B4 Respiration and metabolism

• Respiration releases the energy stored in food so it can be used by organisms for movement, growth and maintaining constant internal temperature
• Respiration is an exothermic reaction as it releases energy
• Respiration happens in the mitochondria of cells
• Special chemicals called enzymes speed up the rate of respiration when you need more energy
• Aerobic respiration equation

  Glucose + Oxygen -> Carbon dioxide + Water
• Anaerobic respiration equation

  Glucose -> Lactic acid
• Muscles need more energy during exercise - they need more blood so they recieve more oxygen and glucose
• During exercise

  Heart rate increases

  Breathing rate increases

  Breath volume increases
• Why does heart rate increase?

  More blood flows to the muscles

  More glucose and oxygen reach the muscles

  More aerobic respiration

  More energy released

  Less anaerobic respiration so less lactic acid
• Why does the breathing rate and volume increase?

  More oxygen enters the blood

  More oxygen reaches the muscles

  More aerobic respiration

  More energy released

  More CO2 leaves the blood

  Less anaerobic respiration so less lactic acid produced
• What is oxygen debt?

  Lactic acid builds up in the muscles causing muscles to become fatigued and stopping muscles from contracting efficiently

  Lactic acid is transported to the liver where it is broken down and turned back into glucose

  Oxygen is needed to break down the lactic

  Extra oxygen is needed after exercise to break down the lactic acid
• Anaerobic respiration in plants and yeast equation

  Glucose -> Carbon dioxide + Ethanol
• At night only respiration occurs in plants
• At daytime respiration occurs and photosynthesis is also occurring at a faster rate
• Metabolism is the sum of all chemical reactions happening in an organism or cell
• The main gland involved in controlling your metabolic rate is the thyroid gland which produces a hormone called thyroxine
• Most chemical reactions are happening in the cytoplasm of a cell and are controlled by enzymes
• Metabolism enables the cell to make new molecules from the products of digestion
• New molecules made from the products of digestion are

  starch, glycogen and cellulose - made from glucose.

  Proteins - made from glucose and nitrates which form amino acids which then join to make proteins