Chapter 7 Respiration

Wolodkowicz

Biology 1H

Chapter 7 Respiration

I.  Respiration-The process of converting glucose and oxygen into energy.

Formula: C6H12O6 + 6O2 6CO2 + 6H2O + Energy

1. Two types of cellular respiration: anaerobic (without the use of

oxygen) and aerobic (with the use of oxygen).

a. Glycolysis-first step of both anaerobic and aerobic respiration. No

oxygen is necessary for this step.

1. Occurs in the cytoplasm.

2. 2 ATP +2 NAD+ +glucose 4 ATP , 2 pyruvic acid (net of

2 ATP) & 2 NADH. Glucose (6 carbon sugar) is broken down

by enzymes into 2- 3 carbon pyruvic acid.

a.  From here the pyruvic acid may enter either an anaerobic

pathway or an aerobic pathway.

1. Anaerobic Pathway

b.  Fermentation-process of breaking down pyruvic acid without the use of oxygen. Occurs in the cytoplasm.

1. Lactic Acid Formation-occurs in unicellular organisms

and in muscle cells (when they run out of O2). When

there is not enough O2, the pyruvic acid is converted

into lactic acid (this can be converted by the liver back

into glucose for a short burst of energy (200 meter race).

2. Alcoholic Fermentation- utilized by some plants and

unicellular organisms like yeast. Here the organisms

convert pyruvic acid into ethyl alcohol (no O2).

2. Aerobic Respiration (requires O2), occurs in the mitochondria.

a.  2 Pyruvic acid converted during glycolysis diffuses from the cytoplasm into a mitochondria when oxygen is present.

b.  CoA or Coenzyme A in the mitochondria converts the 2 pyruvic acid into 2 molecules of acetyl-CoA & 2CO2 (during this time NAD+ in the mitochondria is converted to 2 NADH).

c.  The 2 molecules of acetyl-CoA now enter the Krebs cycle. Here through a series of steps the 2 molecules of acetyl-CoA are transformed into, 4 CO2, 6 NADH, 2 FADH2 (carrier molecules) and 2 ATP are formed. We now have a total of 4 ATP’s. Two from glycolysis & 2 from the Kreb cycle. Note: FAD is similar to NAD in that they are both electron carriers.

d.  Electron Transport Chain- occurs in the mitochondria. Here the energized electrons carried by the NADH and FADH2 move down the energy chain (as in photosynthesis energy is released when the H’s are removed), but the final acceptor of the energy in the mitochondria is O2. No oxygen, no aerobic respiration.

e.  The oxygen combines with the H from the NADH to form water.

f.  ATP is generated by chemiosmosis (movement of H electrons (from the NADH and the FADH2) across the membrane). ATP synthetase an enzyme found in the mitochondria uses the energy generated by the movement of the hydrogen ions to make ATP.

g.  Results: 10 NADH which yield 3 ATP molecules each (30 ATP total) and 2 FADH2 molecules which yield 2 ATP molecule each (4 ATP total) and the 2 ATP from glycolysis and the 2 ATP from the Kreb cycle which yields a total of 38 ATP.

Review Chart

Glycolysis / Transition / Kreb & Electron Transport
Inputs / Glucose
2NAD+
2ATP / 2 Pyruvic Acid
2 CoA
2NAD+ / 2Acetyl CoA
2ATP
2NAD+
2FAD
Outputs / 2 Pyruvic Acids
2NADH
2ATP (4 produced, a net of 2) / 2CO2
2Acetyl CoA
2NADH / 4CO2
2ATP
6NADH
2FADH2
Totals / 2ATP
2NADH =6ATP / 0ATP
2NADH=6ATP / 2ATP
6NADH=18ATP
2FAD2=4ATP
Final Total / 38 ATP