous system stimulate beta cells to release insulin.
This drives the fed state.
Stimulates the storage of fuels and anabolism to reduce levels of sugar in blood.
What processes does insulin stimulate
Glycogen synthesis in liver and muscle
Formation of triglycerides in adipose tissue
Protein synthesis in muscle
Glycolysis and fatty acid synthesis in liver
Uptake of glucose to muscle and adipose
Glucagon stimualtion explained
Low conc of blood glucose due to fasting state stimulates release of glucagon from alpha cells
Main target here is the liver.
Glucagon stimulates which processes to occur
Release of glucagon G6P from glycogen
Gluconeogenesis but inhibits incorporation into glycogen
Breakdown of triglycerides
What levels are glucagon and insulin in fed state and what does this do?
Glucagon is low and insulin is high in fed state
Causes synthesis of glycogen fat and protein
And glycolysis
What levels are glucagon and insulin in fasted state and what does this do?
High glucagon low insulin
Causes glycogenolysis, gluconeogenesis and ketogenesis
Amines (hormones) which regulate metabolism
Adrenaline and noradrenaline
Where are adrenaline and noradrenaline secreted from m
Adrenal medulla and neurones of sympathetic nervous system when blood glucose drops
What is the role of adrenaline and noradrenaline during metabolism
Similar to glucagon, they drive breakdown of glycogen and triglycerides BUT mainly on muscle rather than liver like glucagon
ALSO
increase glucagon secretion and inhibit insulin secretion
Total available energy in the body
162000kcal approx
How long do fuel stores last during starvation
1-3 months dependent upon level of exercise etc
Range of blood glucose and normal
From 80mg/100ml to 120mg/100ml post meal
Normal is 80/100 which is 4-8mmol/litre
Hypoglycaemia and hyperglycaemia ranges
<3 is hypoglycaemia and >11 is hyperglycaemia
What happens durin the first days of starvation?
Glucose conc decreases
Proteins which yield glucose via gluconeogesis preserved
Muscle begins to use fatty acids as fuel
Liver uses fats, pyruvate, lactate and alanine from protein breakdown to make glucose for brain
What happens during day 3 of starvation?
Increase in level of ketone bodies (formed in liver as consequence of breakdown of fatty acids and limits TCA )
Brain uses ketone bodies as fuel
Less glucose needed overall, less amjnoa cids needed for gluconeogenesis
Fatty acids converted to ketone bodies by which process
Beta oxidation
Type 1 vs type 2 diabetes
Type 1 is autoimmune where beta cells of pancreas rare damaged
10% of cases
Treated with insulin
Type 2 causes by lifestyle and genetics
90% of cases
Managed with exercise and weight loss
What happens during diabetes
Blood glucose levels higher than normal which damages tissues, however, blood not taken up by insulin so body goes into fasting state.
Glycolysis is slow
Glucogenogenesis is stimulated from AAs via breakdown of protein muscle
Fatty acids make ketone bodies
Ketone bodies and glucose pass to blood
Why do diabetics pee a lot
Transporters in kidney can’t remove all the glucose
It adds to osmotic strength of urine making it harder for kidney to reabsorb water
Ruins vol hence increases with glucose in
Severe- acidic ketone bodies in urine known as ketoacidosis
