3.2.3.2 - Transport across membranes Unit 2 Cells)

Question 1

Diffusion is an example of

Answer 1

passive transport - energy comes from natural, inbuilt motion of particles

Question 2

In diffusion the motion of the particles is described as

Answer 2

random motion

Question 3

In diffusion the direction of particle movement is

Answer 3

from an area of high concentration to an area of lower concentration - until equilibrium is reached

Question 4

Molecules which can diffuse through the phospholipid bilayer include

Answer 4

non-polar, small molecules e.g. oxygen and carbon dioxide

Question 5

Facilitated diffusion and diffusion differ because

Answer 5

facilitated diffusion requires a special protein molecules e.g. carrier or channel protein

Question 6

Facilitated and diffusion are similar because

Answer 6

they are both passive and molecules move with their concentration gradient (high to low)

Question 7

Molecules which do not diffuse easily across the phospholipid bilayer are

Answer 7

large, charged ions and polar molecules e.g. glucose

Question 8

What prevents large, charged and polar molecules diffusing across the plasma membrane

Answer 8

the hydrophobic fatty acids tails of the phospholipid bilayer

Question 9

Name the two types of protein molecules involved in facilitated diffusion

Answer 9

carrier and channel proteins

Question 10

Carrier proteins transport

Answer 10

molecules like glucose

Question 11

How do carrier proteins transport molecules like glucose?

Answer 11

glucose binds to the carrier specifically, carrier changes shape, releasing it onto the other side of the membrane

Question 12

Channel proteins transport…

Answer 12

water soluble ions

Question 13

How do channel proteins transport molecules like water soluble ions?

Answer 13

ion binds causing a change in the shape of the channel allowing the ion to enter the cell

Question 14

State 3 factors that affect the rate of diffusion

Answer 14

surface area, concentration gradient and thickness of exchange surface

Question 15

For maximum diffusion what adaptations does the exchange surface need

Answer 15

large surface area
Large concentration gradient
Thin - short diffusion distance

Question 16

Name 2 exchange surfaces in living organisms (humans)

Answer 16

alveoli and villi

Question 17

Where does diffusion take place in living organisms

Answer 17

1. alveoli - exchanging oxygen and carbon dioxide
2. Villi - exchange soluble molecules into the blood
3. Leaf (stomata) - carbon dioxide and oxygen
4. Roots - water

Question 18

How would diffusion be affected if the alveoli surface area is doubled

Answer 18

doubles

Question 19

How would diffusion be affected if the surface area is halved but the oxygen concentration gradient is doubled

Answer 19

no change

Question 20

How would diffusion be affected if the oxygen concentration is halved and the total thickness of the exchange surface is doubled

Answer 20

decreases 4 fold/quarter

Question 21

what is a protein channel filled with?

Answer 21

water

Question 22

What do carrier proteins and channel proteins have in order to transport molecules across the membrane?

Answer 22

binding sites

Question 23

How do substances move across the cell surface membrane by facilitated diffusion

Answer 23

1. Carrier/channel protein;
2. (Protein) specific/complementary to substance;
3. Substance moves down concentration gradient;

Question 24

The passive movement of water from an area of high water potential to an area of low water potential through a selectively permeable membrane is…

Answer 24

OSMOSIS

Question 25

Osmosis involves the movement of

Answer 25

water ONLY

Question 26

By adding more solute the a solution how does this affect the water potential

Answer 26

it lowers the WP - becomes more negative

Question 27

Why does pure water have a higher water potential than a solution of sugar

Answer 27

there are more ‘free’ water particles in pure water

Question 28

A potato has a WP of -200kPa was placed in pure water WP 0kPa, what happens?

Answer 28

Water ENTERS the potato by osmosis (water moved from a high WP to a lower WP)

Question 29

water potential is represented by

Answer 29

psi (greek letter)

Question 30

water potential is measured in units of pressure which are

Answer 30

kPa

Question 31

Pure water has a WP of

Answer 31

0kPa

Question 32

How can you determine the the WP of a potato

Answer 32

place potato in a series of solutions of different WP. Where there is no net gain of water by the potato is the WP of the potato.

Question 33

What happens if a red blood cell is placed in pure water

Answer 33

it swells and bursts - water enters the cell

Question 34

What happens if a red blood cell is placed in strong sugar solution

Answer 34

It shrinks - water leaves the cell

Question 35

What happens if a plant cell is placed in pure water

Answer 35

It swells - water enters the cell - it becomes turgid

Question 36

What happens if a plant cell is placed in strong salt solution

Answer 36

water leaves the cell - it shrinks - it plasmolysed

Question 37

What is meant by selectively permeable

Answer 37

Membrane only allows certain molecules through; it is only permeable to water and other small molecules `

Question 38

During an osmosis practical, how and why do you dry the potato chips?

Answer 38

with a paper towel. To remove surface water - This would add to the mass - which we do not want

Question 39

You must control the temperature during your osmosis practical - HOW?

Answer 39

Using a water bath and check the temperature at regular intervals using a thermometer

Question 40

give 2 similarities in the movement of substances by diffusion and osmosis

Answer 40

1. down a gradient (High to Low)

2. passive not active (does not use energy)

Question 41

The movement of molecules or ions AGAINST a concentration gradient using ATP and carrier proteins is describing…

Answer 41

Active transport

Question 42

Difference between active transport and facilitated diffusion

Answer 42

1. active transport uses ATP
2. Active transport uses only carriers (FD uses channels and carriers)
3. Active transport moves molecules against their concentration gradient

Question 43

Differences between active transport and osmosis

Answer 43

1. Active transport moves solutes or ions osmosis water moves
2. Active transport uses a carrier to transport a molecule across the plasma membrane, osmosis water moves through the membrane directly

Question 44

In active transport what does the molecule that is moving bind to on the carrier molecule?

Answer 44

A receptor/binding site

Question 45

After the molecule has bound to the receptor on the carrier (in active transport), what happens next?

Answer 45

ATP binds to the carrier on the opposite side, it splits into ADP and Phosphate (P) (releasing energy) causing the carrier to change shape, allowing the entry of the molecule.

Question 46

Why do some cells like root hair cells possess so many mitochondria?

Answer 46

Because they transport mineral ions against a concentration gradient. This requires energy

Question 47

What is unique about the carrier proteins used in active transport?

Answer 47

they have a specific tertiary structure

Question 48

Where is active transport used in humans?

Answer 48

Gut/Small intestine - Na+/K+ pump (absorption of glucose)

Question 49

How is low levels of glucose absorbed in the small intestine?

Answer 49

Using Na co transporter - ATP used indirectly

Question 50

Which form of cell transport requires energy?

Answer 50

active transport

Question 51

Which type of protein are involved in active transport?

Answer 51

carrier proteins

Question 52

rate of active transport is affected by..

Answer 52

1. speed of carrier molecules
2. number of carrier molecules
3. rate of respiration - ATP availability

Question 53

How does more carrier molecules affect active transport?

Answer 53

increases the rate

Question 54

How does an inhibitor of respiration affect active transport?

Answer 54

Less or NO ATP produced to rate of active transport reduced

Question 55

Where does the energy for active transport come from?

Answer 55

Hydrolysis of ATP (produced in respiration)