B1 cells and organisation Flashcards
what is a light microscope
a microscope that uses a beam of light to form an image of an object
what is an electron microscope
a microscope that uses a beam of electrons to form an image and can magnify up to 2,000,000 times which lets you see the subcellular structures inside cells
what is the equation for calculating image size
magnification x size of real object
what happens in diffusion when SA:V ratio gets smaller
gases and food molecules can no longer reach every cell by simple diffusion
metabolic waste cannot be removed fast enough to avoid poisoning the cells
name adaptations for exchanging materials
1) large surface area
2) thin membrane (short diffusion path)
3) efficient blood supply- maintains steep concentration gradient
what is diffusion
process that allows dissolved substances to pass through the cell membrane (enter or exit cell)
what process is it that moves from high concentration to low concentration
diffusion and osmosis
what factors speed up the rate of diffusion
bigger the difference in concentration gradient
increase in temperature
increase in surface area
what is osmosis
when water molecules move across a partially permeable cell membrane
what is isotonic
when the concentration of solutes in the solution outside the cell is the same as the internal concentration
what is hypertonic
when the concentration of solutes in the solution outside the cell is higher than the internal concentration
what is hypotonic
if the concentration of solutes in the solution outside the cell is lower than the internal concentration
what is turgor
pressure that makes cells hard and rigid
what is plasmolysis
when water is lost by osmosis and the vacuole and cytoplasm shrink and the cell membrane pulls away from the cell wall. these cells die quickly unless osmotic balance restored
what is active transport
when the substances needed by a cell have to be moved against a concentration gradient across a partially permeable membrane
