Biology paper 1 Organisation

• Factors affecting photosynthesis


  • Light intensity
  • Temperature
  • Concentration of carbon dioxide in the air
  • Amount of chlorophyll in plants
• Chlorophyll


  Pigment within chloroplasts that absorbs the light energy needed for photosynthesis
• Plants have less chlorophyll


  They won't be able to carry out as much photosynthesis
• Different plants naturally have different amounts of chlorophyll
• The level of chlorophyll within an individual plant can vary due to disease, environmental stress, or lack of nutrients
• Factors that are normally referred to as limiting factors for photosynthesis are light, carbon dioxide, and temperature
• Graphing the effects of limiting factors on photosynthesis

  1. Plot light intensity on x-axis and rate of photosynthesis on y-axis

  2. As light intensity increases, rate of photosynthesis increases until it plateaus

  3. When photosynthesis plateaus, another factor becomes limiting (carbon dioxide or temperature)

  4. Plot carbon dioxide concentration on x-axis and rate of photosynthesis on y-axis

  5. As carbon dioxide increases, rate of photosynthesis increases until it plateaus

  6. When photosynthesis plateaus, another factor becomes limiting

  7. Plot temperature on x-axis and rate of photosynthesis on y-axis

  8. As temperature increases, rate of photosynthesis increases until enzymes begin to denature, then rate decreases
• Graphs can show the effects of multiple limiting factors by plotting different conditions on the same graph
• Strategies farmers use to optimize photosynthesis

  • Use greenhouses to trap heat and provide artificial light
  • Pump carbon dioxide into greenhouses
  • Use paraffin heaters to provide heat and carbon dioxide
  • Use fertilizers to ensure plants have essential minerals
  • Use pesticides to control pests and pathogens
• Optimizing photosynthesis conditions can be costly for farmers, so they have to weigh the extra cost against the expected yield increase
• Plateau


  A stage in the graph where the rate of photosynthesis remains constant despite changes in a limiting factor
• Carbon dioxide (CO2)


  A limiting factor for photosynthesis that can cause a plateau when its concentration is too low
• what is the equation for the midpoint of a line?


  X1 +X2
• Carrying out chemical tests for carbohydrates, proteins and lipids

  1. Grind food sample with distilled water using mortar and pestle to make a paste

  2. Transfer paste to beaker and add more distilled water

  3. Stir to dissolve chemicals

  4. Filter solution to remove suspended food particles
• Carbohydrates


  Include starch and sugars such as glucose
• Test for starch


  1. Place 2cm3 of food solution in test tube

  2. Add a few drops of iodine solution

  3. Blue-black colour indicates presence of starch

  4. Orange colour indicates no starch
• Test for sugars (e.g. glucose)

  1. Place 2cm3 of food solution in test tube

  2. Add 10 drops of Benedict's solution

  3. Heat test tube in hot water bath for 5 minutes

  4. Green colour = small amount of sugar

  5. Yellow colour = more sugar

  6. Brick red colour = a lot of sugar
• Reducing sugars


  • Sugars that the Benedict's test works for (e.g. glucose)
  • Non-reducing sugars (e.g. sucrose) do not work with Benedict's test
• Test for proteins


  1. Place 2cm3 of food solution in test tube

  2. Add 2cm3 of Biuret solution

  3. Purple/lilac colour indicates presence of protein
• Test for lipids/fats


  1. Grind food with distilled water using mortar and pestle (do not filter)

  2. Transfer 2cm3 of solution to test tube

  3. Add a few drops of distilled water and ethanol

  4. Shake gently

  5. White cloudy emulsion indicates presence of lipids
• Ethanol is highly flammable, so no naked flames should be present
• The further away the source of light from the pondweed, the smaller the volume of oxygen produced.View quiz results
• The process of turning carbon dioxide and water into oxygen and glucose is called photosynthesis.

  Photosynthesis is an endothermic reaction.
• carbon dioxide + water =light= glucose + oxygen
• 6CO2 + 6H2O → C6H12O6 + 6O2. = photosynthesis equation
• Plants use glucose from photosynthesis when they respire.

  Plants also use glucose to make cellulose, which makes cell walls strong.

  Plants can also store the glucose for later by converting it into starch.

  This starch is insoluble in water (it doesn't dissolve).

  Plants can also store glucose by using it to make oil or fat.
• Plants also use glucose with nitrate ions absorbed from the soil to produce amino acids.
• amino acids are then used to make proteins.
• dark night = That condition is called the limiting factor.

  At night, light is the limiting factor for photosynthesis.
• Greenhouses allow farmers to control the limiting factors of photosynthesis.
• When you move a lamp away from a plant, the light is spread over a wider area.

  In other words, when the distance to the light source increases, the light intensity decreases.

  This means there is an inverse relationship between distance and light.
• if the distance is doubled, the amount of light that reaches the plant is quartered.
• If the plant is aquatic (underwater), the oxygen floats to the surface in bubbles.

  That makes it easy to measure the amount of oxygen being produced.
• n order to see if photosynthesis has occurred in a green plant, a leaf can be removed from the plant and tested for the presence of starch.Next question
• In plants, nitrogen is absorbed in the form of nitrate ions
• "when you double the distance between a plant and its light source, the light intensity reduces by a quarter".
• Arteries


  Carry very high pressure blood from the heart to the organs in the body
• Arteries


  • Have very thick muscular walls to withstand the very high pressure of the blood
  • Contain elastic fibers that stretch when the surge of blood passes through and then recoil in between the surges to keep the blood moving
• Capillaries


  Where substances such as glucose and oxygen diffuse from the blood to the cells, and carbon dioxide diffuses from the cells back to the blood
• Capillaries


  • Have very thin walls so the diffusion pathway is very short, allowing substances to diffuse rapidly between the blood and the body cells