M104 T2 L3 Flashcards
Why is pyruvate useful?
bc it can turn into whatever molecule the cell needs it to be
Which enzyme helps pyruvate turn into lactase?
lactase dehydrogenase
What can pyruvate turn into?
lactase
oxaloacetate
alanine
acetyl-CoA
Which enzyme helps pyruvate turn into oxaloacetate?
pyruvate carboxylase
Which enzyme helps pyruvate turn into alanine?
alanine aminotransferase
Which enzyme helps pyruvate turn into acetyl-CoA?
pyruvate dehydrogenase complex
In what conditions does pyruvate turn into acetyl-CoA?
aerobic conditions
with the enzyme pyruvate dehydrogenase complex
What happens to pyruvate under aerobic conditions when turning into acetyl-CoA?
it is oxidised
it is completely degraded
Where in the cell does pyruvate turn into acetyl-CoA?
in the mitochondria
Where in the cell does glycolysis occur?
in the cytosol
In what conditions does glycolysis occur?
aerobic and anaerobic conditions
Where does pyruvate have to move from in the cell to turn into acetyl-CoA?
was made in the cytosol
has to move to the mitochondria
Where does the TCA cycle occur?
in the mitochondria
What are other names for the TCA cycle?
Krebs cycle
citric acid cycle
What is gained from the TCA cycle?
energy is produced
What can FAs be activated by?
the addition of an acyl group
How are activated FAs transported into the mitochondria?
via carnitine shuttles
What happens to activated FAs in the mitochondria?
they are used to generate acetyl CoA
this enters the TCA cycle
How is pyruvate transported into a mitochondrion?
via the MCP-2 carrier protein embedded in the mitochondrial membrane in aerobic conditions
What is the name of the reaction by which pyruvate is converted into acetyle CoA?
oxidative decarboxylation
What does pyruvate turn into after oxidative decarboxylation?
Acetyl CoA
What is the equation by which pyruvate is converted into acetyl CoA?
Pyruvate + CoA + NAD+
acetyl CoA + CO2 + NADH + H+
Is the oxidative decarboxylation of pyruvate reversible?
no
the reaction is irreversible
acetyl CoA can’t turn back into pyruvate
How many carbons are in pyruvate?
three C
How many carbons are in acetyl CoA?
two C
What two stages of metabolism are linked by the oxidative decarboxylation of pyruvate?
links glycolysis and the TCA cycle
What is the role of the PDH complex?
to convert pyruvate to acetyl-CoA
What does a PDH complex consist of?
3 enzymes
5 co-enzymes
Why is the TCA cycle known as a final COMMON pathway for the oxidation of fuel molecules?
bc it doesn’t matter which metabolic fuel is being used, so whether it’s a glucose or lipids or proteins
all of them end up in the TCA cycle
How many steps are in the TCA cycle?
8 steps
What happens overall in the TCA cycle?
acetyl residues from acetyl CoA
they are oxidised to co2
What is the formula for acetyl residues?
(CH3-CO-)
What is the role of reducing equivalents?
to transfer one electron in redox reactions
Where are the reducing equivalents transferred to? What do they form?
NAD+ or FAD to form NADH and FADH2
Why is the generation of NADH and FADH2 useful?
bc later on they will be transferred to the respiratory chain and used to generate ATP
What happens overall in the TCA cycle carbon-wise?
a 4C unit condenses with a 2-C unit.
as the cycle goes on, 2Cs leave the cycle in the form of two CO2 mlcs
the 4-C unit is regenerated
How many redox reactions occur through one TCA cycle?
four redox reactions
What substances are produced for each molecule of acetyl CoA entering the TCA cycle?
NADH x3
CO2 x2
FADH2
GTP (directly makes ATP)
What happens to the GTP molecule produced from one TCA cycle?
it goes on to directly generate a molecule of ATP
What are the eight different intermediates of the TCA cycle?
1 - citrate 2 - isocitrate 3 - a-ketoglutarate 4 - succinyl CoA 5 - succinate 6 - fumerate 7 - L-malate 8 - oxaloacetate
How can you remember the eight intermediates of the TCA cycle?
A Certificate In Kama Sutra Should Further My Orgasm
After Class I Keep Some Specific Facts More Or-less
Of the eight enzymes involved in the TCA cycle, which three do you need to know?
1 - citrate synthase
3 - isocitrate dehydrogenase
4 - a-ketoglutarate dehydrogenase
Why are there only three enzymes of the eight in the TCA cycle that you need to know?
they are very important regulatory points of control for the TCA cycle
their activity is controlled IOT control the speed of the TCA cycle
Which reaction in the TCA cycle does citrate synthase catalyse?
condensation reaction
reaction 1
What happens during the condensation reaction (reaction 1) of the TCA cycle?
oxaloacetate + acetyl CoA < citrate
Which reaction in the TCA cycle does isocitrate dehydrogenase then a-ketoglutarate catalyse?
iso - reaction 3
aket - reaction 4
Which enzyme in the TCA cycle is part of the respiratory chain?
succinate dehydrogenase
At which two points of the TCA cycle is the flow of C-atoms TIGHTLY regulated at?
when pyruvate is converted into acetyl-CoA (under PDH enzyme control)
the entry of acetyl-CoA into the TCA cycle (citrate synthase reaction)
At which additional lesser two points of the TCA cycle is the flow of C-atoms regulated at?
at the isocitrate dehydrogenase reaction
at the a-ketoglutarate dehydrogenase reaction
What happens if the E levels in a cell are high?
the activity of the TCA cycle will be inhibited
What molecules in high levels indicate the presence of high E levels in a cell?
ATP
acetyl CoA
FAs
NADH
What molecules in high levels indicate the presence of low ATP levels in a cell?
AMP (present when ATP has been used up)
CoA
NAD+
Ca 2+
Why can calcium ions increase the rate of the TCA cycle?
they stimulate muscle contraction
they act as second messengers in some cells
What are alternative sources of acetyl CoA (other than glucose)?
FAs
amacs (less common)
Why are intermediate compounds of the TCA cycle constantly being replenished?
bc they have other biological roles in their cells
How are the intermediate compounds of the TCA cycle replenished?
via anaplerotic reactions
What is the role of anaplerotic reactions?
to maintain the concentrations of TCA cycle intermediates so that the cycle can function efficiently
How many turns of the TCA cycle occur from one glucose mlc (6C)?
two turns, so twice the amount of products than from just one mlc of acetyl CoA (3C)
What happens to the products of the TCA cycle that have been reduced in the process?
they are re-oxidised by the electron transport chain
When NADH is produced by glycolysis, where is it located and where does it need to go?
located - in the cytoplasm, this is where glycolysis occurs
going - the mitochondrial inner membrane, this is where the electron transport chain occurs
Why can’t NADH get across the mitochondrial inner membrane?
the inner membrane is impermeable to NADH
there’s no carrier in the membrane to transport NADH across
What happens to the NADH product of glycolysis?
shuttles transfer two electrons from each NADH mlc into the mitochondria rather than transferring the NADH itself
When NADH is produced by glycolysis, why does it need access to the mitochondrial inner membrane?
this is where the electron transport chain occurs
the NADH needs to be re-oxidised
What are the two types of shuttles involved in giving NADH electrons from the electron transport chain?
the glycerol-3-phosphate shuttle
the malate-aspartate shuttle
What areas is the glycerol-3-phosphate shuttle especially prevalent in?
the brain and muscle
What areas is the malate-aspartate shuttle especially prevalent in?
in the liver and the heart
What is the role of shuttles?
to give NADH e-s to the electron transport chain and regenerate NAD+
if the G3P shuttle is used, 1.5 mols of ATP is produced
if the MAS shuttle is used, 2.5 mols of ATP is produced
What does the amount of ATP produced from shuttles depend on?
the type of shuttle used
What is DHAP reduced to and how?
G3P by accepting electrons from NADH
at the same time, NADH is oxidised back into NAD+
The redox reaction involving the reduction of DHAP and the oxidation of NADH is catalysed by what enzyme?
G3P dehydrogenase
What is special about G3P?
this molecule is able to diffuse into the inter membrane space of mitochondria
What happens to G3P once it is in the inter membrane space of mitochondria?
is oxidised back into DHAP by donating its two electrons to FAD
What is FAD reduced to?
FADH2
What happens to the DHAP once it has been converted from G3P?
it is able to diffuse back into the site of the cytosol
the process starts again
What is the effect of FAD turning into FADH2?
the FADH2 goes through the electron transport chain and results in the production of 1.5 M of ATP
Overall what happens in the G3P shuttle reactions?
a molecule of NADH / FADH2 transfers electrons into the mitochondria via a G3P shuttle
1.5 M of ATP is produced
What does the malate-aspartate shuttle involve?
two pools of NADH and NAD+, one in the mitochondrial matrix and the other in the cytosol
How does the process of the malate-aspartate shuttle start?
oxaloacetate in the cytosol accepts electrons from NADH and is reduced to malate
What happens to NAHD once it has donated electrons in the malate-aspartate shuttle?
it is oxisised back to NAD+
In the malate-aspartate shuttle, what is oxaloacetate converted into? What happens to it?
aspartate
transported out of the mitochondria again in exchange for a molecule of glutamate
once in the cytosol it turns back into oxaloacetate
cycle begins again
Overall what happens in the malate-aspartate shuttle reactions?
NADH electrons are transported into the mitochondrial matrix
used to reduce a mlc of NAD+, generates NADH
the electrons are passed onto the electron transport chain
