B1-Cell Biology

• Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration. It describes the movement of particles in fluids (liquids and gases). The particles all move randomly. Substances can move in and out of cells across cell membranes via diffusion (e.g CO2, urea).
• what is diffusion?


  The movement of particles from an area of high concentration to an area of low concentration.
• where does diffusion take place?

  in solutions and gases
• the bigger the concentration gradient(change in gradient)…


  the faster the diffusion rate
• having a higher temperature will have what effect on diffusion?

  Increase the rate, because particles have more energy.
• what do plant and animal cells have enclosed in their nucleus?

  a cell membrane, cytoplasm and genetic material
• what do prokaryotic cells have(bacteria cells)

  They have cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids
• what size are bacteria cells?

  0.2 to 2 micrometres
• which is the best unit for cells?

  Micrometer
• how do you get from millimetres to micrometres?

  Multiply by 1000.
• how do you get from micrometres to nanometres?

  Multiply by 1000.
• what do animal cells have?

  a nucleus

  cytoplasm

  a cell membrane

  mitochondria

  ribosomes
• what extra structures do plant cells often have?

  Vacuole, chloroplasts
• what structures plant and algal cells?

  cell wall
• what size are mitochondria and chloroplasts?

  around 1-10 micrometres
• what size are ribosomes?

  20-30 nanometers
• how are sperm cells specialised for their particular function?

  Fertilizer Species Overview• Streamlined, elongated shape with tail(flagellum) for fertilization.• Head contains enzymes for egg penetration.• Specialization aids in effective egg fertilization.
• how are nerve cells specialised for their particular function?

  • Nerve cells transmit electrical impulses.• Dendrites receive signals.• Axon transmits signals over long distances.• Myelin sheath insulates axon for efficient signal transmission.• Adaptations facilitate efficient communication and coordination in nervous system.
• how are muscle cells specialised for their particular fuction?

  • Consist of myofibrils: actin and myosin filaments slide during contraction.• High mitochondria provide energy for muscle contractions.• Specialization allows efficient force and movement generation.
• how are root hair cells adapted to their particular function?

  • Specialized for absorbing water and minerals from soil.• Long projections increase surface area for absorption.• Located near root tips for efficient nutrient absorption.
• how are xylem cells adapted to their function?

  • Elongated, hollow cells with lignin deposits for water and mineral transport.• Provide strength and support for plants.• Facilitate continuous water movement through cell walls.• Dead at maturity for uninterrupted water flow.• Adaptations make xylem cells efficient for water transport and structural support.
• how are phloem cells adapted to their function?

  • Phloem cells transport dissolved sugars throughout the plant.• They have sieve tubes for nutrient movement.• Companion cells provide metabolic support.• Adaptations facilitate efficient food transport from photosynthetic regions to other parts of the plant.
• Initial growth stage

  • Extra ribosomes, mitochondria and other sub-cellular structures are produced.
  • The cell’s chromosomes (which are made of DNA) are replicated (copied) so that there are two sets of the cell’s chromosomes.
• Mitosis

  • The two sets of chromosomes are pulled to opposite ends of the cell.
  • Then, the nucleus divides into two.
• Cell divides

  • Two identical cells are created by the division of the cytoplasm and cell membranes.
• How can we use microscopy to study the cell cycle?

  • Microscopes allow us to see things we can't with the naked eye.
  • By culturing cells and then viewing them at a high resolution under a microscope, we can identify different cells in different stages of the cell cycle.
• Chromosomes are pulled apart

  • The two sets of chromosomes copied during the initial growth stage are pulled to opposite ends of the cell.
• Nucleus divides

  • The nucleus divides into two.
• Identical daughter chromosomes

  • Mitosis ensures that both daughter cells have the same chromosomes as each other and the parent cell.
  • This is important for processes that require identical cells to be produced.
  • For example, the growth and repair of tissues and asexual reproduction.
• Division

  • Cells undergo mitosis, where they divide into two identical daughter cells.
• Why is it important that the daughter cells, produced during mitosis, have the same chromosomes as each other?

  .

  It is important for processes that require identical cells to be produced, for example the growth and repair of tissues and asexual reproduction
• Embryos

  • The stem cells in embryos can differentiate into most cell types, to produce all of the cell types that will make up the organism.
• Plant meristems

  • Plant stem cells are found in the meristem tissue.
  • Plant stem cells can differentiate into all types of plant cell throughout the life of the plant. This allows plants to grow for their whole lives.
• Bone marrow

  • In human adults, stem cells can be found in bone marrow (as well as other tissues and organs).
  • Adult stem cells differentiate into fewer cell types than stem cells in embryos. They are used to replace dying cells and damaged tissues.
• Stem cell treatments

  • Stem cells may be able to replace damaged cells in the body.
  • For example, stem cells may replace the damaged cells that cause diabetes or paralysis.
• Plant clones

  • Plant stem cells can be used to quickly and cheaply produce cloned plants.
  • This could help to protect rare plant species from extinction and create large populations of plants with special features, such as disease resistance.
• Therapeutic cloning

  • Therapeutic cloning is a process that produces (creates) an embryo that has the same genome as the patient.
  • Stem cells taken from this embryo will have the same DNA as the patient. This means that the patient's body will not reject the stem cells or body cells made from the embryo's stem cells.
  • This is ideal for use in stem cell medical treatments.
• Viral infections

  • Stem cell transplantation could transfer viral infections.
• Ethical beliefs

  • Some people disagree with the use of stem cells on ethical or religious grounds:
  • They believe that life begins at conception, which means that the embryo is alive.
  • They therefore view the use of embryonic stem cells as 'killing' an embryo.
• Perfume

  • When you spray perfume, the smell diffuses across the room from the high concentration (where you just sprayed it) to low concentration (the other side of the room).