B2

• The distance between the areas of higher and lower concentration can affect the rate of diffusion.
• Osmosis is the diffusion of water across a partially permeable membrane.
• The diffusion of particles tends to even out their concentration across a given region.
• The rate of diffusion depends on temperature, surface area, and concentration gradient.
• Diffusion is the movement of particles from an area of high concentration to low concentration.
• The rate of diffusion depends on the concentration gradient across the diffusion pathway.
• The presence of a catalyst can increase the rate of diffusion.
• Increasing temperature increases the kinetic energy of molecules, leading to more frequent collisions with other molecules and an increase in the rate of diffusion.
• Diffusion occurs when there is a difference in concentration or pressure on either side of a semi-permeable membrane.
• how are macromolecules and nutrients transported into and out of the cell?

  they are transported by endocytosis and exocytosis.
• what is a cel membrane pump?

  -these are the carrier proteins that serve in active transport.-they move substances from LOWER to HIGHER concentration.
• define active transport


  the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
• Where do diffusion and osmosis move from compared to active transport regarding water?

  Diffusion and osmosis moves from where there is more water to less water. However, active transport moves from less water to more water.
• What way does diffusion and osmosis move regarding the concentration gradient compared to active transport?

  Diffusion and osmosis moves down the concentration gradient so doesn't require energy but active transport moves up (against) the concentration gradient so it requires energy from respiration.
• Word equation for respiration

  glucose + oxygen --> carbon dioxide + water + energy
• Name and explain another example of active transport.

  The small intestine. This is to ensure that all glucose that has been made available by digestion is absorbed into the blood.
• Name and explain an example of active transport.

  The roots of a plant. Mineral ions in the soil are at a low concentration compared to the cytoplasm of the plant cell.
• When does active transport occur?

  Active transport occurs when a substance must be moved from an area of lower concentration to an area of higher concentration through a cell membrane.

  
• What type of process is active transport and what does this mean?

  Active transport is an active process which means it requires energy from respiration to power it.
• Active transport


  It is another mechanism by which substances can move into and out of cells.

  
• What is the cell cycle?


  It is when cells in the body divide to produce more cells, so your body can grow and replace damaged cells and cells grow and divide over and over again.
• What are the three separate growth stages called?


  G, S and G2
• What is 'gap phase one'?


  At this phase, the cell grows and new cell structures and proteins are made.
• What is the 'S' phase?


  At this phase, cells replicate its DNA, so that when it splits during mitosis and the two new cells will contain identical DNA.
• What is 'gap phase two'?


  At this phase, cells keep growing and proteins needed for cell division are made.
• Where does the cell cycle start and end?

  With mitosis.
• Define mitosis.


  Mitosis is when a cell reproduces itself by splitting to form two identical offspring.
• What is the first stage of mitosis?

  The cell has two copies of its DNA all spread out in long strings.
• What is the second stage of mitosis?


  The DNA forms X-shaped chromosomes. Each 'arm' of a chromosome is an exact copy of the other. This happens before the cell divides.
• What is the third stage of mitosis?


  The chromosomes then line up at the center of the cell and cell fibers pull them apart. The two arms of each chromosome go to opposite ends of the cell.
• What is the fourth stage of mitosis?


  Membranes from around each of the sets of chromosomes. these become nuclei of the two new cells.
• What is the fifth and final stage of mitosis?


  The cytoplasm divides; two new cells containing exactly the same DNA as they're genetically identical to each other and to the parent cell.
• What is differentiation?


  Differentiation is the process by which a cell changes to become specialised for its job.
• What is an example of differentiation in plants?


  Palisade leaf cells carry out photosynthesis as they contain chloroplasts. Their tall shape means that they have a lot of surface area exposed down the side for absorbing carbon dioxide from the air in the leaf, and their thin shape means that you can fit loads of them in at the top of a leaf, so they're nearer the light.
• What is an example of differentiation in animals and humans?


  A sperm's function is to get the male DNA to the female DNA during reproduction. Sperm have long tails and streamlined heads to help them swim, they contain lots of mitochondria to provide them with energy and they have enzymes in their heads to digest through the egg's cell membrane.
• What is an example of an undifferentiated cell?


  Stem cells are undifferentiated but depending on what instructions they're given, they can divide by mitosis to become new cells, which then differentiate.
• Why are embryonic stem cells so important for growth and repair?

  They have the potential to become any kind of cell.
• Where can you find stem cells in the body?

  In adults, stem cells can be found in bone marrow. You can also find them in the umbilical cord.
• What is the main disadvantage of stem cells?


  They cannot turn into any type of cell.
• What are the only cells in plants that divide by mitosis?


  Meristems- they are found in plant tissues.