Cell Biology

• What do animal and plant cells have in common?

  They are both eukaryotic and have a cell membrane, cytoplasm and a nucleus. Eukaryotic cells have cell-bound organelles.
• Prokaryotic cells do not have mitochondria (due to size) or a nucleus and are much smaller. They have a cell wall, cytoplasm, cell membrane and plasmid or chromosomal DNA. The DNA carries antibiotic advantages/resistance.
• What is culturing microorganisms?

  Growing many microorganisms in a lab using nutrients
• What structures are in plant cells and animal cells?

  Nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
• What structures are in plant cells?

  Chloroplasts, vacuole and cell wall
• What does the nucleus do?

  • Stores genetic information
  • Control cellular activites
• What is the function of cytoplasm?

  Site of cellular activities
• What is the function of the cell membrane?

  Controls what enters and leaves the cell and separates the interior of the cell from the outside.
• What is the function of the mitochondria?

  Is the site of aerobic respiration and provides energy for the cell.
• What is the function of the ribosomes?


  Contain amino acids and is the site of protein synthesis.
• What is the function of chloroplasts?

  Site of photosynthesis. Contains chlorophyll which absorbs light.
• What is the function of the vacuole?


  Contains cell sap and provides the cell with rigidity.
• What is the function of the cell wall?

  Made from cellulose to prevent the cell from bursting and provides strength to the cell.
• Cell differentiation is where cells become specialised to carry out specific functions.
• How are sperm cells adapted to their function?

  Streamlined head: to aid swimming

  Acrosome: has digestive enzymes to help break down egg

  Mitochondria: supplies energy to allow cell to move
• How are nerve cells adapted to their function?

  Myelin sheath: Insulates the cell/speeds up transmission

  Axon: long and can carry nerves from long distances

  Dendrites: allows nerves to branch out and connect to other cells
• How are muscle cells adapted to their function?

  Mitochondria: to help with movement and contraction

  Proteins (myosin and actin): to help muscles slide over each other and contract
• How are root hair cells adapted to their function?

  Thin walls/large surface area: More water can move in and shorter diffusion pathway

  Mitochondria: Provide energy for active transport
• How are xylem cells adapted to their functions?

  Walls contain lignin: strengthens the cell to withstand pressure of water

  Hollow centre: Makes a continuous tube for water and mineral ions to move through
• How are phloem cells adapted to perform their function?

  Cells make sieve plates: allow movement of substances from cell to cell

  Few subcellular structures: lots of empty space to allow substances to move

  Companion cells: provide mitochondria
• To become specialised, cells must undergo cell differentiation. In animals, cells differentiate at an early stage for repair/replacement of cells. Many plants retain the ability to differentiate throughout their whole life.
• An electron microscope has much higher magnification and resolution than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures
• To make an image focused on a microscope, use the coarse adjusting/focusing dial
• Resolution is the ability to distinguish between two points and gives a sharper image
• How would you get a magnification of 50?

  Make the eyepiece x5 and the objective lens x10
• Magnification= image size/actual size
• What happens in stage 1 of the cell cycle?

  The cell grows and organelles (ribosomes and mitochondria) increase in mass and grow in number. DNA is replicated to form 2 copies of each chromosome.
• What happens in stage 3 of the cell cycle?

  The cytoplasm and cell membrane divide to form 2 identical daughter cells.
• Explain each stage of the cell cycle.

  Stage 1: The cell grows and the ribosomes and mitochondria increase in mass and number. DNA is then replicated so there are two copies of each chromosome.

  Stage 2: Mitosis. Each chromosome is pulled to the opposite end of the cell and the nucleus divides.

  Stage 3: The cytoplasm and cell membrane divide, forming two identical daughter cells
• The cell cycle is important because it is responsible for growth and repairing tissues and replacing damaged cells
• A stem cell is an undifferentiated cell of an organism which can undergo cell division to produce more cells
• Stem cells from human embryos can be cloned or can replicate themselves to differentiate into most different types of human cells. These can help cure paralysis, diabetes and neural cells for brain diseases.
• Adult stem cells can replaced dead or damaged tissue to form new cells such as blood cells
• Meristem tissue can differentiate into any type of plant and can be used to make clones of a plant to save a rare plant from extinction.
• In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment. These can be grown into any cells needed such as new tissue organs
• Diffusion is the movement of particles in a solution from an area of high concentration to an area of low concentration.
• Explain negatives of stem cell research.

  • Removal of stem cells means destruction of embryo
  • Religious or ethical problems that say it goes against natural process of reproduction
  • Very expensive
• Explain the positives of stem cell research

  • Can be used to replace damaged body parts
  • Unwanted embryos can be reused
• How does concentration gradient affect the rate of diffusion?

  The greater the conc gradient, the faster the rate of diffusion. This is because more particles are randomly moving down a gradient rather than against it.
• How does temperature affect the rate of diffusion?


  The greater the temperature, the greater the movement of particles resulting in more collisions and a faster rate of diffusion