module 2.5 mr hill

Question 1

what are the 5 reasons why plasma membranes are essential

Answer 1

1-partially permeable (to allow particles to pass)
2-signalling to other cells
3-compartmenalizing organelles (forms a boundary of an organelle)
4-allows electrical signals to pass
5-provide attachment sites for enzymes etc…

Question 2

draw the most basic structure ever of a plasma membrane

Answer 2

========== (double membrane)

Question 3

what is the plasma membrane made out of

Answer 3

phospholipids

Question 4

what is the glycocalyx

Answer 4

the combined layer of glycolipids and glycoproteins - carbohydrate groups on the exterior

Question 5

what are glycoproteins

Answer 5

proteins with carbohydrates attached

Question 6

what are glycolipids

Answer 6

lipids with carbohydrates attached

-phospholipid or lipid with chains of carbohydrate molecules

Question 7

what is the plasma membrane held together by and what does this allow for

Answer 7

held by cholesterol-> maintains membrane fluidity

Question 8

what are the 6 factors that affect rate of diffusion

Answer 8

temp, distance travelled, pressure, ph, conc., sa

Question 9

what is equilibrium?

Answer 9

situations where concentrations are balanced and no net movement.

Question 10

what’s a biological example of diffusion

Answer 10

gas exchange

Question 11

what is diffusion

Answer 11

the net movement of molecules/substances from a high conc to a low conc down a concentration gradient

Question 12

what can rapidly diffuse across a cell membrane

Answer 12

small non-polar molecules e.g C02 and O2

Question 13

talk about facilitated diffusion

Answer 13

• charged particles (ions) cannot diffuse across a membrane, even if they are very small.
  -if the molecule is to large or charged to diffuse across on its own…
  it can diffuse if there is a specific transport protein (channel)
  -with an addition of a protein that helps it out if the molecule is large, charged or both.

Question 14

what are the two types of proteins (pm)

Answer 14

channel proteins and carrier proteins

Question 15

channel proteins -state 2 points abt them

Answer 15

• form pores in the membrane

- many only let 1 type of molecule through

Question 16

carrier proteins -state 2 points abt them

Answer 16

• molecules fit in at membrane +specific molecule fits into carrier e.g glucose
• protein changes shape to pass molecule through

Question 17

solute?

Answer 17

any substance dissolved in a solvent

Question 18

solvent?

Answer 18

any fluid which can dissolve a solute

Question 19

solution?

Answer 19

A liquid that consists of a dissolved solute in a solvent

Question 20

what’s osmosis

Answer 20

osmosis is the net movement/diffusion of water. it is the movement of water molecules from a region of high water potential to a region of low water potential, through a partially- permeable membrane.

Question 21

water potential?

Answer 21

the tendency for water to move(diffuse). unit= kPa

Question 22

hypotonic?

Answer 22

higher water potential outside the cell (water moves in)

Question 23

hypertonic?

Answer 23

lower water potential outside the cell (water moves out the cell)

Question 24

what happens when water moves into plant cell via osmosis

Answer 24

membrane pushes against wall.

TURGID

Question 25

what happens when water moves into animal cell via osmosis

Answer 25

animal cell bursts open

CYTOLISED

Question 26

what happens when water moves out plant cell

Answer 26

cell membrane pulls away from cell wall as water leaves.
the cell is PLASMOLYSED
-the tissue becomes FLACID

Question 27

what happens when water moves out animal cell

Answer 27

animal cell shrinks and appears wrinkled

the cell is CRENATED

Question 28

what is active transport used to do

Answer 28

used to move molecules and ions across a membrane against their concentration gradient

Question 29

what does active transport require

Answer 29

• transport proteins( carrier proteins) (which require ATP to function)

Question 30

what do transport proteins use ATP to make

Answer 30

to make a conformational change (change shape) to allow molecules to pass.

Question 31

what 4 processes is active transport used in

Answer 31

• uptake of glucose and amino acids in the small intestine
• absorption of mineral ions by plant roots
• excretion of hydrogen ions and urea by kidneys
• excretion of sodium and potassium ions in neurones and muscle cells

Question 32

what do cells that undertake active transport on a large scale have a lot of

Answer 32

many mitochondria

Question 33

when is bulk transport used

Answer 33

when extremely large substances need to be moved across a cell membrane

Question 34

what are the 2 types of bulk transport and what do they involve

Answer 34

endocytosis and exocytosis (both involve changes to membrane shape)

Question 35

what is exocytosis

Answer 35

movement of volume out of cell

-vesicles fuse with plasma membrane and contents are released

Question 36

what is endocytosis

Answer 36

bulk transport of material into a cell

Question 37

what are the two processes within endocytosis

Answer 37

phagocytosis and pinocytosis

Question 38

endocytosis: what’s phagocytosis

Answer 38

engulfing of SOLIDS

uses pseudopodia to surround and engulf target

Question 39

endocytosis: what’s pinocytosis

Answer 39

• engulfing of LIQUIDS

Question 40

what are examples of proteins that could be attached to carrier proteins

Answer 40

function as:

• enzymes
• antigens
• receptor sites for complimentary shaped signalling chemicals such as hormones

Question 41

in neurones (nerve cells), what do the channel proteins and carrier proteins allow for

Answer 41

-entry and exit of ions to bring about the conduction of electrical impulses along their length.

Question 42

what is the myelin sheath wrapped around in a neurone

Answer 42

its wrapped around the axon

Question 43

what does the plasma membrane of white blood cells contain

Answer 43

special protein receptors that enable them to recognise the antigens on foreign cells.

Question 44

what do root hair cells have many of

Answer 44

• many carrier proteins to actively transport nitrate ions from soil to roots

Question 45

can fat-soluble molecules such as steroid hormones diffuse across the lipid bilayer

Answer 45

-yes as they can dissolve in the lipid bilayer (dont need a channel protein)

Question 46

what specific water channels allow water to move across cell membrane

Answer 46

-specific channel proteins called aquaporins

Question 47

how is conc across a cell membrane obtained?

Answer 47

• many molecules entering the cells then pass into organelles and are used for metabolic reactions
  (o2 for mitochondria and co2 for chloroplasts)

Question 48

5 factors that affect rate of simple diffusion

Answer 48

• temperature ( more k energy)
• diffusion distance (thicker membrane=slower)
• sa (more diffusion can take place across a larger sa)
• size of diffusing molecules
• conc gradient

Question 49

how is glucose moved through phospholipid bilayer

Answer 49

via a transmembrane carrier protein (its a large molecule)

Question 50

what do neurone plasma membranes have many channels specific for

Answer 50

-sodium ions or potassium ions

Question 51

what do epithelial cells have many channels specific for

Answer 51

-chloride ions