Diffusion
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define: DIFFUSION
the NET movement of particles from a region of higher concentration to a region of lower concentration DOWN a concentration gradient
Give 3 examples of where diffusion occurs + brief explanation (I WOULD SKIP THIS)
LUNG DIFFUSION: oxygen diffuses in ,carbon dioxide diffuses out LEAF DIFFUSION: carbon dioxide diffuses into cells, oxygen diffuses out FOOD DIFFUSION: food molecules diffuse through the lining of the small intestine and into the blood stream
define: CONCENTRATION GRADIENT
the difference in concentration between 2 areas -which causes particles to move from a high concentration to a low concentration
when does NET diffusion into a cell occur?
when there is a HIGHER CONCENTRATION of particles outside the cell
When does NO NET diffusion into/out of a cell occur? • (no overall movement)
when there is EQUAL CONCENTRATION of particles inside and outside the cell
Give 4 factors that increase the rate of diffusion
• bigger concentration gradient • higher temperature (higher kinetic energy) 3.larger SA (of the cell membrane) 4.shorter distance
Why do multicellular organisms need special exchange surfaces? + name substances certain organisms need? (I WOULD SKIP)
all organisms need certain substances to keep them alive Oxygen → for aerobic respiration (energy) Glucose → for energy Proteins → for growth and repair Fats → for cell membranes and energy storage Water → for chemical reactions and keeping cells hydrated Minerals → to help enzyme action and keep their water potential + remove wate materials : carbon dioxide ,oxygen ,ammonia
why do multicellular organisms need exchange systems?(2)
• they have a low surface area to volume ratio 2.they’re diffusion distance is too high EXTRA:(They have a low surface area to volume ratio, so diffusion alone is too slow to supply all cells. Exchange systems increase surface area to allow efficient movement of substances in and out.)
find: a) SA of 6 mm cube b) find Volume of 6mm cube b) find SA:Vol of 6 mm cube
a) SA =216m b) Vol = 216 c) ratio = 1:1