Biochemistry Flashcards
what is glycogenesis
synthesis of glycogen from glucose
what is glycogenolysis
breakdown of glycogen to form glucose
what is gluconeogenesis
synthesis of glucose from metabolic precursors
when would gluconeogenesis be raised?
overnight
when would glycogenolysis be raised
in between meals
what is glycogen
storage form of glucose
function of liver glycogen
maintaining blood glucose
function of skeletal muscle glycogen
bursts of energy, not blood glucose
what links keep glucose residues together in glycogen
alpha 1-4 glycosidic links
what links keep glycogen branches together
1-6 glycosidic links
what breaks gucose down into glucose-6-phosphate
hexokinase
what is the primer for glycogen
glycogenin, covalently attached to 4 glucose residues
what enzyme converts glucose 6-phosphate to glucose-1-phosphate
phosphoglucomutase
Addition of UTP to G-1-P is catalysed by _____
UDP-glucose pyrophosphorylase
what enzyme adds glucose residues to glycogen
glycogen synthase
can glycogen synthase create new glycogen molecules
no, it can only add glucose to existing ones
what enzyme is needed to add glucose to a branch of glycogen
transglycolase
what enzyme catalyses glycogenolysis
glycogen phosphorylase
true/false - in the liver G-6-P can be dephosphorylated to go back to glucose
true
true/false - in skeletal muscle G-6-P can be dephosphorylated to go back to glucose
false - it must be broken down via glycolysis and TCA
where does gluconeogenesis occur in the body
liver
is gluconeogenesis the reverse of glycolysis
no!
what enzyme catalyses synthesis of oxaloacetate from metabolites in gluconeogenesis
pyruvate carboxylase
what enzyme bypasses pyruvate kinase
PEP carboxylkinase
what enzyme bypasses phosphofructokinase
fructose-1,6-bisphosphatase
what enzyme bypasses hexokinase to synthesise glucose in gluconeogenesis
glucose-6-phosphatase
how much energy does gluconeogenesis use
4ATP
2GTP
where do amino acids participate for use in gluconeogenesis
enter TCA to be converted to oxaloacetate
what is the cori cycle
recovery of lactate to pyruvate, to glucose via gluconeogenesis
true/false - insulin promotes glycogenesis and glycolysis
true
glucagon increases gluconeogenesis by inhibiting ____ and promotoing ____
phosphofructokinase
fructose-1,6-biphosphatase
what are TAGs made of and where are they stored
glycerol and 3 fatty acid chains
adipose
true/false - fatty acids are usually in trans configuration
false - usually in cis
what causes the kink in fatty acid chains
the double bond
in order for fats to be absorbed into intestinal mucosa cells, they are broken down into ____, ____ or ____
glycerol
fatty acids
monoglycerides
what is lipolysis and what is it catalysed by
breakdown of lipids, catalysed by hormone sensitive lipases
before a fatty acid can be oxidised what must it be converted to?
CoA derivative
is fatty acid oxidation a passive process?
no, it requires energy
what is the carnitine shuttle
carnitine is acylated by acyl-CoA and travels across mitochondria to acylate another CoA to ‘shuttle’ across mitochondria
products of beta oxidation
1FADH
1NADH+H
1 acyl CoA, 2 carbons shorter
1 Acetyl CoA
describe the breakdown of glycerol
glycerol kinase converts it to glycerol-3-phosphate
dehydrogenated to dihydroxyacetone phosphate
where are ketone bodies formed
liver mitochondria
when may ketones be dangerous
in diabetics as they may develop diabetic ketoacidosis due to the inability to produce insulin
where does fatty acid synthesis occur
liver, kidney, adipose, brain
excess carbohydrate intake causes it to be….
converted to TAGs and fatty acids
what is required for triglyceride synthesis
Glucose 3 phosphate, yielded from glycerol or glucose in the fed state
what stimulates triglyceride synthesis
insulin in the fed state
the first step of fatty acid synthesis requires acetyl CoA. what produces it
pyruvate dehydrogenase
how does Acetyl-CoA enter the cytoplasm from the mitochondria
condenses with oxaloacetate to form citrate to transport to cytoplasm
acetyl-CoA carboxylase converts…
acetyl-CoA to manonyl-CoA
structure and function of fatty acid synthase
7 functions and an acyl carrier protein
catalyses synthesis f saturated long chain fatty acids from manonyl-CoA, Acetyl-CoA and NADPH
how many carbons are added to the growing fatty acid chain by fatty acid synthase per cycle
2
what stimulates fatty acid synthesis
insulin
citrate
what opposes fatty acid storage
glucagon
adrenaline
main site for amino acid degradation
liver
what is protein turnover
removal of damaged proteins
describe amino acid absorption
proteolytic enzymes yield amino acids, absorbed by enterocytes that are released into the blood
what toxic chemicals are released by amino acids and how are they safely excreted
ammonia/ammonium
excretion by urea, uric acid and creatinine
aminotransferases turn amino acids to ____
glutamic acid
why does glutamic acid get de-aminated
to yield ammonium
describe the ornithine cycle
carbamoyl phosphate combines with ornithine and aspartic acid added. coverted to urea and ornithine is reused
what happens to the de-aminated carbon skeletons after the ornithine cycle
ketogenic bodies may become ketone bodies or fatty acids
glucogenic bodies may used to produce glucose
