BIOLOGY TOPIC 1 - CELL BIOLOGY

• how are sperm cells adapted to their function?

  - Acrosome contains enzymes so the sperm can penetrate the egg

  - Haploid nucleus

  - Tail so that it can swim to egg

  - Lots of mitochondria for energy
• how are nerve cells adapted to their function?

  - Long axon to transmit impulses long distances - Thin to transmit impulses faster

  - Enclosed in a myelin sheath to speed up transmission and prevent signals leaking out of cell
• how are muscle cells adapted to their function?

  - protein fibres contract to aid movement

  - lots of mitochondria for energy
• how are root hair cells adapted to their function?

  - Long root hair extension to increase surface area for uptake of water and minerals

  - no chloroplasts as they are underground
• how are xylem and phloem adapted to their functions?

  - xylem lose end walls to form hollow tube

  - walls strengthened by lignin

  - holes in cells to allow movement of food
• cell differentiation


  the process by which a cell becomes specialised
• light microscope


  light passes through one or more lenses to produce an enlarged image of a specimen
• electron microscope


  - a microscope that focuses a beam of electrons to magnify objects

  -higher resolution and magnification than light microscope
• equation for magnification


  Magnification = image size / actual size
• aseptic technique


  -petri dish and inoculating loop= sterilised to kill unwanted microorganisms

  - dish lid = taped on to prevent microorganisms entering

  - school labs at 25 degrees = so pathogens grown aren't harmful to humans
• chromosomes


  - carry genes

  -23 pairs in every cell (except gametes)

  - found in pairs
• mitosis


  - genetic material and sub cellular structures double

  - chromosomes pulled to opposite ends of cell

  - nucleus divides

  - cytoplasm and cell membrane divide
• stem cells


  undifferentiated cells that have potential to differentiate into any cell type
• advantages of stem cells


  - can't be rejected by patient

  -can become any type of cell
• disadvantages of stem cells


  - risk of infection

  - moral/religious objections
• diffusion


  Movement of particles from an area of high concentration to low concentration.
• osmosis


  diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
• active transport


  - moves substances from a more dilute solution to a more concentrated solution against a concentration gradient

  - requires energy from respiration