U3. Movement into and out of cells

Question 1

Define diffusion

Answer 1

Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration down a concentration gradient as a result of their random movement

Question 2

What factors affect the rate of diffusion?

Answer 2

• diffusion distance
• temperature
• surface area
• concentration gradient

Question 3

How does diffusion distance speed up diffusion?

Answer 3

shorter diffusion distance

Question 4

How does temperature speed up diffusion?

Answer 4

higher temperature: molecules have more kinetic energy to move (move faster)

Question 5

How does surface area speed up diffusion?

Answer 5

larger surface area to volume ratio

Question 6

How does concentration gradient speed up diffusion?

Answer 6

The steeper the concentration gradient, the faster it will diffuse
(or to maintain the concentration gradient)

Question 7

How are alveoli adapted for efficient gas exchange? (3)

Answer 7

• many alveoli (large surface area)
• short diffusion distance: cell-lining one cell thick, only diffuse two layers of cell
• consistent breathing and blood circulation maintains the concentration gradient

Question 8

How is the small intestine adapted to absorb food substances? (3)

Answer 8

• cell lining only one cell thick (short diffusion distance)
• small intestine folded (large surface area)
• blood consistent circulation (maintains concentration gradient)

Question 9

How are leaves adapted for efficient gas exchange? (2)

Answer 9

• thin leaf (diffusion distance is short)

- large surface area (flat)

Question 10

What is the importance of water in body? Name 3 uses

Answer 10

water acts as a solvent

• digestion of large food substances
• excretion of toxic waste
• transport substances around the body
• in plants: photosynthesis

Question 11

Define osmosis

Answer 11

Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

Question 12

Define partially permeable membrane

Answer 12

Allows some small molecules like water to go through, but not large ones
Cell membrane is a partially permeable membrane

Question 13

Name the three solutions (different concentrations)

Answer 13

• pure water (hypotonic solution)
• dilute solution (isotonic solution)
• concentrated solution (hypertonic solution)

Question 14

Why do plant cells and animal cells behave differently in hypotonic solutions?

Answer 14

plant cells have a cell wall to withstand the turgor pressure, while animal cells do not have a cell wall, leading it to burst

Question 15

What makes plant cell turgid?

Answer 15

plants have an inelastic cell wall that does not change shape
when water pressure acts on the inelastic wall, the cell becomes turgid
plants are supported by the turgor pressure within cells

Question 16

Define active transport

Answer 16

Active transport is the movement of particles through a cell membrane from a lower concentration to a region of higher concentration using energy from respiration (against the concentration gradient)

Question 17

What are found in the cell membrane that transport molecules?

Answer 17

Carrier protein

Question 18

How does the carrier protein transport molecules across the membrane?

Answer 18

Energy from respiration is used to change the shape of the carrier protein