Biology - Gas Exchange, Breathing and Respiration

Aerobic respiration equation

Glucose + oxygen → carbon dioxide + water + energy (ATP). C₆H₁₂O₆ → 6CO₂ + 6H₂O + ATP

Anaerobic respiration in animals

Glucose → lactic acid (+ energy)

Anaerobic respiration in plants and yeast

glucose → ethanol + carbon dioxide (+ energy)

Energy released from respiration is used for:

• Heat generation

• Muscle contraction and movement

• Growth and repair

• Nervous activity

• It allows all other life processes to be carried out

Oxygen debt

Anaerobic respiration produces energy energy to keep the overworked muscles going for a short period time, making lactic acid build up in the blood stream causing muscle cramps. The person then has to rest to allow the body to breakdown the lactic acid using oxygen. The volume of oxygen needed to completely breakdown the lactic acid is called the oxygen debt.

Investigating the evolution of CO₂ from a small animal

Two beakers both with sodium hydrogen carbonate solution in them, then a little tray and in one a dead bug and the other a live bug. The live one will respire aerobically and produce waste products of CO₂ which turns the red solution yellow. The dead one will remain red due to no respiration.

Investigating the heat produced from respiring vs not respiring pea seeds

One set of pea seeds boiled so they die and wont respire, the others soaked in water so they start germinating and respiring. Waste product of respiration is heat so the respiring peas will have a higher temperature

Parts of the gas exchange system

Larynx, trachea (wind pipe), C-shaped rings of cartilage, left and right lung, external and internal intercostal muscles, bronchus, bronchioles, alveoli, ribs, diaphragm, pleural membranes, pleural cavity fluid, sternum

Inhalation (breathing in)

Diaphragm contracts, becoming flatter, moving downwards. The intercostal muscles contract, moving the ribcage up and out. Increases volume of thorax, so pressure of thorax decreases. Air rushes into thorax through nose and mouth due to pressure gradient, which fills up the lungs

Exhalation (breathing out):

Diaphragm relaxes, returning to its dome shape, moving upwards. The intercostal muscles relax, moving ribcage in and down. Decreases volume of thorax, so increases pressure of thorax. Air is forced out of the nose and mouth due to pressure gradient which empties the lungs

Inhaled air percentages

CO₂ = 0.04%

O₂ = 21%

Exhaled air percentages

CO₂ = 4%

O₂ = 16%

Alveoli adaptations

1. Large surface area → millions of alveoli providing a large surface area for a high rate of diffusion

2. Thin walls → 1 cell thick walls of alveoli and capillaries that run across the alveoli so a short diffusion distance for a high rate of diffusion

3. Rich blood supply → a dense network of capillaries surrounding the alveoli, maintaining a steep concentration gradient for a high rate of diffusion

Bronchitis

Where the bronchi and bronchioles are clogged with mucus. Caused by smoking.

Emphysema

Where the surface area of the alveoli decreases. Caused by smoking.

Lung Cancer

Where mutations in the DNA of cells lead to abnormal growth. Caused by smoking.