Citric Acid Cycle and Respiratory Chain Flashcards
What is glycolysis ?
Oxidation of glucose to generate pyruvate (net 2ATP + 2NADH + H+)
State what happens to pyruvate under aerobic conditions
Pyruvate & 2NADH & H+ transported to the mitochondria
State what happens to pyruvate under anaerobic conditions
Pyruvate reduced to lactate and NAD+ regenerated to enable glycolysis to continue (short term)
What are the stages in cellular respiration ?
Stage 1 : Glycolysis
Stage 2 : Citric Acid Cycle
Stage 3 : Oxidative Phosphorylation
Stage 1 of Cellular Respiration
Glycolysis
Generation of pyruvate to form acetyl coenzyme A
(fatty acids and some amino acids also generate acetyl -coenzyme A)
Stage 2 of Cellular Respiration
Citric Acid Cycle
Redox reactions to harness energy via electron carriers (NAD+ and FAD), producing CO2.
Stage 3 of Cellular Respiration
Oxidative Phosphorylation
Oxidation of co-enzymes : electron transfer and reduction of O2 & synthesis of ATP
(ADP phosphorylation)
Where does acetyl-coenzyme A synthesis occur ?
Occurs in the mitochondrial matrix
Describe how acetyl-coenzyme A is produced
Pyruvate (& fatty acids/amino acids) are degraded into acetyl groups
Acetyl groups are added to coenzyme A
This forms acetyl-coenzyme A
What is acetyl-coenzyme A ?
A high energy compound formed by hydrolysis of the thioester bond.
Used in the citric acid cycle.
What is the function of the mitochondrion ?
Site of eukaryotic oxidative metabolism = the cell’s “power plant”
After glycolysis and generation of pyruvate, metabolism takes place within the mitochondria.
Describe the structure of the mitochondrion
2 layered membrane
A number of cristae (varied depending on the cells metabolic requirements)
Function of the membranes of the mitochondrion
The selective permeability of the inner membrane to most ions & metabolites, enables generation of ionic gradients - key to ATP synthesis
What is the citric acid cycle ?
Common pathway by which all fuel molecules (carbohydrates, fats & protein) are broken down to CO2 and H2O.
Give a brief description of the Citric Acid Cycle
2-carbon acetyl-CoA combines with 4-carbon oxaloacetate.
6-carbon citrate broken down in stages to harness energy via electron carriers (NAD+/FAD)
4-carbon oxaloacetate regenerated
What is formed from each cycle of the citric acid cycle ?
2 x CO2
1 x GTP
3 x NADH & H+
1 x FADH2
What is oxaloacetate ?
A keto acid
What happens in the 1st step of the Citric Acid Cycle ?
Condensation of the acetyl group of acetyl coenzyme A with the keto acid OXALOACETATE by citrate synthase.
(acetyl group 2-carbon)
(oxaloacetate 4-carbon)
What type of reaction is the 1st step of the citric acid cycle ?
A highly exergonic reaction due to the thio-ester bond large -delta G, which is essential to drive the cycle forward.
The [oxaloacetate]mito concentration is normally very low.
What happens to the CoA liberated in step 1 of the citric acid cycle ?
Liberated CoA to participate in oxidative decarboxylation of another pyruvate.