biology - cell biology.

• Adaptations of a Sperm Cell?


  • Head contains genetic material for fertilisation
  • Midpiece has mitochondria to release energy needed to swim
  • Tail enables the sperm to swim
• Why do multicellular organisms have problems with their SA:V ratio?


  1. Cells on the surface can get enough oxygen by diffusion

  2. Cells in the centre of the organism cannot get enough oxygen as they are too far from the surface
• Osmosis - Required practical

  1. Peel potato, as skin can affect osmosis

  2. Use cork borer to make 3 cylinders of potato, all with the same diameter

  3. Use scalpel to cut potatoes to 3cm

  4. Measure length of potato (ruler) and mass using a balance

  5. Put potatoes in test tubes, add 10cm³ of 0.5 molar sugar solution to 1st tube, 0.25 molar sugar solution to 2nd tube, and 10cm³ distilled water to 3rd tube

  6. Dry off potato pieces, measure length and masses again

  7. Calculate the percentage change - change/original x100.
• Active transport in plant cells?


  • In plant cells, ions move into the plant by active transport as the concentration of ions in the soil is lower than the concentration in the plant.
• Therapeutic cloning


  An embryo is produced with the same genes as the patient
• What is active transport?


  Molecules move from an area of low (dilute) to an area of high (concentrated) gradient, against the concentration gradient. This process requires energy from active transport.
• Effects of osmosis on a plant cell?


  1. If the plant cell is placed in water, the cell will expand, but will not burst as plant cells have a cell wall. The cell is now turgid.

  2. If a plant cell is placed in a concentrated solution, water moves out, and the cell becomes flaccid.
• Effects of osmosis on an animal cell?


  1. If cell is placed in water, water will move into the cell, and the cell may burst.

  2. If the cell is placed in a concentrated solution, water moves out, causing the cell to shrink.
• Adaptations of filaments (fish)


  • Give gills a large surface area
  • Thin membrane, short diffusion pathway
  • Good blood supply, maintain high concentration gradient
• Adaptations of a muscle cell?


  They contain many mitochondria to provide energy for muscle contraction.
• Adaptations of the nerve cell?

  • Has extensions/branches so it can communicate with other nerve cells.
  • Covered in a fatty sheath, insulates the nerve cell and speeds up impulses.
• Adaptations of root hair cell?

  • Large surface area to provide contact with soil water.
  • Thin walls, to not restrict movement of water and allow in as much water.
• Adaptations of a xylem cell?


  • No top and bottom walls, so there’s a continuous stream.
  • Thick and woody walls, to support the plant.
• Adaptations of phloem?


  Companion cells to provide energy required to transport substances in the phloem.