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biology > 2.1.5: plasma membrane > Flashcards

2.1.5: plasma membrane Flashcards

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1
Q

what is a partially permeable membrane?

A
  • allows certain molecules to enter and exit a cell
  • involved in cell signalling
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2
Q

what is intracellular signalling?

A

communication between one part of a cell and a different part of the same cell (within the a singular cell)

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3
Q

what is intercellular signalling?

A

communication between two different cells

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4
Q

what does compartmentalisation do?

A

to separate organelles from each so reactions don’t interfere

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5
Q

what is a example of membranes being a site of chemical reactions?

A

there are many proteins embedded in the thylakoid membranes and similar enzymes also embedded in mitochondrion

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6
Q

what is the model of a plasma membrane and why?

A

fluid (it is flexible) mosaic (studded with proteins in a random pattern) model

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7
Q

what are the components that make up plasma membranes?

A
  • phospholipids
  • glycolipids
  • cholesterol
  • channel proteins
  • carrier proteins
  • glycoproteins
  • various extrinsic proteins
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8
Q

what is the structure of the phospholipid bilayer?

A

two layers of phospholipid molecules with their hydrophilic heads facing outwards and their hydrophobic tails facing inwards

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9
Q

what is the structure and function of the glycolipids?

A
  • a lipid with attached carbohydrate (sugar) chains
  • recognised by the cells of the immune systems as self or non-self and to maintain the stability of the cell membrane and to facilitate cellular respiration
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10
Q

what is the structure of cholesterol?

A
  • a lipid with a hydrophilic end and a hydrophobic end
  • regulates the fluidity of membranes and adds stability to membranes without making them too rigid
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11
Q

what is an intrinsic protein?

A

proteins that are embedded within the membrane

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12
Q

what is an extrinsic protein?

A

proteins that are loosely bound to the membrane from the outside

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13
Q

what is the shape and function of a channel protein?

A
  • tubular shaped
    -allows the passive movement of polar molecules and ions down a concentration gradient, acting like a pore
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14
Q

what is the structure and function of a carrier protein?

A
  • each type has one more specific binding site for its solute
  • important role in both passive transport and active transport into cells
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15
Q

what is the structure and function of glycoproteins?

A
  • a protein with sugar molecules attached
  • play a role in a cell adhesion and as a receptor for chemical signals
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16
Q

what is the structure and function of various extrinsic proteins?

A
  • primary, secondary, tertiary and quaternary protein structure
  • required for transport
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17
Q

what type of signals do cells use to communicate?

A

chemical signals

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18
Q

how do cells detect a target cells?

A

they have complementary receptors

19
Q

how is the method by which a molecule passes a membrane dependant on?

A
  • size
  • whether it’s charged or polar
  • whether it needs to move down or against a concentration gradient
20
Q

what is passive transport?

A

molecules are moving down a concentration due to their own kinetic energy - no extra energy in the form of atp is needed

21
Q

what is active transport?

A

extra energy in the form of atp is needed to move molecules against the concentration gradient

22
Q

what is diffusion?

A

the net movement of particles from a region of high concentration to a low concentration, down a concentration gradient, until equilibrium is reached

23
Q

what are the 6 factors that affect the rate of diffusion?

A
  • properties of diffusing molecules (non-polar and smaller diffuse faster)
  • concentration gradient (bigger difference = faster diffusion)
  • temperature (higher temperature = more kinetic energy = faster diffusion)
  • surface area to volume ratio (larger sa = faster diffusion)
  • thickness of membrane (shorter diffusion = faster diffusion)
  • number of channel/carrier proteins (more proteins = faster diffusion)
24
Q

what are the 2 types of diffusion?

A

simple and facilitated diffusion

25
Q

what are the types of molecule that can diffuse through a plasma membrane via simple diffusion?

A
  • large and small non-polar molecules
  • small, polar molecules can pass
26
Q

what are the types of molecule that can diffuse through a plasma membrane via facilitated diffusion?

A

charged ions and larger, polar molecules (repelled by core)

27
Q

what is primary active transport?

A

involves the movement of ions/molecules against their concentration gradient with the direct use of atp to power the process

28
Q

what is secondary diffusion?

A

when a concentration gradient established by a transmembrane pump is used to move another molecule into the cell against a concentration gradient

29
Q

what is bulk transport?

A

another form of active transport that transports large molecules (enzymes, hormones etc) that are too large to move through channel and carrier proteins

30
Q

what is endocytosis?

A
  • bulk transport into cells
  • the cell surface membrane bends inwards when it comes in contact with the material to be transported
  • the membrane enfolds the material until a vesicle is formed
  • moves into the cytoplasm to transfer the material further processing within the cells
31
Q

what are the 2 types of endocytosis?

A
  • phagocytosis (solids)
  • pinocytosis (liquids)
32
Q

what is an example endocytosis?

A

vesicles containing bacteria are moved towards lysosomes, where bacteria is digested by enzymes

33
Q

what is exocytosis?

A

the reverse of endocytosis. vesicles, usually formed by the golgi apparatus, move towards and fuse with the cell surface membrane, releasing the contents outside of the cell

34
Q

what is osmois?

A

the movement of water molecules, across a partially permeable membrane, from a high concentration to a low concentration

35
Q

what is the water potential of pure water at standard temperature and pressure?

A

zero

36
Q

what is water potential?

A

the pressure exerted by water molecules on a membrane or a container

37
Q

what does it mean if a solution has a high or low water potential?

A
  • high = has a low concentration of solute and higher concentration of water
  • low = has a high concentration of solute and a lower concentration of water
38
Q

how does adding solutes affect water potential?

A

lowers the water potential, so it makes the water potential more negative

39
Q

how does temperature affect membrane structure and permeability?

A
  • temperature increased = phospholipids have more kinetic energy
  • more fluid and loses structure
  • if continued increase = membrane will break down completely
  • increases the permeability of the membrane
  • carrier and channel proteins will denature
40
Q

how does solvent affect membrane structure and permeability?

A
  • many organic solvents are less polar then water (like alcohols)
  • will dissolve membranes, disrupting cells
  • non-polar alcohol molecules can enter the cell membranes and the presence disrupts the membrane = more fluid = more permeable
41
Q

what is the method for investigating the effect of ethanol concentration on membrane permeability?

A
  • take 5 test tubes and label each on with a different ethanol concentrations
  • trim 5 beetroot cylinders to 30 mm, rinsing each one and then patting it dry
  • label the cuvette tray with the ethanol concentrations
  • swirl the tubes once and remove the cylinders
  • pour the remaining liquid into the cuvette for the corresponding concentration and fill an extra cuvette with distilled water
  • use the colorimeter with a green filter to measure the absorbance of each concentration and plot a graph of ethanol concentration against absorbance
42
Q

what is the variables for when investigating the effect of ethanol concentration on permeability?

A
  • independent = concentration of ethanol
  • dependent = absorbance of the beetroot solution
  • control = size of disks, volume of ethanol, thickness of disk, amount of time in test tubes, same filter colour
43
Q

what is the method for determining the water potential by measuring changes in mass?

A
  • label 6 boiling tubes with different concentrations of salt solution and place 30cm of distilled water in one tube and 30cm of the appropriate salt solution in the others
  • make 5 potato cylinders that are 50mm long and divide a piece of filter paper into 6 sections for each potato and blot the cylinders dry
  • record the mass and put them in the test tubes
  • leave for 45 minutes then take them out and blot them dry again
  • reweigh the cylinders and calculate the percentage change in mass ((change in mass /original mass) x100)

biology (10 decks)

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