cell structure (b1)

• Cell types

  • Plant cell
  • Animal cell
• Cell membrane

  Surrounds the cell and controls what goes in and out
• Nucleus contains the genetic materials
• Cell components

  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Ribosomes
  • Mitochondria
  • Cell wall
  • Chloroplasts
  • Vacuole
• Prokaryotic cells

  • Smaller
  • have cytoplasm, cell membrane and cell wall
  • no nucleus
  • single loop of DNA
  • plasmids
• Eukaryotic cells

  • Larger
  • have cell membrane, cytoplasm and nucleus
• Specialised animal cells

  • Nerve cell
  • Muscle cell
  • Sperm cell
• Nerve cell - Conduction of impulses

  • Lots of dendrites to receive signals
  • axons is long to transmit signals
  • nerve endings have mitochondria for energy
• Muscle cell- contraction 


  • store glycogen that is used in respiration by mitochondria
  • Contain proteins that help layers slide over each other
  • Lots of mitochondria for energy
• Sperm cell- reproduction

  • 23 chromosomes
  • Digestive enzymes to break outer layer of egg
  • Mitochondria for energy
  • Tail for movement
• Specialised plant cells

  • Root hair cell
  • xylem
  • phloem
• Root hair cell

  • Large surface area for water and mineral ion absorption
  • Thin walls for short diffusion distance
  • Permanent vacuole maintains water gradient
  • Mitochondria for active transport
• Transport systems in plants

  • Xylem
  • Phloem
• Xylem

  • Transports water and minerals
  • cells are dead - free water passage
  • no top and bottom walls - continous water flow
  • lignin - strengthen walls + plant
• Phloem- Transports dissolved sugars and amino acids


  • cell walls of each cell form sieve plates allow sugars and amino acid to flow
  • living cells
  • few subcellular structure to aid to flow
• Cell differentiation is when cells become specialised to be suited to its role
• Magnification

  Image size / Actual size
• Electron microscopes have higher magnification and resolving power than light microscopes
• Preparing a slide for microscopy

  1. Add drop of water

  2. Cut thin slice of tissue

  3. Place tissue in water

  4. Add drop of dye

  5. Place coverslip
• Using a light microscope

  1. Clip slide onto stage

  2. Switch on light

  3. Select low power objective

  4. Use coarse focus to get image

  5. Use fine focus to clarify image

  6. Switch to higher power objective
• Binary fission

  Asexual reproduction in prokaryotes where one cell divides into two identical cells
• Culturing microorganisms

  1. Sterilise petri dish and agar by heating

  2. pass inoculation loop through a Bunsen burner flame to sterilise

  3. use loop to evenly spread bacteria onto agar plate

  4. lift lid or petri dish as little as possible to reduce entry of microbes from air

  5. Place antibiotic disks on agar using sterile tweezers

  6. lightly tape the sides of the petri dish

  7. Incubate for 48 hours upside down at 25 degrees Celsius

  8. Measure zones of inhibition
• Chromosomes

  • DNA molecules found in the nucleus
  • Carry genes
• Stem cell types

  • Embryonic stem cells
  • Adult stem cells
  • Plant stem cells
• Embryonic stem cells

  Undifferentiated, can form most cell types, can be cloned by scientists
• Adult stem cells

  found in bone marrow, can form many types of cells
• Plant stem cells

  Found in meristems, can differentiate into any plant cell, used to make clones of plant
• Therapeutic cloning

  Produce embryo with patient's genes

  embryo is harvested

  grown into any cell patients need

  wouldn't be rejected
• Stem cell problems include limited supply, ethical issues, immune rejection, and potential for uncontrolled division
• Plant cloning uses stem cells to quickly and economically produce genetically identical plants
• Diffusion

  Net movement of particles from high to low concentration, doesn't require energy
• Factors affecting diffusion rate

  • Concentration gradient
  • Temperature
  • Surface area
• Surface area to volume ratio

  Decreases as organisms get larger, requiring specialised exchange surfaces
• Specialised exchange surfaces

  • Alveoli (lungs)
  • Villi (intestines)
  • Root hair cells
  • Leaves
• Specialised exchange surface features

  • Large surface area
  • Very thin membrane
  • Short diffusion distance
  • Good blood supply (animals)
  • Good ventilation (animals)
• Osmosis

  Net movement of water from high to low concentration through a partially permeable membrane
• Investigating osmosis in plant tissue

  1. Cut potato cylinders of equal size

  2. Measure initial mass

  3. Place in sugar/salt solutions of varying concentrations

  4. Measure final mass after time period

  5. Calculate percentage mass change
• Active transport

  Movement of molecules against concentration gradient, requires energy from respiration
• Active transport examples

  • Root hair cells absorbing mineral ions
  • Gut absorbing sugar molecules
• ribosomes

  where protein synthesis occurs