Aerobic Carbohydrate Metabolism Flashcards
In the cellular respiration, this cycle follows glycolysis, being the next step in energy production
Kreb’s cycle!
AKA the tricarboxylic acid (TCA) cyle or the citric acid cycle
the TCA cycle is at the crossroads of many metabolic pathways in the body. Also, it generates some ATP directly via GTP, but it more importantly generates several electron carrying molecules that feed into the ETC to generate huge amounts of ATP
Where does the citric acid cycle take place in aerobic prokaryotes?
the cytosol
Where does the citric acid cycle take place?
The mitochondrial matrix
What is one of the end products of aerobic glycolysis that enters the citrcic acid cycle, but must be converted into acetyl-Coa via oxidative carboxylation?
Pyruvate
For every molecule of pyruvate that is decarboxylated by pyruvate dehydrogenase, how many molecules of NADH and CO2 are generated?
1 NADH and 1 CO2
this takes place in the mitochondria in the PDC
PDC = pyruvate dehydrogenase complex
Describe the PDC structure and function
The pyruvate dehydrogenase complex (PDC) is called a complex because it is composed of multiple mplecules. It is made up of 3 distinct enzymes, but the most important one is pyruvate dehydrogenase. It also requires the action of 5 coenzymes thiamine phyrophosphate TPP, FAD, NAD+, CoA and lipoate (note, the first 4 coenzymes are B vitamin derived). The purpose of this complex is to convert pyruvate into acetyl-CoA
What is the main entry-point/kickstarter of the Kreb’s cycle?
acetyl-CoA
When acetyl-CoA joins with oxaloacetate at the begining of the Kreb’s cycle, whaty six-carbon molecule is formed?
Citrate
oxaloacetate + acteyl-CoA → citrate = Step 1 of Kreb’s Cycle
Citrate then undergoes a series of redox and decarboxylation reactions to generate. The final product is pxolacetate, which joins with acetyl-CoA to restart the Kreb’s cycle process again
The mnenonic for the Kreb’s Cycle intermediates is: Can I Keep Selling Sex For Money, Officer? What are the intermediates?
Citrate
Isocitrate
Oxoglutarate (aka α-Ketoglutaric acid)
Succinyl-CoA
Succinate
Fumarate
Malate
Oxaloacetate (oxaloacetic acid)
What is the 3rd intermediate in the Kreb’s cycle – oxoglutarate – also called?
α-Ketoglutaric acid
What are the net products of the Kreb’s per one turn?
hint: there’s 4
- 1 GTP (or ATP)
- 3 NADH
- 2 FADH2
- 2 CO2
per glucose, it would be double the amount of each product
How many turns of the TCA cycle are there per glucose?
2 turns of the TCA cycle per glucose
true or false
Intermediates of the TCA are precursors for other metabolic pocesses
True.
The TCA is the metabolic crossroads of the body
byproduts of other processes (lipids, proteins) can also center the TCA cycle
What are the irreversible steps of the Kreb’s cycle?
Step 1, Step 3
Step 4
This means that these steps are so highly exergonic that they cannot effectively be reversed
Summarize step 1 of the Kreb’s cycle
acetyl-CoA (2C) → oxaloacetate (4C) → citrate (6C)
Catylyzed by citrate synthase
Irreversible
Summarize step 3 of the Kreb’s cycle
isocitrate (6C) → α-Ketoglutaric acid
Catylyzed by isocitrate dehydrogenase
This is the first time in the TCA where we lose 1 carbon; the decarboxylation of isocitrate results in 1 CO2. This step also produces a NADH. It is rate-limiting and irreversible
Summarize step 4 of the Kreb’s cycle
α-Ketoglutaric acid (5C) → succinyl-CoA (4C)
this is catylyzed by α-Ketoglutarate dehydrogenase and involves the release of 1 CO2. Like step 3, this step involves the loss of a carbon from the skeleton of what was once citrate, produces 1 NADH, and is irreversible
What are the two electron carriers involved in the ETC?
uniquinone (Q) often written as CoQ and cytochrome c
uniquinone (Q) is also called…
CoQ
ATP synthase is fueled by…
a proton gradient
this is key to the ETC
____ attaches a phosphate group to ADP to form ATP
ATP synthase
this process is fueled by a proton gradient
How do ATP and ADP regulate the citric acid cycle?
↑ATP, ↑ products of TCA cycle = ↓ TCA activity
↑ ADP (showing that cell needs energy) = ↑ TCA cycle
thus ↑ ADP = ↑ ETC/oxidative phosphorylation
What clinical condition is a classic example in which the ETC function is impaired?
cyanide poisoning
when you see cyanide on MCAT, think ETC
What does a high ADP:ATP ratio imply?
The cell needs more energy
↑ ADP = ADP that this needs to be converted to ATP
The series of spontaneous electron transfer reactions in the ETC can be modeled after what concept (that is also tested on the MCAT?)
Galvanic cells
