Biochemistry of Metabolism Summary Flashcards
can fatty acids be used for gluconeogenesis?
yes
true or false, some lipids contain phosphate groups, carbohydrates or proteins
true
Lipid absorption is required for the absorption of some vitamins, true or false?
true
what are the main storage form of lipids in the human body?
triglycerides
what is the first step of catabolism?
lipolysis
do fatty acids have to first be activated to acetyl-CoA in fat metabolism?
no
they have to be activated to acyl CoA
where does activation occur in fat metabolism?
cytoplasm
what is beta-oxidation?
the pathway for the breakdown of fatty acids
where does beta oxidation occur?
in the mitochondrial matrix
how many oxidation occur in beta-oxidation, Eg for a C14 fatty acid?
6
14/2 -1 = 6
For even numbered fatty acid (C2n), Number of oxidations = n-1
How many steps are in each cycle of beta-oxidation?
4
What are the products of each beta-oxidation cycle?
1 acetyl CoA
1 FADH2
1NADH + H+
1 fatty acyl CoA, shortened by 2 carbon atoms (goes on to restart cycle)
what would be the products of the breakdown of a C14 fatty acid?
6 acetyl CoA
6 NADH + H+
6 FADH2
Where are ketone antibodies formed and how?
formed in liver under fasting conditions from acetyl CoA and Beta-oxidation and diffuse into the blood
what is the function of ketone antibodies? How do they do this?
sustain normal function during starvation via energy production and neurotransmitter synthesis
Converted back to acetyl CoA which enters TCA cyle
name the 3 ketone bodies
Acetoacetate
D-3-hydroxybutyrate
Acetone (causes fruity breath)
can ketone bodies act at sites distal to site of synthesis?
yes
Ketone bodies are toxic to peripheral tissues which prefer glucose, true or false?
false
ketone bodies can lead to ketoacidosis, true or false?
true
what are the steps in fatty acid synthesis (eg insulin or glucagon)?
glucose used to generate Acetyl CoA
Acetyl CoA carboxylase converts acetyl CoA to malonyl CoA (regulated by nutrient/energy status)
Malonyl CoA = major fatty acid synthesis precursor
what 2 substances stimulate acetyl CoA carboxylase in the conversion of acetyl CoA to Malonyl CoA?
Inulin (signals fed state)
Citrate (stimulates allosterically when Acetyl CoA and ATP are abundant)
what 4 substances inhibit acetyl CoA carboxylase in the conversion of acetyl CoA to Malonyl CoA?
Palmitoyl CoA (when excess fatty acids)
AMP
Glucagon (in starved state)
Epinephrine
is fatty acid synthesis reductive?
yes
citrate transports acetyl groups from mitochondria to the cytoplasm, true or false?
true
fatty acid synthesis is induced during conditions of glucagon-mediated glucose release, true or false?
false
induced in fed state
what is the donor molecule of carbon atoms to a growing fatty acid?
Malonyl CoA
what does the phrase “citrate stimulates allosterically” mean?
citrate binds to separate site on acetyl CoA carboxylase activating the catalytic activity when there is lots of citrate
how is urea synthesised?
complex series of reactions in (mainly) the liver driven by ornatheen(urea/ornithine cycle)
what is the purpose of the urea cycle?
method of dealing with excess nitrogen
where are the nitrogen and carbon required for the urea cycle taken from?
1 nitrogen from free ammonium (toxic)
1 nitrogen from aspartic acid (aspartate)
Carbon from CO2
how are amino acids converted into urea and where does this happen?
removal of amino group > amino acid skeletons enter TCA cycle
Occurs in the mitochondrial matrix
what is the rate limiting step in glycogen breakdown?
phosphorylation of glycogen to glucose 1 phosphate via glycogen phosphorylase
what are the 2 possible outcomes of glycogen breakdown?
glycolysis
conversion of glucose 6 phosphate to glucose > glucose transported into blood via GLUT2 transporter
Does gluconeogenesis require ATP?
yes
requires hydrolysis of ATP
what is the difference between glycolysis and gluconeogenesis?
gluconeogenesis requires 4 unique enzymes
what substance allows TCA cycle in gluconeogenesis to proceed by accepting acetyl groups ?
oxaloacetate
synthesised in the mitochondria
what is glycogenin?
protein that sits at the centre of a glycogen polymer and can bind up to 4 glucose molecules to start the formation of glycogen
amino acids serve as precursors for gluconeogenesis, true or false?
true
when are amino acids oxidised?
during the TCA cycle
can glycogen synthase introduce new branches?
no
what is liver glucose and muscle glycogen used for?
liver = blood glucose muscle = energy generation in muscle
glucose has to be bound to UDP before it can be transferred onto glycogen, true or false?
true
what does glucagon do?
inhibits glycogen synthesis and stimulates glycogen breakdown
what does insulin do?
inhibits glycogen breakdown and stimulates glycogen synthesis
glucagon inhibits gluconeogenesis, insulin stimulates it, true or false?
false
other way around
