B4

B4

1. Photosynthesis and Respiration

   • Photosynthesis - Process where plants make their own food
   • Respiration is the process by which all organisms release energy from food

2. Enzymes

   • Chemicals that speed up the rate of chemical reactions
   • Enzymes are proteins. They are long chains of amino acids
   • The chemicals that enzymes work on are called substrates
   • Active site - special shape to fit certain substrates - Like key and lock
   • After enzymes react their substrates product molecules are released
   • Enzymes need a specific pH and temperature to work at their optimum
   • They stop working if the pH is inappropriate or the temperature is too high
   • 37 degrees is the most common optimum for mammals enzymes
   • As the temperature increases, enzyme activity increases as temperature increases rate of reaction
   • High temperatures or unsuitable pH can denature an enzyme / change the shape of its active site

3. Glucose

   • Photosynthesis happens in plant cells and in some microorganisms such as phytoplankton
   • Sunlight is absorbed by the green chlorophyll which are found in chloroplasts
   • Uses
     • Converted to chemicals needed for the plants growth
     • Converted into starch for storage
     • Used in respiration
   • 6 CO2 + 6 H2O --> C6H12O6 + 6 O2

4. Cells

   • Surrounded by cell membrane, which controls what enters and leaves the cell
   • Animals
     • Nucleus - cytoplasm - cell membrane - mitochondria
   • Plants
     • Nucleus - cytoplasm - cell membrane - mitochondria - cell wall
   • Microorganisms
     • Cytoplasm - Cell membrane - Cell wall
     • Bacteria cells have no nucleus
     • Yeast have mitochondria - bacteria dont

5. Transport of chemicals

   • Diffusion
     • Movement of chemicals from high to low concentrations
     • In photosynthesis
       • Water is taken up by plant roots by diffusion
       • CO2 diffuses through plant leaves
       • Oxygen leaves plants by diffusion
     • Its passive - doesnt require any energy as it happens by random molecule movement
   • Osmosis
     • Special kind of diffusion involving water
     • Happens when chemicals are separated by a semi-permeable membrane
     • Overall movement of water from an area of high concentration to low concentration
     • Movement of water into roots
   • Active transport
     • Nitrates are normally in higher concentrations in plants so they can't use diffusion
     • Active transport uses energy from respiration to transport chemicals across a cell membrane

6. Factors with photosynthesis

   • Can be limited by CO2, light intensity and temperature
   • If light intensity or CO2 levels are increased the rate of photosynthesis increases and then levels off
   • At the point the graph levels out something is limiting it, this is called the limiting factor
   • As temperature increases the rate increases up to a certain point and then decreases due to denaturing of enzymes

7. Investigation

   • Use an identification key / survey to identify plants - measure how common they are - use a light meter to measure intensity
   • Ecologists investigate the abundance and distribution of plants - at different locations and in different areas
   • A quadrat (wooden frame) is used to sample an area
     • It is thrown randomly - a number of times so that an average is taken
   • If there is an obvious change in the plants in the area use the quadrat in a line called a transect
   • Trees and stuff provide shade and can often affect the growth of plants
   • May be a correlation between the distance from a tree or something and the growth of nearby plants at high or low densities

8. Respiration

   • Aerobic
     • glucose + oxygen --> carbon dioxide + water (energy released)
     • C6H12O6 + 6 O2 -> 6 CO2 + 6 H20
     • Only done when organism has enough oxygen
     • It is done by a series of enzyme reactions
   • Occurs in every cell in the body
   • Anaerobic
     • When oxygen is low
     • glucose -> lactic acid (energy)
     • C6H12O6 --> 2 C3H6O3
     • Done in animal muscle cells during vigorous exercise - plant roots in waterlogged soil - bacteria in deep puncture wounds
   • Fermentation
     • Type of anaerobic respiration used by some microorganisms
     • Yeast and some plants do this
     • glucose --> ethanol + CO2 (energy)
     • Ethanol is alcohol so it is useful for us
     • Bubbles of CO2 make bread rise and alcoholic drinks sparkle
     • In bread alcohol is evaporated as it is cooked

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