Cells

The cell is the smallest unit of life. All living cells contain the following elements:

  • plasma membranes - a barrier that controls which substances can pass in and out of the cell, and allows the cell to maintain order
  • cytoplasm - the watery jelly in which all the cells reactions occur
  • DNA - genetic material that determines which proteins are made and, through enzymes, controls the cells chemical reactions
  • ribosomes  - organelles that are the site of protein synthesis
  • Endoplasmic reticulum - a series of membranes forming a transport system within the cell.  Steroid are also synthesised by the ER. Ribosomes may be attached to the ER - this is Rough ER.  If no ribosomes are attached it is Smooth ER.
  • Golgi apparatus - modified ER that envelopes the products of synthesis in a membrane vesicle to be released by the cell.  (eg hormones)

Biggest division between cells:

  • prokaryote (no nucleus)
  • eukaryote (nucleus)

Common features:

cells

Prokaryotic Cells
  • Mesosome – plasma membrane infolding to aid compartmentalisation
  • Capsule – sticky outer protective layer
  • Cell wall – rigid structure to help maintain shape
  • Plasma – separates cell from environment membrane
  • Nucleoid – where DNA is found

prokaryotic cells

Eukaryotic Cells: Plants

Specific to plant cells:

  • Vacuole
  • Chloroplast
  • Plasmodesma
  • Cell wall

eukaryotic cells

Eukaryotic Cells: Animals

Specific to animal cells:

  • Centriole

eukaryotic cells

Similarities & Differences

cells differences