Biochemistry Flashcards
Define glycogenesis
The synthesis of glycogen from glucose
For glucose to do anything it must first be phosphorylated to ____1_______
In conversion to glycogen there is also a second phosphorylation to _____2_____ which is a good way to determine that glycogen is being made
This is then converted to ____3_____
1) Glucose-6-phosphate
2) Glucose-1-phosphate
3) UDP glucose
What is the rate limiting enzyme of glycogenesis and what does it do? Why is it rate limiting?
Glycogen synthase which synthesises glycogen from UDP glucose. It can only add one glucose molecule to glycogen at a time and cannot add branches.
Define glycogenolysis
This is the breakdown of glycogen to form glucose
Glycogenolysis is catalysed by ______1______
In the liver G6P can be ________2_________
In skeletal muscle G6P cannot be dephosphorylated but instead _________3__________
1) glycogen phosphorylase
2) dephosphorylated and resulting glucose released into the blood stream
3) used to provide energy by glycolysis and TCA
Define gluconeogenesis
This is the synthesis of glucose from metabolic precursors
Gluconeogenesis involves highly unfavourable reactions and requires energy as ______1_______
It requires four rate limiting enzymes which are ______2________
1) the three irreversible reactions of glycolysis must be bypassed
2) Pyruvate kinase and PEP carboxykinase which are in the mitochondria. Fructose-1,6-bisphosphatase and Glucose-6-phosphatase which are in the cytosol.
What is the cori cycle?
A process in which lactate can be converted to glucose during exercise.
Describe basic idea of the cori cycle
Blood transports lactate to the liver
Liver concerts lactate back to glucose
Glucose is released into the blood stream
This buys time and shifts metabolic burden from muscle to other organs.
What is the main energy store in adipose tissue?
Triglycerides
What is lipolysis?
The breakdown of triglycerides to fatty acids and glycerol
Before fatty acids can be oxidised they have to be converted to____1_____ this occurs in the _____2____
1) coA derivatives
2) cytoplasm
Acyl-coA is transported into the ___1_____ by the ___2_______
1) mitochondrial matrix
2) carnitine shuttle
The four products of each beta oxidation cycle are
acetyl-coA
FADH2
NADH + H+
A fatty acyl-coA shortened by two carbons
Ketone bodies are formed in ______1______ from the __________2___________
They diffuse into the ____3_____ and ______4_______
They are important molecules of energy metabolism for the _____5______ and _____6______
1) Liver mitochondria
2) acetyl-coA of beta oxidation
3) bloodstream
4) peripheral tissues
5) heart muscle
6) renal cortex
The most common ketone body is
acetylacetate
In lipid anabolism citrate from the TCA is metabolised in the ___1_____ to form ____2____ which is then used to generate ___3______
1 cytoplasm
2 acetyl-coA
3 malonyl-coA
What reaction is the rate limiting step in lipid anabolism?
generation of malonyl-coA from acetyl-coA by acetyl-coA carboxylase
Synthesis of fatty acids occurs in cytoplasm of _____________ this happens when ______
liver cells
citrate concentrations are high and excess is transported out of the mitochondrial matrix
Why must excess amino acids be metabolised as nitrogen waste products?
There is no storage form and ammonia and ammonium ions are highly toxic
What is the major site of amino acid degradation?
The liver
4 major nitrogen contains excretion products?
urea, uric acid, creatine kinase and ammonium ions. Most is secreted as urea in ureine
3 steps involved in urea synthesis?
Transamination
Deamination
Ornithine urea cycle
After removal of urea group what happens to the the remaining carbon skeletons?
converted into major metabolic intermediates
What are ketogenic amino acids degraded to>
Acetyl-coA or acetoacetyl-coA and can give rise to ketone bodies or fatty acids
What are glucogenic amino acids degraded to?
Pyruvate or TCA cycle intermediates and can be converted into phosphoenolpyruvate and then glucose
