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Biology AS (Mr Copp) > 1.3 cell membranes and transport > Flashcards

1.3 cell membranes and transport Flashcards

ALWAYS ALWAYS REMEMBER ABOUT MITOCHONDRIA AND RESPIRATION AND ITS IMPORTANCE!!!!

1
Q

What cell organelles are found in the plasma membrane?

A
  • glycoprotein
  • glycolipid
  • extrinsic protein
  • protein channel
  • intrinsic protein
  • hydrophobic tail
  • hydrophillic head
  • filaments of cytoskeleton
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2
Q

How do you calculate the actual width of a cell between two points, eg A-B?

A

Measure the real life size from A-B with a ruler
Then divide by the magnification (should be given)
Then multiply by 1000 to convert from mm to μm

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3
Q

Why is the fluid mosaic model called the fluid mosaic model?

A

Fluid - individual phospholipid molecules can move within a layer relative to one another (fluid)
Mosaic - proteins embedded in the bilay vary in shape and size and in their distribution among the phospholipid layer (mosaic)

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4
Q

What are extrinsic proteins and where are they found?

A

-act as receptors for hormones and as recognition sites
-found on the surface of the membrane

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5
Q

What are intrinsic proteins and where are they found?

A

-extends across both layers, act as channels and carrier proteins for the transport of molecules
-found within he membrane

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6
Q

what are glycoproteins? what do they act as?

A

-carbohydrates attached to a protein
-as antigens

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7
Q

what are glycolipids? what do they act as?

A

-carbohydrates attached to a lipid
-as receptor sites for molecules such as hormones

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8
Q

What is simple diffusion?

A

the movement of substances from higher concentrations of that substance to areas of lower concentration of that substance

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9
Q

Why can’t protein hormones, eg insulin and adrenaline, diffuse through the phospholipid bilayer? How do they move through?

A

Because they are insoluble in lipids and so bond to extrinsic protein receptor molecules which influence the behaviour of cells.

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10
Q

what does the cholesterol in the phospholipid bilayer do?

A

makes the membrane stable at high temps and more fluid at low temps

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11
Q

how do lipid soluble subtances transport across membrane and why can they do so?

A

they dissolve in the phospholipid membrane and diffuse across
can do so as the phospholipid bilayer is hydrophobic and therefore lipid-soluble molecules can move through the membranne more easily than water soluble substances

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12
Q

give an example of lipid-soluble substances

A

vitamin A

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13
Q

how do water soluble substances pass through the membrane?

A

pass through intrinsic proteins which form water-filled channels across membrane

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14
Q

give some examples of water soluble substances

A

glucose, polar molecules and ions

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15
Q

What sort of particles can be diffused by simple diffusion? give an example

A
  • the particles must be small and charged
    eg oxygen, carbon dioxide, vitamins
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16
Q

What factors affect simple diffusion?

A
  • the concentration gradient : the greater the conc, the more molecules that can diffuse
  • diffusion distance
  • the surface area of the membrane
  • the thickness of the exchange surface
  • an increase in temperature
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17
Q

specifically to the beetroot experiment, what factors affect the permeability of cell beetroot cell membranes? briefly for each explain how

A
  1. increasing temp (kinetic energy increase pl vibrates further apart so permeability increases)
  2. increasing conc of alcohol eg ethanol (organic solvents dissolve pl, the greater the conc the more permeable)
  3. increasing NaCl conc (Na+ attach to O2 atoms on phosphate heads which reduces the mobility of phospholipid molecules so less betalain released, as NaCl increases, permeability decreases)
  4. increasing detergent conc (reduces surface tension of phospholipids and disperses membrane)
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18
Q

What is diffusion proportional to?

A

(surface area x difference in conc) ÷ length of the diffusion path

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19
Q

How does facilitated diffusion differ to simple diffusion?

A
  • it relies on transport proteins found within the membrane to assist the movement of polar molecules
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20
Q

is facilitated diffusion passive? what limits the rate of facilitated diffusion?

A

passive
the number and availability of transport protein molecules limits the rate of diffusion

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21
Q

Why can’t polar molecules be diffused through simple diffusion?

A

because they are relatively insoluble in lipids

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22
Q

will stopping respiration/killing cells stop diffusion? why?

A

no as no ATP is needed for diffusion to occur, it’s a passive process

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23
Q

What do channel proteins do and what are they made of?

A
  • they are specific to one type of ion and can be opened or closed to regulate the movement of particular molecules (allows substances in)
  • they consist of pores with a hydrophillic lining, allowing charged ions and polar molecules to pass through
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24
Q

what is the role of carrier proteins?

A
  • allow diffusion across the membrane of larger polar molecules such as sugars and amino acids
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25
how does a carrier protein work?
molecules attach to the binding site on a carrier protein and cause the carrier protein to change shape of rotate within the membrane; this action releases a molecule on the other side of the membrane
26
in terms of channel proteins and carrier proteins, describe their rates of diffusion
- initially rate of diffusion increases as the conc grad steepens bc they facilitate the process - rate of diffusion plateaus at higher conc bc they're occupied therefore limits rate of diffusion
27
how are channel and carrier proteins affected by respiratory inhibitors?
they aren't as it's a passive process
28
compare a channel protein to a carrier protein
channel - carrier ~yes pores - no pores ~allows s.d or f.d - allows s.d, f.d or a.t ~only transports down conc grad - can transport against conc grad ~solute not binded - solute binds on one side and released on other ~doesn't change shape - yes change shape ~only transports H2O soluble - transports soluble+insoluble ~rapid transport 10^8 ions per second - slower 10^4 ions per second
29
What is co-transport?
a type of facilitated diffusion that brings molecules and ions into cells together on the same carrier protein
30
What is the mechanism by which glucose is absorbed in the ileum of mammals?
co-transport
31
why is sodium-glucose transport significant?
in absorbing glucose and Na ions across cell membranes and into blood in ileum and kidney nephron glucose
32
Describe the co-transport process of glucose moving across a cell membrane (5 steps)
1. glucose molecule and 2Na+ ions outside cell bind to same carrier protein in cell membrane 2. the carrier protein changes shape and deposits glucose and Na+ inside cell (f.d) 3. glucose and Na+ separately diffuse through cytoplasm to opposite membrane 4. glucose passes into blood by f.d 5. Na+ carried to epithelial cells by AT by some carrier protein which moves K+ in and therefore Na+ conc remains low in epithelial cells so more Na+ moves in from lumen, bringing in glucose (step1)
33
What does active transport require?
-energy in the form of ATP
34
Define Active transport.
Active transport is the movement of molecules across a biological membrane from an area of lower concentration to an area of higher concentration, against the concentration gradient, with the assistance of energy.
35
What does ATP stand for?
Adenazine triphosphate
36
Does active transport also use carrier proteins? If so what does thus do?
- yes - therefore the maximum rate will be ultimately limited by the number and availability of these transport proteins
37
when there is no net movement, how do we define this?
equilibrium
38
What is co-transport?
the transportation of two different molecules together
39
what is an example of co-transport
glucose and sodium ions
40
Describe the steps in which sodium ions and glucose ions go through co-transport.(3)
1. sodium ions are transported out of epithelial cells lining the ileum into the blood, creating a low conc of Na ions within cells 2. there's a higher conc of Na ions in the lumen of gut which causes Na ions to diffuse into epithelial ells via co-transport protein (during this they couple with glucose molecules) 3. glucose molecules pass via facilitated diffusion in the blood capillaries and Na ions by AT
41
Define Osmosis
the movement of water molecules from an area of higher water potential to an area of lower water potential through a selectively permeable membrane
42
define water potential
the tendency for water to move into or out of a system, and is the pressure created by water molecules
43
what is a hypertonic solution?
if water potential of external solution is lower than solution inside cell, external solution is hypertonic and water flows out
44
what is a hypotonic solution?
if water potential of external solution is higher than the solution inside cell, external solution is hypotonic and water flows into cell
45
what is an isotonic solution? what does the cell become?
solution which has the same water potential relative to the solution inside the cell balanced
46
what does adding a solute to a cell do?
lowers the potential for water molecules to move therefore lowering the water potential making it more negative
47
what is pressure potential eg
when water enter a plant cell by osmosis, the vacuole expands pushing the cytoplasm against the cell wall, the cell wall can only expand so much and so develops an opposing force
48
what is the calculation for water potential in a cell?
water potential = solute potential + pressure potential
49
what happens when a cell is placed into a hypotonic solution?
water flows into the cells bc the solution has a higher water potential than the cell
50
what happens when a cell is placed into a hypertonic solution?
water flows out of the cells bc the solution has a lower water potential than the cell
51
what is plasmolysis?
the vacuole shrinking and the cytoplasm drawing away from the cell wall
52
what is incipient plasmolysis?
the point at which the cell membrane just begins to move away from the cell wall
53
what is the pressure potential during incipient plasmolysis?
0kPa
54
when looking at a graph which shows the percentage of plasmolysed cells, when is incipient plasmolysis reached?
when 50% of cells are plasmolysed as that means 50% are turgid and therefore pressure potential is 0kPa
55
what is the equation for when a cell is turgid?
water potential = - solute potential
56
what is the equation for when a cell has reached incipient plasmolysis?
water potential = solute potential
57
what is the equation for when a cell has reached plasmolysis?
water potential > solute potential
58
what is haemolysis?
when red blood cells in a hypotonic external medium burst
59
what is bulk transport?
where the cell transport material in bulk across the cell membrane
60
what is endocytosis?
the engulfing of material by infolding of the plasma membrane bring it into the cell enclosed within a vesicle
61
what is phagocytosis?
the process by which the cell can obtain solid materials that are too large to be taken in by other methods eg phagocytes and bacteria
62
what is pinocytosis?
the process by which the cell can obtain liquid materials, similar to phagocytosis but vesicles are smaller
63
what is exocytosis and give an example
substances leaving the cell after being transported through the cytoplasm in a vesicle eg digestive enzymes are secreted in this way
64
why does the mass of a potato decrease as salt conc increases?
bc as salt conc increases, water potential decreases as there is a higher water potential inside the cell vs outside

Biology AS (Mr Copp) (5 decks)

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