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Biology 101 > Membranes and Transport B2.1 > Flashcards

Membranes and Transport B2.1 Flashcards

1
Q

Lipid bilayers as the basis of cell membranes; what do they do?

A

he are the structural make up of the cell membrane, forming the border between a cell and its environment: protecting its contents, providing a surface for exchange.

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2
Q

Where are lipid bilayers found?

A

on the cell membrane and also inside of cells as compartmentalization for organelles.

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3
Q

What are integral proteins?

A

embedded in the phospholipid layer. portions of he protein found inside the membrane are hydrophobic.

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4
Q

What are the two types of integral proteins?

A

transmembrane and nontransmembrane.

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5
Q

What are peripheral proteins?

A

on surface of the phospholipid and hydrophilic on the surface. they can also be attached to the surface of integral proteins.

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6
Q

What does the protein content depend on?

A

the function of cells.
more active cell = high protein content

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7
Q

What is the percentage of proteins that are fully embedded?

A

50%

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8
Q

What is the percentage of protein that mitochondria and chloroplasts have?

A

75%

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9
Q

What are channel/carrier proteins?

A

they span the membrane and transport large or impermeable substances across the membrane.

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10
Q

What are enzymatic proteins?

A

proteins that act as enzymes which catalyze metabolic reactions. these proteins can be interior or exterior of membrane.

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11
Q

What are hormone binding proteins?

A

these proteins have a binding site for signaling molecules such as hormones or neurotransmitters causing a message to be transmitted to the inside.

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12
Q

What is cell to cell communication?

A

glycoproteins can serve as identification tags that are recognized by membrane proteins of other cells.

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13
Q

What is cell adhesion?

A

membrane proteins of adjacent cells may hook together to form tissues?

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14
Q

What does the fluid mosaic model of the membrane refer to?

A

the fact that the membrane is always moving and fluid.

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15
Q

What are glycoproteins?

A

sugar molecule that is attached to a membrane protein.

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16
Q

What are glycolipids?

A

sugar molecule that is attached to a phospholipid

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17
Q

How come the membrane is selectively permeable?

A

only some molecules pass through the membrane while other needs help

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18
Q

Which type of molecules cannot move through the membrane w/o help?

A
  • large molecules
  • charged molecules
  • ions
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19
Q

How come charged molecules cannot pass through the membrane?

A

although the head of the phospholipid is attracted to other polar molecules, the nonpolar tail repels them (polar and charged molecules) and prevents passage.

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20
Q

What is passive transport?

A

transport that does not require ATP

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21
Q

What are types of passive transport?

A
  • simple diffusion
  • facilitated diffusion
  • osmosis
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22
Q

What is simple diffusion?

A

passive transport of materials from a region of high concentration to low, across a semi-permeable membrane until dynamic equilibrium is reached.

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23
Q

What is the concentration gradient?

A

measurement of how the concentration of something changes from one place to another. difference in concentration between 2 areas

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24
Q

What is “steepness” in the context of concentration gradients?

A

the greater the difference between 2 areas concentrations, the steeper the concentration gradient.

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25
Q

Examples of molecules to which simple diffuse through the membrane?

A
  • O2
  • CO2
  • ethanol
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26
Q

What are the factors affecting the rate of diffusion?

A
  • concentration gradient (steeper inc)
  • distance of diffusion (short inc)
  • surface area (of membrane entry point) (larger inc)
  • size and type of molecule (small inc)
  • temperature (high inc)
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27
Q

What is facilitated diffusion?

A

passive diffusion of materials through membrane (channel) proteins

28
Q

What are characteristics of the channel proteins used in facilitated diffusion?

A
  • most allow only one type of molecule or ion to diffuse through them
  • most common type of channel protein is K+
  • most ion channels are gated; meaning entry and exit is controlled
    -large, hydrophilic, charged, polar
29
Q

How come an increase of substance concentration does not increase rate of diffusion?

A

particles can only pass through the membrane channels and therefore the increased substrate does not increase rate

30
Q

What is osmosis?

A

the passive movement of water from an area of low solute concentration to high.

31
Q

What is the reason for osmosis?

A

due to differences in concentration of substances dissolved in water. when the substances dissolve, they become surrounded by water molecules which restrict the movement of water molecules therefore ares with higher solute have fewer water molecules to move.

32
Q

What are aquaporins? What do they do? Where are they found?

A

channel proteins that specifically allow water to pass through.
they increase permeability.
found in kidneys and root hair cells

33
Q

What is active transport?

A

ATP is needed for transport, delivering substances against the concentration gradient.

34
Q

What are protein pumps?

A

an integral protein that transports material against the concentration gradient.
- requires ATP
- release of ATP induces shape change

35
Q

What are the types of protein pumps?

A
  • uniporter
  • symporter
  • antiporter
36
Q

What is a uniporter?

A

carriers one specific ion or molecule (one direction)

37
Q

What is a symporter?

A

carriers two diff ions/molecules in the same direction

38
Q

What is a antiporter?

A

carries two diff ions/molecules in diff directions

39
Q

What are glycoproteins and glycolipids used for?

A
  • cell to cell recognition
  • immune system
  • form the glycocalyx: a carbohydrate rich layer on the outer surface of the plasma membrane of animal cells, with an aqueous solution in the gaps.
40
Q

In what way does fatty acid composition affect the fluidity of membranes?

A

phospholipids of cell membranes have saturated and unsaturated fatty acids, the composition of them affect the fluidity.
- flexible

41
Q

What are factors that affect the fluidity?

A
  • more unsaturated (more double bonds) fatty acids = more fluid
  • shorter hydrocarbon tail = more fluid
42
Q

What is the ideal composition of fatty acids?

A

depend on temperature of the surroundings. a membrane should have a right ratio

43
Q

In what way does cholesterol affect the fluidity of membranes?

A

it is a fluidity buffer that contributes to the stability and fluidity at temperature outside of the optimum; permeability would be compromised without it

44
Q

How does the cholesterol affect the fluidity of the membrane?

A

the rigid, steroid rings of the cholesterol interact with the regular packing of the hydrocarbon tail creating space.

45
Q

How does cholesterol affect the membrane in high temperatures?

A

normally the high temp causes the membrane to be more mobile but with cholesterol, the fluidity is decreased and the membrane is constrained by the cholesterol

46
Q

How does cholesterol affect the membrane in low temperatures?

A

normally the low temp causes the membrane to be less fluid but with cholesterol, the fluidity is increased and the close packing of the phospholipids are disrupted.

47
Q

What are vesicles?

A

fluid-filled sacs composed of a single phospholipid layer that surrounds the fluid/solutes inside

48
Q

What are the functions of vesicles?

A
  • movement of material into and out of the cell
  • transport of substances internally
  • transport of proteins from rER to the golgi and finally the membrane
49
Q

What are the steps of endocytosis?

A
  1. vesicle approaches membrane
  2. membranes begin to fuse, requiring ATP, fluidity allows membrane to flow around each other
  3. for a moment there is a single phospholipid bilayer at the point of contact
  4. membrane pores open, allowing contents
50
Q

What is pinocytosis?

A

the uptake of liquid substances

51
Q

What is phagocytosis?

A

the uptake of solid substances

52
Q

What is endocytosis?

A

invagination or infolding of plasma membrane, forming vesicles that become detached and enter the cytoplasm

53
Q

What is exocytosis?

A

occurs by fusion of the vesicle membrane and the plasma membrane, followed by the release of the contents to the outside

54
Q

What are some examples of endocytosis?

A
  • transport of large hydrophilic particles like food in single-celled organisms
  • fetus take up antibodies in mother’s womb
  • photocytosis of bacteria by phagocytosis
  • uptake of viruses by white blood cells
55
Q

What are some examples of exocytosis?

A
  • protein synthesis in rER with vesicles transporting to golgi
  • secretion of enzymes from the synopse in neurons
  • secretion of sweat from sweat glands
  • secretion of breast milk
56
Q

Explain the existence of gated ion channels in neurons

A

in an axon of a neuron, electrical impulses are conducted away from the cell body, transmitting information to diff neurons, muscles, and glands. the rapid movement of sodium and potassium ions across the axon membrane establishes a voltage across the membrane (membrane potential) which is due to the imbalance of positive and negative charges inside and outside the membrane

57
Q

What is membrane potential (voltage) due to?

A

the imbalance of positive and negative charges inside and outside the membrane

58
Q

What are gated ion channels? Most common?

A

the most common type of sodium and potassium gated ion channels allow these ions to pass across in either direction, opening/closing reversibly, being switched on/off. K+ in and Na+ out. these channels close again via the extra globular protein subunit that is attached to the flexible AA.

59
Q

Exception to the voltage responsive gated ion channels?

A

some gated channels respond to the binding of a ligand rather than voltage. these channels have nicotinic acetylcholine receptors equipped proteins and bind to acetylcholine. Na+ can leave upon the binding of a neurotransmitter when acetylcholine detaches, the channel closes.

60
Q

What are sodium potassium pumps?

A

they actively transport ions against the concentration gradient.

61
Q

What are the steps of the transport of K+/Na+ across a sodium potassium pump?

A
  1. concentration of na+ higher on the outside/K+ higher on the inside
  2. interior of sodium potassium pump is open and 3 Na+ ions enter and attach to binding sites
  3. release of ATP cause ADP creation and conformational change in protein pump closes.
  4. protein is open to outside and Na+ ions are released
  5. 2 K+ ions attach, AP added shape changes and K+ released
62
Q

What is the reason for glucose sodium potassium cotransporters?

A

glucose cannot pass by simple diffusion because it is polar and therefore cotransport system with Na+ is put in place.

63
Q

What are the steps of the transport of glucose through a cotransporter?

A
  1. maltose is hydrolyzed into glucose
  2. the sodium-glucose linked transporter transport glucose into the cytoplasm of villus via facilitated diffusion
  3. Na+/K+ pumps transfer Na+ out, creating a low concentration of Na+ in the villus
  4. glucose moves via protein channels from villus to capillary.
64
Q

Where does the transport of glucose through a cotransporter occur? Why?

A

in the kidneys to reabsorb glucose filtered to the blood toprevent it being lost in urine.

65
Q

How come the glucose can move against it concentration gradient?

A

it is because it depends on the Na+ ion concentration gradient, by leveraging with the Na+ as it moves down its concentration gradient

66
Q

How are cells in tissues linked together?

A

by cell to cell junctions (cell adhesion molecules) in the membranes of adjacent cells. different molecules exist depending on the function

67
Q

What are cell adhesion molecules CAMs?

A

proteins with one part embedded in the membrane other projecting outward to the extracellular environment. CAMs bind with ones of adjacent cells to form a complex.

Biology 101 (14 decks)

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