Cell Organelles: Nucleus and Chloroplast

Study Notes

The cell nucleus is a large organelle in eukaryotic organisms that protects most of the DNA within each cell.
It produces precursors necessary for protein synthesis.
The DNA housed within the cell nucleus contains information necessary for creating most proteins needed to keep a cell functional.

Chloroplasts are found only in algal and plant cells and produce energy through photosynthesis.
They have a high concentration of chlorophyll, the molecule that captures light energy, giving plants and algae a green color.
Chloroplasts are thought to have evolved from once free-living bacteria.
They are essential for the growth and survival of plants and photosynthetic algae.

Chloroplasts carry out photosynthesis, converting light energy to energy stored in the form of sugar and other organic molecules.
Photosynthesis has two stages: light-dependent reactions and light-independent reactions (Calvin cycle).
In light-dependent reactions, chlorophyll and carotenoids capture sunlight to form ATP and NADPH.
In the Calvin cycle, NADPH converts inorganic carbon dioxide to an organic molecule in the form of a carbohydrate (CO2 fixation).
Carbohydrates and other organic molecules can be stored and used at a later time for energy.

Rafflesia, a parasitic plant genus, has lost its chloroplasts and obtains its nutrients from other plants.
CAM (Crassulacean Acid Metabolism) is a method of carbon fixation evolved by some plants in dry circumstances.
CAM plants open their stomata at night to take in CO2 and release O2, reducing water loss.

Catabolism is the part of metabolism responsible for breaking complex molecules down into smaller molecules.
During catabolism, energy is released from the bonds of large molecules and stored in ATP.
ATP concentrations increase as nutrients and food are broken down, making it more likely to be used for energy.