lecture 6 - Alternative energy pathways: Gluconeogenesis & the pentose phosphate pathway Flashcards
what are alternative energy pathways?
what is gluconeogenesis?
reverse of glycolysis, takes place in the liver - where several diff substates can be converted into glucose
what is lactic acid?
lactate and hydrogen
what is lactate?
single molecule formed from the breakdown of pyruvate formed from glycolysis
what causes fatigue?
hydrogen - causes a change in pH and burning
what does pyruvate do?
either enters the krep cycle or we accumulate it for when o2 delivery is limited
when is lactate needed?
as a safety net to be transformed into pyruvate if we don’t have enough for glucose
when is lactate produced?
High intensity exercise and resting sits
can lactate be used in the muscle?
no - it undergoes gluconeogenesis and produces glucose
what does lactate allow for?
NAD to be regenerated from NADH. In low intensity exercise, NAD can be regenerated from NADH in the mitochondria with 02 available.
what does the Cori cycle do?
Helps with glycogen storage even at rest
Needs to be converted back to glucose before it can be used again
what happens during the intermediate step do?
costs us energy – 4 ATP whereas only 2 are made in glycolysis
Need to overcome the 3 irreversible reactions
- this is important as it is willing to give more energy than other metabolic pathways
what does conversion of oxaloacetate into PEP require?
an energy rich molecule
is this an irreversible reaction?
yes, it cant remove the phosphate group so use a diff enzyme which is able to remove the final phosphate group – have a freely available glucose molecule
is glucose made when we sleep?
yes, although we dont consume it whilst we sleep it is still made so that we can be supplied with it
how can you inhibit gluconeogenesis?
consume a sports drink
what hormone is needed for this process?
glucagon
can we get better at using gluconeogenesis?
yes through training
when is gluconeogenesis activated?
After 30 - 45 minutes of exercise or when energy in the body is low because we haven’t consumed any glucose! Can occur when fasting or approx. 10-18 h when glycogen runs out.
what substrates can we use in gluconeogenesis?
lactate, amino acids and glycerol
what is the pentose phosphate pathway?
Can be used to oxidize glucose , no ATP is generated - NADPH is formed
how is NADP converted into NADPH?
in a reduction reaction and end up with a molecule Ribulose 5C – can be converted to Ribose 5C which is a core part of the DNA structure or will convert back to fructose 6P and can renenter this process – a cycle
what is NADPH used to make?
glutathione - an important antioxidant
what are free radicals?
steals healthy electrons from molecules
what increases free radical production?
the ETC and aerobic exercise
what do antioxidants do?
provide their electrons to the free radicals so that they leave the healthy atoms alone – need the antioxidants and to make them we need NADPH
what can NADPH be used for?
fatty acid synthesis
