2. Chemical Energy
• Living things get energy from the food they
consume
• Calorie – the amount of energy needed to
raise the temperature of 1 gram of water 1
°C
• 1 gram of glucose when burned in the
presence of oxygen releases 3811 C
3. Cellular respiration
• Process that releases energy by breaking
down glucose and other food molecules in
the presence of oxygen (aerobic)
• 6O2 + C6H12O6 → 6CO2 + 6H2O + energy
• Oxygen + glucose → carbon dioxide + water + energy
• Three main stages:
– Glycolysis
– Krebs Cycle
– Electron transport
4. Glycolysis
• The process in which one molecule of
glucose is broken in half producing two
molecules of pyruvic acid; a 3-carbon
compound
• 2 ATP molecules are used to get the
reaction going and will produce 4 ATP
molecules when the process is complete
5. Cont.
• NAD+ (electron carrier) accepts 4 high
energy electrons and becomes NADH
• This process can produce thousands of
ATP molecules in a few milliseconds
• Does not require oxygen (anaerobic)
• Energy is used up quickly
6.
7. Fermentation
• Production of ATP in the absence of
oxygen (anaerobic)
• Two types: Alcoholic fermentation and
Lactic acid fermentation
• Alcohol fermentation: NADH is converted
back to NAD+ by passing high energy
electrons back to pyruvic acid
• Pyruvic acid + NADH → alcohol + CO2 and NAD+
8. Cont.
• Lactic fermentation: NADH is converted
back to NAD+ by passing high energy
electrons back to pyruvic acid and
producing lactic acid
• Lactic acid is produced in muscle when
the body cannot supply enough oxygen
• Pyruvic acid + NADH → lactic acid + NAD+
9. Krebs Cycle
• End of glycolysis, 90% of chemical energy
in glucose is still unused, cell will use
oxygen to extract the remaining energy
• Krebs cycle begins when pyruvic acid
produced by glycolysis enters the
mitochondrion
• Pyruvic acid is used to make carbon
dioxide, ATP, NADH, and FADH2
10. Electron Transport Chain
• Uses the high energy electrons from the
Krebs cycle to convert ADP to ATP
• In eukaryotes: inner membrane of the
mitochondrion
• In prokaryotes: in the cell membrane
• H+ builds up in the intermembrane space
making it positively charged…other side,
is now negatively charged
11. • As H+ escape through membrane, the
mitochondria contain proteins (ATP
synthase) which rotates, the enzyme
grabs the low energy ADP and attaches a
phosphate forming high energy ATP
• Process is repeated over and over
12. Energy for the body
• Quick – gylcolysis or fermentation
• Long term- cellular respiration
13. Summary
• Cellular respiration has 3 stages:
– Glycolysis
– Krebs cycle
• Electron transport chain
