Cells biology

• When someone first 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 Prokaryotes or Eukaryotes
• All living things are made of cells
• Cells


  • Can be either prokaryotic or eukaryotic
  • Eukaryotic cells are complex and include all animal and plant cells
  • Prokaryotic cells are smaller and simpler, e.g. bacteria
• Eukaryotes


  Organisms that are made up of eukaryotic cells
• Prokaryote


  A prokaryotic cell (it's a single-celled organism)
• Plant and Animal Cells have Similarities and Differences
• Subcellular structures


  The different parts of a cell
• Subcellular structures in animal cells

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


  • Gel-like substance where most of the chemical reactions happen
  • Contains enzymes that control these chemical reactions
• Mitochondria


  • Where most of the reactions for aerobic respiration take place
  • Respiration transfers energy that the cell needs to work
• Ribosomes


  • Where proteins are made in the cell
• Additional subcellular structures in plant cells

  • Rigid cell wall
  • Permanent vacuole
  • Chloroplasts
• Rigid cell wall


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


  • Contains cell sap, a weak solution of sugar and salts
• Chloroplasts


  • Where photosynthesis occurs, which makes food for the plant
  • Contain chlorophyll, which absorbs the light needed for photosynthesis
• Bacterial Cells Are Much Smaller
• The cells of algae (eg seaweed) also have a rigid cell wall and chloroplasts
• Subcellular structures in bacterial cells

  • Cell membrane
  • Cytoplasm
  • Cell wall
• Bacterial cells


  • Don't have chloroplasts or mitochondria
  • Don't have a 'true' nucleus, instead they have a single circular strand of DNA that floats freely in the cytoplasm
  • May also contain one or more small rings of DNA called plasmids
• You might see the sizes of cells written in standard form
• Differentiation


  The process by which a cell changes to become specialised for its job
• Differentiation


  1. Cell changes

  2. Develop different subcellular structures

  3. Turn into different types of cells
• Most differentiation occurs as an organism develops
• In most animal cells, the ability to differentiate is then lost at an early stage, after they become specialised
• Lots of plant cells don't ever lose the ability to differentiate
• Undifferentiated cells


  Stem cells
• Specialised cells


  • Sperm cells
  • Nerve cells
  • Muscle cells
  • Root hair cells
  • Phloem and xylem cells
• Sperm cells


  • Long tail
  • Streamlined head
  • Many mitochondria
  • Enzymes in head
• Nerve cells


  • Long
  • Branched connections
• Muscle cells


  • Long
  • Many mitochondria
• Root hair cells


  • Grow into long "hairs" that stick out into the soil
• Phloem and xylem cells

  • Long and joined at the ends
  • Phloem cells have very few subcellular structures
  • Xylem cells are hollow in the centre
• Embryonic stem cells


  Can turn into any type of cell
• Adult stem cells


  Can only turn into certain cell types, such as blood cells
• Stem cell research


  1. Grow stem cells in lab

  2. Differentiate into specialised cells

  3. Use in medicine or research
• Therapeutic cloning


  Embryo made to have same genetic information as patient, so stem cells wouldn't be rejected
• Stem cells grown in lab may become contaminated with virus
• Arguments against stem cell research

  • Embryos are potential human lives
  • Helping existing patients is more important
  • Embryos would be destroyed anyway
  • Find other sources of stem cells
• Stem cell research is allowed in the UK as long as it follows strict guidelines