(LE2) Carbohydrate Catabolism Flashcards
Describe carbohydrate catabolism
Glucose is oxidized into 6CO2
- e- are transferred from glucose to electron carriers (NAD+ or FADH). Taken to electron transport chain
Oxygen is reduced into H2O
Energy is released
NADH/FADH2 is oxidized back into its original form NAD+/FADH
What are the three types of carbohydrate catabolism?
- Aerobic respiration
- Anaerobic respiration
- Fermentation
Describe aerobic respiration
- Utilizes ETC
- Fastest
- the final e- acceptor is an inorganic molecule (O2)
Describe anaerobic respiration
- Utilizes ETC
- final e- acceptor is a different inorganic molecule (NO3-, SO4^2-, CO3^2-)
Describe fermentation
- slowest
- final e- acceptor is an organic molecule (e.g. pyruvate) (incomplete glucose oxidation)
- no O2 is used
- glycolysis only
What is the ATP yield during aerobic respiration for prokaryotes? Where does it occur?
- 38 ATP/glucose
- occurs in cytoplasm and across the plasma membrane
phospholipid bilayer needed for ETC
What is the ATP yield for aerobic respiration for eukaryotes? Where does it occur?
- 36 ATP/glucose
- occurs in cytoplasm and mitochondria
What are the steps of aerobic respiration?
- Glycolysis
- Kreb’s (citric) cycle
- Electron transport chain
What is the main purpose of Glycolysis and the Kreb’s cycle?
to make electron carriers to power the ETC
What organisms can perform glycolysis?
All organisms (aerobic and anaerobic)
Does not need O2 to occur
Occurs in respiration and fermentation
What is your net yield in glycolysis?
2 ATP
2 NADH
2 Pyruvate (3C)
What 10 steps are occurring in glycolysis? What are there yields?
Preparatory steps: Glucose (6C) -> 2 (3C) molecules
- requires 2 ATP
Energy yielding steps: 2 (3C) molecules -> 2 Pyruvate
- generates 2 NADH
- generates 4 ATP
What is happening in this image?
Glyceraldehyde-3-phosphate is oxidized and phosphorylated into1,3-Diphosphoglyceric acid
NAD is reduced into NADH
What is happening in this image?
1,3-Diphosphoglyceric acid is dephosphorylated into 3-phosphoglyceric acid
ADP is phosphorylated into ATP
ATP via SLP
What is happening in this image?
Phosphoenolpyruvic acid is dephosphorylated into Pyruvic acid
ADP is phosphorylated into ATP
ATP via SLP
Do fermenters perform the Kreb’s cycle?
No
Where does Kreb’s cycle occur for prokaryotes? Eukaryotes?
P: cytoplasm
E: mitochondrial matrix
What main steps occur during the second step of aerobic respiration?
- Pyruvate -> Acetyl CoA
- Kreb’s cycle
What is the formula for pyruvate to Acetyl CoA?
Pyuravte + NAD + CoA -> Acetyl CoA + CO2 + NADH
- Pyruvate is oxidized & decarboxylated to Acetyl-CoA
- NAD reduced to NADH
What is the yield per glucose in Pyruvate oxidation to Acetyl CoA?
2 CO2
2 Acetyl CoA
2NADH
What is happening in step one and two of the image?
- Pyruvate is decarboxylated
- Pyruvate is oxidized. NAD+ reduced to NADH
What step does complete oxidation of glucose occur?
Kreb’s cycle
Where is pyruvate oxidized into Acetyl CoA in eukaryotes?
on membrane
What is the net yield for each Acetyl CoA in the Kreb’s cycle?
2 CO2
3 NADH
1 FADH2
1 ATP
What is the net yield per glucose in the Kreb’s cycle?
4 CO2
6 NADH
2 FADH2
2 ATP
Explain what is happening in step 3
Isocitric acid is oxidized and decarboxylated into alpha-Ketoglutaric acid
NAD+ is reduced to NADH
Explain what is happening in step 5
ADP is phosphorylated into ATP
ATP via substrate-level phosphorylation
What step of aerobic respiration is occurring in this picture? What is the purpose?
Electron transport chain
- create ATP via oxidative phosphorylation (series of redox)
Where does ETC happen for prokaryotes? Eukaryotes?
P: periplasmic space and intracellular membrane
E: across the inner mitochondrial membrane (intramembranous space)
What do e- carriers do in the ETC?
pass e- to membrane complexes
- pumps H+ across membrane
- creates H+ gradient
final e- carrier is O2 (O2-> H2O)
What is the net yield of ATP for e- carriers in the ETC?
3 ATP/NADH
2 ATP/FADH2
What is chemiosmosis?
the use of energy in a H+ gradient to drive cellular work
What structure is shown here? How does it operate?
ATP synthase
- uses energy released by H+ movement to phosphorylate ADP
How many total electron carriers are made during aerobic respiration? What are their net yields? What is the total yield per glucose in prokaryotes? Eukaryotes?
10 NADH (3 ATP/NADH) = 30 ATP
2 FADH2 (2 ATP/FADH2) = 4 ATP
P: 38 ATP/Glucose
E: 36 ATP/Glucose
Why do eukaryotes only generate 36 ATP compared to prokaryotes?
2 ATP are needed to transport the 2 NADH generated from glycolysis into the mitochondria (ETC)
Calorie content of each macronutrient?
Carb: 4 kcal
Fat: 9 kcal
Protein: 4 kcal
How are proteins converted into ATP?
Broken down to amino acids
Amino acid catabolism lets it enter Kreb’s cycle and ETC
- Most skip glycolysis
How are fats converted into ATP?
- Glycerol goes to glycolysis
- Fatty acids undergo Beta-oxidation, then Kreb’s cycle and ETC
What is fermentation’s net ATP yield?
2 ATP/Glucose
What type of fermentation is this? Explain the steps after typical glycolysis. What is the final e- carrier?
Alcohol fermentation
- pyruvate is decarboxylated into acetaldehyde
- acetaldehyde is reduced into ethanol
- NADH is oxidized into NAD+
Acetaldehyde is the final e- carrier
What type of fermentation is this? Explain the steps after typical glycolysis. What is the final e- carrier?
Lactic acid fermentation
- pyruvate is reduced into lactate
- NADH is oxidized into NAD+ to restart glycolysis
Pyruvate is the final e- carrier
What steps are performed in anaerobic respiration?
- Glycolysis
- modified Kreb’s cycle
- ETC
What is the energy yield of anaerobic respiration?
Variable: 2 < x < 38 ATP
Nitrate reduction
Nitrate cycle in soils
- members of Bacillus and Pseudomonas
- NO3- (nitrate) -> NO2- (nitrite) usable form for plants
Sulfate Reduction
(wetlands, swamps)
- SO4^2- (sulfate) -> H2S (hydrogen sulfide gas)
Carbonate Reduction
Sewage Treatment
- CO3^2- (carbonate) -> (methane)
