Three components of DNA and RNA
- Nitrogen (containing base, either purine or pyrimidine)
- Pentose (5-carbon sugar, ribose or deoxyribose)
- Phosphate
Pyrimidines
have a single ring composed of four carbon and two nitrogen atoms:
- Cytosine
- Thymine in DNA or Uracil in RNA
Purines
have a double ring structure:
- Adenine
- Guanine
ATP bonds
- Hydrolysis of the ester linkage yields about 14 kJ/mol
- Hydrolysis of each anhydride bond yields about 30 kJ/mol
- ATP needs to be regenerated from ADP and Pi
Three moments of Cellular Respiration
- Glycolysis
- Link Reaction (formation of AcetylCoA through peruvate)
- Krebs cycle or TCA
- Oxidative Phosphorylation
Glycolysis: Within what it occurs? How many molecules of ATP are regenerated?
- it occurs within the cytosol.
- 4 ATP molecules (2 per pyruvate) + 2 NADH molecules
Oxidative Phosphorylation: where is it occurred? How many molecules of ATP are regenerated?
- it occurs in the mitochondria and it requires O2
- ATP is regenerated by ADP+Pi via electron transport chain. NADH and FADH2 donate electrons into the chain:
NADH -> 3 ATP
FADH2 -> 2 ATP
NAD+ vs NADH
N gains 2 electrons and a proton (H+) -> NADH.
NADH oxidised -> loses electrons and proton -> NAD+
Generated 3 ATP from the reaction of ADP and Pi = important role in OXIDATIVE PHOSPHORYLATION
FAD vs FADH2
two N gains 2 electrons and a proton (H+) -> FADH2.
FADH2 oxidised -> loses electrons and proton -> FAD
Generated 2 ATP from the reaction of ADP and Pi = important role in OXIDATIVE PHOSPHORYLATION
Pyruvate
- end product of glycolysis
- enters Krebs cycle/TCA in two ways, through an aerobic metabolism or through an anaerobic metabolism being converted to lactate
Anaerobic metabolism (Lactate production)
described by the Cori Cycle.
Pyruvate is converted in lactate thanks to a reaction called “oxidation-reduction reaction”:
1. pyruvate is reduced to lactate as NADH is oxidised in to NAD+ in order for glycolysis to continue
2. ATP generation is continued by substrate levels phosphorylation
3. Lactate is transported to liver and converted again to pyruvate so that new glucose can be produced
NADPH (+) vs. NADH (+)
very similar.
difference = a phosphate on the hydroxyl group of 2’C
NOT involved with oxidative phosphorylation and NO role in ATP regeneration
Function of NADPH (+)
- synthesis of fatty acids and cholesterol
- protection against oxidative stress
- phagocytosis
- drug metabolism - conversion of hydrophobic molecules to hydrophilic molecules
- nitric oxide synthesis - PPP (Pentose Phosphate Pathway)
Two types of Coenzyme A
ACETYL CoA =
needs to be bound to coA to be metabolically active
FATTY ACYL CoA =
needs to be bound to coA to be metabolically active
Definition of Cellular Respiration
The process in which cells consume O2 and produce CO2.
- O2 is used in the electron chain for producing ATP
- CO2 will bind to haemoglobin and then release from blood to lungs
- Portion of CO2 will be dissolved in the blood as bicarbonate
First stage of CR
Using Glucose:
1. Glucose converted to pyruvate in glycolysis
2. After remotion of one CO2, the two CO2 left are converted in Acetyl CoA
Using Fatty Acids:
1. metabolised via b-oxidation
2. removes two CO2
3. two C converted in Acetyl CoA
Using Amino Acids:
Amino Acids are carbon skeleton -> can be directly to Acetyl CoA.
Ammonia converted to urea (mammals), to uric acid (birds, reptiles), or excreted directly (fish).
Second stage of CR
Acetyl CoA enters into the Krebs cycle ( aka TCA or Citric acid cycle).
End products:
- NADH
- FADH2
Third stage of CR
NADH and FADH2 carry electrons for the electron transport chain in oxidative phosphorylation.
ADP+Pi = ATP
O2 reduced to H2O
cAMP (Cyclic AMP)
- is a common second messenger produced in response to hormones and chemical signals.
- is formed from ATP in a reaction catalysed by Adenylate cyclase.
