C4 Transport Across Cell Membranes

Question 1

Solvent

Answer 1

The liquid in which a solute is dissolved to form a solution

Question 2

Solute

Answer 2

The minor component in a solution, dissolved in the solvent.

Question 3

Fluid-mosaic model

Answer 3

Fluid - properties and lipids are free to move around. Mosaic - an assortment of components of different sizes and shapes embedded in the phospholipid bilayer

Question 4

Phospholipid bilayer

Answer 4

Phospholipids arrange themselves into a bilayer so that the hydrophilic heads are facing out (towards water) and the hydrophobic tails are facing in

Question 5

Cholesterol

Answer 5

Membrane Stability:
1. Prevents membrane from becoming too FLUID by reducing phospholipid movement; pull together the fatty acid tails of the phospholipid molecules
2. Prevents membrane from becoming too RIGID by reducing cell frigidity @ low temperatures

Question 6

Extrinsic proteins

Answer 6

Present on only one side of the phospholipid bilayer - provide support to the membrane or may be involved in cell signalling.

Question 7

Intrinsic proteins

Answer 7

Embedded through both sides of the phospholipid bilayer - channel and carrier proteins which transport large molecules and ions across the membrane

Question 8

Glycoproteins

Answer 8

Attached to Intrinsic proteins: Cell adhesion - This is the attachment of cells to one another.
Cell recognition - This allows cells to recognise one another.
Cell signalling - This is communication between cells.

Question 9

Glycolipids

Answer 9

Attached to lipids Cell adhesion - This is the attachment of cells to one another.
Cell recognition - This allows cells to recognise one another.
Cell signalling - This is communication between cells.

Question 10

Simple Diffusion

Answer 10

• Simple diffusion does not require energy, and is a net movement of molecules from a high concentration to a low concentration that occurs down a concentration
  gradient
  (energy exists as kinetic energy but doesn’t need an external source of energy ie. ATP, therefore passive movement)

Question 11

Facilitated Diffusion

Answer 11

Diffusion that is made easier by transmembrane channels and carriers in the membrane (channel and carrier proteins) as ions cannot pass through the membrane due to the hydrophoic fatty acid tails

Question 12

Factors that affect diffusion

Answer 12

1. concentration gradient
2. higher temperature
3. larger surface area
4. smaller molecule
5. shorter distance for diffusion

Question 13

How does a smaller molecule/ion affect diffusion rate

Answer 13

Less kinetic energy is needed to move a smaller molecule, so it’ll move faster at the same temperature, increasing the rate of diffusion

Question 14

How does the concentration gradient affect diffusion rate

Answer 14

The bigger the difference of concentration, the greater the probability of molecules colliding over the region, therefore increasing the rate of diffusion

Question 15

How does a shorter diffusion pathway affect diffusion rate

Answer 15

If the speed is the same, but the distance is smaller, then the time taken to travel the distance must be smaller
!cell membranes cannot be made thinner!

Question 16

How does a higher temperature affect diffusion rate

Answer 16

Molecules have more kinetic energy, so they move faster, and they are more likely to be more collisions, increasing the rate of diffusion

Question 17

How does a larger surface area affect diffusion rate

Answer 17

The more space there is for diffusion to occur, the faster it can happen as there are more opportunities for diffusion to happen

Question 18

How does having more protein carriers affect the diffusion rate

Answer 18

The more protein carriers, the more opportunities for molecules to diffuse through the membrane, increasing the rate of diffusion

Question 19

Similarities & Differences between facilitated and simple diffusion

Answer 19

SIMILARITIES:
1. Passive process; no energy from EXTERNAL sources
2. Occurs down a concentration gradient
DIFFERENCES:
1. Facilitated requires/occurs at specific points on the cell membrane, i.e., channel and carrier protein

Question 20

Molecules that can pass through the phospholipid bilayer

Answer 20

1. Hydrophobic molcules (O2, CO2, N2)
2. Small uncharged non-polar molecules (H2O, Glycerol, Urea, Ethanol)

Question 21

Molecules that cannot pass through the phospholipid bilayer

Answer 21

1. Large molecules
2. Polar molecules

Question 22

Diffusion of NON-POLAR (attracted to lipids/ lipid soluble) molecules through phospholipids

Answer 22

RAPIDLY diffuse

Question 23

Diffusion of POLAR molecules (water soluble) through phospholipids

Answer 23

SLOW diffuse

Question 24

Diffusion of CHARGED particles (ions/polar molecules)

Answer 24

UNLIKELY to diffuse

Question 25

Osmosis

Answer 25

The net movement of water from a high water potential (dilute solution) to a lower water potential (more concentrated solution) through a partially permeable membrane. This will happen until equilibrium is reached

Question 26

Water Potential

Answer 26

the pressure created by water molecules - therefore adding solute to pure water will lower the water potential

Question 27

HYPOtonic

Answer 27

Solution with a LOWER concentration outside the cell (solution has a HIGHER water potential than the celll0

Question 28

HYPERtonic

Answer 28

Solution with a HIGHER solute (sugar,salt,etc.) concentration outside of the cell (therefore the solution has A LOWER water potential than the cell)

Question 29

Isotonic

Answer 29

Same water potential inside and outside of the cell

Question 30

Turgid

Answer 30

Enlarged and swollen with water (plant cells stay like this, and don't burst due to strength from CELL WALL)

Question 31

Cell Lysis

Answer 31

When animal cells BURST after they become TURGID due to them not having a cell wall

Question 32

Plasmolysis

Answer 32

When the cell membrane becomes INTACT from the cell wall (detached)

Question 33

Flaccid

Answer 33

Cell shrinking due to loss of water after being in a hypertonic solution for long periods

Question 34

Co-transport

Answer 34

Coupled movement of substances across a cell membrane

Question 35

Symporter

Answer 35

Membrane protein that is involved in the transport of two or more different molecules across the cell membrane in the same direction

Question 36

Active Transport

Answer 36

The movemnt of molecules or ions against the conentration gradient from a low concentration to a high concentration, using ATP and carrier proteins

Question 37

Similarities & Differences between active transport and passive movement

Answer 37

1. active transport uses metabolic energy in the form of ATP, and passive movements rely on the concentration 2. active transport; substances are moved AGAINST the concentration gradient, passive movement; molecules move DOWN the concentration gradient 3. active transport; carrier proteins are involved, FACILITATED uses carrier and channel, simple doen't require either

Question 38

Steps of active transport

Answer 38

1. molecule binds to the receptor site of the **carrier** proteins 2. On the inside of the cell/organelle, ATP binds to the protein, causing it to split into ADP and phosphate molecules. Therefore, the protein changes shape and opens to the opposite side of the membrane 3. The molecule/ion is then released to the other side of the membrane 4. The phosphate molecule is released from the protein, causing it to revert to its original shape. The phosphate molecule recombines with the ADP to form ATP during respiration

Question 39

Fick's Law

Answer 39

rate of diffusion = (s.a x difference in concentration gradient)/thickness of surface