Ch 2.3 - Fuel sources of the body

Photosynthesis:

• Endothermic chemical reaction carried out in the chloroplasts in the cells of green leaves. Energy from sunlight is used to produce glucose from carbon dioxide and water. Oxygen gas is the other product.

• 6CO2 + 6H2O —> C6H12O6 + 6O2

Glucose:

• Glucose contains chemical energy and is a monomer that is used to form natural polymers such as starch and cellulose.

Cellular Respiration:

• Glucose is used to obtain energy in a process known as cellular respiration/aerobic respiration (as oxygen gas is required).

• C6H12O6 (aq) + 6O2(g) —> 6CO2 (g) + 6H2O (l) change in enthalpy = -2803 kJ

• The products of photosynthesis become the reactants of cellular respiration

• RESPIRATION occurs in PLANTS + ANIMALS

Carbohydrates:

• Made from carbon, hydrogen and oxygen.

• Enzymes in our saliva break the starch molecules back into glucose. The glucose is transported in the blood to body cells where respiration can occur. Energy is required to form the many bonds in these large carbohydrates and that energy is released during digestion.

Fats:

• Large non-polar molecules with 3 long hydrocarbon chains.

• Fats provide and store energy in the body

• Digestion breaks down fats releasing large amounts of energy.

• Fats have higher energy values as these have a greater potential of oxidation and release more energy upon combustion.