2nd year science

• Biochemical processes


  Chemical reactions that happen in the cells of living things
• Two important biochemical processes


  • Respiration
  • Photosynthesis
• Metabolism


  The sum of all the chemical reactions in an organism
• Catabolic reactions


  Release energy and break large molecules down into smaller molecules
• Anabolic reactions


  Require energy and build large molecules from smaller ones
• Activities that need energy


  • Running
  • Walking
  • Sleeping
  • Talking
  • Thinking
• Where the body gets energy from


  The food that we consume. Food is digested, then it is transported to cells in the bloodstream where it is respired to release energy.
• Respiration


  The release of energy from food
• Mitochondria


  Tiny organelles in the cytoplasm of a cell where respiration takes place
• Aerobic respiration


  Respiration that takes place in the presence of oxygen
• Requirements for aerobic respiration


  • Glucose, a sugar that stores chemical energy
  • Oxygen, to release the energy stored in glucose
• Anaerobic respiration


  Respiration that can happen if cells do not get enough oxygen
• If a person consumes more energy than they need

  The excess energy will be stored in the body as fat
• Anaerobic respiration in yeast cells


  Produces alcohol, carbon dioxide and some energy
• Factors that affect respiration


  • Availability of glucose and oxygen
  • Temperature
  • Water
  • pH
• Enzymes


  Proteins produced inside cells that control the rate of chemical reactions
• Enzyme properties


  • Act on substrate molecules to form products leaving unchanged enzymes behind
  • Work faster as temperature increases but become damaged at very high temperatures
  • Optimum temperature for human cell enzymes is 37°C
  • Optimum temperature range for yeast enzymes is 32-35°C
  • Plant enzymes work within 10-30°C
• Enzymes are sometimes called 'biological catalysts'
• Importance of drinking water during exercise


  • Water is an important component of cells and allows chemical reactions to occur
  • Water contains salts important for muscle contraction and nerve impulse transmission
  • Water helps remove toxic waste substances from cells
• Photosynthesis


  Plants absorb energy directly from the Sun to make their food
• Chloroplasts


  Small organelles in the cytoplasm of plant cells where the reactions of photosynthesis take place
• Chlorophyll


  A green pigment in the chloroplast which absorbs the light energy and uses it to power chemical reactions
• Requirements for photosynthesis


  • Carbon dioxide
  • Water
  • Sunlight
  • Chlorophyll
• Oxygen is a waste product of photosynthesis and is released from leaves through the stomata
• Organisms use oxygen


  For aerobic respiration
• Factors affecting photosynthesis


  • Light intensity
• Leaves are adapted to absorb as much light as possible for photosynthesis through a large surface area, thin cross section, and presence of stomata
• The processes of respiration and photosynthesis


  Are almost the reverse of one another
• Respiration and photosynthesis as chemical processes


  A series of steps are involved, reactants are used, products are made and energy is transformed from one form to another
• Respiration and photosynthesis as biological processes


  Reactions take place in cells and enzymes play a role in controlling the rate of both processes
• Key terms


  • Biochemical processes
  • Respiration
  • Mitochondria
  • Aerobic respiration
  • Anaerobic respiration
  • Photosynthesis
  • Chloroplasts
  • Chlorophyll
• Cardiac muscles make up the walls of the heart and contract involuntarily to pump blood.