Respiration and Gas Exchange

• Respiration is the process of transferring energy from glucose. It goes on in every cell in you body.
• The energy transferred by respiration can't be used directly by cells so it's used to make a substance called ATP. ATP stores the energy needed for many cell processes. When a cell needs energy, ATP molecules are broken down and energy is released.
• There are two types of respiration: anaerobic and aerobic.
• Aerobic respiration just means respiration with oxygen and it's the efficient way to transfer energy from glucose. It produces lots of ATP.
•  C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy)
• When you do vigorous exercise your body can't supply enough oxygen to your muscles for aerobic respiration. It just means without oxygen. It releases less energy - glucose is only partially broken down and latin acid is also produced.
• Lactic acid builds up in the muscle, it's painful and leads to cramps.
• In humans the word equation for anaerobic is:

  glucose → lactic acid (+energy)
• Anaerobic respiration in plants is different:

  glucose > ethanol + carbon dioxide (+ energy)
• A hydrogen-carbonate indicator turns from orange to yellow in prescene of CO2.
• Respiration transfers some energy by heat.
• When plants photosynthesis they use up Co2 and produce O2 as a waste product. When plants respire they use up 02 and produce CO2 as a waste product. The waste products are lost through stomata on the underside of the leaf.
• Photosynthesis only happens during the day when lights available but plants must respire all the time, day and night.
• During the day plants make more oxygen by photosynthesis than they use in respiration. So in day they release oxygen. They also use more CO2 than they produce so they take in CO2.
• At night, the plants only respire - there's not enough light for photosynthesis. This means they take in oxygen and release C02
• Leaves are adapted for efficient gas exchange.

  • leaves are broad so there's a large surface area for diffusion
  • they are also thin, gases only have to travel a short distance to reach the cells where they are needed.
• • there are air spaces inside the leaf - lets CO2 and O2 move easily between cells. It also increases the surface area for gas exchange.
  • Stomata let gases like CO2 + O2 diffuse in and out, they allow water to escape which is known as transpiration.
• • stomata closes up as it gets dark, photosynthesis can't happen ih the dark so they don't need to be open to allow CO2. When the stomata are closed water can't escape which stops the plant drying out.
• • stomata also close when supplies of water form the roots start to dry up. This stops the plant from photosynthesis but if they didn't close, the plants might dry out and die.
• • the opening and closing of stomata is controlled by the guard cells. Guard cells change their shape and volume. Guard cells increase in volume to open stomata and decrease in volume to close stomata.
• the thorax is separated from the lower part of the body by a muscle called diaphragm.
• the lungs are surrounded by the pleural membranes which are then protected by the rib cage and the intercostal muscle that run in between the ribs.
• the air that you breathe goes in through the trachea and then splits into two tubes called bronchi (each one is called bronchus) that go to each lung.
• The bronchi split into smaller tubes called the bronchioles which end at small bags called alveoli where the gas exchange takes place.
• When you breathe in:

  • intercostal muscles and diaphragm contract
  • thorax volumes increases
  • this decreases pressure drawing air in. (Extra info. muscles between ribs pull ribcage and sternum up and out + diaphragm flattens out)
• When you breathe out:

  • intercostal muscles and diaphragm relax
  • thorax volume decreases
  • air is forced out
• Alveoli carry out gas exchange in the body. The blood passing next to the alveoli has just returned to the lungs from the rest of the body so it has lots of CO2 and little oxygen. Oxygen diffuses out of the alveolus (high conc) into the blood (low conc). Carbon dioxide diffuses out of the blood into the alveolus to be breathed out.
• When the blood reaches body cells, oxygen is released from the red blood cells and diffuses into the body cells. At the same time CO2 diffuses out off the body cells into the blood cells where it's then carried back to the lungs.
• Alveoli are specialised for gas exchange as they have a large surface area to volume ratio, they have very thin walls, they have a great blood supply to maintain a high concentration gradient.
• Smoking damages the walls inside the alveoli reducing the surface area for gas exchange and leading to diseases like emphysema.
• Tar in cigarettes damage the cilia in your lungs and trachea. These hair along with mucus catch dust and other particles. The cilia also sweep mucus back towards the mouth, when they are damaged, chest infections are more likely.
• Tar also irritates the bronchi and bronchioles encouraging mucus to be produced which can't be cleared very well by damaged cilia - this causes smokers cough and chronic bronchitis.
• Carbon Monoxide reduces the amount of oxygen carried around by the body and to make up for this the heart rate increases leading to an increase in blood pressure. High blood pressure damages the artery walls, making the formation of blood clots more likely and increasing the risk of coronary heart disease.
• Tobacco also has carcinogens which are chemicals that lead to cancer.