Cell Mem

Question 1

Diffusion

Answer 1

The net movement of particles from an area or higher concentration to an area of lower concentration.

Question 2

Facilitated diffusion

Answer 2

Moves particles down a concentration gradient, from a higher to a lower concentration.

Question 3

Carrier proteins

Answer 3

Large molecules attach to carrier in mem.
Protein changes shape.
Releases the molecule on the opposite side of mem.

Question 4

Channel protein

Answer 4

Form pores in the membrane for charged particles to diffuse through down a conc gradient. Different channel proteins facilitate the different charged particles.

Question 5

Osmosis

Answer 5

Diffusion of water molecules across a partially permeable membrane, from an area of higher water potential to an area of lower water potential

Question 6

Water potential

Answer 6

Potential of water molecules to diffuse out of or into a solution

Question 7

Pure water

Answer 7

Highest water potential

Question 8

Isotonic

Answer 8

Two solutions separated by partially permeable membrane and solute concentration that have the same water potential.

Question 9

Solute

Answer 9

Any substance that is dissolved in a solvent.

Question 10

Solvent

Answer 10

Water that the solute is dissolved in.

Question 11

Solution

Answer 11

Solute and solvent together

Question 12

Soon as you add a solute to water, you lower the

Answer 12

Water potential because water molecules are attracted to the solute and less free to move around.

Question 13

The lower the water potential and the higher the salt solution,

Answer 13

The more negative the value

Question 14

When is dynamic equilibrium reached

Answer 14

When water molecules have moved from high to low and equal number of water particles (no net movement).

Question 15

Factors that affect rate of osmosis

Answer 15

1. Water potential gradient
2. Thickness of exchange surface
3. Surface area of exchange surface

Question 16

What happens to pure water outside the cell

Answer 16

Osmosis. Water goes into cell and will burst it - haemolysed

In plant cells, swelling in cytoplasm and vacuole will push against the cell wall and make it turgid.

Question 17

What happens when high sugar conc outside the cell

Answer 17

Concentrated sugar solution makes low water potential so water moves out of the cell by osmosis down a water potential gradient. Animal cell shrinks and wrinkles.

Question 18

Hypotonic

Answer 18

Contain low solute conc and high water

Question 19

Hypertonic

Answer 19

High solute conc and low water

Question 20

Simple dilutions

Answer 20

The stepwise dilution of a substance in a solution.
Use the dilution factor at each step. It’s constant.

C1V1=C2V2

Question 21

How can you make sucrose solutions of any conc

Answer 21

By finding the scale factor.

1. Known conc
2. Find scale factor by conc of solution/ conc of solution you want to make.
3. Make solution weaker by cm^3/ scale factor.
4. Top up with distilled water with vol u want. So cm^3-weaker solution = distilled water

Question 22

Use solution to find water potential of potato cells

Answer 22

1. Cork borer to cut potatoes into identically sized chips, about 1cm in diameter.
2. Divide chips into 3 groups and measure mass of each group using mass balance.
3. Place 1 group into each of sucrose solution.
4. Leave chips in solutions for at least 20 mins.
5. Remove and dry gently and weigh again.
6. Record and calculate % change in mass for each group.
7. Make calibration curve - % change in mass against sucrose conc.

Question 23

How to find water potential on a graph

Answer 23

The point where the curve crosses the x-axis (where % change in m is 0) and is the point where water potential of sucrose solution is the same as water potential of potato cells.

Find the conc at that point then look up the water potential for the conc of sucrose solution.

Question 24

Experiment to investigate water potential

Answer 24

Use potato cylinders to find water potential of plant tissue.

Make servers solutions of different known conc to test in cylinders.

1. 5 test tubes
2. Add 10cm3 of the giving conc. I.e. 2M of sucrose solution to the first test tube and 5cm3 of distilled water to the other four test tubes.
3. Use a pipettes and take 5cm3 of solution from the first test tube and add to distilled water in second and mix throughly.
4. U now have 10cm3 of solution that’s half as concentrated as the solution 1M.
5. Repeat process three more times.

Question 25

Active transport

Answer 25

Moves particles from a low to high conc. Uses energy to move molecules and ions across membrane, against a conc gradient.

Question 26

What are involved in active transport

Answer 26

Carrier proteins. The molecules attach to carrier, protein changes shape and this moves the molecules across the membrane releasing it onto other side.

Question 27

Two main difference between facilitated diffusion

Answer 27

1. Active transport moves from low to high. Facilitated is always high to low. 2. Active transport requires energy - ATP releases energy as ADP and Pi when hydrolysed. Facilitated doesn't require energy and it's a passive process. 3. Active transport doesn't use channel proteins. Only carrier. Facilitated uses both.

Question 28

What is a type of carrier protein that works with active transport / name a carrier protein

Answer 28

Co-transporters. They bind two molecules at a time. The conc gradient of one of the molecules is used to move the other molecule against its own conc gradient.

Question 29

Explain an example of co-transport

Answer 29

Sodium ions move into the cell down their Conc gradient. That moves glucose into the cell against the conc gradient.

Question 30

How does glucose enter the ileum epithelium cell with sodium ions

Answer 30

Glucose is absorbed from the lumen of the ileum into bloodstream in the small intestine by co-transport. 1. Sodium ions transport out of ileum epithelial cells into the blood by the sodium potassium pump. 2. A concentration gradient is created. Higher conc of sodium ions in the lumen of the ileum than inside the cells. 3. Sodium ions diffuse from lumen of ileum into epithelial cells, down their conc. gradient. They do that through the sodium-glucose co-transporter proteins. 4. The co-transporter carries glucose into the cell with the sodium. The conc of glucose inside cell increases. 5. Glucose diffuses out of the cell into the blood down its conc gradient through a protein channel by facilitated diffusion.

Question 31

Factors affecting rate of active transport

Answer 31

1. Speed of individual carrier proteins - faster = faster. 2. No. Of carrier proteins- more = faster. 3. Rate of respiration in cells and availability of ATP - if respiration inhibited, active transport can't happen.

Question 32

Water potential (psi) measured in

Answer 32

kPA - kilopascals

Question 33

0M salt solutions

Answer 33

0kPa

Question 34

0.2M salt solutions

Answer 34

-100kPa

Question 35

0.4M salt solutions

Answer 35

-200kPa

Question 36

When won't osmosis occur

Answer 36

When solution is isotonic

Question 37

What does facilitated diffusion use

Answer 37

Carrier and channel proteins

Question 38

Large molecules would diffuse ___ through phospholipid bluster because

Answer 38

Slowly because they're so big

Question 39

Charged particles would diffuse ___ through phospholipid bluster because

Answer 39

Ions diffuse slowly because they're water soluble and the centre of the bilayer is hydrophobic

Question 40

Factors affecting facilitated diffusion

Answer 40

1. Conc gradient - higher = faster. 2. No. Of channel or carrier proteins - once all particles in membrane are in use, facilitated diffusion can't happen any faster even if u increase concentration gradient so the greater no. Of C or C, the faster.

Question 41

What are aquaporins

Answer 41

Special channel proteins that allow facilitated diffusion of water through cell membrane.

Question 42

What can diffuse thru

Answer 42

O2+CO2 because they're small and non polar so they're soluble in lipids and can dissolve hydrophobic bilayer.

Question 43

Factors affecting rate of diffusion

Answer 43

1. Conc gradient = higher - faster 2. Thickness - thin = shorter 3. Surface area = larger - faster

Question 44

What do microvillis do

Answer 44

Increase surface area as they are folds of the cell surface membrane.

Question 45

Polar

Answer 45

Can't pass through - requires proteins and have a partially positive and negative charge.

Question 46

Non polar

Answer 46

Can't pass/ diffuse through bilayer

Question 47

How can you investigate effect of solvents on permeability of cell membrane

Answer 47

Surround cells in increasing conc. if solvent increases membrane permeability because solvent dissolves the lipids in the cell membrane, causing it to lose structure

Question 48

Effects of cholesterol

Answer 48

Fits between phospholipids and bind to hydrophobic tails, causing them to pack more closely. That restricts movement of phospholipids, making membrane less fluid and more rigid. Maintains shake of animal cells.

Question 49

Phospholipids

Answer 49

Head = hydrophilic - water lover Tail = hydrophobic- water hater Centre = hydrophobic. Membrane doesn't allow water soluble substances through. Acts as a barrier. Arranged in a bilayer- head out on either side

Question 50

Some proteins have what attached

Answer 50

Polysaccharide chain (carbohydrate) called glycoproteins.

Question 51

Some lipids gave what attached

Answer 51

Polysaccharide chain called glycolipids

Question 52

Three features of cell surface membrane

Answer 52

Phillic head and phobic tail. String barrier from aqueous environment. Selective permeability. Proteins intrinsic and extrinsic. Intrinsic span full plasma membrane surface. Channel and carrier. Cholesterol- preventing water loss and limit lateral moving of membrane. Regulate membrane to have fluidity.

Question 53

Barrier is

Answer 53

Partially permeable

Question 54

Why fluid mosaic structure

Answer 54

Bilayer is fluid because phospholipids are always moving. Proteins are scattered thru out bilayer like mosaic. Include channel n carrier proteins. Receptor proteins on cell surface membrane allow cell to detect chemicals released from other cells. Chemical signals cell to respond.