Aerobic and Anaerobic Respiration

• Respiration is a chemical process in all living cells releasing energy from glucose.
• Gas exchange involves obtaining oxygen from the environment and removing carbon dioxide.

Aerobic Respiration

• Aerobic respiration requires oxygen.
• Glucose breaks down into carbon dioxide and water.
• A large amount of energy is released.
• Word equation: Glucose + Oxygen → Carbon Dioxide + Water (+ Energy).
• Balanced chemical equation: C6H12O6 + 6O2 → 6CO2 + 6H2O (+ Energy).
• Most energy released is in the form of ATP (adenosine triphosphate).

Anaerobic Respiration

• Anaerobic respiration doesn't require oxygen.
• Glucose breaks down into different products depending on the organism.
• In animals, glucose converts to lactic acid, releasing a small amount of energy.
• Word equation (animals): Glucose → Lactic Acid (+ Energy).
• In yeast and some plants, glucose converts to ethanol and carbon dioxide.
• Word equation (yeast): Glucose → Ethanol + Carbon Dioxide (+ Energy).
• Anaerobic respiration is less efficient than aerobic respiration.
• It yields less energy per glucose molecule.
• Oxygen debt is the additional oxygen needed after anaerobic respiration.
• It breaks down accumulated lactic acid.

Gas Exchange in Humans

• The human gas exchange system includes lungs, trachea, bronchi, bronchioles, alveoli, and diaphragm.
• Air enters through the nose and mouth.
• Air passes through the trachea, splitting into two bronchi.
• Each bronchus branches into bronchioles, ending in alveoli.
• Alveoli are the primary site of gas exchange in the lungs.
• Lungs are located in the chest cavity.
• The rib cage protects the lungs.
• Ventilation is the process of moving air in and out of the lungs.
• It consists of inspiration (inhalation) and expiration (exhalation).

Inspiration (Inhalation)

• During inspiration, the diaphragm contracts and moves downwards.
• Intercostal muscles contract, lifting the rib cage up and outwards.
• These movements increase the chest cavity volume.
• This decreases the air pressure inside the lungs.
• Air flows into the lungs from the atmosphere due to the pressure gradient.
• Air flows in until the pressure inside the lungs equals atmospheric pressure.

Expiration (Exhalation)

• During expiration, the diaphragm relaxes and moves upwards.
• Intercostal muscles relax, lowering the rib cage down and inwards.
• These movements decrease the volume of the chest cavity.
• This increases the air pressure inside the lungs.
• Air flows out of the lungs into the atmosphere due to the pressure gradient.
• Air flows out until the pressure inside the lungs equals atmospheric pressure.

Alveoli

• Alveoli are tiny air sacs in the lungs where gas exchange occurs.
• Alveoli have thin walls (one cell thick) to minimize diffusion distance.
• Alveoli have a large surface area to maximize gas exchange rate.
• Alveoli are surrounded by a dense network of capillaries.
• This ensures a constant blood supply for gas exchange.
• The concentration gradient between the air in the alveoli and the blood in the capillaries drives the diffusion of oxygen and carbon dioxide.
• Oxygen diffuses from the air in the alveoli into the blood.
• Oxygen binds to hemoglobin in red blood cells.
• Carbon dioxide diffuses from the blood into the air in the alveoli to be exhaled.
• The alveolar epithelium is moist.
• Allowing gases to dissolve and diffuse more efficiently.

Gas Exchange in Fish

• Fish use gills for gas exchange.
• Gills are on either side of the head.
• Gills consist of gill filaments and gill lamellae.
• Gill filaments are thin, highly folded structures.
• They increase the surface area for gas exchange.
• Gill lamellae are even smaller structures on the gill filaments.
• They further increase the surface area.
• Water flows over the gills in one direction.
• Blood flows through the gill lamellae in the opposite direction (countercurrent flow).
• Countercurrent flow maintains a concentration gradient.
• It maximizes oxygen uptake from the water.
• As water flows over the gills, oxygen diffuses from the water into the blood.
• Carbon dioxide diffuses from the blood into the water.
• The operculum is a bony flap.
• It covers and protects the gills.
• It helps pump water over the gills.
• Fish ventilate their gills by opening and closing their mouth and operculum in a coordinated manner.

Gas Exchange in Plants

• Gas exchange in plants occurs primarily through stomata.
• Stomata are small pores on the surface of leaves.
• Stomata are surrounded by guard cells.
• Guard cells regulate the opening and closing of the stomata.
• During the day, stomata open.
• This allows carbon dioxide to enter for photosynthesis.
• This allows oxygen to exit as a byproduct.
• At night, stomata usually close.
• This reduces water loss through transpiration.
• Gas exchange also occurs through lenticels.
• Lenticels are small pores on the stems and roots of plants.
• Lenticels allow for the exchange of oxygen and carbon dioxide between the plant tissues and the environment.
• The rate of gas exchange in plants is affected by light intensity, temperature, and humidity.

Factors Affecting Respiration and Gas Exchange

• Temperature: Higher temperatures generally increase the rate of respiration and gas exchange, up to a certain point.
• Oxygen concentration: Higher oxygen concentrations increase the rate of aerobic respiration.
• Carbon dioxide concentration: Higher carbon dioxide concentrations can decrease the rate of respiration in some organisms.
• Surface area: Larger surface areas for gas exchange increase the rate of diffusion.
• Diffusion distance: Shorter diffusion distances increase the rate of gas exchange.
• Ventilation rate: Higher ventilation rates increase the rate of gas exchange by maintaining a concentration gradient.
• Metabolic rate: Higher metabolic rates increase the demand for oxygen and the production of carbon dioxide, affecting respiration and gas exchange.

Health Issues

• Asthma: A chronic respiratory disease.
• It causes inflammation and narrowing of the airways.
• This makes it difficult to breathe.
• Bronchitis: Inflammation of the bronchi.
• Often caused by infection or irritants.
• Leads to coughing and mucus production.
• Emphysema: A lung disease in which the alveoli are damaged.
• This reduces the surface area for gas exchange.
• Pneumonia: An infection of the lungs.
• It causes inflammation and fluid buildup in the alveoli.
• Cystic Fibrosis: A genetic disorder.
• It causes the production of thick mucus.
• This can block the airways and lead to lung infections.