Topic 4: Bioenergetics

• Metabolism is the sum of all reactions that happen in cells or in the body
• This a diagram of a leaf

  A) cuticle

  B) Upper epidermis

  C) Chloroplast

  D) vacuole

  E) Spongy mesophyl

  F) Xylem

  G) Phloem

  H) vein

  I) Air chanel

  J) stoma

  K) guard cell

  L) lower epidermis

  M) cuticle

  
• carbon dioxide + water = glucose + oxygen
• The lower epidermis of a leaf contains stomata, which are small openings that allow for the exchange of gases and water vapor.
• The spongy mesophyll is a layer of loosely packed cells in the leaf that allows for gas exchange and photosynthesis.
• The upper epidermis of a leaf is a single layer of cells that protects the leaf and prevents water loss.
• Guard cells surround the opening of the stomata and regulate its size to control gas exchange.
• Stomata can be closed during dry conditions to prevent excessive loss of water from the plant.
• The upper epidermis of a leaf has a waxy coating called the cuticle to prevent water loss through transpiration.
• Xylem is a type of tissue found in plants that conducts water and minerals from the roots upwards towards the leaves.
• The xylem transports water and minerals from the roots to the rest of the plant.
• The phloem transports sugars produced during photosynthesis throughout the plant.
• Chloroplasts contain chlorophyll, which absorbs light energy needed for photosynthesis.
• uses of glucose?

  respiration

  cellulose for the strong cell wall

  produce amino acids for protein synthesis

  to produce fats
• Aerobic respiration equation?

  glucose + oxygen = carbon dioxide + water

  C6H12O6 + 6 O2 = 6 CO2 + 6H2O
• Anaerobic respiration equation?

  glucose = lactic acid
• As the oxidation of glucose is incomplete in anaerobic respiration much less energy is transferred than in aerobic respiration.
• why do organism need energy?

  • chemical reactions to build larger molecules

  • movement

  • keeping warm.
• when excising the body requires more energy as the heart rate and breathing rate is increasing to supply the muscles with more oxygenated blood.
• If not enough oxygen is supplied then anaerobic respiration takes place in muscles. The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.
• Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose
• what is oxygen debt?

  Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
• metabolism is the sum of all the chemical reactions occurring in the body or cell
• The energy transferred by respiration in cells is used by the organism for the continual enzyme controlled processes of metabolism that synthesise new molecules.
• metabolism includes?

  respiration

  the use of glucose and nitrate ions to form amino acids which are used to synthesise proteins

  forming lipids from a molecule of glycerol and three molecules of fatty acids

  converting glucose into starch , glucagon and cellulose

  breakdown of excess proteins to form urea for excretion
• what factors limit the rate of photosynthesis?

  light intensity

  carbon dioxide concentration

  temperature

  amount of chlorophyll
• what factor is limiting photosynthesis?

  carbon dioxide

  
• what factor is limiting photosynthesis here?

  light intensity

  
• what factor is limiting photosynthesis here?

  temperature

  
• Photosynthesis

  The process by which plants synthesise glucose using light energy from the Sun. Light energy is converted into chemical energy.
• Photosynthesis

  Carbon dioxide + water → glucose + oxygen
• Photosynthesis

  An endothermic reaction - energy is transferred from the environment to chloroplasts by light
• Showing that a plant gives off oxygen during photosynthesis

  Using a water plant (eg. Elodea), collect gas bubbles produced during photosynthesis. The gas will relight a glowing splint as it contains oxygen.
• Leaf adaptations that maximise the rate of photosynthesis

  • Broad leaves - maximise surface area
  • Thin leaves - short diffusion distance
  • Chlorophyll present - trap light energy
  • Veins - transport water to leaves via xylem, remove photosynthesis products via phloem
  • Air spaces - allow CO2 to enter and O2 to leave
  • Guard cells - control opening of stomata for gaseous exchange and prevent water loss
• Factors that affect the rate of photosynthesis

  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • Amount of chlorophyll
• Increasing temperature

  Increases the rate of photosynthesis as the kinetic energy of particles is increased. The rate decreases past a certain temperature as enzymes become denatured.
• Increasing light intensity

  Increases the rate of photosynthesis until another factor becomes limiting
• Increasing carbon dioxide concentration

  Increases the rate of photosynthesis (until another factor becomes limiting) as CO2 is required to make glucose
• Decreasing the amount of chlorophyll

  Decreases the rate of photosynthesis as chlorophyll is required to absorb light energy
• Limiting factor

  An environmental factor which can restrict the rate of photosynthesis eg. light intensity