Photosynthesis and respiration

• • Some is kept for storage in the plant and re-used for photosynthesis
  • Equations:
  • Water + carbon dioxide → Glucose + oxygen
  • HO + 6CO → CHO + 6O
• Photosynthesis:

  • Endothermic reaction – Energy is taken from the surroundings (light from chloroplasts)
  • Reactants and products:
  • Water:
  • Enters the roots via osmosis
  • Travels the plants in the transpiration stream
  • Transported by the xylem cells
  • Carbon dioxide:
  • Enters the plant in the stomata via diffusion during gas exchange
  • Guard cells control the opening and closing of the stomata
  • Oxygen:
  • Leaves the plant in the stomata via diffusion
  • Glucose:
  • Travels the plant in the phloem (called translocation)
• Adaptations of the leaf:

  • Air spaces:
  • Allows the gases to move in and out
  • Thin:
  • Shorter diffusion pathway, allowing for quicker diffusion
  • Guard cells and waxy cuticles:
  • Allow only carbon dioxide and oxygen that enter and leave the leaf
  • Lots of chloroplasts:
  • Contain chlorophyll to absorb sunlight
  • Large surface area:
  • More sunlight can be absorbed
  • Xylem and phloem cells:
  • Bring water to the leaf and remove glucose
• Factors affecting the rate of photosynthesis:

  • Temperature, light intensity, chlorophyll concentration, light intensity, and carbon dioxide concentration
• Required practical:

  • Place a beaker with a test tube of water and a pond weed in it a metre ruler away from a lamp
  • Turn the lamp on and count the bubbles produced by the pond weed in one minute
  • Independent variable: Distance of beaker to the lamp
  • Dependent variable: Amount of oxygen bubbles
  • Control variable: Volume of sodium bicarbonate and pond weed
• Limitations and adaptations of the required practical:

  • We don’t know what gas the bubbles we count are. You could use a gas syringe to collect the volume of gas produced
• Plants and glucose:

  • Protein:
  • Glucose is mixed with nitrates to make amino acids which are then made into proteins (e.g. ribosomes, enzymes, nuts, and seeds)
  • Lipids:
  • Made up of glycerol and three fatty acids (we can extract oil from plants and seeds)
  • Cellulose:
  • Used for making cell walls especially in a rapidly growing plant – provides cells with structural support, allows plants to grow tall without support and acts as a pressure vessel preventing over-expansion from osmosis
  • Stored as starch:
• • So that food/nutrients are ready for when there is no photosynthesis happening (e.g. at night and in winter); examples of this are carrots and potatoes
• Aerobic respiration and exercise:

  • How plants and animals use energy:
  • Plants:
  • Need energy for active transport of minerals into the roots
  • Build larger molecules from smaller ones (e.g. amino acids into proteins)
  • Animals:
  • Build larger molecules from smaller ones (e.g. amino acids into proteins)
  • Muscle contraction/movement
  • Needed in the digestive system and other systems for active transport
  • Animals need energy to maintain body temperature so that enzymes work and don’t denature
• What happens to our bodies during exercise:

  • Increase in breathing rate
  • More CO removed from the body
  • More oxygen is transported to cells
  • Increase in heart rate
  • Transports more glucose so aerobic respiration can work
  • Increased blood flow so cells receive more oxygen which is important as cells are releasing more energy to move through aerobic respiration which needs oxygen
  • Sweat:
  • Cools the body down to maintain body temperature so enzymes do not denature
• Anaerobic respiration:

  • Incomplete breakdown of glucose
  • Less energy released than in aerobic respiration
  • Causes muscle cramps and fatigue
  • Creates an oxygen debt – when there is a lack of oxygen in the body as it is needed to breakdown lactic acid
  • Equations:
  • In the body: Glucose → Lactic acid (+energy)
  • In plants: Glucose → ethanol + carbon dioxide (+energy)
  • Oxygen debt: Lactic acid + oxygen → carbon dioxide + water
• Metabolism:

  • The sum of all the reactions in the cell or in the body
  • Metabolic reactions:
  • Photosynthesis
  • Respiration
  • The conversion of glucose to starch, glycogen, and cellulose
  • Formation of lipids from a molecule of glycerol and three fatty acids molecules
  • The use of glucose and nitrate ions to form amino acids that are then used to make proteins
• The liver:

  • Weighs 1.4kg and is the heaviest organ in the body
  • Filters the body’s blood
  • Stores iron, vitamins, and other essential chemicals
  • Processes the products of digestion
  • Controls the levels of fats, amino acids, and glucose in the blood
  • Breaks carbs down into sugars and stores the excess
  • Moderation helps keep the liver from shutting down