Biochemistry Need to Know Flashcards
where does fatty acid synthesis and activation occur?
cytoplasm of liver cells
what activates fatty acids?
addition of acyl coa
what is the precursor for fatty acid synthesis?
malonyl CoA
as malonyl CoA is the precursor for acyl CoA
what is the process of fatty acid synthesis?
glucose > acetyl CoA > malonyl CoA > Acyl CoA > Fatty acid
what enzyme converts Acetyl CoA to malonyl CoA?
acetyl CoA carboxylase
what regulates Acetyl CoA carboxylase locally?
citrate
stimulates by binding allosterically
what activates acetyl CoA carboxylase?
insulin in the fed state
stimulates fuel storage and protein synthesis
what deactivates acetyl CoA carboxylase?
glucagon in the starved state
epinephrine (adrenaline) signals energy requirement and inhibits release
what is the pathway for fatty acids breakdown?
beta oxidation
where does beta oxidation occur?
in the mitochondrial matrix of liver cells
how many steps are in each cycle of beta oxidation?
4
what are the products of one cycle of beta oxidation?
1 acetyl CoA
1 FADH2
1 NADH + H+
1 fatty acyl CoA, shortened by 2 carbon atoms
how can the number of oxidations required for complete catalysis of a fatty acid be calculated?
for an even number of carbons (C2n), number of oxidations = n-1
E.g: 12 carbon fatty acid, n=6, number of oxidations required = 5
When are ketone bodies formed?
during fasting conditions from acetyl-CoA from beta oxidation
where are ketone bodies formed?
in liver cell mitochondria
why are ketone bodies important, give an example of one
diffuse into blood stream and into peripheral tissues
important for energy metabolism in brain, heart muscle and renal cortex
E.g = acetone
how is urea synthesised?
through urea/ornithine cycle in liver
where are the components of urea derived from?
1 nitrogen from free ammonium
1 nitrogen from aspartic acid
carbon from carbon dioxide
what is gluconeogenesis?
formation of glucose from non-carbohydrate compounds (amino acids from TCA cycle)
how does gluconeogenesis proceed?
via synthesis of oxaloacetate (TCA cycle intermediate which accepts acetyl groups)
requires 4 unique liver enzymes
energy consuming
where does gluconeogenesis occur?
mitochondria
what does glycogenin do?
covalently binds 4 glucose molecules to itself via catalytic activity to form a glycogen polymer
why is glycogenin needed?
as glycogen synthase can only add glucose to an existing glycogen chain
