b4

• what is photosynthesis

  the process which plants synthesise glucose using light energy from the sun. Light energy is converted into chemical energy
• where does photosynthesis take place

  Within chloroplasts in leaf palisade cells. They contain chlorophyll, a pigment which absorbs light energy
• is photosynthesis endothermic or endothermic? why?

  endothermic because energy is transferred from the environment to chloroplasts by light
• 4 main factors which affect the rate of photosynthesis

  Temp

  light intensity

  carbon dioxide concentration

  amount of chlorophyll
• leaf adaptations which maximise rate of photosynthesis

  broad leaves to maximise surface area

  Thin leaves for short diffusion distance

  Air spaces to allow carbon dioxide to enter and oxygen to leave

  Guard cells control opening of stomata for gas exchange and prevent water loss
• how does temp affect rate of photosynthesis

  Increased temperature increases rate if photosynthesis as kinetic energy from particles increases. Rate decreases past a certain temperature as enzymes denature.
• how can farmers use their knowledge of limiting factors to increase their profits

  They control temperature, light intensity and carbon dioxide concentration to achieve fastest possible rate of photosynthesis, leading to a greater yield
• state 5 uses of glucose produced during photosynthesis

  Respiration

  Starch for storage

  Cellulose for strength

  Amino acids and protein synthesis

  Lipids for energy storage in seeds
• what is aerobic respiration

  An exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells
• where does aerobic respiration take place

  mitochondria
• why do organism require energy released by respiration

  synthesis of larger molecules

  muscle contraction

  maintenance of body temperature

  active transport
• what is anaerobic respiration

  An exothermic reaction which glucose is broken down to release energy in the absence of oxygen
• why can anaerobic respiration lead to muscle fatigue

  lactic acid builds up in muscles, preventing efficient contraction
• what is an oxygen debt

  amount of oxygen needed to convert lactic acid back into glucose after anaerobic respiration
• what is fermentation

  A type of anaerobic respiration that occurs in yeast cells
• why is fermentation reaction important

  used in the production of bread and alcohol drinks
• how do muscles store glucose

  as glycogen
• what changes take place when muscular activity increases in the body

  heart rate increases and arteries dilate which increases the flow of oxygenated blood to muscles

  Breathing rate increases which increases rate of gas exchange

  Stored glycogen is converted back to glucose
• how is lactic acid transported away from muscles

  Blood flow through the muscles transports lactic acid to the liver where it’s oxidised back to glucose
• what is metabolism

  The sum of all the reactions that take place in a cell or organism
• How do cells use energy transferred by respiration

  To continuously carry out enzyme controlled processes which lead to the synthesis of new molecules
• Examples of metabolic reactions

  Photosynthesis

  Respiration

  Breakdown of excess protein into urea

  Glycerol and fatty acids into lipids

  Glucose into starch, glycogen, cellulose