B1: EXCHANGING SUBSTANCES

Question 1

What is diffusion?

Answer 1

the net movement of particles from an area of high concentration to an area of low concentration

Question 2

What is osmosis?

Answer 2

the net movement of water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane

Question 3

What is active transport?

Answer 3

the net movement of particles agaisnt the concentration gradient (requires energy)

Question 4

Adaptations of exchange surfaces

Answer 4

-thin membrane (short diffusion pathway)
-large surface area
-good blood supply
-ventilated

Question 5

Alveoli

Answer 5

-gas exchange (in the lungs)
-large surface area
-moist lining
-thin walls
-good blood supply

Question 6

Villi

Answer 6

-absorption (in the small intestine)
-folds increase surface area
-thin walla
-good blood supply

Question 7

Leaves

Answer 7

-gases diffuse in and out of leaf
-stomata
-flattened shape increases surface area
-walls of cells in leaves form another exchange surface (air spaces in leaf increase surface area

Question 8

Gills

Answer 8

-gas exchange surface in fish
-gill filaments and lamellae increase surface area
-lamellae have losts of capillaries to speed up diffusion
-thin surface layer of cells

Question 9

RP- Osmosis: method

Answer 9

-cut identical potato cylinders and measure their masses
-measure 10cm^3 of different concentrations of a sugar solution into some beakers (one should be pure water and another should be very concentrated sugar solution with different concentrations in between)
-add 1 potato cylinder to each beaker for a set amount of time
-take the potato cylinders out, dry them with a paper towel and then measure their masses again
-calculate % change in mass (final mass - initial mass / initial mass)

Question 10

RP-Osmosis: variables

Answer 10

IV - conc. of sugar solution
DV - change in mass of potato cylinders
CVs - time left in solution, temp of solutions