Bioenergetics

• What is photosynthesis?

  An endothermic reaction where light energy is tranferred by chloroplasts to produce glucose.
• What is the word equation for photosynthesis?

  carbon dioxide + water -->glucose + oxygen
• What is the symbol equation for photosynthesis?

  CO2 + H2O --> C6H12O6 + O2
• Where in a plant does photosynthesis take place?

  Inside chloroplasts in plant cells.
• Do all plant cells have chloroplasts?

  No, only the ones that receive light.
• Which plant cells have the most chloroplasts?

  The cells that receive the most light. The palisade mesophyll cells in leaves.
• What factors affect the rate of photosynthesis?

  Light intensity, carbon dioxide concentration, temperature and also the amount of chlorophyll.
• Why does temperature affect photosynthesis?

  Photosynthesis is a process that uses enzymes. If the enzymes get warmer, photosynthesis happens at a faster rate, but if the enzymes get too hot, they will denature and photosynthesis will stop.
• What other organisms photosynthesise?

  Algae (pondweed and seaweed), as well as some bacteria. If there is a chloroplast, it will absorb light energy and photosynthesise.
• What is the inverse square law?

  The light energy reaching a certain point is equal to the inverse square of the distance to that point. We can turn distance into light intensity by using 1/d2 (d squared)
• Why does anyone care about rate of photosynthesis?

  Anyone producing food crops will want to maximise profit. Adding lighting, carbon dioxide or heat into a greenhouse/glasshouse will give faster growth but may cost more, so may not be worth doing.
• What is the glucose produced in photosynthesis used for?

  Respiration by all living cells. Also some is converted into starch, fats/oils, cellulose and amino acids.
• Why do plants store glucose as starch?

  Starch is insoluble, so doesn't affect osmosis. Also it is more compact, so easier to store large amounts. The starch is used by cells as a source of glucose for respiration when it is dark.
• Why do plants convert some glucose to oils?

  Seeds have oils stored in them as the energy supply for the new plant to start to grow (germinate).
• Why do plants convert some glucose to cellulose?

  Cell walls are made of cellulose. It is strong and helps to support the plant. All plant cells have cell walls.
• Why do plants convert some glucose to amino acids?

  Amino acids are the building blocks of protein (for growth and repair). Plants need amino acids for protein synthesis. (Plants are responsible for producing many of the amino acids that we rely on too)
• What else do plants need to turn glucose into amino acids?

  Glucose just contains the elements C, H, O. Amino acids contain CHON. Plants need to get nitrate ions from the soil to make amino acids.
• What is respiration?


  An exothermic reaction where energy is released from glucose molecules. It happens continuously in all living cells.
• Why do living cells need to respire?


  Living cells need an energy supply for all the process they carry out (eg, chemical reactions, keeping warm and movement). Without this energy supply, cells would die.
• What are the two types of respiration?

  Aerobic (with oxygen) and anaerobic (without oxygen)
• Is all anaerobic respiration the same?

  No, it is different in animal, plant and yeast cells.
• What's the anaerobic respiration equation in plants/yeast?

  glucose --> ethanol + carbon dioxide
• Why is anaerobic respiration sometimes called fermentation?

  Fermentation is just anaerobic respiration in plants and yeast, and it is economically important as it is how we produce bread and alcoholic drinks.
• What happens to respiration when we exercise?

  Respiration rate increases as our cells require more energy.
• What happens to heart rate when respiration increases?

  Heart rate increases so that blood circulates faster. This helps supply more oxygen and glucose to muscle cells (and removes lactic acid more quickly too).
• What happens to breathing rate when respiration increases?

  Breathing rate increases so that more oxygen enters the blood. This also helps supply more oxygenated blood to muscle cells (and removes carbon dioxide more quickly too).
• What happens to breath volume when respiration increases?

  Each breath volume is bigger as we breathe more deeply during exercise. This also helps supply more oxygenated blood to muscle cells.
• What if not enough oxygen gets to muscle cells?

  Anaerobic respiration will start to take place (as well as aerobic, with whatever oxygen is delivered to muscle cells). Lactic acid levels will start to build up, creating an oxygen debt.
• What is the problem with lactic acid build up?

  Muscle cells become fatigued if there is too much lactic acid produced. They stop contracting efficiently.
• What happens to the lactic acid?

  Blood flowing through the muscles transports lactic acid to the liver where it is converted back into glucose. Oxygen debt is the amount of oxygen needed to react with the lactic acid and remove it.
• What is metabolism?

  The sum of all the reactions in a cell or a body.
• What is the energy transferred from respiration used for?

  Building up new molecules using enzymes inside cells.
• Does metabolism include carbohydrate production?

  Yes. Converting glucose to starch, cellulose and glycogen.
• Does metabolism include lipid production?

  Yes. Joining 3 fatty acids and 1 glycerol to make a lipid molecule (a fat or an oil).
• Does metabolism include protein production?

  Yes. Using glucose and nitrate ions to form amino acids, and then joining them to synthesise proteins.
• What else does metabolism include?

  Respiration itself is a metabolic process. Also excess proteins are broken down in the liver to form urea which is excreted.
• What is the word equation for anaerobic respiration?

  glucose --> lactic acid

  (plus energy is transferred...not as much as in aerobic respiration as it is not as efficient due to the oxidation of glucose being incomplete)
• What is the word equation for aerobic respiration?

  glucose + oxygen --> carbon dioxide + water

  (plus energy is transferred, but it is not a chemical so can't go in a chemical equation)