Respiration

• Respiration


  A biological process that continually releases energy from food (usually glucose)
• Aerobic respiration


  Glucose + oxygen → carbon dioxide + water + energy
• Respiration is an exothermic reaction (it releases energy to the surroundings)
• The sites of respiration are the mitochondria, which are found in the cytoplasm of animal and plant cells
• Aerobic respiration


  Respiration in the presence of oxygen
• Anaerobic respiration


  Respiration in the absence of oxygen
• Anaerobic respiration in mammalian muscle

  Glucose → lactic acid + energy
• Anaerobic respiration in yeast


  Glucose → alcohol + carbon dioxide + energy
• Anaerobic respiration releases much less energy than aerobic respiration
• Anaerobic respiration in yeast is a very useful commercial process - it is important in beer and wine making and also baking (the carbon dioxide released causes bread and cakes to rise)
• Anaerobic respiration in muscles


  Only likely to take place during strenuous exercise - it is only then that we are respiring at a rate at which we cannot supply enough oxygen to our muscles to respire aerobically
• Similarities between aerobic and anaerobic respiration


  • They both produce energy
  • They both use glucose as an energy source
• Differences between aerobic and anaerobic respiration

  • Aerobic respiration produces more energy than anaerobic respiration
  • Oxygen is not used in anaerobic respiration
  • Water is not produced in anaerobic respiration
  • Lactic acid is produced in anaerobic respiration in mammalian muscle and alcohol is produced in yeast - carbon dioxide is produced in yeast but not in mammalian muscle
• Figure 5.1 shows how anaerobic respiration can be demonstrated in yeast
• This apparatus can be used to investigate how different factors, such as temperature and the type of sugars added, affect the rate of anaerobic respiration in yeast
• Layer of oil


  • Prevents oxygen entering the glucose solution
• Limewater


  • Turns milky as bubbles of carbon dioxide pass through it
• Solution of glucose with yeast


  • After a period of time it is slightly warmer and contains alcohol
• Demonstrating anaerobic respiration in yeast

  1. Layer of oil prevents oxygen entering

  2. Limewater turns milky with CO2 bubbles

  3. Glucose solution with yeast becomes warmer and contains alcohol
• This apparatus can be used to investigate how different factors, such as temperature and the type of sugars added, affect the rate of anaerobic respiration in yeast
• You should be able to work out the controlled variables when investigating different independent variables
• Prescribed practical
• The rate of breathing increases
• This means we breathe

  More times per unit time, taking in more oxygen per unit time
• Respiration


  A series of chemical reactions that release stored chemical energy from food
• Function of the respiratory system

  • Provides the cells and tissues with oxygen
  • Removes carbon dioxide to facilitate the process of respiration
• Respiration (often called cellular respiration) is a series of chemical reactions that occur in the mitochondria
• Exothermic


  Releases stored chemical energy from food
• Breathing moves air in and out of the lungs
• Every cell in every living organism needs energy (i.e., plants and animals)
• Cells get energy by releasing energy from food (stored chemical energy)
• Energy is needed for


  • Heat
  • Movement
  • Growth
  • Reproduction
  • Active transport
• Active transport


  Molecules are moved against a concentration gradient (from where they are in a low concentration to where they are in a high concentration)
• Active transport requires energy, from respiration
• Plants use active transport to move nitrates into roots
• Animals use active transport to transmit impulses through nerve cells
• Respiration equation


  Glucose + oxygen -> energy + Carbon dioxide + Water
• The glucose comes from the food that we eat
• The oxygen comes from the air that we breathe
• Aerobic respiration


  Oxygen is used to break down the food