Cellular Respiration

1
Cellular Respiration

• In photosynthesis, light energy is stored in the
  bonds of glucose molecules in the chloroplasts of
  plant cells (or other autotrophs).

• In respiration, energy is released from the
  glucose molecules so the cells of organisms can
  use it for basic cell functions.

2
Compare CO2 H2O --- light energy --?
C6H12O6 O2 C6H12O6 O2 ----? CO2 H2O
energy (3811 calories of energy to be exact)
3

• The breakdown of glucose
• I Glycolysis
• Takes place in the cytoplasm
• Glucose is broken in half forming two 3 carbon
  molecules
• of pyruvic acid
• Requires 2 ATP molecules to get the process
  started
• Produces 4 ATP (net gain of 2 ATP)
• NAD accepts high energy electrons, forms NADH
• Cells can produce thousands of ATP in
  milliseconds
• Process does not require oxygen

4
After glycolysis, pyruvic acid can follow one of
two paths

• When oxygen is NOT present...
• Anaerobic pathways called fermentation
• Either alcoholic or lactic acid fermentation

• When oxygen IS present
• Aerobic pathway called cellular respiration
• Consists of the Krebs Cycle and Electron
  Transport chain

5

• II Fermentation (anaerobic)
• Alcoholic fermentation
• Yeastswine, beer, bread
• Produces ethyl alcohol and CO2 (waste products)
  ATP
• from glycolysis
• Regenerates NAD so it can be used again in
  glycolysis
• Lactic acid fermentation
• When the body cannot supply enough O2 for the
• aerobic pathwayburning sensation in muscles
• Regenerates NAD so it can be used again in
  glycolysis
• Lactic acid (waste product) ATP from glycolysis
• Bacteria produce cheese, yogurt, sour cream,
  pickles,
• sauerkraut

6

• III Cellular respiration (aerobic)
• Krebs Cycle (citric acid cycle)
• Pyruvic acid enters mitochondria
• Produces CO2 as waste product
• 1 molecule of ADP ? ATP
• 4 NAD ? NADH
• 1 FAD ? FADH2
• NADH and FADH2 carry high energy electrons
• Electron Transport Chain
• High energy electrons passed from carrier to
  carrier
• Their energy is used to convert ADP to ATP
• Once the electrons have lost most of their
  energy, they
• are accepted by H and O2, forming water

7
Cellular Respiration (cont) From 1 glucose
molecule Glycolysis ? 2
ATP Krebs Cycle and Electron Transport ?
34 ATP Total for Cellular Respiration
? 36 ATP (compared to only 2
ATP in the anaerobic pathway) You recover 38
of the energy in each glucose molecule. The
rest is lost as heat energy.