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PH112 > Cellular Process ✅ > Flashcards

Cellular Process ✅ Flashcards

receptor mediated endocytosis

1
Q

what is a solvent?

A

the liquid doing the dissolving this is usually water.

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2
Q

what is a solute?

A

the dissolved material (particles or gas)

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3
Q

what is concentration?

A

amount of solute in a given amount of solvent

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4
Q

what is the concentration gradient?

A

the difference in concentration between 2 areas of solution (from the inside to the outside of the plasma membrane)

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5
Q

what fluid is the body most made up of?

A

intracellular (ICF) which is within cells. makeup about 2/3 of the total (around 67%) . found in the cytosol of the cell.

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6
Q

what is the extracellular fluid (ECF)?

A

The fluid which is outside of the cell

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7
Q

where can ECF be located?

A
  • between cells = interstitial
  • in blood vessels = plasms
  • in lymphatic vessel = lymphatic fluid (lymph)
  • within the brain and spinal cord - cerebrospinal fluid

the = are what the fluid is known as for where it is located.

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8
Q

what does the molecule movement across the membrane depend upon?

A

the gradient across the plasms membrane.

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9
Q

what does selective permeability allow?

A

allows a living cell to maintain different concentrations of substances on either side of the plasma membrane.

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10
Q

what is an electrical gradient?

A

the difference in electrical charges between two regions.

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11
Q

where are any ions or molecules most concentrated in?

A

cytosol
or extracellular fluid.

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12
Q

what charge is the outer surface of the plasma membrane

A

positively charged

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13
Q

what charge is the inner surface of the plasma membrane

A

negatively

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14
Q

where does the electrical gradient occur? and what is the charge difference known as?

A

plasma membrane
known as membrane potential

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15
Q

why is the concentration gradient and the electrical gradient important?

A

help move substances across the plasa membrane.

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16
Q

what is the electrochemical gradient?

A

the combined influence of conc gradient and electrical gradient on movement of a particular ion

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17
Q

where do negatively charged ions typically move to?

A

to a positively charged area to reach equilibrium and vise verse with positively charged ions.

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18
Q

in which direction of the gradient does passive transport occur?

A

down the concentration gradient across the membrane using its own energy
e.g. simple diffusion

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19
Q

what is endocytosis?

A

where the vesicles from the plasma membrane detach while bringing material into a cell

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20
Q

what is exocytosis?

A

merging of vesicles from the plasma membrane to release material.

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21
Q

what does endocytosis include?

A

phagocytosis
fluid endocytosis
receptor-mediated endocytosis

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22
Q

how does diffusion take place?

A

random micing of particles in solution which occur due to the kinetic energy of the particles.

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23
Q

what factors affect the rate of diffusion?

A

-the steepness of the concentration gradient,
-temp
- mass of the diffusing substance - larger mass slower rate
- surface area - larger the membrane surface area available for diffusion, faster the rate.
- diffusion distance

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24
Q

simple diffusion?

A

a passive process in which substances move freely through the lipid bilayer of the plasma membranes of the cells without the help of membrane transport proteins.

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25
Q

is energy required for simple diffusion?

A

no

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26
Q

why do substances move for simple diffusion?

A

move due to gradient
difference in conc, pressure, charge

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27
Q

how do non polar hydrophobic molecules move across the lipid bilayer?

A

simple diffusion

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28
Q

what is facilitated diffusion?

A

a passive process where an integral membrane protein assists the substances across the membrane. the membrane protein can either be a membrane channel or a carrier.

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29
Q

why might facilitated diffusion occur?

A

if the solute is too polar or highly charged to move across the lipid bilayer by simple diffusion, then facilitated diffusion may occur to pass the plasma membrane.

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30
Q

in what way does the solute go on the conc gradient through facilitated diffusion?

A

down the concentration gradient.

31
Q

what are most membrane channels?

A

ion channels

32
Q

facilitated diffusion ion channels

A

move down the concentration gradient
the channel is gated - part of the channel protein acts as a plug or gate where the pore changes shape to open pore and allow ions to get through and changes again to close

33
Q

what are the ions which are diffused through specific protein channels? e.g. for k+ a k+ gated channel.

A

Na+ K+ Cl- Ca++

34
Q

what are the types of gated channels?

A

ligand-gated
voltage-gated
mechanically gated

35
Q

role of the carrier/transporter in facilitated diffusion carrier?

A

used to move solute down the conc gradient across the plasma membrane.

36
Q

where is a solute most likely to bound to (facilitated diffusion carrier)

A

to the side of the membrane with a higher conc of solute

37
Q

when is the solute released?
facilitated diffusion carrier

A

when the carrier changes shape

38
Q

how to the soluted bind on the carrier?
facilitated diffusion carrier

A

bind to the carrier on the cytosolic side and move to the extracellular fluid as rapidly as they bind to the carrier on the extracellular side and move into the cytosol

39
Q

what is the transport maximum?
facilitated diffusion carrier

A

max amount of carriers available to transport substances

40
Q

what are the substances that move across the plasma membrane by carrier-mediated facilitated diffusion?

A

glucose
fructose
galactose
and some vitamins

41
Q

facilitated diffusion diagram

A
42
Q

simple diffusion diagram

A
43
Q

what is osmosis?

A

diffusion of water through semi-permeable membrane

44
Q

how to water molecules pass through plasma membrane via osmosis?

A

moving through lipid bilayer through simple diffusion

moving through aquaporins, integral membrane proteins that function as water channels.

45
Q

on what way of the gradient does osmosis work?

A

area of how concentration to an area of low concentration

46
Q

osmosis

A

permeable to solvent
impermeable to solute

47
Q

what is osmolarity?

A

total solute concentration of a solution

48
Q

how much is one osmol equivalent to?

A

1 mol of solute

49
Q

what can osmolarity also determine?

A

water concentration in a solution as the higher the osmolarity the lower the water concentration

50
Q

what is tonicity?

A

ability of a solution to change the shape or tone of cells by altering their internal water volume

51
Q

what is isotonic solution?
tonicity

A

cells have their normal size and shape in isotonic solutions as the solute/water concentration is the same as inside the cells. water moves in and out.

52
Q

what is hypertonic solution?
tonicity

A

where cells loose water through osmosis and shrink. contains higher conc of solutes than present inside of cell

53
Q

polar or charged solutes are to pass the plasma membrane require what type of transport?

A

active transport as they need to move uphill against their concentration gradient.

54
Q

can pumps be saturated?

A

yes

55
Q

primary active transport steps

A
56
Q

how do molecules move across membranes?

A

passive transport
active transport
endocytosis
exocytosis

57
Q

what are the types of passive transport?

A

simple diffusion
facilitated diffusion
osmosis

58
Q

active transport

A

uses energy to move against the concentration gradient
transported known as pumps which can be saturated.

pumps use two types of energy sources:
- direct use of ATP in primary active transport
- use of electrochemical gradient across membrane to drive the process in secondary active transport

59
Q

primary active transport

A
  • Na +- K +- ATPase is the primary active transporter
  • major proteins found in Na +- K +- ATPase; Ca2+ ATPase, H+-ATPase, H+-K+-ATPases.
  • found in every cell and helps establish and maintain the membrane potential of the cell.
60
Q

secondary active transport

A

different from primary active transport as it uses electrochemical gradient across plasma membrane as a source of energy.

transporters in this process have two binding sites

binding sites used for ion is Na+, for cotransporter molecule is glucose.

cotransporter (symporters) move molecules in the same direction

counter transported (antiporters) move molecules in opposite directions

61
Q

active transport|passive transport diagram

A
62
Q

vesicular transport - endocytosis

A

-packaging of extracellular materials in vesicles at cell surface
-involves large volumes of extracellular material
-requires ATP energy
-three major types; receptor-mediated endocytosis, phagocytosis, pinocytosis.

63
Q

receptor mediated endocytosis

A
  • highly selective process
  • vesicle forms after receptor protein in the plasma membrane recognises and binds to a particular particle in the extracellular fluid.
    -involves formation of vesicles at surface of membrane
    -clathrin-coated vesicle in cytoplasm.
64
Q

example of receptor-mediated endocytosis

A

cells take up:
cholesterol-containing low-density lipoproteins (LDLs), transferrin (iron supporting protein in the blood), some vitaminds, antibodies and certain hormones.

65
Q

pinocytosis

A
  • plasma membrane forms an invagination, sinks inwards, pinches off and forms a vesicle
    -materials dissolve in water to be brought into cell (also known as ‘cell drinking’)
    -this is the most common form of endocytosis, where it is most absorptive cells in the intestines and kidneys. most proteins and other large molecules are taken up this way.
66
Q

a summarised version of receptor-mediated endocytosis.

A

1- binding
2- vesicle formation
3- un-coating
4- fusion with endosome
5- recycling of receptors to plasma membrane
6- degradation in lyosomes.

67
Q

phagotysosis

A

used to engulf large solid particles, such as food, bacteria etc into vesicles.
-‘cell eating’
- phagocytes are able to carry phagocytosis
-vital defence mechanism that helps protect the body from disease.

68
Q

exocytosis functions

A
  • provides a way to replace portions of the plasma membrane that endocytosis has removed.
  • adds new membrane components to the membrane
  • provided a route for membrane impermeable molecules, e.g. protein hormones, the cell synthesizes can be secreted into the extracellular fluid.
69
Q

how does exocytosis work?

A

cytoplasmic vesicle merges with the plasma membrane and releases its contents. This requires ATP and Ca2+ ions.

70
Q

example of exocytosis

A
71
Q

exocytosis and nervous system function

A

nerve cell communicated to another cell by releasing chemicals via exocytosis at the synaptic terminal.
-nerve cells release neurotransmitters (diagram)

72
Q

exocytosis in presynaptic neuron

A
73
Q

transcytosis

A
  • used to successively move a substance into, across and out of a cell.
  • active process
  • vesicles undergo endocytosis on one side of the cell and exocytosis on the other
  • most common on endothelial cells that line blood vessels and when a woman is pregnant. some of the antibodies cross the placenta into the fetal circulation using transcytosis, vesicle merges with the plasma membrane and releases its contents.

PH112 (17 decks)

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