Cells and Sub-cellular Structures

All living things are made up of cells. Cells can either be prokaryotic or eukaryotic. Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller and simpler, e.g. bacteria. Eukaryotes are organisms that are made up of eukaryotic cells. A prokaryote is a prokaryotic cell (a single-celled organism).

Most animal cells have a nucleus, cytoplasm, cell membrance, ribosomes and mitochondria. The nucleus contains genetic material that controls the activities of the cell. The cytoplasm is a gel-like substance where most of the chemical reactions take place. It also contains enzymes that control these chemical reactions. The cell membrance holds the cell together and controls what goes in and out of the cell. Most of the reactions for aerobic respiration takes place in the mitochondria. This allows the mitochondria to provide energy to the cell. The ribosomes are responsible for making proteins in the cell.

Plant cells usually have all the sub-cellular structures that an animal cell contains however they also have extra structures. Plant cells have a rigid cell wall which is made up of cellulose. This supports the cells and strengthens it. The permanent vacuole contains cell sap which is used to store materials or transport substances. Chroloplasts contain a substance called chlorophyll which absorbs the light needed for photosynthesis and therefore makes food for the plant.

Bacterial cells are prokaryotes and they are much smaller in size. A typical bacterial cell would contain cytoplasm, a cell membrance, a cell wall, a singular strand of DNA and small rings of DNA called plasmids. Bacterial cells don't have a nucleus containing genetic material which means strands of DNA flow freely in the cytoplasm. Bacterial cells do not have mitochondria or chloroplasts to provide energy for the cell.