B4- Using Food and controlling growth

• Respiration


  The process of transferring energy from the breakdown of glucose (a sugar)
• Respiration is NOT "Breathing In and Out"
• Respiration


  1. Breakdown of glucose

  2. Transfer of energy
• Plants


  • Make their own glucose for respiration through photosynthesis
• Animals (consumers)


  • Produce glucose by breaking down the biomass they get when they eat other organisms
• Organisms need the energy transferred by respiration to survive, so respiration happens in every cell in all living organisms
• ATP


  Stores the energy transferred by respiration, which is then used for essential processes
• Cellular respiration


  1. Involves several different chemical reactions

  2. Controlled by enzymes

  3. Affected by temperature and pH

  4. Exothermic - transfers energy to the environment
• Substrates for respiration


  • Glucose
  • Other carbohydrates
  • Proteins
  • Lipids
• Aerobic respiration


  • Happens when there's plenty of oxygen available
  • Breaks down glucose and combines the products with oxygen to make carbon dioxide and water
  • Most efficient way to transfer energy from glucose, producing 32 ATP molecules per molecule of glucose
• Aerobic respiration in eukaryotic cells

  1. Mostly takes place in mitochondria

  2. Mitochondria contain most of the enzymes needed to control aerobic respiration reactions
• Aerobic respiration in prokaryotic cells


  All reactions take place in the cytoplasm
• You can investigate the effect of different substrates on respiration rate in yeast
• Investigating respiration rate in yeast

  1. Put a set volume and concentration of substrate solution in a test tube

  2. Put the test tube in a water bath set to 25 °C

  3. Add a set mass of yeast to the test tube and stir for 2 minutes

  4. Attach the test tube to a gas syringe and measure the volume of CO₂ produced in a set amount of time

  5. Divide the volume of CO₂ by the time taken to calculate the overall rate of respiration
• Anaerobic respiration


  Respiration that doesn't use oxygen
• Anaerobic respiration transfers much less energy per glucose molecule than aerobic respiration, just 2 molecules of ATP are produced
• Anaerobic respiration


  • Takes place in the cytoplasm of animal and plant cells (and some microorganisms) when there's very little or no oxygen
• Anaerobic respiration in


  • Human cells during vigorous exercise
  • Plant root cells in waterlogged soil
  • Bacterial cells under the skin
• Anaerobic respiration in animals and some bacteria

  1. Glucose is only partially broken down

  2. Lactic acid is formed as a waste product
• Anaerobic respiration in yeast and some microorganisms

  1. Glucose is broken down

  2. Ethanol and carbon dioxide are produced
• Fermentation


  Anaerobic respiration in yeast
• Differences between aerobic and anaerobic respiration

  • Conditions
  • Inputs
  • Outputs
  • ATP yield
• Aerobic respiration has a high ATP yield of 32 ATP per molecule of glucose
• Anaerobic respiration has a much lower ATP yield of 2 ATP per molecule of glucose
• Anaerobic respiration


  Respiration that doesn't use oxygen
• Anaerobic respiration transfers much less energy per glucose molecule than aerobic respiration - just 2 molecules of ATP are produced
• Anaerobic respiration


  • Takes place in the cytoplasm of animal and plant cells (and some microorganisms) when there's very little or no oxygen
  • Examples: Muscle cells during vigorous exercise, plant root cells in waterlogged soil, bacterial cells under the skin
• Anaerobic respiration in animals and some bacteria

  1. Glucose is only partially broken down

  2. Lactic acid is formed as a waste product
• What is the word equation for anaerobic respiration in animals

  Glucose to lactic acid plus energy
• What is the word equation for aerobic respiration

  Glucose plus oxygen to carbon dioxide and water and energy
• What is the word equation for anaerobic respiration of yeast

  Glucose to ethanol and carbon dioxide
• Cell Cycle


  Series of stages that allow cells to divide and produce new cells for growth and repair
• Mitosis


  • The stage of the cell cycle when the cell divides
• Cell Cycle


  1. chromosomes duplicates

  2. Chromosomes line up

  3. Chromosomes separate

  4. Nuclei form

  5. Cytoplasm and cell membrane divide
• Cells spend most of the cell cycle in interphase
• Interphase


  • DNA is spread out
  • Cell grows and increases subcellular structures
  • DNA is duplicated
• Mitosis produces two new daughter cells that are genetically identical to the parent cell
• Formula to calculate number of cells after multiple divisions

  Number of cells = 2^n, where n is the number of divisions
• After 4 hours (approximately 8 divisions) there will be 2^8 = 256 cells
• The rate of cell division depends on environmental conditions and some cells may die, so the final number may differ from the estimate