2.3

• What are the features of photosynthesis?

  • Plants use photosynthesis to make their own food in the form of glucose
  • It’s an endothermic reaction carried out in chloroplasts in the cells of green leaves
  • Energy from the sunlight is used to produce glucose from CO2 and H2O
  • O2 gas is the other product

  
• What is the thermochemical equation for photosynthesis?

  6CO2 (aq) + 6H2O (l) à C6H12O6 (aq) + 6O2 (g)                                  ∆H = +2803
• What is cellular respiration?

  • The process through which cells convert sugars into energy.
  • CO2 and H2O are typical products of this process
• What is the thermochemical equation for cellular respiration?

  C6H12O6 (aq) + 6O2 (g) à 6CO2 (aq) + 6H2O (l)                                  ∆H = −2803
• What is the difference between photosynthesis and cellular respiration?

  • Photosynthesis occurs in plant cells, while respiration occurs in both animal and plant cells
• Why is energy needed for the body?

  • Energy is need for physical activity, for warmth and for functions such as breathing
  • Energy is also required to build the large molecules in our systems and this energy can be released as the molecules are digested, or metabolised back to smaller units
• What occurs during digestion?

  • Enzymes (Organic catalysts that increase the rate of biochemical reactions) in our saliva and small intestine break the starch molecules back into glucose
  • The glucose is transported in the blood to the body cells where respiration occurs
• Why do fats and oil have a significantly higher energy value than carbohydrates and proteins?

  • Carbohydrates tend to contain more oxygen than fats and oils do.
  • At a simple level, the carbon atoms in carbohydrate molecules have a higher ‘degree of oxidation’.
  • Therefore, fats and oils have a greater potential for oxidation and release more energy on combustion.