Bioenergetics Flashcards
What is the purposed of the TCA cycle
1) To generate NADH and FADH2 from Acetyl-CoA, which will be used in OxPhos
2) Generate energy via GTP
What conditions does TCA occur under?
In the mitochondrial matrix and under aerobic conditions
What Biomolecules can create ACETYL-CoA and, as such, how do they enter the TCA cycle?
Carbohydrates - enter via glycolysis, whereby one molecule of glucose is turned into 2, 3-carbon molecules of pyruvate
Lipids - enter via beta-oxidation, whereby they are broken down into fatty acids and turned into ACETYL-CoA
Proteins - enter via a variety of methods but are broken into 1 of 7 amino acids, which are capable of being converted into acetyl-CoA
Compare the energy obtained from glucose vs. fatty acids
Glucose, after going through glycolysis, TCA and OxPhos, will yield approx. 36-38 ATP molecules.
Fatty acids, such as palmitic acid, following beta-ox, can lead to the creation of ~130 ATP
What is CoEnzyme A and why is it important?
Molecule present in Acetyl-CoA that serves as an activator for acyl groups in other molecules. Activation by CoA allows/facilitates transcription,redox rxns and condensation rxns.
i.e. it is the rxns hub that is highly reactive and needed to activate enzymes
Other than TCA, why is ACETYL-CoA important
Acetyl-CoA serves an important function as the foundation for the creation of 1) lipids and 2) isoprenoids (fatty acids and steroids).
- Both catabolic and anabolic
- Needed to make ketone bodies, last energy source for brain and muscles
What are the energy products from TCA and how many ATP will they ultimately produce?
For the oxidation of 1 ACETYL-CoA molecule, the following is produced:
3 NADH, 1 FADH2, 1 GTP
Since 2.5 ATP and 1.5 ATP are produced from a single molecule of NADH and FADH2, respectively, the following occurs
3 NADH = ~9ATP ///// 1 FADH2 = ~2ATP ////// 1 GTP = 1ATP
How does rat poison inhibit the TCA cycle?
Rat poison = flouroacetate
Flouroacetate inhibits TCA cycle by inhibiting Aconitase, leading to the build up of citrate at the start of the cycle. It also stops glycolysis by inhibiting PFK-1.
What does amphibolic mean?
Catabolism and anabolism
-breaks down carbs and fatty acid but also synthesizes molecules for AA syntheses (a-ketogluterate and oxaloacate)
How is Succinyl-CoA involved in heme sysnthesis
Because TCA is amphibolic, acetyl-CoA can be used to make precursors for Biomolecules like the first step in heme sysnthesis (alpha-aminolevulinic) by condenstation with glycine.
Explain citrate’s role on rate-limiting enzymes w/ respect to energy demand
When citrate levels are high within the cell, it means the cell is ATP rich. Citrate is an allosteric inhibitor of PFK-1, the first step in glycolysis, which will limit the breakdown of glucose.
Citrate is also an activator in the synthesis of fatty acids from ACETYL-CoA.
What molecules inhibit and encourage the TCA cycle during the following steps: 1) acetyl-CoA -> citrate // 2) Isocitrate -> a-ketogluterate //// 3) a-ketogluterate -> succinyl-CoA
(1) The inhibitors are: citrate, ATP, NADH, Succinyl-CoA and the upregulators are Insulin, acetyl-CoA, oxaloacetate
(2) The inhibitors are: ATP, NADH and the upregulators are ADP and Ca2+ (from muscle contraction signal - need energy)
(3) The inhibitors are: ATP, NADH, Succinyl-CoA, GTP and the upregulator is Ca2+
