cell met 2 Flashcards
What does the Krebs cycle produce per cycle, net?
3x NADH, 1x FADH2, 1x GTP, 2x CO2
What are two alternative names for the Krebs cycle?
Tricarboxylic acid (TCA), citric acid cycle
Is the Krebs cycle aerobic or anaerobic?
strictly aerobic, unlike glycolysis
What is a description about the Krebs cycle enzymes?
they are soluble proteins located in the mitochondrial matrix space (with one notable exception)
When is the bulk of ATP generated (Krebs cycle)?
when the reduced coenzymes are re-oxidised with the help of oxygen (oxidative phosphorylation)
-> this re-oxidation means that the tca cycle only operates under aerobic conditions
Can amino acids enter the TCA cycle?
yes
What is the general strategy of amino acid degradation?
- remove the amino group (which is eventually excreted as urea)
- whilst the carbon skeleton is either funnelled into the production of glucose OR fed into the TCA cycle
What does the degradation of all twenty amino acids give rise to?
only seven molecules: pyruvate, acetyl coa, acetoacetyl coa, aketoglutarate, succinyl coa, fumarate and oxaloacetate
What are the names of the seven molecules which are given rise to by the degradation of all 20 amino acids?
- pyruvate
- acetyl coa
- acetoacetyl coa
- aketoglutarate
- succinyl coa
- fumarate
- oxaloacetate
What are the two types of amino acids? (in terms of what they give rise to)
glucogenic and ketogenic
What type of reaction is a transamination reaction?
group transfer
What involves transamination reactions?
protein metabolism
What happens in a transamination reaction?
an amine group is transferred from one amino acid to a keto acid
forming a new pair of amino and keto acids
Give an example of a transamination reaction?
alanine metabolism
Describe the alanine metabolism reaction?
alanine (C3) + alpha-ketoglutarate —alanine aminotransferase—> pyruvate + glutamate
What does the decarboxylation of pyruvate generate?
acetyl coa
which can then enter the tca cycle
What happens to the glutamate produced in alanine metabolism/transamination?
- re-converted to alpha-ketoglutarate by glutamate dehydrogenase
- this generates NH4+ which is ultimately converted to urea
Where does the NADH produced in glycolysis need to go and why?
- the mitochondria
- to be utilised by ox phos
- and to regenerate NAD+
What happens if NAD+ is not regenerated?
there is only a finite amount of NAD+ and unless regenerated, glycolysis will quickly grind to a halt
How does NADH (or its high-energy electrons) cross from the cytosol into the matrix of the mitochondria?
- glycerol phosphate shuttle (skeletal muscle, brain)
- malate-aspartate shuttle (liver, kidney, heart)
Which tissues/organs is the glycerol phosphate shuttle for?
skeletal muscle, brain
Which tissues/organs is the malate-aspartate shuttle for?
liver, kidney, heart
What are carried across the mitochondrial membrane via the glycerol phosphate shuttle?
electrons from NADH, rather than NADH itself
What is step 1 of the glycerol phosphate shuttle?
cytosolic glycerol 3-phosphate dehydrogenase transfers electrons from NADH to DHAP to generate glycerol 3-phosphate
What is step 2 of the glycerol phosphate shuttle?
a membrane bound form of the same enzyme transfers the electrons the FAD.
these then get passed to co-enzyme Q (part of electron transport chain)
What happens to the electrons after they are transferred to FAD in the glycerol phosphate shuttle?
they get passed to co-enzyme Q (part of the electron transport chain)
What (type of) reactions are happening in the malate-aspartate shuttle?
redox
What does AT stand for? (malate-aspartate shuttle)
aspartate transaminase
What does MDH stand for? (malate-aspartate shuttle)
malate dehydrogenase
What are the names of the antiporters in the malate-aspartate shuttle?
- glutamate-aspartate antiporter
- malate-alpha-ketoglutarate
What are the two reactions in the malate-aspartate shuttle?
aspartate—
