Gaseous Exchange / Respiration - BiologySc

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Gas exchange from Magdaléna Kubešová

Gaseous Exchangeis the process of swapping one gas for another. It occurs in the alveoli of the lungs. Oxygen diffuses into the capillaries from the air in the alveoli and carbon dioxide diffuses out of the capillaries and into the air in the alveoli. Both oxygen and carbon dioxide are transported around the body in the blood – through arteries, veins and capillaries. They bind to hemoglobin in red blood cells although this is more effective with oxygen. Carbon dioxide also dissolves in the plasma or combines with water to form bicarbonate ions. The main respiratory surface in humans are the alveoli. Alveoli are small air sacs branching off from the bronchioles in the lungs. They are one-cell thick and provide a moist and extremely large surface area for gas exchange to occur. Capillaries carrying deoxygenated blood from the pulmonary artery run across the alveoli - they are also extremely thin so the total distance gases must diffuse across is only around 2-cells thick. Inhaled oxygen is able to diffuse into the capillaries from the alveoli, while carbon dioxide from the blood diffuses in the opposite direction into the alveoli. The waste carbon dioxide can then be exhaled out of the body. Continuous blood flow in the capillaries as well as constant breathing maintains a steep concentration gradient.REASONS FOR GASEOUS EXCHANGE :*To maintain the concentration gradients of oxygen and carbon dioxide in the alveoli. *The body needs oxygen to make ATP via cell respiration.The body needs to get rid of carbon dioxide which is a product of cell respiration.*Oxygen needs to diffuse from the alveoli into the blood. Carbon dioxide needs to diffuse from the blood into the alveoli.*To do so there must be a high oxygen concentration and a low carbon dioxide concentration in the alveoli. *This makes it possible by getting rid of the carbon dioxide in the alveoli and bringing in more oxygen.FEATURES COMMON TO ANY GASEOUS EXCHANGE SURFACE:1. Large Surface Area to Volume Ratio2. Effective transport System (Good Blood Supply)3. Thin to allow difussion4. Moist to allow gases to dissolve5. Constant supply of gases eg. Oxygen

THE RESPIRATORY SYSTEM OF A HUMAN

STRUCTURE OF ALVEOLUS

Inhalation: - The external intercostal muscles contract. This moves the ribcage up and out. - The diaphragm contracts. As it does so it moves down and becomes relatively flat. - Both of these muscle contractions result in an increase in the volume of the thorax which in turn results in a drop in pressure inside the thorax.- Pressure eventually drops below atmospheric pressure. - Air then flow into the lungs from outside the body, through the mouth or nose, trachea, bronchi and bronchioles. - Air continues to enter the lungs until the pressure inside the lungs rises to the atmospheric pressure.

Exhalation: - The internal intercostal muscles contract. This moves the ribcage down and in. - The abdominal muscles contract. This pushes the diaphragm up, back into a dome shape. - Both of these muscle contractions result in a decrease in the volume of the thorax. - As a result of the decrease in volume, the pressure inside the thorax increases. - Eventually the pressure rises above atmospheric pressure.- Air then flows out of the lungs to outside of the body through the nose or mouth. - Air continues to flow out of the lungs until the pressure in the lungs has fallen back to atmospheric pressure.

RESPIRATIONRespiration is the process of releasing energy from the breakdown of glucose.Respiration takes place in every living cell, all of the time and all cells need to respire in order to produce the energy that they require.What is the energy is used for? The energy produced during respiration is used in many different ways, some examples of what it is used for are:1.Working your muscles2.Growth and repair of cells3.Building larger molecules from smaller ones i.e. proteins from amino acid4.Allowing chemical reactions to take place5.Absorbing molecules in active transport6.Keeping your body temperature constant7.Sending messages along nervesTypes of RespirationThere are two main types of respiration, aerobic and anaerobic we will look at each one of these in detail now. Aerobic Respiration Aerobic means “with air”. This type of respiration needs oxygen for it to occur so it is called aerobic respiration. The word equation for aerobic respiration is: Glucose + Oxygen =====> Carbon dioxide + Water + Energy The chemical equation is: C6H12O6 + 6O2 ======> 6CO2 + 6H2O + 2880 KJ In the above equations we see that glucose is broken down by oxygen to release energy with carbon dioxide and water being produced as by-products of the reaction. Approximately 2880KJ of energy is released when only one glucose molecule is broken down by six oxygen molecules. The released energy is used to make a special energy molecule called Adenosine Tri Phosphate (ATP). ATP is where the energy is stored for use later on by the body. Aerobic respiration occurs in plants as well as animals. Oxygen enters plant cells through the stomata. Plants produce their food via photosynthesis and release energy from it through the process of respiration. N.B. Respiration occurs both at night and during the day in plants. Anaerobic Respiration Anaerobic means without air (“an” means without). Sometimes there is not enough oxygen around for animals and plants to respire, but they still need energy to survive. Instead they carry out respiration in the absence of oxygen to produce the energy they require this is called anaerobic respiration. a) In animals Our muscles need oxygen and glucose to respire aerobically and produce the energy they require, these are carried to the muscle via the blood. However if we were to carry out vigorous exercise our heart and lungs would not be able to get sufficient oxygen to our muscles in order for them to respire. In this case muscles carry out anaerobic respiration. The word and chemical equation for anaerobic respiration in is: Glucose=====> Lactic acid + Energy C6H12O6======>2C3H6O3 + 150 KJ As you can see anaerobic respiration is not as efficient as aerobic and only a small amount of energy is released. This is because glucose can only be partially broken down. As well as this inefficiency a poisonous chemical, lactic acid is also produced, if this builds up in the body it stops the muscles from working and causes a cramp. To rid the body of lactic acid oxygen is needed, the amount of oxygen required to break down the lactic acid is referred to as the oxygen debt. b) In Plants The oxygen supply to plants can also run out, this happens for example if the soil gets waterlogged. In this case they have to obtain their energy via anaerobic respiration. Below is the word and chemical equation for anaerobic respiration in plants:Glucose====>Ethanol + Carbon dioxide + Energy C6H12O6====>2C2H5OH + 2CO2 + 210KJ When the above reaction occurs in yeast cells it is referred to as fermentation. Fermentation is the process used for baking bread and brewing alcohol. Powered by Create your own unique website with customizable templates. Get Started

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  • Ecology
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  • Gaseous Exchange / Respiration
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