– needed for: – movement
– synthesis of complex compounds
– active transport
– provides energy needed by cells
– broken down > heat (body heat, excess removed)
chemical storage form
– is the process by which chemical energy stored in food (usually glucose, but may be protein and lipids is released by cells to be used to carry out life processes (ex: locomotion, cell division, active transport)
– takes place in a series of steps involving many enzymes located in mitochondria
Energy Storage and Release
Two steps involved:
1. breakdown of glucose leads to storage of energy in ATP
2. breakdown of ATP provides cell with energy
ANAEROBIC RESPIRATION (Fermentation)
- · release of energy stored in food molecules such as glucose without oxygen
- · very in efficient process à glucose is only partially broken down
- · occurs in yeast, certain bacteria, fungi and active muscle cells
A. Glycolysis (splitting of glucose)
- · through a series of steps, glucose, which is a six-carbon compound (C6H12O6) is converted
into two three-carbon compounds of pyruvic acid.
- · this results in a net gain of 2 ATP
glucose ————–> 2 pyruvic acid
(Note: net yield is 4 ATP-2ATP = 2ATP)
B. Next, carbon dioxide and ethanol (ethyl alcohol) or lactic acid are produced without the yield of any additional energy.
pyruvic ————–> carbon dioxide + ethanol or lactic acid
A great deal of energy is still present in the ethanol or lactic acid molecules.
C. Summary of Alcohol Fermentation
glucose ————–> ethanol + carbon dioxide + 2 ATP
D. Lactic Acid Fermentation
- · produced in some bacteria and fungi
- · also occurs in active muscles, where anaerobic respiration occurs.
- · accumulation of lactic acid results in muscle fatigue and muscle pain
glucose ————–> lactic acid + carbon dioxide + 2 ATP
- · respiration requiring oxygen
- ·efficient process —> glucose is completely broken down to carbon dioxide and water
- · involves two stages:
A. Glycolysis (Anaerobic phase)
B. Kreb’s Cycle or Citric Acid Cycle (Aerobic Phase)
- · the pyruvic acid molecule from glycolysis undergo a series of chemical reactions which result in the formation of CO2 and H2O.
- · energy is released in small units and stored in 36 ATP molecules.
C. Net Yield of Energy from One Molecule of Glucose:
i) Glycolysis: 2 ATP (Anaerobic)
ii) Kreb’s Cycle: 36 ATP (Aerobic)
Total: 38 ATP
D. Word Equation for Aerobic Respiration:
glucose + oxygen ———-> carbon dioxide + water + 38 ATP
E. Chemical Equation for Aerobic Respiration:
C6H12O6 + 6O2 ———–> 6 CO2 + 12 H2O + 38 ATP