B9 - respiration

respiration

• cellular respiration is an exothermic reaction which is continuously occurring in living cells

• the chemical process of cellular respiration releases energy

uses of energy

• organisms need energy for:

  • chemical reactions to build larger molecules from smaller molecules

  • muscle contraction to allow movement

  • keeping warm (to maintain a constant temperature suitable for enzyme activity)

aerobic respiration

• respiration in cells can take place aerobically (using oxygen) to transfer energy

• glucose is reacted with oxygen in this process

word equation of aerobic respiration

glucose + oxygen ----→ water + carbon dioxide

symbol equation for aerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

anaerobic respiration in animals

• respiration in cells can take place anaerobically (without oxygen), to transfer energy; it involves the incomplete breakdown of glucose into lactic acid

• this occurs when the body can’t supply enough oxygen for aerobic respiration, during exercise

word equation of anaerobic respiration

glucose ----→ lactic acid

symbol equation for anaerobic respiration

C6H12O6 ----→ 2C3H6O3

anaerobic respiration in plants n yeast

• plants n yeast can respire without oxygen, breaking down glucose in the absence of oxygen to produce ethanol n carbon dioxide

• anaerobic respiration in yeast cells is called fermentation

• fermentation is economically important in the manufacture of bread (where the production of carbon dioxide makes dough rise) n alcoholic drinks (as ethanol is a type of alcohol)

anaerobic respiration in plants and yeast equation

glucose ---→ alcohol + carbon dioxide

body’s response to exercise

• increase in heart rate, breathing rate n in breath volume

• glycogen stores in the muscles are converted to glucose for cellular respiration

• flow of oxygenated blood increases

oxygen debt

the amount of oxygen required to remove the lactic acid, n replace the body's reserves of oxygen

use of metabolites

• Conversion of glucose to cellulose in plants to build n strengthen cell walls

• conversion of glucose into glycogen in animals n starch in plants for storage

• the formation of lipid molecules from a molecule of glycerol n three molecules of fatty acids to form triglycerides which are used for energy storage n as insulation in animals

• In plants:

  • the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins required by cells (such as enzymes)

  • glucose is broken down in the process of respiration to release energy in all cells

• in animals, the breakdown of excess proteins to form urea for excretion

metabolism

metabolism is the sum of all the reactions in the body.