Bioenergetics

• What are the uses of glucose in photosynthesis?

  • used for respiration
  • converted into insoluble starch for storage
  • To produce fat or oil for storage
  • Produce cellulose, which strengthens the cell wall
  • To produce amino acids for protein synthesis.
• How do plants produce proteins?

  Plants use nitrate ions that are absorbed from the soil.
• What is the formula for aerobic respiration?

  glucose + oxygen -> carbon dioxide + water + energy

  C₆H₁₂O₆ + 6O2 -> 6CO2 + 6H₂O + ATP
• What is the formula for anaerobic respiration in the muscles?

  glucose -> lactic acid
• What is the formula for anaerobic respiration in yeast cells?

  glucose -> carbon dioxide + ethanol
• Anaerobic respiration produces less energy because the oxidation of glucose is incomplete.
• How is fermentation used?

  Beer: Ethanol produced by fermentation

  Bread: Carbon dioxide creates bubbles, causing bread to rise
• The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood.
• What changes happen to the body during exercise?

  Aerobic respiration increases because body requires more oxygen so muscles can contract.

  Breathing rate and breath volume increases to get more oxygen into the blood. Heart rate also increases to pump said blood around faster and to remove carbon dioxide.
• What happens during anaerobic respiration?

  Body cannot supply oxygen to muscles fast enough so they begin respiring anaerobically. This causes lactic acid build up which is painful. Long periods of exercise can cause muscle fatigue where muscles get tired and stop contracting efficiently.
• What is oxygen debt?

  Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
• Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose. Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
• Metabolism is the sum of all the reactions in a cell or the body.
• What are examples of metabolic reactions?

  • Converting starch to glucose, glycogen and cellulose
  • Respiration
  • Using glucose and nitrate ions to form amino acids which are used to synthesise proteins
  • Breakdown of proteins to form urea for excretion
  • Turning lipids to fatty acids and glycerol
• What are metabolic reactions in plants?

  Glucose -> cellulose: strengthen plant cell wall
• What type of energy does a plant use during photosynthesis?

  Light energy
• The flagellum helps the cell to move through water. Scientists think that the flagellum and the light-sensitive spot work together to increase photosynthesis. Suggest how this might happen.

  The light sensitive spot detects the light and tells the flagellum to move towards the light. A higher light intensity means more photosynthesis.
• Explain why single-celled organisms, like algae, do not need complex structures for gas exchange.

  The cells have a larger volume: surface area ratio so there is a shorter diffusion distance. Diffusion through the cell is sufficient. A smaller organism has a larger volume:SA ratio, meaning diffusion is efficient.
• Air in the atmosphere contains less oxygen than exhaled air.
• Exercise cannot be sustained when anaerobic respiration takes place in muscle cells. Explain why.

  The muscles stop contracting and muscles become fatigued because not enough energy is transferred.
• Explain how oxygen passes from the blood to the mitochondria.

  Diffusion from an area of high concentration to low concentration through the cell membrane.
• Explain how the ribosomes and mitochondria help the cell to make enzymes.

  Ribosomes make proteins using amino acids and the mitochondria provide energy for this process.
• Explain why it is helpful that more oxygen is carried to the muscles during exercise.

  Allows more respiration to prevent build up of lactic acid to release/produce energy.
• What changes happen to breathing during exercise?

  • Increased breathing rate
  • Increased depth of breathing / heavier breathing
• Why can the fermentation reaction stop?

  The glucose can run out.
• How is a leaf adapted to photosynthesis?

  • Flat surface
  • Large surface area
  • Thin walls
  • Lots of chloroplasts
• When running, muscle activity increases. To do this, muscle cells respire at a faster rate to give more energy. The muscles need to be supplied with glucose and oxygen faster. The heart beats faster to increase the flow of blood which carries the products carbon dioxide and heat away from the muscles.
• How do the materials for photosynthesis get into the plant?

  Water: Osmosis through the root hair cell

  Carbon dioxide: Diffusion through leaf and stomata
• How do arteries supplying the leg muscles alter the rate of blood flow through them during exercise?

  The arteries dilate
• How does an increase in heart rate help during excercise?

  • Supplies more oxygen so muscles respire faster
  • Prevents aerobic respiration which leads to build up of lactic acid
  • Removes carbon dioxide
• The air breathed in contains more oxygen than the air breathed out.

  The air breathed out contains more carbon dioxide than the air breathed in.
• Respiration has to take place faster during exercise because more energy is required because the muscles are working faster.
• How could limiting factors be useful to a farmer?

  They can change optimum levels to get a larger economic yield
• Why is light needed for photosynthesis?

  To transfer energy
• Explain why anaerobic respiration can only sustain exercise for a short time. 


  The muscles become fatigued and stop contracted because not enough energy is released.