Biology Chapter: Aerobic Cellular Respiration

Aerobic Cellular Respiration

• Cells require oxygen to survive and obtain energy from food.
• Aerobic cellular respiration is the process.
• Glucose reacts with oxygen, producing carbon dioxide and water, releasing energy.
• 64% of energy released is thermal energy.
• 36% is stored in adenosine triphosphate (ATP) molecules.
• ATP powers cellular processes like growth, movement, and molecule building.

Gas Exchange and Ventilation

• Gas exchange involves oxygen diffusing into cells, and carbon dioxide diffusing out.
• Simple organisms diffuse directly through cell membranes.
• Larger organisms use specialized organ systems (e.g., lungs) for efficient gas exchange.
• Gas exchange occurs at cells and lungs.
• In lungs, oxygen diffuses into the bloodstream for transport throughout the body.
• At cells, oxygen diffuses from the blood into tissue fluid.
• Cells release carbon dioxide into the tissue fluid, bloodstream and eventual removal in lungs.
• Ventilation moves oxygen-rich air into and carbon dioxide-rich air out of the lungs.

Respiratory Structures

• The human respiratory system has key features for effective gas exchange.
• A thin, permeable respiratory membrane for diffusion.
• Large surface area for efficient gas exchange.
• Extensive blood supply to facilitate oxygen uptake and carbon dioxide removal.
• The lungs are the main sites for gas exchange.
• Lungs contain a respiratory membrane with a large surface area and abundant blood supply.
• Situated within the thoracic cavity, protected by the rib cage.

Air Pathway

• Air enters the body through the nose or mouth.
• Nasal passages warm and moisten the air, filtering dust and particles.
• The pharynx connects the nasal passages/mouth to the trachea.
• The epiglottis covers the glottis during swallowing.
• The trachea is a semi-rigid tube, supported by cartilage to maintain its structure.
• It's lined with mucus-producing cells and cilia for trapping foreign particles and moving them out.
• The trachea branches into two bronchi, leading to the lungs.
• Bronchi branch into smaller bronchioles.
• The bronchioles terminate in alveoli.
• Alveoli are tiny sacs where gas exchange occurs and are in enormous numbers to maximise gas exchange.

Gas Exchange in Alveoli

• Alveoli are filled with fresh air at 37°C.
• The respiratory membrane is also moist (essential for oxygen diffusion).
• Oxygen must be dissolved in liquid to diffuse across the membrane.
• The alveoli have a very thin (single-cell-layer) membrane for rapid diffusion.

Partial Pressures

• Air pressure is measured in kilopascals (kPa).
• Atmospheric pressure at sea level is 101.3 kPa.
• Partial pressure is the pressure contributed by each gas.
• Oxygen makes up approximately 20.9% of air.
• Carbon dioxide makes up approximately 0.0391% of air.

Oxygen Transport and Diffusion

• PO2 in alveoli is higher than in capillaries, driving oxygen into the capillaries.
• Hemoglobin, a protein in red blood cells, binds to oxygen (forming oxyhemoglobin) to carry oxygen.
• Hemoglobin carries oxygen about 70 times better than if dissolved in blood plasma.
• At tissues, oxygen diffuses into cells.
• Blood returning to the heart still contains oxygen.

Carbon Dioxide Transport and Diffusion

• Carbon dioxide, a cellular respiration byproduct, must be removed.
• CO2 diffuses from tissues into the bloodstream.
• 7% dissolves in plasma, 20% attaches to hemoglobin and 73% forms carbonic acid.
• Excess hydrogen ions are carried on hemoglobin to prevent dangerously low blood pH.
• In the lungs, CO2 diffuses from the blood into the air.

Altitude and Respiration

• Atmospheric pressure and oxygen partial pressure decrease with elevation.
• Low oxygen levels at high altitudes cause altitude sickness.
• The body responds by producing more red blood cells to compensate.

Mechanism of Ventilation

• Inspiration: External intercostal muscles contract, diaphragm contracts, increasing thoracic cavity volume and lowering pressure thus drawing air into the lungs.
• Expiration: Intercostal muscles relax, diaphragm relaxes, decreasing thoracic cavity volume and increasing pressure thus expelling air from the lungs.

Lung Capacity

• Total Lung Capacity (TLC) is the maximum air held.
• Tidal Volume (TV) is a normal breath.
• Inspiratory Reserve Volume (IRV) is extra inhaled air.
• Expiratory Reserve Volume (ERV) is extra exhaled air.
• Residual Volume (RV) is air left after exhalation.
• Vital Capacity (VC) is the maximum air exhaled. VC = TV + IRV + ERV.

Discover the intricate processes of aerobic cellular respiration and gas exchange. This quiz covers how cells utilize oxygen to obtain energy, the mechanics of gas diffusion, and the role of ATP in cellular functions. Test your understanding of these essential biological processes.