B9: Respiration

• cellular respiration is an exothermic reaction that occurs continuously in living cells.

glucose + oxygen -----> carbon dioxide + water + energy transferred to the environment. 

• the energy transferred supplies all the energy needed for living processes. 

• the energy that is transferred during respiration is used to enable muscles to contract.
• during exercise the human body responds to the increased demand for energy.
• body responses to exercised
  • increased heart rate, breathing rate and breath volume
  • glycogen stores in muscles are converted to glucose for cellular respiration.
  • the flow of oxygenated blood to the muscles increases.
• these act to increase the supply of glucose and oxygen to muscles are removal of carbon dioxide from the muscles. 

• if muscles work for a long time, they become fatigues and don't contract efficiently. if they don't get enough oxygen they respire anaerobically. 

• anaerobic respiration is respiration without oxygen. glucose is incompletely broken down and forms lactic acid in animals. 
• the anaerobic breakdown of glucose produces less energy that aerobic respiration.

• after exercise oxygen is needed to break down the lactic acid. the amount of oxygen needed is called oxygen debt.

• anaerobic respiration in plants and some microorganisms like yeast produce ethanol and carbon dioxide. 

• metabolism is the sum of all the reactions in the body
• the energy transferred by respiration in cells is used by an organism for the enzyme-controlled processes of metabolism which creates new molecules.

• metabolism includes the converion of glucose to starch, glycogen and cellulose. 

• it also includes the formation of lipid molecules, the use of glucose and nitrate ions to form amino acids which are used to synthesise proteins and breakdown excess protein into urea. 
• blood flows through the muscles and transports lactic acid to the liver where it is converted back into glucose.