chapter 5 - plasma membranes

Question 1

what is the fluid mosaic model a diagram of?

Answer 1

the cell surface membrane / plasma membrane

Question 2

what is the function of the phospholipid bilayer

Answer 2

separates the cell from the outside
fluid - moves more freely
selective permeability (permeable to small or non-polar molecules but impermeable to large molecules)

Question 3

what is a phospholipid made up of?

Answer 3

a glycerol, two fatty acids (tails) and a phosphate-linked head group

Question 4

how is the phospholipid bilayer arranged?

Answer 4

two layers of phospholipids, with their tales pointed inwards.

Question 5

where are carbohydrate groups present in the plasma membrane ?
what do they form?

Answer 5

only on the outer surface of the membrane and are attached to proteins
forming glycoproteins, or attached to lipids forming glycolipids

Question 6

which part of the phospholipid is hydrophilic and which part is hydrophobic?
and what does this mean?

Answer 6

the head is hydrophilic - water loving
the fatty acid tail is hydrophobic - water fearing

Question 7

what are proteins called that extend all the way across the membrane?

Answer 7

transmembrane
integral
intrinsic

Question 8

what are the top 3 major components in the cell membrane

Answer 8

1. phospholipids
2. proteins
3. carbohydrates

Question 9

why is it important for carbohydrate to form distinctive cellular markers?

Answer 9

so the immune cells can differentiate between body cells, which they shouldn’t attack and foreign cells or tissue which they should attack

Question 10

how do saturated and unsaturated fatty acids react differently when temperature drops?

Answer 10

at cooler temperatures the saturated fatty acids pack tightly together, making a dense, fairly rigid membrane

unsaturated fatty acids can not pack together as tightly due to the bent structure of their tales.

because of this, a membrane containing unsaturated fatty acid tails with remain fluid at lower temperatures than a membrane of saturated ones

Question 11

how does cholesterol minimize the effects of low and high temperatures

Answer 11

keeps phospholipids from packing tightly together.
at high temperatures the cholesterol reduces fluidity, allowing for a wider range of temperatures in which a membrane maintains a functional, healthy fluidity

Question 12

what is important about the charge of the phospholipids

Answer 12

the head is polar - charged at the top
causing the phospholipid to become amphiphatic (some parts charged, others aren’t)

Question 13

what are the 6 main functions of the cell surface membrane

Answer 13

1. partially permeable (controls what enters and leaves the cell)
2. protection from external environment
3. surface proteins (antigens) bind and allow binding sites
4. compartmentalise the cell
5. cell communication & signalling
6. hormone, toxin and medicinal drugs binding site

Question 14

how thick is the surface membrane typically?

Answer 14

7-10nm thick

Question 15

what is the name for the carbohydrate chain that forms glycoproteins or glycolipids? (sugar)

Answer 15

“saccharide” sugar
mono-saccharide = one sugar
poly-saccharide = many sugars

Question 16

what are the names of proteins that go all the way through the membrane?

Answer 16

transmembrane
integral
intrinsic

Question 17

what is the difference between extracellular and cytosolic peripheral proteins?

Answer 17

extra-cellular = on the outside of the cell - act as receptors and normally glycoproteins

cytosolic = on the inner side of the cell surface membrane - for cell signalling or chemical reactions

Question 18

what are the 2 types of cholesterol apparent in the cell surface membrane?

Answer 18

LDL - low density
HDL - high density

Question 19

what are the main functions of integral/ transmembrane proteins?

Answer 19

-transport of ions, sugars and amino acids
- some are receptors for hormones, neurotransmitters or enzymes

Question 20

how does
-temperature
-solvents
and -detergents
affect the permeability of cell surface membranes?

Answer 20

• temperature = increase permeability - more Kinetic energy
  at extremely high temperatures enzymes denature increasing fluidity further.
• low temperature - ice crystals form, piercing membrane, increasing permeability
• solvents - increase (dissolve phospholipids)

-detergents - increase (strips phospholipid heads away)

Question 21

what are the two passive processes to move molecules across membranes

Answer 21

diffusion
facilitated diffusion

Question 22

define net movement

Answer 22

the overall movement

Question 23

what molecules need facilitated diffusion
b. and what is used to “facilitate” this and how is it done?

Answer 23

1. large molecules and charged particles
2. channel proteins - form a pore/channel in membrane
   carrier proteins - shaped so specific molecule fits into it then changes shape to permit molecule to pass

Question 24

why do small molecules diffuse quicker

Answer 24

it takes more kinetic energy to get larger molecules moving

Question 25

define - (in relation to water solutions) a. isotonic b. hypertonic c. hypotonic

Answer 25

a. isotonic - the same water potential inside the cell and outside the cell (no movement of water) b. hypertonic - (lower water potential) less water molecules outside the cell than inside the cell (water leaves cell) c. hypotonic - (higher water potential) more water molecules outside the cell than inside the cell (water enters cell)

Question 26

how to animal and plant cells react to being placed in hypotonic solutions

Answer 26

plant- water enters cell -vacuole swells - contents push against cell wall, - turgid - doesn't burst due to cell wall exerting an equal and opposite pressure to turgor pressure from the water. animal - water enters cell - no cell wall so cell bursts or lysis haemolysis (RBC) (destruction of red blood cells)

Question 27

how do animal and plant cells react to being placed in hypertonic solutions?

Answer 27

plant - water leaves cell and vacuole cell membrane pulls away from cell wall plasmolysis (contraction of plant cell) flaccid (loose or hanging limply) animal - water leaves cell cell shrinks cell crenation (describing the round-toothed edge and notched or scalloped surface)

Question 28

what molecules can be moved by regular diffusion? and why?

Answer 28

1. very small molecules - will fit between phospholipids 2. lipid based molecules - fat= soluble

Question 29

what are the two active processes involved in movement across membranes and what do they require

Answer 29

active transport - energy in the form of ATP and a carrier protein bulk transport - uses membranes to transport large amounts of material - needs ATP

Question 30

why do active processes require energy

Answer 30

moving against the concentration gradient

Question 31

why do passive processes not require ATP

Answer 31

because they move molecules down a concentration gradient

Question 32

how do active processes differ to facilitated diffusion ?

Answer 32

uses ATP moves specific molecules one way across a membrane must faster than FD opposite direction of the concentration gradient

Question 33

what are the two types of bulk transport and what do they mean?

Answer 33

endocytosis - enter the cell exocytosis - exit/leave the cell

Question 34

define phago and pino

Answer 34

phago - solid pino - liquid

Question 35

what is a plasmolysed cell

Answer 35

a cell that's lost water through osmosis causing it's cell membrane to shrink away from the cell wall

Question 36

why don't plant cells undergo lysis

Answer 36

because the cell wall contains an equal and opposite pressure to TURGOR pressure (expelled by the water), stopping too much water from entering the cells

Question 37

when carrying out an experiment to test the affect of temperature on membrane permeability, why would the absorption eventually stop increasing?

Answer 37

when the pigment is in equal concentration, inside and outside the cells

Question 38

what happens at the isotonic point of movement across membranes?

Answer 38

the movement of water into cells is equal to the movement of water out of cells

Question 39

does cholesterol bond to the phospholipid head or the fatty acid tail?

Answer 39

fatty acid tail

Question 40

what is the difference between pinocytosis and phagocytosis

Answer 40

pinocytosis = liquid into a cell phagocytosis = solid into or out of cell

Question 41

what are the 3 different parts of ATP

Answer 41

adenine - base ribose - sugar 3 phosphate groups

Question 42

in active transport, how does ATP release energy?

Answer 42

ATP is dephosphorylated, (dephosphorylation) releasing a phosphate group and the energy stored, activating the enzymes ATP changes to ADP + P ADP+P is then phosphorylated as the reaction is reversible, deactivating the enzymes

Question 43

what is the highest water potential achievable?

Answer 43

0kPa (distilled/pure water)

Question 44

define water potential

Answer 44

a measure of the ability of water molecules to move freely in a solution

Question 45

define osmosis

Answer 45

the NET movement of water molecules from a region of HIGHER water potential to a region of LOWER water potential DOWN a water potential gradient ACROSS a partially permeable membrane

Question 46

why might some cells not bind to the stain, even at low temperatures?

Answer 46

if the cells are dead or not respiring. no metabolic energy, ATP to take up stain

Question 47

7 functions of glycoproteins

Answer 47

1. acting as antigens 2. identification/ recognition of cells as self or foreign 3. cell signalling eg communication between cells 4. receptors/ binding site for hormones/ chemical signals/ medicinal drugs 5. binding site/ receptor on transport proteins 6. cell adhesion, hold cells together in a tissue 7. attach to water molecules to stabilise membrane/cell

Question 48

how can glycoproteins act as receptors

Answer 48

they have a tertiary structure complimentary to the shape of the trigger molecule. trigger molecule binds to receptor/ glycoprotein

Question 49

define cell signalling

Answer 49

the communication of cells, to trigger a response/ reaction inside the cell

Question 50

define reliability how can you improve it in an experiment?

Answer 50

the variation between the data take more samples/ readings

Question 51

define accuracy how can you improve it in an experiment?

Answer 51

how close your data is to the true value use higher resolution equipment, more significant figures keep equipment calibrated

Question 52

what is ATP made up of?

Answer 52

adenine ribose 3 phosphates

Question 53

what is the equation that represents how factors effect diffusion rate

Answer 53

temperature x surface area x concentration difference / diffusion distance x size of particle

Question 54

if two sucrose solutions are separated by a partially permeable membrane. what change will occur to the less concentrated solution?

Answer 54

less concentrated solution will decrease in volume because it has a higher water potential, therefore water molecules will move via osmosis to a lower water potential

Question 55

if four 10 g L-1 solutions were made out of 1. sucrose 2. glucose 3. DNA 4. haemoglobin which would have the lowest water potential

Answer 55

B. glucose all of the molecules are polar and therefore soluble in water. the more OH groups forming hydrogen bonds with water the lower the water potential, glucose has more OH groups

Question 56

what is not an acceptable description of the permeability of the plasma membrane?

Answer 56

"semi"

Question 57

Which part of the membrane restricts movement of small, lipid insoluble molecules

Answer 57

The fatty acid tails (in the bilayer)