cell structure

• • Cells that have a nucleus, such as plant and animal cells, are eukaryotic cells and cells without a nucleus, such as bacteria, are prokaryotic cells.
  • Organisms made up of eukaryotic cells are called eukaryotes and prokaryotic organisms are called prokaryotes.
  • Eukaryotes are often multicellular whereas prokaryotes are often single-celled.
• Animal cells contain:

  • mitochondria containing enzymes needed for respiration, releasing energy for the cell to use. 
  • A nucleus holds genetic material (including DNA) needed to control the cell’s activities.  
  • Cytoplasm, jelly-like substance, contains nutrients, salts and enzymes required for chemical reactions to take place.
  • A semi-permeable cell membrane that controls what comes in and out of the cell. 
  • Ribosomes for the production of proteins.

  
• Plant cells contain the same features as animal cells but they also have:

  • A cell wall made of cellulose that provides structure and protection to the cell. Algal cells also have this feature.
  • A vacuole that a holds weak solution of sugar and salts called cell sap that keeps the cell swollen.
  • Many chloroplasts that are the site of photosynthesis in the cell. They contain chlorophyll, a green pigment that absorbs the light and specific enzymes required for photosynthesis to occur and food to be produced.  

  
• Bacterial cell structure:

  • No nucleus, their genetic material is free in the cytoplasm. 
  • They have a main circular strand of DNA and small rings of DNA called plasmids.
  • Flagella, hair-like structures that help the bacteria move.
  • Bacteria do not contain chloroplasts or mitochondria but do have a cell wall, cell membrane and cytoplasm.