Ch. 11 - Respiration and Gas Exchange

• Contraction of muscles for movement • Protein synthesis • Cell Division • Active Transport • Growth • Maintaining body temperature

Aerobic respiration refers to the chemical reactions in the mitochondria by which glucose and other nutrient molecules are broken down with the help of oxygen, in order to release energy for the cells. Carbon dioxide and Water are formed as by-products.

Word equation: Glucose + Oxygen –> Carbon Dioxide + Water Chemical Equation: C6H12O6 + 6O2 –> 6CO2 + 6H2O

Anaerobic respiration refers to the chemical reactions in cells by which glucose and other nutrient molecules are broken down without the help of oxygen. In muscles it leads to the formation of lactic acids while in yeast and plants it leads to the formation of alcohol (C2H5OH) and Carbon Dioxide.

Word equation: Glucose –> Ethanol + Carbon Dioxide Chemical Equation: C6H12O6 –> 2C2H5OH + 2CO2

Word Equation: Glucose –> Lactic Acid

• Oxygen: Aerobic respiration uses oxygen while anaerobic respiration doesn’t • Alcohol Production: Anaerobic respiration results in the formation of alcohol in yeast and plant cells while there is no alcohol formation in aerobic respiration • Energy production: There is a large amount of energy released in aerobic respiration from each molecule of glucose while much less energy is released in anaerobic respiration from each molecule of glucose. • Carbon Dioxide production: Aerobic respiration results in the formation of carbon dioxide while there is only carbon dioxide formation in anaerobic respiration in plant and yeast cells, not animals.

Oxygen is taken in the nose (Inhalation) Moves to the lungs via the trachea (windpipe) From the lungs to goes to the pulmonary vein Enter the left atrium Moves down to the left ventricle Exits via the aorta Goes to the different parts of the body where the blood gets deoxygenated as oxygen is used for various processes Carbon dioxide enters the blood Blood moves to the vene cava Enters the right atrium Moves down to the right ventricle Exits through the pulmonary artery Enters the lungs Carbon dioxide is exhaled and oxygen is inhaled.

The trachea, or the wind pipe, is the tube through which air travels to the lungs. It has rings of cartilage in its walls, to support it.

The alveoli are tiny air-filled sacs in the lungs where gas exchange takes place.

Walls of the Alveoli - gas exchange surface 1. Large Surface Area 2. Thin wall to minimise diffusion distance 3. Good blood supply/Efficient transport system 4. Good ventilation with air - maintains concentration gradient

Air enters the body through the nose (nasal cavity), where it is filtered by hairs and mucus, and warmed and moistened. It then passes through the pharynx (throat). Air moves down into the trachea (windpipe), which is supported by rings of cartilage to keep it open. The trachea carries air into the thorax (chest cavity). In the thorax, the trachea divides into two bronchi, one leading to each lung. Each bronchus enters a lung and branches repeatedly into smaller tubes called bronchioles. The bronchioles further divide and lead to air sacs called alveoli, where gas exchange occurs.

During exercise, the lungs and heart cannot supply oxygenated blood fast enough, so muscles do not receive enough oxygen for aerobic respiration. Therefore, the muscles switch to anaerobic respiration, which results in the formation of lactic acid. This lactic acid builds up in the muscles, causing fatigue. After exercise, extra oxygen is required to break down the lactic acid. Oxygen is also used in the transport of lactic acid from the muscles to the liver. This extra oxygen required is known as oxygen debt.

When the lactic acid concentration increases, the pH of the blood decreases. The brain monitors this change and as a result sends out signals to increase the breathing rate to get more oxygen as oxygen is used both fo the transport of lactic acid to the liver and in the breakdown of lactic acid in the liver.

• The volume of the chest cavity increases • Air pressure decreases (as volume increases) • Ribcage moves upwards and outwards • Internal intercostal muscles relax • External intercostal muscles contract • Diaphragm contracts and moves downward. Exhalation (Expiration) is the opposite.

The intercostal muscles are antagonistic muscles, meaning that they work oppositely.