Photosynthesis Overview Quiz

Study Notes

Photosynthesis is the process where light energy is captured and stored as chemical energy in organic molecules (like sugar).
Plants, algae, and some microorganisms use photosynthesis to harness solar energy and convert it into chemical energy.
In lakes and oceans, photosynthetic protists and bacteria perform photosynthesis, while on land, plants mainly carry out this process.

The summary equation for photosynthesis is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
This reaction uses carbon dioxide and water, with light energy, to produce glucose and oxygen.

Leaves and chloroplasts are specific features for maximizing photosynthesis.
A transparent layer of cells on both the upper and lower surfaces of a leaf helps protect the inside while allowing light penetration.
A waxy, waterproof covering over the epidermis reduces water loss.
Stomata, adjustable pores on the leaf surface, allow the uptake of carbon dioxide.
The mesophyll, a layer of cells in the leaf's center, houses chloroplasts where gases (CO₂ and O₂) are exchanged.

Photosynthesis happens inside chloroplasts.
Photosynthesis occurs within the stroma, a semifluid substance inside the chloroplast.
Mesophyll cells in leaves are packed with chloroplasts.
Grana are stacks of thylakoid membranes within the chloroplast, crucial for light reactions.
Pigment molecules embedded in thylakoid membranes are important for absorbing light.

Sunlight is the energy source for photosynthesis.
Visible light is a small portion of the electromagnetic spectrum, a broader range of radiation frequencies.
Different wavelengths of light possess different energy levels.

Photosynthetic pigments capture light energy needed for photosynthesis.
Chlorophyll a is a major pigment, responsible for absorbing light in plants, algae, and cyanobacteria.
Accessory pigments (Chlorophyll b and Carotenoids) absorb different wavelengths.
Plants appear green because they reflect green light and absorb other colors more readily.

Photosynthesis occurs in two main stages:
- Light reactions (in thylakoids): Sunlight is used to convert ADP into ATP and NADP+ to NADPH.
- Dark reactions (Calvin Cycle in stroma): ATP and NADPH are used to convert carbon dioxide into sugars (glucose). It can happen anytime, light or dark.

Light reactions take place in the thylakoid membranes of chloroplasts.
They involve photosystems (II & I), linked by the Electron Transport Chain (ETC).
Pigments absorb light energy and convert it into chemical energy (ATP and NADPH), and release oxygen.

The Calvin cycle takes place in the stroma of chloroplasts.
This cycle uses ATP and NADPH produced during light reactions to convert carbon dioxide into glucose, a simple sugar.
This cycle is also known as the Calvin-Benson cycle and discovered in the 1950s by Melvin Calvin and his fellow chemists (Andrew Benson and James Bassham).
The process involves three stages: carbon fixation, synthesis of G3P, and regeneration of RuBP.
Key components of the cycle include RuBP and the enzyme Rubisco.