Biology

The Respiratory SystemRespiration 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 O2 (aerobic), or not (anaerobic).

Breathing is the movement of air in and out of the lungs.

Structure of the Respiratory System Components: Nose, pharynx, larynx, trachea,

bronchi, and lungs (containing alveoli).The air that we breathe contains: 21 % O2, 78

% N, 0.04 % CO2 (and other gases as well).How is breathing controlled? When the level

of CO2 rises, the breathing center sends out nerve impulses that cause the diaphragm to contract and bring air into the lungs.

Aerobic RespirationWord equation for aerobic respiration: Glucose + Oxygen Carbon dioxide + Water

+ EnergyThis 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.

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).

Anaerobic RespirationIt 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 + EnergyThis 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.

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.