Cells

• When someone peered down a microscope at a slice of cork and drew the boxes they saw, little did they know that they'd seen the building blocks of every organism on the planet
• Organisms


  Can be Eukaryotes or Prokaryotes
• All living things are made of cells
• Cells


  Can be either eukaryotic or prokaryotic
• Eukaryotic cells


  • Complex and include animal and plant cells
• Prokaryotic cells


  • Smaller and simpler, e.g. bacteria
• Eukaryotes


  Organisms that are made up of eukaryotic cells
• Prokaryote


  A prokaryotic cell (a single-celled organism)
• Plant and animal cells have similarities and differences
• Subcellular structures


  The different parts of a cell
• Subcellular structures most cells have


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Nucleus


  Contains genetic material that controls the activities of the cell
• Cytoplasm


  Gel-like substance where most of the chemical reactions happen
• Cell membrane


  Holds the cell together and controls what goes in and out
• Mitochondria


  Where most of the reactions for respiration take place
• Ribosomes


  Involved in translation of genetic material and synthesis of proteins
• Additional structures plant cells have


  • Rigid cell wall
  • Large vacuole
  • Chloroplasts
• Rigid cell wall


  Made of cellulose, supports and strengthens the cell
• Large vacuole


  Contains cell sap, a weak solution of sugar and salts, maintains internal pressure to support the cell
• Chloroplasts


  Where photosynthesis occurs, making food for the plant
• Bacterial cells


  • No nucleus, smaller than plant or animal cells
• Subcellular structures bacterial cells have


  • Chromosomal DNA
  • Ribosomes
  • Cell membrane
  • Plasmid DNA
• Chromosomal DNA


  One long circular chromosome that controls the cell's activities and replication, floating free in the cytoplasm
• Plasmid DNA


  Small loops of extra DNA that aren't part of the chromosome, contain genes for things like drug resistance, can be passed between bacteria
• Flagellum


  A long, hair-like structure that rotates to make the bacterium move, can be used to move away from harm and towards beneficial things
• Cells aren't all the same, they have different structures depending on the function they do
• Multicellular organisms contain lots of different types of cells with different structures
• You need to know how sperm and ciliated epithelial cells are adapted to their functions
• Egg cell


  Carries the female DNA and nourishes the developing embryo in the early stages
• Egg cell


  • Contains nutrients in the cytoplasm to feed the embryo
  • Has a haploid nucleus
  • Membrane changes structure after fertilisation to stop more sperm getting in
• Sperm cell


  Transports the male's DNA to the female's egg
• Sperm cell


  • Has a long tail to swim to the egg
  • Has lots of mitochondria in the middle section to provide energy for swimming
  • Has an acrosome at the front of the head that stores enzymes needed to digest the egg cell membrane
• Ciliated epithelial cells


  Line the surfaces of organs and have cilia (hair-like structures) that move substances in one direction along the surface of the tissue
• The lining of the airways contains lots of ciliated epithelial cells that help move mucus and trapped particles up to the throat