Cell theory states that:

1. Cell is the simplest unit of any living being which is capable of carrying out all processes to sustain life.

2. Cells are produced by other living cells.

3. All living beings are made up of one (single cell organisms) or more cells (multi-celled organisms).

Cells in a human body are eukaryotic in nature. They contain the nucleus which is essential for cell to carry out its specialist tasks required to sustain a multi-cellular organism.

The most obvious difference between prokaroytic and eukaryotic cells is the absence of nucleus in prokaroytic cells.

Nucleus is the brain of the cell and coordinates the activities going on in it just as a human brain coordinates the activities in a human body. The nucleus contains the genetic information of the cell and the specialist tasks it is required to do and therefore it ensures that these activities are done at the correct time and sequence.

To support the body movements needed for exercise, our organelles and cells must work harder and faster. In order for the organelles to be able to work they require basic nutrients, energy, and oxygen, which causes us to breathe harder in an attempt to acquire more oxygen for our cells

Plant cells that are specialist in doing photosynthesis for the plant need to have chloroplast in them while those plant cells that do not participate in photosynthesis, do not need to have chloroplast in them. For example, the cells of a plant root do not photosynthesize food for the plant and therefore absence of chloroplast in them totally makes sense.

Cell wall surrounds a plant cell, protecting it and providing the necessary support required to keep the plant erect and upright. Plants do not have bones in them to hold them straight upright, this is done by the cellulose made cell wall of the plant cell.

Mitochondria is the power house of each living cell. It is responsible for keeping the cell energized by breaking the glucose molecule in the presence of oxygen to form carbon dioxide, water and energy to power various cell activities. Plants are able to manufacture their food – glucose by the process of photosynthesis, but nevertheless, they do require a mitochondria to utilize this glucose and convert it to energy.