Bioenergetics

What type of reaction is photosynthesis?

An endothermic reaction in which energy is transferred from the environment to the chlorophyll in chloroplasts by light.

What is the word equation for photosynthesis?

carbon dioxide + water → glucose + oxygen

What is the symbol equation of photosynthesis?

6CO2+6H2O → C6H12O6+O2

What is the glucose produced in photosynthesis for?

• used for respiration to transfer energy

• converted into insoluble starch for storage

• used to produce fat or oil for storage

• used to produce cellulose, which strengthens the cell wall

• used to produce amino acids for protein synthesis.

How do plants produce protein?

• plants also use nitrate ions that are absorbed from the soil

What are the limiting factors of photosynthesis?

• concentration of CO2

• Temperature

• Amount of chlorophyll

• Light intensity

How does increasing temperature increase rate of photosynthesis?

Enzyme has more kinetic energy therefore reactions happen faster

Why does rate of photosynthesis remain constant when light intensity keeps increasing?

• light intensity is no longer a limiting factor

• Something else is the limiting factor

How to measure the rate of photosynthesis?

• Fill the pondweed with sodium bicarbonate (NaHCO3) solution and calculate the number of oxygen bubbles it creates in a min

What is the inverse square law in photosynthesis?

• light intensity Is inversely proportional to (distance of lamp)²

• This means that if you multiply light intensity by 9, distance decreases by 3 times

• this means light intensity x (distance of lamp)² equals to a constant

What is respiration?

An exothermic reaction which transfers energy from the breakdown of glucose to the environment

What do organisms need the energy for?

• chemical reactions to build larger molecules

• contraction of muscles for movement

• Keeping warm

What is the equation of aerobic respiration, and where and when does it take place?

• glucose +oxygen → carbon dioxide +water

• C6H12O6 + 6O2 → 6CO2 + 6H2O

• Takes place in mitochondria and happens all the time in plants and animals

What is the equation of anaerobic respiration, and where and when does it take place?

• glucose → lactic acid

• Takes place in cytoplasm when body cannot supply enough oxygen to muscles

• This may be during high intensity activities like sprinting

  
  

What are the problems with anaerobic respiration?

• only 5% of energy transferred compared with aerobic respiration

• Lattic acid causes muscle fatigue and muscle cramps

What is the equation for anaerobic respiration in plant and yeast (fermentation)?

glucose →  ethanol⁢  +  carbon dioxide

Why is fermentation useful?

• Carbon dioxide which makes bread rise

• Ethanol which is used to make alcohol drinks

• However ethanol would eventually kill the yeast

What is oxygen debt?

• Body sometimes works anaerobically when exercising

• Because there is insufficient oxygen in blood

• Oxygen debt is the amount of oxygen body needs to react with lactic acid and remove it from cells

• Oxygen + lactic acid → carbon dioxide + water

• The extra oxygen can also be used to remove heat

• Therefore body keeps taking deep and rapid breaths for a period of time

Why does heart rate increase when exercising?

• exercising requires more energy then normal, therefore more oxygen and respiration is required

• As a result heart rate increases to ensure muscles getting more oxygenated blood

What is metabolism?

• all the chemical reactions that take place in living organisms

• usually catalysed and controlled by many enzymes

  
  

What is catabolism?

• Reactions that break down larger molecules into smaller molecules

• For example, digestion and respiration

What is anabolism?

• Reactions that combine smaller molecules into larger molecules

• In plants, glucose molecules are joined together to form starch and cellulose

• Glucose is combined with nitrate ions in soil to form amino acids to synthesise protein

• In animal cells, glycerol and fatty acids combine to form lipid molecules

Difference between endothermic and exothermic

• Endothermic absorbs energy from surroundings

• Exothermic transfers energy to surroundings