Respiration. Flashcards
What are the 4 stages of aerobic respiration?
- Glycolysis
- Link reaction
- Krebs cycle
- Oxidative phosphorylation
What are the three stages of glycolysis?
- Phosphorylation
- Splitting of hexose i phosphate
- Oxidation of triose phosphate to pyruvate.
Explain glycolysis.
- Two molecules of ATP are hydrolysed and release phosphate groups (one each)
- The Pi groups are added onto the glucose molecules to create hexose biphosphate (a 6c molecule)
- The hexose biphosphate is split into two triose PHOSPHATE (3c) molecules
- Triose phosphate is dehydrogenated, dehydrogenase enzymes alongside NAD (a coenzyme) remove hydrogens from triose phosphate.
- The two molecules of NAD (co-enzymes) accept the hydrogen atoms and become REDUCED (NADH)
- 2 molecules of NAD are reduced for every molecule of glucose undergoing the process. In addition, 4 molecules of ATP are made for every 2 triose phosphate molecules being oxidised.
- Oxidation of 2 molecules of triose phosphate produces 2 molecules of pyruvate.
What are the products of glycolysis?
- 2 molecules of ATP (2 were used)
- 2 molecules of reduced NAD (NADH)
- 2 molecules of pyruvate
What are the products of glycolysis?
- 2 molecules of ATP (2 were used)
- 2 molecules of reduced NAD (NADH)
- 2 molecules of pyruvate
Where does glycolysis take place?
The cytoplasm
Which stages of respiration occur only aerobically and which can occur anaerobically?
- Aerobic: Link reaction, Krebs cycle, Oxidative phosphorylation
- Anaerobic: only glycolysis can occur in anaerobic conditions, occurring in both aerobic and anaerobic.
Where does the link reaction take place?
The mitochondrial matrix
Explain the link reaction
- Pyruvate (3c) is decarboxylated (a carbon is removed from pyruvate) to form CO2 —> this converts pyruvate to a 2x molecule called acetate.
Dehydrogenation also occurs as hydrogen is removed from pyruvate which is taken up by NAD to form NADH - Acetate (2c) is combined with coenzyme A to form acetyl CoA.
How often does the link reaction occur for every glucose molecule
2x
Write the equation for the link reaction.
2 Pyruvate + 2NAD + 2CoA —> 2CO2 + 2NADH + 2 acetyl CoA
Where does the krebs cycle occur?
In the mitochondrial matrix
What happens in the krebs cycle?
- An acetyl group (2c) is released from acetyl CoA and combines with the 4c compound oxaloacetate to form a 6c compound called citrate
- Citrate is decarboxylated (looses a carbon) and produces a 5c compound, alongside one CO2 molecule and one molecule of NADH (reduced NAD)
- The 5c compound is further decarboxylated AND dehydrogenated - producing a 4c compound along with one CO2 molecule and one NADH.
- The 4c compound temporarily combines with, and is released from coenzyme A - substrate level phosphorylation occurs here which produces 1 ATP.
- The 4c compound is dehydrogenated, producing a different 4c compound and a molecule of FADH (reduced FAD)
- The 4c compounds atoms are rearranged, catalyzed by isomerase enzymes and then undergoes further dehydrogenation. This regenerates oxaloacetate and the cycle continues.
In short, what is oxidative phosphorylation?
The production of ATP in the presence of oxygen
What is produced by the Krebs cycle?
- 6 NADH
- 2 FADH
- 4 CO2
- 2 ATP
Where are electron transport chains found?
Embedded in the inner mitochondrial membranes (cristae)
What is chemiosmosis?
The flow of protons, down their concentration gradient across a membrane - through a channel associated with ATP synthase.
Why is folded cristae advantageous for oxidative phosphorylation?
- Folded cristae give a large surface area for the electron carrier proteins and ATP synthase enzymes.
How are carbohydrates broken down, or converted, to glucose?
- Glycogen and starch can be hydrolysed into glucose
- Disaccharides can be digested to monosaccharides for respiration
- Monosaccharides that aren’t glucose are changed by isomerase enzymes to glucose for respiration.
How do lipids enter respiration?
- Lipase breaks down triglycerides into glycerol and 3 fatty acids.
- With energy from the hydrolysis of one molecule of ATP to AMP - each fatty acid combines with coenzyme a.
- The fatty acid-CoA complex is transported to the mitochondrial matrix where it is broken down into 2 carbon acetyl groups, each attached to CoA.
- The beta-oxidation pathway generated NADH and FADH.
- The acetyl groups are released from CoA and enter the Krebs cycle, combining w/ oxaloacetate.
What is the formula of anaerobic respiration in animals?
C6H12O6 —> (2)C3H6O3 (+2 ATP)
What is the formula of anaerobic respiration in yeast?
C6H12O6 —> (2)C2H5OH + (2)CO2
What is the formula of aerobic respiration?
C6H12O6 + (6)O2 —> (6)CO2 + (6)H2O + 32 ATP
For each thing in the Kreb cycle, how many carbons do they have?
- Acetyl CoA —> 2C
- Acetyl group —> 2C
- Citrate —> 6C
- Intermediates: 1x 5C, 2x 4C
- Oxaloacetate —> 4C
