photosynthesis

• Photosynthesis is represented by the equation:

  carbon dioxide + water --> glucose + oxygen
• photosynthesis is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.
• factors that affect photosynthesis are:

  • temperature
  • light intensity
  • carbon dioxide concentration
  • amount of chloroplast
• The inverse square law affects the rate of photosynthesis by decreasing the amount of light energy that reaches a plant as the distance from the light source increases.
• Limiting factors are important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit
• The glucose produced in photosynthesis may be:

  • used for respiration

  • converted into insoluble starch for storage

  • used to produce fat or oil for storage

  • used to produce cellulose, which strengthens the cell wall

  • used to produce amino acids for protein synthesis
• To produce proteins, plants use nitrate ions that are absorbed from the soil.
• cellular respiration is an exothermic reaction which is continuously occurring in living cells.
• Organisms need energy for:

  • chemical reactions to build larger molecules

  • movement

  • keeping warm
• Aerobic respiration is represented by the equation:

  glucose + oxygen --> carbon dioxide + water
• Anaerobic respiration in muscles is represented by the equation: glucose--> lactic acid
• As the oxidation of glucose is incomplete in anaerobic respiration much less energy is transferred than in aerobic respiration.
• Anaerobic respiration in plant and yeast cells is represented by the equation:

  glucose --> ethanol + carbon dioxide
• Anaerobic respiration in yeast cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks
•  oxygen debt is the amount of extra oxygen needed to react with lactic acid in muscles and remove it from cells.
• The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood.
• The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.
• Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose.
• label dadagram

  A) carbohydrases

  B) glucose

  C) proteases

  D) amino acids

  E) lipases

  F) fatty acids

  G) glycerol

  
• the glucose molecule is small enough to be absorbed directly through the walls of the digestive system
• Starch is a polymer of glucose. It must be broken down into glucose molecules – it is too large to pass through the gut
• Once inside the body, the amino acids are reassembled into the proteins the individual requires – the process of protein synthesis
• Metabolism is the sum of all the reactions in a cell or the body.
• The energy transferred by respiration in cells, is used by the organism for the continual enzyme-controlled processes of metabolism that synthesise new molecules.
• Metabolism includes:

  • conversion of glucose to starch, glycogen and cellulose

  • the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids

  • the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins

  • respiration

  • breakdown of excess proteins to form urea for excretion.