Chapter 9

• What is respiration?


  Respiration is the process of transferring energy from glucose, which goes on in every cell. It is an exothermic reaction (it transfers energy to the environment)
• What is aerobic respiration?

  Aerobic respiration is respiration using oxygen. It's the most efficient way to transfer energy from glucose.

  Glucose + Oxygen -> carbon dioxide + water

  C6H12O6 + 6O2 → 6CO2 + 6H2O

  
• What ways may an organism use the energy from photosynthesis?

  -Organisms use energy to build up larger molecules from smaller ones (proteins from amino acids)

  -Animals use energy to allow their muscles to contract

  -Mammals and birds use energy to keep their body temperature steady

  -To move substances around cells. In plants energy from respiration is transferred to move mineral ions such as nitrates from the soil into the root hair cells
• What is anaerobic respiration?

  During vigorous exercise, your body can't supply enough oxygen to your muscles so they start doing anaerobic respiration. It's the incomplete breakdown of glucose, making lactic acid

  Glucose -> Lactic acid
• What is the word equation for anaerobic respiration in plants and yeast?

  Glucose -> ethanol + carbon dioxide
• What is fermentation?

  Anaerobic respiration in yeast cells is called fermentation. In the food and drinks industry, fermentation by yeast is of great value as it's used to make bread and alcoholic drinks, playing an important part in the economy.
• What's oxygen debt?

  An oxygen debt is the amount of extra oxygen your body needs after exercise to react with the build up of lactic acid and remove it from the cells.
• How is lactic acid removed from the muscles?

  -The pulse and breathing rate stay high whilst their are high levels of lactic acid and carbon dioxide to deliver more oxygen to the cells and take away the carbon dioxide

  -The blood that enters your muscles transports the lactic acid to the liver. In the liver the lactic acid is converted back to glucose.
• What happens during exercise?

  When you exercise, some of your muscles contract more frequently than normal , so you need more energy. This energy comes from increased respiration. The increase in respiration in your cells means you need to get more oxygen into them. For this to happen, the blood has to flow at a faster rate

  Physical activity-

  -increases your breathing rate and breath volume to meet the demand for extra oxygen

  -increases your heart rate to make your blood flow more quickly, delivering more oxygen and glucose to cells for respiration, and taking more carbon dioxide away.
• What causes muscle fatigue?

  -During vigorous exercise your body can't supply oxygen to your muscles quickly enough, so they start respiring anaerobically.

  -This is not the best way to transfer energy from glucose because lactic acid builds up in the muscles, which can be painful.

  -Long periods of exercise also cause muscle fatigue- the muscles get tired and stop contracting efficiently.
• What is the recovery period?


  After anaerobic exercise stops, there will be an 'oxygen debt'. Heart rate and breathing rate stay higher than normal for a while after exercise whilst the oxygen debt is being paid back. This is known as the recovery period.
• What is metabolism?

  In a cell there are lots of chemical reactions happening all the time, which are controlled by enzymes. Many of these reactions are linked together to form bigger reactions

  -In some reactions, larger molecules are made of smaller ones. These are called endothermic reactions

  -In other reactions, larger molecules are broken down into smaller ones. These reactions are exothermic

  -The sum of all of the reactions that happen in a cell or the body is called the metabolism
• Give examples of endothermic reactions

  -Lots of small glucose molecules are joined together in reactions to form starch, glycogen and cellulose

  -Lipid molecules are each made from one molecule of glycerol and three fatty acids.

  -Glucose is combined with nitrate ions to make amino acids, which are then made into proteins
• Give examples of exothermic reactions


  -Glucose is broken down in respiration. Respiration transfers energy to power all the reactions in the body that make molecules

  -Excess protein is broken down in a reaction to produce urea. Urea is then excreted in urine.
• What is the role of the liver?

  -detoxifying poisonous substances (ethanol from alcoholic drinks)

  -passing the breakdown products into the blood so they can be excreted in the urine via the kidneys

  -breaking down old, worn out blood cells and storing the iron until it is needed to synthesise more blood cells