Respiration

RESPIRATION

• Muscles contractions • Active transport Living things need • Transmission of nerve energy for survival impulses Energy is needed continuously

RESPIRATIO N

External Two types Internal Main substrate : glucose

Two types of cellular respiration Aerobic

Anaerobic

Energy from glucose is released through cellular respiration

RESPIRATIO N External respiration • Mechanical process • Maintains a continuous exchange of gases between the respiratory surfaces of an organism and its environment

Internal respiration • Also known as cellular respiration • Biochemical process • Energy is made available to all living cells

Process of obtaining oxygen and delivering it to the cells for cellular respiration and removing carbon dioxide produced by the cells

RESPIRATION Internal

External

Cellular respiration Aerobic

Anaerobic

Aerobic Respiration • Require continuous supply of oxygen • Oxygen obtained from air • C6 H12 O2 + 6O2

6CO2 + 6H2 O

• Complete breakdown of glucose in the presence of oxygen • Releases all available energy stored in glucose • Driven by sequence of biochemical reaction (catalyzed by respiratory enzymes) • Most energy released is used to synthesize ATP from ADP and inorganic products • ATP : - instant source of energy - drives cellular processes - consists of phosphate bonds (can be easily broken to release energy)

• Normal condition : - external respiration able to supply enough oxygen • Prolonged physical activity / strenuous exercise : - need more oxygen - ATP is used more quickly than the lungs and circulatory system can deliver oxygen to cells (for cellular respiration) - Cells are forced to do work without enough oxygen supply • In this situation cells undergo anaerobic respiration • Anaerobic respiration : - Cells continue to generate ATP without oxygen

Anaerobic Respiration in Human • Vigorous activities : - Rate of respiration & heartbeat high but - Still cannot supply enough oxygen to meet the demand for ATP • Muscles are in the state of oxygen deficiency • Cells undergo anaerobic respiration • Glucose breaks down partially into lactic acid instead of carbon dioxide • Incomplete breakdown of glucose release much less energy than in aerobic: - Aerobic : 1 glucose 38 molecules of ATP (2898kJ) - Anaerobic : 1 glucose 2 molecules of ATP (150kJ)

• Body needs to rest to recover • High concentration of lactic acid can cause fatigue and muscle cramps • Fast and deep breathing enables a person to inhale more oxygen • Excess oxygen helps to oxidized lactic acid to carbon dioxide and water (then excreted) • Oxygen debt = amount of oxygen needed to remove lactic acid from muscle cells

• Oxidation of lactic acid occurs mainly in liver • Some lactic acid are oxidized to produce energy • The remaining is converted to glucose then glycogen • Glycogen is then stored in muscle cells • Oxygen deficit (debt) is paid when all the lactic acid has been eliminated through increased breathing

Anaerobic Respiration in Yeast • Yeast capable of both aerobic and anaerobic respiration • It depends on the availability of oxygen • Normally respire aerobically • However without enough oxygen supply, yeast undergo anaerobic respiration • Contrast with human, in yeast ethanol is produced instead of lactic acid • This process is called fermentation (used in making wine and beer)

zymase • C6 H12 O2

6C2H5OH + 2CO2 + 210 kJ

• Making bread : carbon dioxide released causes dough to rise