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plasma membrane Flashcards

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Biology 101 flashcards
1
Q

true or false: plasma membrane is present in all living cells

A

true

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2
Q

what is the cell membrane composed of?

A

two layers of lipids with a variety of proteins and carbohydrates incorporated into it

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3
Q

true or false: All biological membranes are lipid bilayers

A

true

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4
Q

describe freeze-fracture electron microscopy

A

biological membrane is frozen and then mechanically split down the middle

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5
Q

list the three major types of lipids that make up cell membranes

A

phospholipids
cholesterol
glycolipids

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6
Q

what makes up the cell coat or glycocalyx on the surface of eukaryotic cells?

A

carbohydrates

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7
Q

what are the lipids of the cell membrane soluble and insoluble in?

A

insoluble in water
soluble in organic solvents

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8
Q

define amphipathic

A

have both a hydrophilic and hydrophobic end

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9
Q

what is the phospholipid polar head group made of?

A

phosphate, glycerol, and choline

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10
Q

what is a phospholipid non-polar tail group made of?

A

hydrocarbon tails

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11
Q

list examples of phospholipids

A

phosphatidylethanolamine
phosphatidylserine
phosphatidylcholine
phosphatidylinositol

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12
Q

list the two ways amphipathic molecules will burry and protect the hydrophobic tails and leave the hydrophilic heads exposed to water.

A
  1. forming micelles – spheres with hydrophobic tails inward
  2. forming bilayers – with hydrophobic tails sandwiched together between the hydrophilic head groups
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13
Q

why is the formation of the lipid part of the biological membranes spontaneous?

A

due to the amphipathic nature of these molecules

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14
Q

what are the two main types of movement within the lipid bilayer?

A

flip-flop and lateral diffusion.

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15
Q

when does flip flop movement occur?

A

when molecules from one side of the monolayer migrate to the other side (i.e: a molecule from the top half moves to the bottom). This type of movement occurs less frequently.

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16
Q

when does lateral diffusion occur?

A

molecules within the same monolayer switch positions with their neighbors. This occurs at a very rapid rate

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17
Q

true or false: In general, molecules are not mostly confined to their own monolayers.

A

false: In general, molecules are MOSTLY confined to their own monolayers.

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18
Q

Movement of phospholipids within the cell membrane gives rise to membrane ______.

A

fluidity

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19
Q

what factors can the fluidity of the cell membrane be affected by?

A

outside factors: temperature

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20
Q

In hotter environments, do cell membranes tend to be more fluid or less fluid?

A

more

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21
Q

how do hydrocarbon tails in phospholipids contribute to membrane fluidity?

A

They can have cis bonds which create a “kink”, affecting the fluidity of the cell membrane.
Along with these “kinks”, the varying lengths of the hydrocarbon tails can also influence the membrane fluidity.

The longer the hydrocarbon chain and the more cis bonds present, the more fluid the membrane.

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22
Q

how does cholesterol play an important role in membrane fluidity?

A

It can insert itself between phospholipids and enhance the mechanical stability of the membrane, making it less likely to fracture in colder temperatures, and keeping it from being too fluid in hotter temperatures.

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23
Q

what proteins does the plasma membrane consist of?

A

transmembrane proteins
ion pores
channels
other transport proteins

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24
Q

what is the overall purpose of the cell membrane?

A

separate the intracellular environment from the extracellular environment, and also acts as a solvent for membrane proteins

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25
Q

what prevents the diffusion of many polar substances into the cell and is highly impermeable to these molecules?

A

hydrophobic interior of the lipid bilayer

26
Q

what structures allow the passage of larger molecules across the cell membrane?

A

transport protein

27
Q

what molecules help establish transmembrane ion potentials that are an integral part of ATP synthesis?

A

ions

28
Q

The rate at which molecules diffuse across the membrane depends on what?

A

their size and their relative solubility in oil

29
Q

The smaller a molecule and the more soluble in oil, the more ____ diffusion across the cell membrane.

A

rapid

30
Q

In cell membranes, molecules such as ions, metabolites, sugars, etc. require the help of ________________________ to cross over to the intracellular environment

A

membrane transport proteins

31
Q

what are the different kinds of transport proteins?

A

uniports, symports, and antiports.

32
Q

what do uniports transfer?

A

a solute from one side of the membrane to the other

33
Q

what are co-transporters and what is the example?

A

two solutes are transferred together
ex. Symports and antiports

34
Q

what is the difference between symports and antiports?

A

Symports transport two solutes in the same direction

antiports transport two solutes in opposite directions.

35
Q

what is passive transport? does it require energy?

A

Passive transport depends on the concentration gradient or electrochemical gradient of the molecule in question.

does not require energy

36
Q

what is active transport and does it require energy?

A

used when the molecule in question needs to be transported against its electrochemical/concentration gradient (like pushing a ball uphill).

requires energy.

37
Q

what diffusions is passive transport made of ?

A

simple diffusion and facilitated diffusion

38
Q

when does simple diffusion occur?

A

when the molecules flow passively across the membrane without the assistance of membrane proteins.

39
Q

what structures are needed for facilitated diffusion to occur?

A

through the action of channel proteins or carrier proteins

40
Q

what are channel proteins vs carrier proteins?

A

channel proteins: allow passive transport of the molecules that are appropriate in size

carrier proteins: can bind to a specific molecule and help it cross the membrane

41
Q

what are the two types of active transport?

A

primary and secondary

42
Q

what does active transport require?

A

direct use of ATP

43
Q

what does secondary active transport require?

A

use of another solute that is moving down its concentration gradient

favorable and therefore produces energy which is used in secondary active transport.

44
Q

what are the two channels crucial for maintaining the membrane potential of a cell?

A

Na+/K+ pump
K+ leak channel

45
Q

what does the Na+/K+ pump do?

A

via active transport pumps 3 Na+ out of the cell and 2 K+ ions in the cell

46
Q

what does K+ leak channel do?

A

allows K+ to move down its concentration gradient out of the cell

47
Q

what does the Na+/K+ pump and K+ leak channel result in for the cell?

A

the cell has a net negative charge inside, and a net positive charge outside.

48
Q

what is the resting membrane potential generally around?

A

-75 mV.

49
Q

what is ATPase, which transport does it use, and which pump is an example?

A

directly hydrolyzes ATP to ADP and is therefore a form of primary active transport

can also help control cell volume by controlling the number of solutes inside of the cells

Na+/K+ pump

50
Q

hypertonic vs isotonic vs hypotonic

A

Hypertonic environments will cause the cell to shrink

hypotonic environments will cause the cell to swell and lyse.

Isotonic environments cause no change in the size or shape of the cell

51
Q

what macromolecules require the formation of membrane bound vesicles for transportation?

A

proteins, polynucleotides, polysaccharides

52
Q

what are the two types of membrane-bound vesicular transport?

A

exocytosis and endocytosis.

53
Q

when does exocytosis occur?

A

when a cell needs to secrete a substance, whether that is a waste product or a protein product such as insulin

54
Q

what happens to the vesicles formed during exocytosis?

A

intracellularly fuse with the plasma membrane to release the contents that are held within the vesicles

55
Q

describe secretory vesicles

A
  • where product is stored from a cell secreting a specific product
  • only released once there’s an appropriate rise in intracellular Ca2+ concentrations
56
Q

when does endocytosis occur?

A

when cells take in macromolecules and particles

57
Q

what are the two types of endocytosis?

A

pinocytosis and phagocytosis.

58
Q

what is the most common type of vesicle of endocytosis and what is specific about them?

A

clathrin- formed from coated pits

coated with proteins

59
Q

what process is used for the uptake of specific macromolecules?

A

receptor-mediated endocytosis

60
Q

what is pinocytosis and what vesicles do they use?

A

cell drinking
small vesicles

61
Q

what is phagocytosis and what vesicles do they use and for what?

A

cell eating
uses large vesicles for the uptake of other microorganisms or cell debris so that they can be digested by the cell.

62
Q

The vesicles that are created by endocytosis usually fuse with _______, which are used for ________________

A

lysosomes
intracellular digestion

cell bio (12 decks)

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