Photosynthesis

Question 1

Photosynthesis is

Answer 1

Photosynthesis is the process in which planet cells convert light energy from the sun into chemical energy (like carbohydrates – glucose). In this process, inorganic carbon dioxide (𝐶𝑂2) is converted to organic
glucose, with the help of water which acts as an electron donor to keep the reaction going. In this
process, oxygen is emitted as a byproduct.

In this process water is oxidized and oxygen is released, while carbon dioxide is reduced into glucose.

This process is reversible to cells respiration

Question 2

The difference between animal and plant cells:

Answer 2

Photosynthesis occurs in planet cells – eukaryotic cell that differ from animal cells, due to the presence

of:
* Cell wall – composed of cellulose and hemicellulose.
* Vacuoles – maintains osmotic pressure of the cell.
* Chloroplast – site of photosynthesis.

Question 3

Chloroplasts:

Answer 3

These are organelles within plant cells that conduct photosynthesis – converting light energy into
chemical energy (sugars) that can be used by the cell. They are located in the mesophyll region of leaves
(inner layer).
Chloroplasts have three membrane systems:
& Outer – permeable.
& Inner – non-preamble.
& Thylakoid – site of light dependent reaction that forms stacks of discs known as grana that house
chlorophyll.

**The Stoma is a gel like fluid located in the inner membrane where the thylakoid system floats

Question 4

Chlorophyll

Answer 4

Molecule that provides plants with their green pigment and is the key element in the photosynthesis
process. It allows plants to absorb energy from light.
It is located in the thylakoid membrane of chloroplasts.

• Structure:
  
  • Chlorine ring with magnesium ion at the center.
  • Carbohydrate side tail.

Question 5

Process of photosynthesis:

Answer 5

1. Light Dependent reaction – capture photons which are energy particle of light, and converts them into high energy molecule. (𝑁𝐴𝐷𝑃𝐻 and 𝐴𝑇𝑃).
2. Light independent reaction (the Calvin cycle) – can function with or without light. It uses the
   energy molecules to cover carbon dioxide into carbohydrates.

Question 6

Light dependent reaction

Answer 6

Light Dependent reaction (𝑧-scheme) occurs on the thylakoid membrane using 4 major protein complexes photosystem 1 and 2, cytochrome 𝑏6𝑓 complex and 𝐴𝑇𝑃𝑠𝑦𝑛𝑡ℎ𝑎𝑠𝑒.
Reaction:
1. Starting at 𝑃𝑆 2, one molecule of pigment chlorophyll absorbs one photon, causing a release of
one electron.
*𝑃𝑆 2 breaks down water into two electrons and two
hydrogen ions with one oxygen.
Water helps replace lost electrons which helps
continue the reaction.

2. The lost electron moves onto 𝑏6𝑓, providing the energy to pump 2 hydrogens from the stroma
   to the inner membrane space.
3. The lost electron moves onto PS 1 where another electron is released by the absorption of photons. Both electrons provide the energy to reduce 𝑁𝐴𝐷𝑃+ to 𝑁𝐴𝐷𝑃𝐻.
4. The protons released from 𝑃𝑆 2 and 𝑏6𝑓 travel to 𝐴𝑇𝑃𝑠𝑦𝑛𝑡ℎ𝑎𝑠𝑒 to from 𝐴𝑇𝑃. Oxygen is
   produced as byproduct and is emitted out of the cell.

Question 7

Light independent reaction

Answer 7

Light independent reaction or Calvin cycle occur in the stroma and uses energy molecule 𝑁𝐴𝐷𝑃𝐻 and 𝐴𝑇𝑃 from light dependent reaction to make glucose from carbon dioxide.
12𝑁𝐴𝐷𝑃𝐻 +18𝐴𝑇𝑃+6𝐶𝑂2 → 𝐶6𝐻12𝑂6 +12𝑁𝐴𝐷𝑃+ +18𝐴𝐷𝑃+18𝑃𝑖 +6𝐻2𝑂