1. Biology

2. The Respiratory System Respiration is the exchange of gases that takes place in the alveoli of the lungs. In Biology respiration also refers to the release of energy from the breakdown of molecules in food in the presence of O 2 (aerobic), or not (anaerobic). Breathing is the movement of air in and out of the lungs.

3. Structure of the Respiratory System Components: Nose, pharynx, larynx, trachea, bronchi, and lungs (containing alveoli). The air that we breathe contains: 21 % O 2, 78 % N, 0.04 % CO 2 (and other gases as well). How is breathing controlled? When the level of CO 2 rises, the breathing center sends out nerve impulses that cause the diaphragm to contract and bring air into the lungs.

4. Aerobic Respiration Word equation for aerobic respiration: Glucose + Oxygen  Carbon dioxide + Water + Energy This process takes place in our cells (in the mitochondria). Oxygen is brought to cells through breathing, and glucose is obtained from food. The energy is released from glucose.

5. What is energy needed for? All organisms need energy for: Growth, cell division, transporting chemicals, and just staying alive. Animals need energy for: making muscle contract, sending messages along nerves, and keeping warm. Plants need energy for taking up mineral salts from the soil and opening and closing their pores (stomata).

6. Anaerobic Respiration It is “respiration without air”. It occurs when cells need to obtained energy from glucose and there is no oxygen available. Word equation for anaerobic respiration: Glucose  Lactic acid + Energy This process gives a lot less energy than aerobic respiration. Lactic acid is a mild poison that makes muscles ache. It must later be broken down into CO2 and H2O. Oxygen is needed for this process. The oxygen needed to get rid of lactic acid is called oxygen debt.

7. Comparing Aerobic and Anaerobic types of Respiration 1. Aerobic respiration requires oxygen. 2. Aerobic respiration produces more energy than the anaerobic type. 3. Aerobic respiration can go on for a much longer time than the anaerobic type.