Tricarboxylic Acid Cycling Flashcards
ATP
Energy currency of the cell
What supplies ATP?
Carbs/Lipids/Proteins
What uses ATP?
Muscle contraction, active ion transport, biosynthesis, detoxification and thermogenesis
How much ATP does one heartbeat use?
2% / heart beat
Why is it important that the heart regenerates its ATP?
If the heart couldn’t regenerate its ATP then all of its ATP would be depleted in less than one minute
How does the heart produce ATP?
Oxidative phopsphorylation, this is why a blockage in the C.A is so problematic
Anaerobic vs Aerobic glycolysis, which creates more ATP and how much does each type make?
Aerobic glycolysis makes more, 36 ATP/glucose (aerobic), 2 ATP/glucose (anaerobic)
Which tissues use anaerobic glycolysis?
Tissues with low O2 or no mitochondria, or hypoxic tissues
What does lactate in the blood indicate?
Poor tissue perfusion
What does too much lactate cause?
Acidosis
Acetyl CoA
Substrate for the TCA cycle
2 phases of energy metabolism
- Oxidation of fuels to get it to Acetyl CoA
- Generation of ATP via TCA and ETC
Anoxia
Total lack of O2
Tissue hypoxia
Cell death in that area
What occurs with tissue hypoxia?
Na+/K+ pump no longer works, increased Na+ in the cell, Ca2+ can infiltrate the cell, H2O follows in, cellular swelling, leads to formation of mitochondrial permeability transition pore, programs cells to die
Cyanide
Blocks O2 utilization, prevents energy generation and shuts cells down
Anaerobic glycolysis occurs in the …
Cytosol
Aerobic glycolysis occurs in the …
Mitochondria
Mitochondria are …
The powerhouse of the cell
Mitochondria (function)
Produce energy, also the site of the TCA cycle and the ETC
Outer membrane of the mitochondria is …
Permeable to small ions
Inner membrane of the mitochondria is …
Impermeable so that the H+ gradient can be maintained to drive the synthesis of ATP
TCA cycle occurs in the …
Matrix of the mitochondria (creates electrons which are taken to the ETC, as electrons shuttled through enzymes, H+ is brought in between inner and outer membrane space and they build up until they can be forced through the ATP synthase, this provides energy needed to make the ATP
TCA cycle is also known as
Krebs cycle, citric acid cycle, occurs in the mitochondria
What is the link between glycolysis and the TCA cycle?
Pyruvate dehydrogenase enzyme complex, PDC converts the two 3-C pyruvate molecyles generated from one molecule of glucose by glycolysis to the 2-C acetyl CoA. O2 is the ticket for entry into the TCA cycle to generate ATP more efficiently
Oxidation and reduction
Reactions that drive energy generation
How is ATP produced from ADP?
NAD+ and FAD reduced in the TCA cycle and then regenerated by oxidation in the ETC, electrons shuttled and H+ pumped, helps turn ADP –> ATP
NADH dehydrogenase
Pulls electron and H+’s off of NADH
Cyanide poisoning
Binds where O2 should be on the heme group, binds tighter than O2, everything backs up, no energy produced and person dies
Complex II
Part of the TCA cycle, where FADH2 drops off electrons
Pyruvate dehydrogenase complex
Take pyruvate and turn it to Acetyl CoA which is the substrate for the TCA cycle, if it can’t go to Acetyl CoA, its reduced to lactate, lactic acid builds up and causes acidosis
OXPHOS disease
Involve mutations in DNA that code for mitochondrial proteins
Which tissues are most affected by OXPHOS diseases?
CNS and muscles (highest ATP requirement)
All mitochondrial DNA/ mitochondria come from …?
Mother
In the absence of O2, pyruvate becomes …
Lactate
What are oxidation/reduction reactions used for?
Regenerate electron transferring molecules in the mitochondria (need oxygen) If done anaerobically, reactions can only be reduced if pyruvate –> lactate
Why might tissues not have mitochondria?
They may interfere with their function
RBC’s don’t have mitochondria because …
of their function in O2 transport. RBC’s get their energy from anaerobic glycolysis
Tissues in the eye don’t have mitochondria because …
Need to be free from light deflecting structures
Causes of lactic acidosis
- Tissues that use aerobic glycolysis are now unable to
- Poor perfusion
- Cyanide/CO block cytochrome P450
- Genetic defects
- Deficiencies/inhibition of TCA cycle
- Decreased oxidation of NADH and FAD(2H) in ETC
Why are fatty acids the best energy source?
Have lots of carbons, which contain lots of energy, main source of energy during fasting
Why is it called “beta-oxidation”?
Bond is cut @ the beta bond, creates a 2-carbon Acetyl CoA molecules that can enter the TCA cycle
In the last mile of a marathon you would be using _____ as your source of energy because you’ve used up your carbs, and you have more of these stored.
Fatty acids
Pathways of glucose turning into pyruvate?
- turn into acetyl coA which needs an enzyme to enter TCA cycle
- if that pathway is shut off it will be turned into lactate b/c the NADH buckets are filled with electrons that need to be emptied
perfusion
getting oxygen to tissue
Things that interfere with oxygen distribution can cause
life or death situations
How is energy created
protons build up and push through to get through; requires oxygen to keep electrons shuttling and enzymes that keep the TCA cycle running
Where does TCA occur
mitochondria
What molecule is the ticket for TCA cycle?
oxygen
What happens if there is no oxygen for TCA?
turns into lactate
loss of electrons
oxidation (gain of O)
gain of electrons
reduction (loss of O)
Are NAD+ and NADH reduced or oxidized in the TCA cycle?
reduced (lose O, gain electron)
Electron transport chain is known as
oxidative phosphorylation
Is complex 2 apart of electron transport
no
What is complex 2?
start of TCA cycle
Glycolysis role
generate energy
Glycolysis is present in
all cell types who have glycolytic enzymes
- can function with or without oxygen
How is ATP produced in glycolysis
by substrate level phosphorylation
Product of glycolysis and its function
pyruvate can go on to produce more ATP through oxidative phosphorylation
