Respiration and gas exchange

• Humans need energy for contracting muscles, making proteins, making new cells, cell division, and producing heat.
• The main nutrient used to provide energy in cells is glucose.
• Most of the time our cells release energy from glucose combining with oxygen. This is called aerobic respiration.
• Glucose + oxygen --> carbon dioxide + water
• It is possible to release energy from sugar without using oxygen. This is a less efficient method and not much energy is released per glucose molecule. This is called anaerobic respiration.
• Yeast is a single celled fungus that can respire anaerobically.
• Yeast breaks glucose into alcohol and carbon dioxide.
• Muscle cells can respire anaerobically for short periods of time. They make lactic acid instead of alcohol and no carbon dioxide is produced.
• The lungs are filled with many air spaces called the alveoli. This is where oxygen diffuses into the blood.
• The lungs are supplied with air through the trachea.
• From the nose or mouth, air passes through the trachea.
• The larynx is the voice box that contains the vocal chords. The muscles tighten when air is passed over it, making sounds.
• The trachea goes down the neck and into the thorax.
• The thorax is the upper part of your body from your neck down to the bottom of the ribs.
• In the thorax, the trachea divides into the left and right bronchi.
• One bronchus goes into each lung and they branch out into smaller tubes called bronchioles.
• At the end of each bronchiole there are many tiny air sacs or alveoli. This is where gas exchange takes place.
• Some of the cells that line the passages through which air moves towards the alveoli are goblet cells.
• Goblet cells secrete a sticky mucus. As the air passes over the mucus, microorganisms and particles get trapped in it.
• Cilia cells have hair like extensions. They sweep the mucus to the back of the throat and once it is there, it is swallowed.
• Goblet cells and ciliated cells protect the lungs from any harmful microorganisms from reaching them. This helps to reduce the chance of infection.
• The walls of the alveoli are the gas exchange surface.
• Tiny capillaries are closely wrapped around the outside of the alveoli. Oxygen diffuses across the walls of the alveoli and into the blood. Carbon dioxide diffuses the other way.
• The walls of the alveoli have several features that make gas exchange efficient: the walls are only one cell thick so its easy for oxygen to diffuse through, they have a good transport system meaning that blood is constantly pumped into the lungs along the pulmonary artery, they have a large surface area, and they have a good supply of oxygen.
• When breathing rate increases, it eventually reaches its limit. This is when anaerobic respiration is used from the glucose stored in the body to make lactic acid and energy.
• The rate at which your breathing muscles work is controlled by the brain.
• The brain constantly monitors the pH of the blood tha flows through it. If there is a lot of CO2 or lactic acid, the pH falls. The brain then sends nerve impulses to the muscles to cause breathing movements.
• Nicotine damages the circulatory systems, making blood vessels get narrower. This can increase the blood pressure.
• Tar contains many different chemicals that can cause cancer by dividing of cells and the formation of lumps or tumors.
• Smoking can cause chronic obstructive pulmonary disease (COPD), which is when the walls of the alveoli break down and therefore there is less surface area across which gas exchange can take place.
• Smoking increases the risk of high blood pressure.