10. Structure and functions of carbohydrates II -- Glucose metabolism Flashcards
In anaerobic glycolysis, what are the products that can be formed?
- Ethanol
- lactic acid
Why is there a need for TCA cycle, instead of fully relying on anaerobic respiration for energy?
Only a fraction of energy is utilized from anaerobic respiration, and it does not yield much energy (2 ATP only).
- TCA cycle generates the most amount of ATP and thus, the most energy
Why is ATP the main energy currency in cells?
phosphoanhydride bonds have bond energy, and amount of energy released when hydrolyzing these bonds are significant
What is the role of NAD+ and FAD?
They are electron carriers
How is NADH / FADH2 used to generate ATP?
Is NADH or FADH2 primarily used , why?
NADH and FADH2 give up electrons and protons through the protein complexes in the electron transport chain. These protons flow back through ATP synthase to convert ADP + P –> ATP
NADH is primarily used as electrons are at a higher energy level, allowing for more efficient pumping of protons through protein complexes. Also, NADH produces 2.5 ATP, compared to FADH2 which produces 1.5 ATP
AEROBIC RESP STEP 1 : GLYCOLYSIS PART 1
What is the function of kinase?
Catalyze transfer of phosphoryl (PO3) group from ATP to acceptor
- but when –OH group (from glucose) attacks phosphoryl (PO3) group, the end group on glucose is phosphate (PO4-) cuz O from the -OH group is there
- kinases require divalent metal ions for enzymatic activity (overcome repulsion between negatively charged phosphate grps and electron on target molecule, and to stabilise the negative charge of phosphate grps)
AEROBIC RESP STEP 1 : GLYCOLYSIS PART 1
Does hexokinase (glucose –> glyceraldehyde-3-P) OR phosphokinase (fructose-6-phosphate –> fructose 1,6-biphosphate) determine the rate of glycolysis and why?
Phosphokinase, as conversion of fruct-6-phosphate to fruct 1,6-biphosphate is irreversible. However, glyceraldehyde-3-p is not a unique intermediate of glycolysis and can be converted into glycogen.
Note: enzymes determine ROR bc they r in smaller amt and rmb frm LYC lect, catalytic step is slow and thus rate limiting
AEROBIC RESP STEP 1 : GLYCOLYSIS PART 1
How many ATP is generated / consumed in stage 1 for 1 glucose molecule?
2 ATP consumed as adding of phosphoryl (PO3(2-)) grp from ATP to acceptor by kinases (to 6C molecules) requires energy (overcome repulsion)
AEROBIC RESP STEP 1 : GLYCOLYSIS PART 2
How many ATP is generated for 1 glucose molecule in stage 2 of glycolysis?
For 1 x glyceraldhyde-3-P:
- 1 ATP generated from 1,3-biphosphoglycerate → 3-phosphoglycerate
- 1 ATP generated from Phosphoenolpyruvate → pyruvate
total : 2ATP
for 1 glucose, have 2 glyceraldehyde-3-P
total : 4 ATP
AEROBIC RESP STEP 1 : GLYCOLYSIS PART 2
What is the main product at the end of glycolysis stages to enter into TCA cycle?
Pyruvate
AEROBIC RESP STEP 1 : GLYCOLYSIS
What is the net yield of ATP generated from stages 1 and 2?
-1-1+2+2 = 2 ATP molecules
AEROBIC RESP STEP 1 : GLYCOLYSIS PART 2
Where does glycolysis occur?
Cytoplasm of cell
AEROBIC RESP STEP 2: TCA cycle
What is pyruvate converted to before entering TCA cycle?
pyruvate reduced to acetyl CoA via decarboxylation
AEROBIC RESP STEP 2: TCA cycle
Where does TCA cycle occur?
Mitochondrial matrix
AEROBIC RESP STEP 2: TCA cycle
How is acetyl CoA utilised in the TCA cycle, and what molecule is it regenerated as? Also, state the products from the cycle
Acetyl CoA (2C) combines with oxaloacetate (4C) to form citrate (6C).
Citrate goes through decarboxylation and oxidation.
It generates 2 CO2 and reduces 3 NAD+ into 3 NADH and 1 FAD into 1 FADH2, electrons are given. One of the steps also directly yields 1 ATP molecule.
After going through the whole cycle, oxaloacetate is regenerated, which reacts with more acetyl CoA….
