C1.3.1 - C1.3.8 - Photosynthesis SL Bio

photosynthesis

the process by which cells synthesise organic compounds (e.g. glucose) from inorganic molecules (CO2 and H2O) in the presence of sunlight.

This process requires a photosynthetic pigment → chlorophyll and can only occur in certain organisms

Photosynthetic organisms contain pigments that

capture the light energy from the sun to create chemical energy (ATP)

ATP is then used to

• Synthesise organic compounds via anabolic reactions

• Contribute to cellular structure

Photosynthesis equation

6CO2 +6H20 → C6H12O6 + 6O2

Light spectrum

• Electromagnetic spectrum

• Colours represent different wavelengths of visible light and range from red (longest) to violet (shortest)

Absorption of light

mediated by specific pigment molecules (e.g., chlorophyll)
-electrons absorb light at specific frequencies
-energy from these electrons harnessed by cell to make chemical energy (ATP)

Photosynthesis is a (what process)

2 step process
- light dependent reactions → convert light energy from the Sun into ATP
-light independent reaction → use chemical energy to synthesis organic compounds (e.g., carbohydrates)

light independent reactions/calvin cycle

-occur within the interior of the chloroplast → stroma
-ATP and hydrogen (carried by NADPH) transferred to site of light independent reactions
-Hydrogen is combined with CO2 to form complex organic compounds
-Carbon fixed by the enzyme rubisco with ATP providing chemical energy required to join the molecules together

in essence, light independent reactions use ATP and H+ ions to absorb CO2 and create glucose.

Light dependent reactions

-occurs in the thylakoid membranes of the chloroplast.

-goal is to convert light energy into chemical energy stored in the forms of ATP and NADPH.

1. pigments like chlorophyll absorb light energy,

2. Photolysis occurs → split into oxygen, protons (H⁺), and electrons.

   -Oxygen is released as a waste product
   -Hydrogen (protons): generate NADPH

3. ATP and NADPH ‘transported’ to the dark cycle where they are used

chromatography

experimental technique by which mixtures can be seperated

absorption spectrum

indicates the wavelengths of light absorbed by each pigment (e.g. chlorophyll)

action spectrum

indicates the overall rate of photosynthesis at each wavelength of light

limiting factor

factors that limit production

limiting factors in photosynthesis

occurs at optimum until there is a limiting factor, e.g., CO2, H2O which leads to the reach in plateau (denaturation of enzymes)

measuring photosynthesis

-through an uptake of CO2 and production of O2
-via change in biomass

CO₂ enrichment

process of increasing the amount of carbon dioxide to a level higher than what is normally in fresh air

methods for CO2 enrichment

-enclosed greenhouse experiments
-free air carbon dioxide enrichment (FACE experiments)