b2 Flashcards
Define diffusion
Movement of particles from high to low concentration.
Name 3 factors that affect the rate of diffusion
Surface area, concentration gradient, temperature.
Define osmosis
Diffusion of water from dilute to concentrated solution, across a partially permeable membrane.
Define active transport
Movement of substances from low to high concentration. Requires energy.
Describe how the alveoli in the lungs are adapted for gas exchange
Large surface area, good blood supply, thin walls.
Describe how the microvilli in the small intestine are adapted to absorb glucose
Large surface area, good blood supply, thin walls, lots of mitochondria.
Name the three stages of the cell cycle
Replication, Mitosis, division.
Describe what happens during replication.
Cell grows and DNA is copied.
Describe what happens during mitosis.
Contents of the cell are rearranged - one set of chromosomes are pulled to each end of the cell. Nucleus divides.
Describe what happens during division.
Cytoplasm and cell membrane divides. Two identical daughter cells are produced.
Define a stem cell.
Unspecialised cell.
Define differentiation
Process by which cells become specialised.
Give the three types of stem cells.
Embryonic, adult and plant stem cells.
State the advantage of using embryonic cells
They can differentiate into almost all types of cells.
Give the location of adult stem cells.
Bone marrow.
