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Biology Exam Prep > Membrane Structure & Function > Flashcards

Membrane Structure & Function Flashcards

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1
Q

what is the plasma membrane?

A

the plasma membrane surrounds the cell providing a boundary between the cells internal environment and the outside world.

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2
Q

what is the structure of the plasma membrane?

A

phospholipid bilayer

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3
Q

what does the phospholipid bilayer contain?

A

hydrophobic tails and hydrophilic head.

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4
Q

what is a phospholipid?

A

2 fatty acid tails, glycerol, a phosphate group

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5
Q

in animal cell membranes, the steroid…?

A

cholesterol is also found. it is located between the phospholipids in the bilayer.

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6
Q

what does the plasma membrane consist of?

A

phospholipids, cholesterol, and protein, carbohydrates

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7
Q

what are the two different types of membrane proteins?

A

integral and peripheral proteins.
integral: 80%
peripheral: 20%

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8
Q

what are integral proteins?

A

proteins that are embedded in the lipid bilayer by their hydrophobic regions.
they may have a hydrophilic region extending on one or both sides of the membrane called transmembrane proteins.

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9
Q

what are peripheral proteins?

A
  • these proteins dont penetrate the lipid bilayer
  • they are loosely associated with the inner OR outer side of the plasma membrane
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10
Q

how are membrane proteins held in place?

A

by attaching to the fibers of the extracellular matrix or by attaching to the cytoskeleton

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11
Q

functions of membrane proteins?

A
  • transport: moving substances across the cell membrane
  • enzymatic activity: membrane proteins act as enzymes that speed up chemical reactions.
  • signal transduction/receptor molecules: membrane proteins serve as receptors that detect signals. when a signal binds to the receptor, it triggers a response inside a cell, helping it react to changes in its environment.
  • cell-cell recognition: specifically glycoproteins: protein that has a carbohydrate group attached, they help distinguish between self and foreign. important for immune response and embryonic development.
  • intercellular joining: membrane proteins can help cells stick together. some form gap junctions that are channels that allow materials to pass directly from one cell to another.
  • attachment to the cytoskeleton and ecm: membrane proteins anchor the cell to its cytoskeleton. helps maintain the cells shape and provides structural support.
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12
Q

most membranes contain?

A

small but significant amounts of carbohydrates.

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13
Q

carbs in membranes?

A
  • usually branched chains that have 15 sugar units.
  • most of the carbohydrates are in the form of glycoproteins: protein with a carbohydrate attached to it.
  • some are in the form of glycolipids: lipid with carbohydrate attached to it.
    MAINLY GLYCOPROTEINS
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14
Q

the carbohydrates protrude to the?

A

external side of the membrane: the function is playing a role in cell to cell recognition, especially glycoproteins.

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15
Q

the type of blood type you are depends on?

A

the type of carbohydrate you have sticking out of the surface of the red blood cells.
4 blood types: ab,a,b,o

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16
Q

the carbohydrates found differ between?

A

cell types, between species, and differ between members of the same species

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17
Q

what is the fluid mosaic model?

A

most accepted current model that is used to describe the structure of a membrane.
- mosaic refers to the different types of proteins present within the phospholipids. ex: rbc have 50+ different types of proteins in its plasma membrane.
- fluid refers to the membrane being fluid. the phospholipids and the proteins can move freely about the membrane, move laterally, flip from one side to another, but proteins move but they dont move too much because they are large.

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18
Q

membrane fluidity is important for cell functionality and is affected by?

A
  • temperature
  • the type of lipids that the membrane is composed of
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19
Q

the fluidity of the membrane increases with?

A

increasing temperature

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20
Q

the fluidity of the membrane decreases with?

A

decreasing temperature

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21
Q

membranes with longer chain fatty acids are?

A

less fluid than those with shorter chains.

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22
Q

membranes with short chain fatty acids are?

A

more fluid than those with longer chains.

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23
Q

membranes that contain more unsaturated fatty acids are?

A

more fluid.

24
Q

cholesterol is found?

A

between the phospholipids in either layer.

25
Q

cholesterol acts as?

A

a temperature buffer

26
Q

at high temperatures, cholesterol makes the membrane?

A

less fluid because it restrains the movement of phospholipids.

27
Q

at low temperatures, cholesterol makes the membrane?

A

more fluid. it interacts with the hydrocarbon chains so that they do not fit as tightly together.

28
Q

most organisms that experience temperature fluctuations can?

A

regulate their membrane fluidity by changing the lipid composition of their membrane, called HOMEOVISCOUS ADAPTATION.

29
Q

fish in an outdoor pond, when cold, there are more unsaturated or saturated fatty acids?

A

unsaturated fatty acids

30
Q

archaea in a hot spring, when hot, there are more unsaturated or saturated fatty acids?

A

saturated fatty acids

31
Q

membrane asymmetry?

A

membranes contain different kinds of lipids and proteins.
- they are randomly distributed between the two monolayers.
- each membrane has a distinct side that has a unique composition.

32
Q

extracellular face vs cytoplasmic face?

A

extracellular face: outside
cytoplasmic face: inside

33
Q

membranes are selectively?

A

permeable

34
Q

solutes are carried across membranes via?

A

3 different mechanisms: simple diffusion, facilitated diffusion, and active transport

35
Q

passive process?

A

simple diffusion and facilitated diffusion
- no energy is required to move solutes across.
- movement is with the concentration gradient: high to low.
- for facilitated diffusion, transport proteins are required: channel or carrier proteins.

36
Q

what kind of transport proteins are required for facilitated diffusion?

A

channel or carrier proteins

37
Q

active process?

A

active transport:
- energy is required
- movement is against the concentration gradient: low to high
- transport proteins are always involved in this process: carrier proteins

38
Q

function of active transport?

A
  1. allows the cell to uptake essential nutrients from the environment when they are lower outside the cell than inside the cell.
  2. it allows secretory or waste products to be removed from the cell even when the concentration is higher outside the cell.
  3. it allows a constant nonequilibrium concentration of certain ions inside the cell.
39
Q

in an animal cell there are more potassium ions inside the cell than outside the cell. more sodium ions outside the cell than inside the cell? how is this maintained?

A
  • sodium is pumped out of the cell and potassium is pumped into the cell.
  • both are pumped against their concentration gradient.
  • a transport protein called sodium potassium pump located in the plasma membrane of animal cells moves these ions.
40
Q

more about the sodium potassium pump?

A

3 sodium out for every 2 potassium in. this results in a difference of charge between the outside and inside of the cell. the cytoplasm is negative in charge compared to the extracellular fluid.

41
Q

cells have voltages across their plasma membrane, this voltage is referred to as?

A

membrane potential.

42
Q

pumps that generate a voltage are called?

A

electrogenic pumps.

43
Q

whats the major electrogenic pumps in animal cells?

A

sodium potassium pump.

44
Q

whats the major electrogenic pumps in plant cells?

A

proton pump.

45
Q

why are these pumps useful?

A

by generating these voltages across membranes, these pumps help the cell to store energy that can be used for future cellular work.
ex: transport of materials across the membrane

46
Q

in plants, the proton pump is used to?

A

transport sucrose into a sieve tube cell.

47
Q

what is cotransport?

A

cotransport occurs when a pump transporting a specific solute across the membrane is responsible for indirectly pumping another solute across the membrane against its concentration gradient.

48
Q

molecules such as water and small solutes can move across the membrane via?

A

diffusion

49
Q

how do large proteins and polysaccharides enter and exit the cell?

A

large molecules generally cross the membrane by a mechanism involving vesicles.

50
Q

large molecules exit via?

A

exocytosis: example is pancreatic cell secreting insulin.

51
Q

large molecules enter via?

A

endocytosis: the cell takes in molecules by forming new vesicles from the plasma membrane.

52
Q

3 types of endocytosis are?

A

phagocytosis, pinocytosis, and receptor mediated endocytosis.

53
Q

what is phagocytosis?

A
  • cellular eating
  • folds of the plasma membrane called pseudopods surround a particle.
  • a phagocytic vacuole is formed
  • the vacuole fuses with a lysosome and the material is digested

ex: used as a means of acquiring food, and defence by certain white blood cells.

54
Q

what is pinocytosis?

A
  • pinocytosis are cellular drinking
  • results from the inward folding of the plasma membrane to form a pocket.
  • it fuses to form a vesicle
  • the vesicle fuses with a lysosome for breakdown of the internalized materials.
55
Q

what is receptor mediated endocytosis?

A
  • on the plasma membrane there are receptors for certain substances.
  • when the receptor binds to the ligand, the complex moves to a special region on the plasma membrane called a coated pit.
  • forms a vesicle
  • the vesicle fuses with a lysosome.

Biology Exam Prep (24 decks)

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