Biology B2

• What is diffusion?


  The net (overall) movement of particles from a region of high concentration to a region of a low concentration
• What does diffusion do?


  Move down a concentration gradient and continues until the concentration of the particles is the same everywhere
• What factors increase the rate of diffusion?


  Decrease the distance the particles need to move, increase the concentration gradient and increase the surface area
• What is osmosis?


  The diffusion of water molecules from a region of a high concentration to a low concentration through a selectively permeable membrane
• Where does osmosis occur in a plant cell?

  In the root cell
• What does osmosis cause to a plant cell?


  Water enters the root cells by osmosis and moves into tubes called xylem vessels to be transported to the leaves.
• Where does osmosis occur in an animal cell?

  Across the plasma membrane and into the cell
• What does osmosis cause to an animal cell?

  Causes the cell to expand and swel and to expand in volume
• What is active transport?


  Movement of molecules against their concentration gradient
• What does active transport allow?

  Allows cell to move substances from an area of low concentration to an area of high concentration
• What is a key feature of active transport?


  Particles are transported (pumped) against a concentration gradient
• Gimme another key feature of active transport


  ATP is required - this comes from respiration
• And another key feature of active transport

  The process makes use of carrier proteins in the cell membrane
• Cells that carry out a lot of active transport contain what? What does this mean>


  Many mitochondria so that they can respire rapidly to produce large quantities of ATP.
• When can the rate of active transport occur?

  Depend on the rate of respiration to produce the required ATP
• What are carrier proteins?

  Special proteins that span (stretch across) the width of the cell membrane
• What is transferred to make the protein change shape or rotate

  Energy
• What is an example of active transport


  During digestion - carbohydrates are broken down into glucose then glucose is actively transported into the bloodstream through the villi. The blood takes the glucose to wherever it is needed in the body
• Another example of active transport


  In nerve cells - a carrier protein actively pumps sodium ions out of the cell. At the same time potassium ions are pumped back in.
• And another example of active transport

  Plants - To take in minerals from the soil
• Explain why plants use active transport, rather than diffusion, to absorb mineral from the soil


  To ensure that the required mineral ions are absorbed from the dilute solutions within the soil into the root hair cells.
• What is mitosis?


  The process by which body cells divide
• How is DNA replicated?

  The two strands of DNA unzip, new bases are added (ATGC).
• How do chromosomes move in mitosis?


  Chromosome lines up at the center of the cell. Two identical copies of each chromosome form and move to opposite ends of the cell. Each end contains a full set of identical chromosomes. Two new nuclei form.
• Stage the three stages of the cell cycle

  Interphase, Mitosis and Cytokinesis
• What does the interphase part do in mitosis?


  The cells get ready to divide. The cell grows, DNA duplicates and more organelles are made.
• How does mitosis work?


  The genetic material separates to different ends of the cell, and the cell gets ready to divide into two daughter cells
• What does the cytokinesis part do in mitosis?

  At the end of mitosis, the cytoplasm and cell membrane spilt, and two new daughter cells are made
• State three reasons for mitosis?


  Growth, repair, and asexual reproduction.
• Explain how the skin produces new skin cells to repair the damage caused by a cut?


  Blood cells, including oxygen-rich red blood cells, arrive to help build new tissue. Chemical signals tell the cells to create collagen.
• What is blood that is coloured red called?

  Oxygenated blood
• What is cell differentiation?

  The process in which cells become specialised.
• What happens when cells differentiate?

  Its structure change so that is better adapted to perform its function.
• Gimme some examples where plant cells differentiate?

  In root cells and leaf palisade cells
• What is a sperm cell specialised to do?


  To transfer genetic material from the male to the ovum (egg)
• What is a feature of a sperm cell adaptations?

  Flagellum (tail) - Whips from side to side to propel the sperm to the ovum
• Another feature of a sperm cell adaptations


  Lots of mitochondria - Respiration occurs in mitochondria, and the reactions of respiration transfer energy from chemical stores o that the flagellum can move
• And another feature of a sperm cell adaptations

  Acrosome - Stores digestive enzymes, which break down the outer layers of the ovum to allow the sperm to transfer and incorporate its genetic material
• What are fat cells specialised to do?

  To store fat
• What do fat cells provide to animals?


  Insulation - Are used to form a protective layer around some organs such as the heart