Cell Biology

• All animals & plant cell, are eukaryotic
• Eukaryotic cells


  • Have a cell membrane
  • Have cytoplasm
  • Have genetic material enclosed in nucleus
• Bacterial cell


  • Have a cytoplasm & cell membrane surrounded by cell wall
  • Genetic material is not enclosed in a nucleus - single DNA loop in the cytoplasm
  • May have smaller rings of DNA called plasmids in the cytoplasm
• Prokaryotes


  Much smaller than eukaryotes
• Cell scale & size


  • Eukaryotic cells (micrometres - um)
  • Prokaryotic cells (nanometres - nm)
• Bacterial cells are very small, can only be seen with a microscope
• Prokaryotes (a tenth) much smaller than eukaryotes
• Plant cells have the same sub-cellular structures as animal cells, but also have chloroplasts
• Plant cells have a permanent vacuole & a cell wall made of cellulose (algae also have this) to strengthen the cell
• Cell membrane


  Strengthens the cell
• Animal cell components


  • Nucleus
  • Mitochondria
  • Cytoplasm
• Plant cell components


  • Nucleus
  • Mitochondria
  • Chloroplast
  • Cell wall (Cellulose - alage also have it - to strengthen the cell)
  • Ribosomes
  • Permanent Vacuole (Cell Sap)
  • Cytoplasm
  • Cell membrane
• Nucleus


  Contains genetic material & controls cell
• Mitochondria


  Provides energy by carrying out respiration
• Ribosomes


  Carry out protein synthesis
• Cytoplasm


  Jelly-like, where chemical reactions take place
• Cell membrane


  Controls movement of substances in and out of the cell
• Chloroplast


  Absorbs light for photosynthesis
• Permanent vacuole


  Filled with cell sap to help keep cell turgid (stores food)
• Cellulose cell wall


  Gives strength to the cell and supports the plant
• Plasmids


  Additional genetic material
• 
  

  Cells are modified in order to carry out a particular function
• Sperm cells have a tail for swimming, are packed with mitochondria to provide energy, and have enzymes in the head to break into the egg
• Nerve cells are long and thin to allow nerve impulses to travel along them, and have many dendrites to pass the nerve impulse to nearby nerve cells
• Muscle cells have lots of mitochondria to provide energy for movement (contract and relax as part of muscle tissue)
• Root hairs are long and thin to increase surface area for absorbing water and mineral ions
• Xylem transports water from roots to leaves, has no ends and is hollow to form a continuous tube & lignin waterproofs cell wall
• Phloem transports sugars around the plant, has small holes in the end plates to allow sugars to move, the cross walls with pores allows flow of sap - translocation
• Single-celled organisms must carry out all functions to keep the cell alive
• In multicellular organisms, each cell type becomes specialised to carry out one function, with the work divided between the cells
• As cells differentiate, they acquire different sub-cellular structures to enable them to carry out their specialised function
• Cells are too small to be seen with the naked eye, so microscopes are used to study them
• Microscopes have developed over time to provide higher magnification and resolution, allowing the details within sub-cellular structures to be seen
• Magnification


  Size of image / Size of real object
• Binary fission


  1. Cell doubles in size

  2. Cell divides into 2 daughter cells

  3. Cell division can occur as quickly as 20 minutes
• Bacterial growth


  • Bacteria can grow in nutrient broth solution or as colonies on agar plate
  • Nutrient broth contains all nutrients bacteria need to live
• Uncontaminated cultures

  • Required to test effectiveness of disinfectants and antibiotics
• Sterilising procedures


  1. Sterilise all petri dishes and culture media before use

  2. Sterilise inoculation loops by passing through a flame

  3. Secure lid of dish with tape and place upside down

  4. Do not incubate bacterial cultures above 25°C (school labs)
• Chromosomes

  • Found in the nucleus of a cell, made of DNA molecules
  • Each chromosome carries a large number of genes
  • Body cells chromosomes normally found in pairs
  • Human body cells have 23 pairs of chromosomes
• Cell division- Cell Cycle


  STAGE 1:

  Cell grows, genetic material is doubled and divided into 2 identical cells

  Pre - division: number of sub-cellular structures (ribosomes and mitochondria) is increased

  DNA replicates to form 2 copies of each chromosome

  STAGE 2:

  Mitosis - one set of chromosomes is pulled to either side of the cell

  Nucleus divides

  STAGE 3:

  Cell membrane and cytoplasm divide (cytokinesis)

  Two genetically identical cells are formed