bioenergetics

• What type of reaction is photosynthesis?

  Endothermic - energy is transferred from the environment to the chloroplasts by light
• What are 5 ways plants use glucose?

  - for respiration

  - making cellulose (to make strong plant cell walls)

  - making amino acids (glucose is combined with nitrate ions to make amino acids, which are then made into proteins

  - stored as oils or fats (turned into lipids for storing in seeds)

  - stored as starch (starch is insoluble so better for storing than glucose)
• What are the 4 limiting factors for photosynthesis?

  - light intensity

  - concentration of carbon dioxide

  - temperature

  - chlorophyll
• What does a limiting factor mean?

  Stopping photosynthesis from happening any faster
• What conditions may limit a factor?

  - at night it will be light intensity

  - in winter its often temperature

  - if its warm and bright enough the amount of CO2 is usually limiting
• What factors may limit a plant to not having enough chlorophyll?

  - disease eg tobacco mosaic virus and rose black spot)

  - lack of nutrients eg magnesium defiency

  - variegated leaves
• What affect does light intensity and CO2 have on the rate of photosynthesis?

  - the rate will increase but only up to a certain point

  - after that another factor is limiting
• What affect does temperature have on the rate of photosynthesis?

  - increases up to the optimum temperature that the enzymes work at

  - but if the plant gets too hot, the enzymes needed for photosynthesis will become denatured (active site changes shape and the substrate no longer fits)
• How do you do the photosynthesis practical?

  1. put some sodium hydrogen carbonate solution (control carbon dioxide) in a test tube

  2. add the pond weed to the test tube

  3. clamp it with a bung connected to a gas syringe

  4. place a light source at a set distance away from the pond weed

  5. the pond weed is then left to photosynthesise for a set amount of time

  6. measure the amount of oxygen produced and collected in the gas syringe. This is equal to the volume of oxygen produced

  7. repeat experiment twice with the same distance and calculate a mean of oxygen produced

  8. repeat whole experiment with differing distances the lamp is away

  Controls- temperature (heat shield) and Led light, time its left, concentration of sodium hydrogen carbonate
• What relationship do distance and light intensity have?

  inversely proportional - as one increases, the other decreases
• What is the inverse square law?

  Light intensity = 1 ÷ (d)^2
• What does the inverse square law mean?

  If you halve the distance, the light intensity will be 4 times bigger and if you third the distance the light intensity will be 9 times greater
• How can farmers use their knowledge of limiting factors to increase their profits?

  - using a greenhouse - help trap the suns heat and make sure temp doesn't become limiting

  - In winter a farmer may also use a heater to keep the temperature at an ideal level. In summer they may use shades and ventilation to ensure the enzymes don't denature

  - artificial light to ensure the plant's can still photosynthesise when the sun goes down

  - paraffin heater controls temp and carbon dioxide to ensure they don't become a limiting factor

  - keeping the plants enclosed also makes it easier to keep them free of pests and diseases. the farmer can add fertilisers to the soil to provide all the minerals needed for healthy growth
• What is respiration?

  The process of transferring energy from the breakdown of glucose which goes on in every cell continuously
• What type of reaction is respiration?

  exothermic - transfers energy to the surroundings
• What are 3 ways in which organisms use energy from respiration?

  - build up larger molecules from smaller ones (like proteins from amino acids

  - in animals its used to allow the muscles to contract

  - keep their body temp steady
• What is metabolism?

  sum of all chemical reactions in an organism
• What are examples of larger molecules being made from smaller ones?

  - lots of small glucose molecules join together to form starch, glycogen and cellulose

  - lipid molecules are made from one molecule of glycerol and 3 fatty acids

  - glucose is combined with nitrate ions to make amino acids, which are then made into proteins
• What are examples of larger molecules being broken down into smaller ones?

  - glucose is broken down in respiration. respiration transfers energy to power all the reactions in the body that make molecules

  - excess protein is broken down in a reaction to produce urea. Urea is then excreted in urine
• What is aerobic respiration?

  -respiration with oxygen

  -the most efficient way to transfer energy from glucose

  -occurs all the time in plants and animals

  -most happen in the mitochondria
• What is anaerobic respiration?

  - occurs when you do vigorous exercise and your body cant supply enough oxygen to your muscles

  - occurs in a lack of oxygen and is the incomplete breakdown of glucose, making lactic acid

  - does not transfer nearly as much energy as aerobic respiration - because glucose isn't fully oxidised
• What is anaerobic respiration in plants and yeast?

  - Glucose -> ethanol + carbon dioxide

  - anaerobic respiration in yeast cells is called fermentation

  - in the food industry fermentation is of great value because its used to make bread and alcoholic drinks

  - the carbon dioxide helps make bread rise

  - ethanol used to produce alcohol
• Why do you need energy when exercising?

  - muscles need energy from respiration to contract

  - when exercising you muscles contract more frequently than normal so you need more energy

  - this energy comes from increased respiration

  - this increase in your cells means you need to get more oxygen into them
• What does your body do to help when exercising?

  - your breathing rate and breath volume increase to get more oxygen into the blood

  - your heart rate increases to get this oxygenated blood around the body faster. This removes carbon dioxide more quickly at the same time
• What happens when you do really vigorous exercise?

  -your body can't supply oxygen to your muscles quickly enough, so they start respiring anaerobically

  -this is not the best way to transfer energy from glucose because lactic acid builds up in the muscles, which gets painful

  -long periods of exercise also cause muscle fatigue - the muscles get tired and then stop contracting efficiently
• What is another way your body deals with lactic acid?

  the blood that enters your muscles transports the lactic acid to the liver, where the lactic acid is converted back into glucose
• What is oxygen debt?

  -the amount of oxygen needed react with the build up of lactic acid and remove it from the cells. Lactic acid is oxidised to form carbon dioxide and water

  - you have to 'repay' the oxygen that you didn't get to your muscles in time, because your heart, lungs and blood couldn't keep up with the demand earlier on
• What happens to your pulse and breathing rate after exercise?

  remains high whilst there are still high levels of lactic acid and carbon dioxide
• How can you investigate the effect of exercise on the body?

  1. you can measure the breathing rate by counting breaths and heart rate by taking the pulse

  2. then take your pulse after

  - sitting down for 5 minutes

  - then after 5 mins of gentle walking

  - then again after 5 mins of slow jogging

  - then after 5 mins of running

  3. and plot your results on a graph

  your pulse rate will increase the more intense the exercise is as your body needs to get more oxygen to the muscles and take more carbon dioxide away from your muscles