F211-Transport Across Membranes

Question 0

What 4 factors determine the rate of diffusion?

Answer 0

1~The concentration gradient-the steeper the gradient, the quicker the rate of diffusion.

2~Temperature-high temp=more kinetic energy so faster diffusion.

3~The surface area- greater the SA, faster the diffusion.

4~Type of molecule or ion diffusing-larger molecules need more kinetic energy to move so they diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.

Question 1

What 6 ways can molecules be transported through the plasma membrane?

Answer 1

~diffusion
~osmosis
~facilitated diffusion
~active transport 
~endocytosis
~exocytosis

Question 2

Define Diffusion

Answer 2

This is the NET movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient until they are in a state of dynamic equilibrium.

Question 3

What molecules can diffuse through the membrane via diffusion?

Answer 3

Oxygen (non polar)
Carbon Dioxide (polar but small)
Water (polar but small)

Question 4

Define Facilitated Diffusion

Answer 4

The passage of molecules from an area of high concentration to an area of low concentration across the membrane through a carrier or channel protein.

Question 5

What molecules can transport through the membrane via facilitated diffusion?

Answer 5

Large polar molecules - such as Glucose and Amino Acids
Charged ions (Na+ of Cl-)

Question 6

Define Osmosis

Answer 6

Osmosis is the passive moment of water molecules from a region of high water potential to a region of low water potential through a partially permeable membrane

Question 7

What is water potential?

Answer 7

The tendency of water molecules to move from one place to another. Some molecules collide with the membrane as they move around at random. This will exert a pressure on the membrane.

Question 8

What is the highest water potential?

Answer 8

0kPa

Question 9

Define Hypertonic Solution

Answer 9

A hypertonic solution has a lower (more neg) water potential (water moves out)

Question 10

Define Hypotonic Solution

Answer 10

A hypotonic solution has a higher (less neg) water potential (water moves in)

Question 11

Define Isotonic Solution

Answer 11

An isotonic solution has fb exams water potential

Question 12

Define Incipient Plasmolysis

Answer 12

Incipient Plasmolysis is when the cytoplasm of a plant cell just begins to shrink away from the cell wall. 50% of cells will be plasmolysed when the mean solute potential equals the water potential of the external solution.

Question 13

What happens when an animal cell is places in a Hypotonic Solution?

Answer 13

Water enters by osmosis, the cell bursts which is called Lysis

Question 14

What happens when an animal cell is places in an Isotonic Solution?

Answer 14

Water movement is equal, the cell stays the same

Question 15

What happens when an animal cell is places in a Hypertonic Solution?

Answer 15

Water moves out of the cell by osmosis, the volume decreases, the membrane shrinks which is called Crenation

Question 16

What happens when a Plant cell is placed in a Hypotonic Solution?

Answer 16

Water enters by osmosis, the cell becomes Turgid

Question 17

What happens when a Plant cell is placed in an Isotonic Solution?

Answer 17

Water movement is equal, the cell stays the same

Question 18

What happens when a Plant cell is placed in a Hypertonic Solution?

Answer 18

Water leaves by osmosis, the cell shrivels which is called Plasmolysis

Question 19

Define Facilitated Diffusion

Answer 19

The passive net movement of molecules from a region of high concentration to a region of a lower concentration gradient through a channel or carrier transport protein

Question 20

Suggest why different red blood cells haemolyse at different salt concentrations?

Answer 20

All cells can have slightly different water potentials

Question 21

Define Active Transport

Answer 21

This is the movement of substances across the membrane from an area of low concentration to an area of high concentration against the concentration gradient

Question 22

What does Active Transport require?

Answer 22

Specific carrier proteins and Energy in the form of ATP

Question 23

Cells which have active transport occurring may have Microvilli to increase the surface area, why?

Answer 23

They do this so more carrier proteins are available for active transport

Question 24

Cells which have active transport occurring may have many mitochondria, why?

Answer 24

This is for energy-it provides aerobic respiration - provides ATP for ATPsynthase

Question 25

What is Bulk Transport?

Answer 25

Moving large quantities of material in or out of a cell with the requirement of energy

Question 26

What are the two types of bulk transport?

Answer 26

Exocytosis - material out of cell Endocytosis - material into cell

Question 27

What are the two types of endocytosis? And what do they mean?

Answer 27

Phagocytosis-takes in solid molecules&forms a vesicle

Pinocytosis-takes in solutes and forms a vesicle

Question 28

Define endo/exocytosis

Answer 28

The bulk movement of molecules into or out if a cell