O Level Revision : Integrated Science - Gaseous Exchange and Respiration

Respiratory system

The respiratory system is made up of organs and structures to help the body obtain air from the environment into the lungs and then to the blood stream so that it can be transported to the different parts of the body.

Parts of the Respiratory system

Respiratory system of a human

Gaseous exchange

• Air is breathed into and out of the body.
• Breathing in is called inhaling and breathing out is called exhaling.
• Air from the environment (atmosphere) has a different composition to air that has been expelled from the body.
• Oxygen is removed from inhaled air and carbon dioxide is added to exhaled air.

The percentage composition of inhaled and exhaled air

Mechanism of gaseous exchange

• There will be more oxygen in the alveoli than in the blood capillaries thus oxygen diffuses from the alveoli into the capillaries.
• The capillaries reunite (rejoin) to form the pulmonary vein and transport the now oxygenated
• blood to the left atrium of the heart.
• The concentration of carbon dioxide is higher in the capillaries than in the alveoli therefore carbon dioxide diffuses from the capillaries into alveoli.
• Carbon dioxide is exhaled in the air that is breathed out.

Respiration

• Oxygen from the respiratory system and glucose from the digestive system react in the body. tissues to provide energy for the body processes during a process known as respiration.
• Respiration is a process involving chemical reactions.
• Respiration that takes place in the presence of oxygen is called aerobic respiration.
• Respiration that takes place in the absence of oxygen is called anaerobic respiration.
• Aerobic respiration releases more energy than anaerobic respiration.
• Anaerobic respiration sometimes occurs during periods of vigorous exercise where the lungs fail to supply enough oxygen to meet demand.

Definition: Respiration is the release of energy from the breakdown of glucose in the presence of oxygen.

The word equation for aerobic respiration

GLUCOSE  +   OXYGEN      →        CARBON DIOXIDE   +     WATER  +     ENERGY

The word equation for anaerobic respiration

GLUCOSE         →         ALCOHOL  +     WATER    +     ENERGY

The experiment described below can be carried out to show that energy is released during respiration.

Requirements

• Thermos flask
• Unboiled bean seed
• Boiled dead bean seed
• Cotton wool
• Thermometer

 The Procedure

1. The seeds are washed in a disinfectant before the experiment to kill any fungi on the seeds.
2. The flask with the dead seeds is the control.
3. The flasks are suspended upside down to ensure that water does not accumulate in flask and make the seeds to rot.

4. The temperature of each flask is recorded at the beginning of the experiment.
5. The temperature is recorded thereafter on each day for four consecutive days.

Results:

The temperature in the flask with living seeds will be higher than the temperature of the control.

Conclusion

Energy is released by germinating seeds.