Biochemistry Flashcards
What is the role of glycogen as an energy store?
Liver glycogen - broken down in-between meals to maintain blood glucose levels
muscle glycogen - provides energy via glycolysis
How can glucose residues be added to a glycogen chain?
can only be added to an existing glycogen chain with a primer being used that is attached to a protein called (glycogenin)
What is UDP-glucose?
activated form of glucose and can synthesise glycogen from it
How is glycogen cleaved to produce glucose?
glucose 1 phosphate is converted to glucose 6 phosphate that can be dephosphorylated in the liver and released into the blood stream
Define glycogenesis, glycogenolysis and gluconeogenesis
synthesis of glycogen from glucose
breakdown of glycogen to form glucose
de novo synthesis of glucose from metabolic precursors
How can new glucose be synthesised during prolonged starvation?
(study summary on notion)
lactate - skeletal muscle
amino acids - muscle protein
glycerol - triglycerides
What is the general structure of triglycerides
- glycerol and 3 fatty acids
General structure of fatty acids?
mainly straight chains can have double bonds or no double bonds
What is the difference between plant fats and animal fats
Plant fats are unsaturated = liquid
animal fats are solid.
What are the main products of fat digestion?
glycerol, fatty acids and monoglycerides
What are the products of beta oxidation?
1 acetyl coA, 1FADH2, 1 NADH and H+ and 1 fatty acid acyl CoA, shortened by 2 carbon atoms
What condition must be filled in order to oxidise fatty acids?
converted into CoA derivatives to be transported to cell matrix
Where are ketones formed and why are they important?
liver mitochondria and important in energy metabolism for heart muscle and renal cortex - diffuse into peripheral tissues
Why are ketones important in starvation or diabetes?
oxaloacetate is consumed for gluconeogensis
Acteyl CoA is converted into ketone bodies which if present in high levels in the blood cause severe acidosis
smell of acetone can be detected in breath
Describe the process of synthesising new triglycerides from citrate (from the TCA cycle)
citrate transports acetyl group into cytoplasm, Acetyl CoA is activated to malonyl CoA (caroxylase) , this then turns into fatty acyl CoA which turns into triglycerides (esterification)
How is nitrogen excreted (degradation of proteins)
urea, uric acid and creatinine - exerted ammonium is toxic at high concentrations
what are major carriers of nitrogen in the blood to liver?
alanine and glutamine
What is the carbon skeleton left over after alpha amino group is removed used for?
converted to glucose or oxidised in the TCA cycle
Describe the pathway of glycogen synthesis
Glucose to glucose 6 phosphate (catalysed by hexokinase) then to glucose 1 phosphate (phosphglucomutase) then UDP glucose (UDP=glucose pyrophosphorylase) then to glucose (glycogen synthase)
What are some limitations of glycogen synthase?
adds one glucose molecule to glycogen at a time, only extend chains and not introduce branches (UDP glucose is rate limiting enzyme)
What catalyses glycogenolysis?
Glycogen phosphorylase - rate limiting step… (breakdown of glycogen to glucose 1 phosphate)
where does gluconeogensis take place?
energy is from what? released from where?
usually in the liver and the energy is from oxidation of fatty acids released from adipose tissue
How does gluconeogenisis proceed?
via the synthesis of oxaloacetate in mitochondria - TCA cycle intermediate that accepts acetyl intermediates which is important for accepting acetyl groups in fat breakdown
What is the product of gluconeogensis
glucose, 4ADP, 2GDP, 6phosphate, 2NAD+ and 2 protons
Why is the cori cycle useful?
buys time and shifts metabolic burden from muscle to other organs
What hormones are useful in the control of glycolysis and gluconeogenisis
glucagon - inhibits glycolysis
insulin - inhibits gluconeogensis
What is the products of amino acid degradation
Produces amonia and ammonium ions - NH4+ is toxic at high concentrations, build up leads to severe problems
How is urea synthesised?
ammonium ions and aspartic acid
What is the product of producing urea
urea, 2ADP, AMP and fumarate (plus others)
what are the two functions of ketogenic and glycogenic amino acids?
degraded to acetyl COA
degraded to pyruvate or TCA cycles
What is the treatment for excess ammonia in the blood
low protein diet - or use drugs that are involved in the removal of nitrogen
what are lipids?
Collection of different compounds - simple, compound or steroids
hydrocarbon, insoluble in water and contain long chain fatty acid
What is the threshold of fatty acids at room temperature for the state it is in?
up to 8Carbons are liquid at room temp but longer ones are solid
What happens to chylomicrons?
attacked and cleaved by lipoprotein lipases, synthesised into triglycerides or to provide energy
What is the carnitine shuttle?
used to transport acetyl across the cell membrane
What is required for the breakdown of glycerol?
Activated to glycerol 3 phosphate by glycerol kinase and then dehydrogenated to dihydroxyacetone phosphate
where does beta oxidation take place?
Mitochondrion
Where does fatty acid synthesis take place
Mainly in cytoplasm of liver, takes place during excess energy intake
Why are elecrons required in lipgenesis?
It is a reductive process
Why is citrate useful in lipogenesis?
Transports actyl groups into cytoplasm
What is the longest fatty acid released ?
palmitic acid (C16) is the longest fatty acid created by fatty acid synthase
What enzyme regulates the conversion of acetyl CoA to Malonyl CoA?
What are the
acetyl CoA carboxylase
What are the regulatory components included in Acetyl CoA carboxylase
insulin - signals fed state
glucagon - signals starved state
Epinephine - requirement for energy
citrate stimulates allosterically - levels are high when acetyl-CoA and ATP are abundant
antagonised by palmitoyl-CoA
What does the synthesis of triglycerides require?
glycerol 3 phosphate from liver, adipose tissue(fed state)
