Biochemistry Flashcards
glycogenesis
synthesis of glycogen from glucose
glycogenolysis
breakdown of glycogen to form glucose
gluconeogenesis
de novo synthesis of glucose from metabolic precursors such as lactate, amino acids and glycerol
role of glycogen synthase
adds one glucose molecule to a glycogen at a time (cannot introduce branches)
role of transglycosylase
produces branches in glycogen
which hormone enhances glycogen synthase
insulin
which hormone inhibits glycogen synthase
glucagon
which enzyme catalyses glycogenolysis
glycogen phosphorylase
what enhances the action of glycogen phosphorylase
glucagon, adrenaline and cortisol
what inhibits glycogen phosphorylase
insulin
what is used to convert lactate to glucose that is released into the blood?
cori cycle
two places of glycogen storage
liver
muscle
how are amino acids produced in gluconeogensis
proteolysis
how is glycerol produced in gluconeogenesis
lipolysis
what happens in glycogen storage disease
increased glycogen deposition in liver or muscle or both.
what is lipid catabolism
breakdown of lipids
what is the main energy storage form in adipose tissue?
TAGs
what do TAGs consist of?
glycerol and three fatty acids
what are chylomicrons cleaved by?
lipoprotein lipases at muscle and adipose tissue
what happens to free fatty acids once they have been cleaved?
- resynthesises to TAGs OR
- oxidised for energy
what do free fatty acids have to be converted to so they can be oxidised for energy
CoA-derivatives called acyl-CoA
what transports acyl-CoA into the mitochondria from the cytoplasm in lipid breakdown
acyl-carnitine transporter
what happens to acyl-CoA once they reach the mitochondria in lipid breakdown
they undergo beta-oxidation
which enzyme activates glycerol to glycerol-3-phosphate
glycerol kinase
where are ketone bodies formed?
mitochondria from acyl-CoA
what is dangerous about ketone bodies
they can diffuse from the liver mitochondria into the blood and accumulate causing acidosis
how is ketonic acidosis detected?
acetone on breath
what is lipid anabolism
synthesis of fatty acids from acetyl-CoA
where does synthesis of fatty acids occur?
cytoplasm of the liver
how does acetyl-CoA groups reach the cytoplasm for fatty acid synthesis
citrate
what converts acetyl-CoA to malonyl-CoA
acetyl-CoA carboxylase
role of fatty acid synthase
catalyses synthesis of long chain fatty acids from malonyl-CoA, acetyl-CoA and NADPH
what increases the action of acetyl-CoA carboxylase
citrate
insulin
what inhibits the action of acetyl-CoA carboxylase
palmitoyl-CoA
AMP
glucagon
epinephrine
synthesis of TAGs
glycerol-3-phosphate and esterification
is there a storage form of amino acids?
no
what does amino acid breakdown produce
NH3
NH4+
what is amino acid breakdown products secreted as
urea
uric acid
creatinine
NH4+
three stages in the synthesis of urea
- transamination
- de-amination
- urea cycle
transamination
aminotransferases move amino group from amino acid to ketone acids. alanine and glutamine transfer nitrogen in the blood to the liver
de-amination
occurs in the liver, amino group is converted to NH4+
define carbon skeletons
amino acids with the alpha amino group removed
ketogenic amino acids
degraded to acetyl-CoA which can give rise to ketone bodies and fatty acids
glucogenic amino acids
degraded to pyruvate or TCA then glucose
inherited disorders of amino acid degradation
- alkaptonuria
- maple syrup urine disease
- phenyloketonuria
