B2

• Define diffusion


  -the net movement of particles from an area so higher concentration to an area of lower concentration along a concentration gradient
• give an example in our bodies where diffusion take place

  -blood carries glucose and oxygen around out body and the substances diffuse into cells that need them
• how does decreasing the distance that particles have to travel increase the rate of diffusion?

  -less time taken to travel a shorter distance
• How does a steeper concentration gradient affect the rate of diffusion

  -the steeper the concentration gradient. the greater the net movement of particles, therefore the higher rate of diffusion
• does a small surface area increase or decrease the rate of diffusion?

  state reasons why

  -decrease the rate of diffusion

  -less available space for diffusion so fewer particles can move in a period of time.
• Define osmosis


  -the net movement of water particles across a partially permeable membrane from a region of higher concentration to a region of lower concentration.
• What is a partially permeable membrane?

  provide an example

  -Membrane with small holes to allow only tiny particles to pass through

  -example is a cell membrane
• What is water potential?

  Water potential is the likelihood of water molecules to diffuse out of or into a solution.
• If a solution has a high water potential, does it have a high or low concentration of water molecules?

  -high concentration of water molecules
• What is the formula to work out percentage change?

  change in result

  -------------------- (x 100)

  original result
• Example question: A potato cylinder has a starting mass of 1.32g. This decreases by 0.19g. Calculate the percentage change.

  change in result = - 0.19g

  original result = 1.32g

  
  

  -0.19 / 1.32 = -14.39% (2dp)
• Define active transport

  -the movement of particles across a membrane against a concentration gradient from an area of lower concentration to an area of higher concentration
• Provide an example of active transport

  -plants use active transport to take minerals from the soil. There is usually less concentration of nitrate ions for example in the surrounding soil compared to the plant's roots.
• What is mitosis?

  -mitosis is the process by which body cells divide to form genetically identical daughter cells.
• What are the 4 stages of the cell cycle? (mitosis)

  -DNA replication

  -movement of chromosomes

  -cytokinesis

  -growth of daughter cells
• What is complementary base pairing and what does T bind with?

  -Complementary base pairs are pairing of different bases ( A,T,C,G)

  t pairs with a
• What happens during the prophase?

  -the chromosomes start to condense

  -the nucleus disappears
• What happens during the metaphase?

  Chromosomes line up in the middle of the cell
• What happens during anaphase?

  The chromosomes separate and move along spindle fibers to opposite ends of the cell
• What happens during the telophase?

  -2 new nuclei form nd membranes reappear
• What is the name given to the process by which a cell changes to become specialised for it's job?

  cell differentiation
• Why is it important that organisms have specialised cells?

  -enables them to work more efficiently
• A sperm cell is a specialised cell to help male DNA into the female's DNA.

  what features does it have to help it carry out its job?

  -flagellum to help to swim faster

  -acrosome to break down layers in the ovem

  -streamlined head to move faster

  -mitochondria to transfer energy

  
• A palisade cell is a specialised cell to carry out photosynthesis.

  what features does it have to help it carry out its job?

  -chloroplasts which contain chlorophyll

  -tall shape to expose more surface area

  -thin shape to fit more into 1 leaf

  
• Red blood cells are specialised to transport oxygen.

  What features does it have to help it carry out its job?

  -biconcave shape to increase surface area

  -no nucleus to contain more haemoglobin

  -haemoglobin (protein which binds to oxygen)

  
• What are stem cells?

  -undifferentiated cells which can divide by mitosis and develop into any type of specialised cell depending on the instruction given
• What are the 2 types of stem cells in animals?

  -embryonic

  -adult
• True or false: Embryonic stem cells are found in early human embryos and have the potential to turn into any type of cell.

  -TRUE
• True or false: adult stem cells are only found in some places like bone marrow. These aren't very versatile and cant turn into any stem cells, only certain ones from the tissue they originally came from.

  -TRUE
• What is a difference between an animal stem cell and a plant meristem cell?

  Meristem cells can divide for as long as the plant lives.
• True or false: Cells that have a large surface area to volume ratio have a higher rate of diffusion, osmosis or active transport

  true
• Why do substances move in and out of cells quicker at a higher temperature?

  -This is because a higher temperature gives the particles more energy