BIOENERGETICS

Photosynthesis

• Occurs in plants in the chloroplasts in the leaves

  • The leaves contain chloroplasts with lots of chlorophyll (green pigment) that absorbs sunlight - needed for photosynthesis

• Carbon dioxide + water $\rightarrow$ glucose + oxygen (using sunlight)

  • 6CO₂ + 6H₂O $\rightarrow$ C₆H₁₂O₆ + 6O₂

  • Is an endothermic reaction

• Carbon dioxide diffuses through the leaf through the stomata, and water is transported up the stem from the roots by the xylem

Uses of glucose

• Glucose from photosynthesis is used for:

  • Cellular respiration - breaks apart glucose to release energy

  • Makes cellulose - strengthens walls

  • Makes starch - long term storage of glucose

  • Makes oils and fats - future energy sources

Rate of photosynthesis

• The rate of photosynthesis depends on light intensity, temperature, carbon dioxide concentration and chlorophyll levels

• Chlorophyll levels - Is found in chloroplasts

  • If there is less chlorophyll, less photosynthesis will be able to carry out

  • Can decrease due to diseases, like tobacco mosaic virus, environmental stress and a lack of nutrients

• Light intensity - The higher the light intensity, the higher the rate of photosynthesis

  • It will reach a point where it levels out, as either CO₂ or temperature becomes a limiting factor instead

• Carbon dioxide concentration - When CO₂ is in excess, the rate of photosynthesis increases as it is a reactant

• When it is plentiful and easily available, carbon dioxide stops becoming a limiting factor and instead light or temperature becomes limiting

• Temperature - As temperature increases, so does the rate of photosynthesis as the particles have more energy so can therefore move and work faster - molecules work faster

  • As the temperature increases, the rate will start to drop as the enzymes begin to die and become denatured - limiting factor

  • At 45°, the enzymes will be fully denatured and the rate of photosynthesis will be 0.

• Artificially created conditions can be created for increased rate of photosynthesis

  • In colder climates - crops in greenhouses to trap sun’s heat

  • Artificial light for photosynthesis at night

  • Pump for CO₂

  • Paraffin heater for CO₂ and heat

  • Enclosed greenhouses to prevent bugs

  • Fertiliser for essential minerals

  • Pesticides to kill unwanted bugs

Aerobic and anaerobic respiration

• Respiration is the process of transferring energy from glucose and it continuously occurs in living cells   

  • Cellular respiration is exothermic (photosynthesis is endo)

• Organisms use energy for:

  • To build larger molecules from smaller ones - amino acids to proteins

  • For muscle contraction

  • Maintaining body temperature

• Aerobic respiration takes place when there is enough oxygen as is the most efficient in animals and plants

  • It takes place in the mitochondria

  • Glucose + oxygen $\rightarrow$ carbon dioxide + water

    • C₆H₁₂O₆ + 6O₂ $\rightarrow$ 6CO₂ + 6H₂O

• Anaerobic respiration takes place when there is no oxygen (or limited) and only occurs when necessary

  • It doesn’t fully break down glucose

  • Lactic acid is toxic and has to be removed

  • Glucose $\rightarrow$ lactic acid

• In plants and yeast, anaerobic respiration is called fermentation and is used in bread/alcohol…

  • Glucose $\rightarrow$ ethanol + yeast

Response to exercise

• During exercise, our muscles move more, and contract more so need more energy

  • Therefore need more oxygen and GLUCOSE

  • Our rate of breathing and volume of breath increases

  • Our heart rate increases - both also need more energy

• If there is not enough oxygen present, we anaerobically respire

  • Is used only in intense exercise

  • Produces lactic acid, which builds up in tissues

    • Creates a burning sensation

    • Is remove by reacting with oxygen - creates oxygen debt

  • Lactic acid is transported to the liver via the blood stream, where it reacts with oxygen to produce either

    • Glucose (often stored as glycogen after)

    • OR carbon dioxide + water

• Investigating effects of exercise

  • Heart rate - count pulse for 60 seconds before, directly after and a while after exercise

  • Breathing rate - count the number of breathes per minute

Metabolism

• Metabolism is all the chemical reactions in an organism’s body

  • Changes between person

DONE!!!