Bob's 3 Flashcards
Name two important intermediates of glycolysis?
Glycerol phosphate which is used in triglyceride and phospholipid synthesis. Also 2-3 bisphosphoglycerate which is used to regulate haemoglobin O2 affinity.
What would cause glycolysis to stop?
Low NAD+ levels.
When is NAD+ regenerated from NADH?
Stage 4 of metabolism
Why do we need another route to regenerate NADH?
NADH regeneration happens in stage 4 of metabolism which doesn’t occur in RBC’s for example. Stage 4 of metabolism also requires oxygen which isn’t always available in certain tissues like muscles.
What two ways do we have of regenerating NADH?
Stage 4 metabolism or using lactate dehydrogenase.
When do you get lactate production?
When there isn’t enough oxygen and when metabolism is under stress for example in a fuel overload.
Also during pathological situations like shock and congestive heart disease and during strenuous exercise.
What happens in the lactate dehydrogenase reaction?
Pyruvate and NADH are converted to lactate and NAD+.
When lactate is produced in the body where is it metabolised?
In the liver and heart which always have a steady oxygen supply. Here the reaction reverses so lactate and NAD+ become pyruvate and NADH.
What is the difference between hyperlactaemia and lactic acidosis?
Hyperlactaemia is where you have a high lactate of between 2-5 mM, however this is below renal threshold and can be managed to prevent blood pH from decreasing. Lactic acidosis on the other hand is where the concentration is greater than 5mM and above renal threshold so blood pH is lowered. This along with a low pH IS A CLINICAL MARKER OF A CRITICALLY ILL PATIENT.
Name two clinical problems associated with fructose metabolism?
Essential fructosuria- missing fructokinase enzyme, fructose not metabolised and simply passes through body and gives no clinical problem.
Fructose intolerance- no aldolase enzyme so fructose-1-P accumulates and damages liver, prevent by removing fructose from the body.
What is lactose made from?
Galactose and glucose
What are the two fates of galactose in the diet?
Will either go through glycolysis or become glycogen
What is a galactose build u in the diet called?
Galactosaemia
What happens to galactose in galactosaemia?
Galactose will be converted to galactitol using NADPH and the H+ ions released can cause disulphide bonds to form between proteins and cataracts of the eye can result.
What is galactitol?
The substance formed from galactose if
Where do fructose and galactose enter glycolysis?
Early on before pyruvate formation
What is the purpose of the penthouse phosphate pathway?
It synthesises 5 carbon sugars for DNA and RNA, nucleotides, coenzymes and produces NADPH. It occurs when we are well fed.
What controls whether pentose phosphate pathway will occur?
High NADPH to NAD+ ratio at g6p dehydrogenase
Where does the penthouse phosphate pathway begin and what enzyme starts it?
With glucose-6-P and glucose-6-p dehydrogenase.
What is NADPH used for?
Fatty acid biosynthesis,steroid biosynthesis, glutathione (GSH) regeneration
What makes penthouse phosphate pathway unidirectional?
The step which involves the loss of a CO2 molecule.
Functions of pentose phosphate pathway?
Make NADPH which retains free SH groups on proteins and prevents disulphide bond formation.
Biosynthetic reducing power for lipid synthesis, steroid synthesis etc.
C5 sugars for DNA and RNA
What happens with glucose 6 phosphate dehydrogenase deficiency?
pentose phosphate pathway wont run resulting in disulphide bond formation in lens of eye and cataracts. Consequences similar to that of galactosaemia.
