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BIOL 1306 > CH 6 > Flashcards

CH 6 Flashcards

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1
Q

plasma (cell) membrane

A
  • separates life from nonlife
  • layer of molecules that surrounds & separates the cell interior from envt
  • selective barrier
  • causes reactants to collide more frequently = allow chem rxn necessary for life to occur more efficiently
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2
Q

Lipid

A

carbon-containing compound that is insolube in water
- results form high proportion of nonpolar c-c & c-h bonds
- dissolve in organic solvents consisting of nonpolar compounds like benzene
- Hydrophobic
- store chem energy, pigments that capture/respond to sunlight, serve as signals btwn cells, form waterproof coatings on leaves & skin, vitamins used in many cellular processes
- CELL MEMBRANE
- nonpolar, hydrophobic tail
- polar, hydrophilic head
- some are amphipathic

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3
Q

Hydrocarbons

A

organic molecule that contains only hydrogen & carbon atoms
- nonpolar bc electrons shared equally in C-H bonds (similar electronegativities of C & H)

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4
Q

Fatty acid

A

lipid consisting of hydrocarbon chain bonded to a polar carboxyl group
- used by many organisms to store chem energy
- major component of animal & plant fats & phospholipids

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5
Q

Two carbon atoms form a double bond

A
  • attached atoms found in plane
  • cannot rotate freely
  • cis bonds
  • certain 2x bonds produce “kinks” in straight hydrocarbon chains
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6
Q

Saturated lipid

A
  • all C-C bonds are single bonds
  • high melting pts
  • many interactions so lipids more packed
  • butter
  • solid @ RT
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7
Q

Unsaturated lipid

A

1+ 2x bonds exist in hydrocarbon chain
- decreased melting pt
- fewer interactions so move freely
- liquid @ RT
- oils

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8
Q

waxes

A

saturated lipid w/extremely long hydrocarbon tail
- solid @ RT

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9
Q

Hydrogenation

A

unsaturated lipids converted to saturated lipids by breaking double bonds & adding hydrogen atoms

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10
Q

3 important types of lipids found in cells

A

steroids, fats, phospholipids

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11
Q

Steroids

A

Class of lipid with characteristic bulky, 4-ring hydrocarbon structure
- differed from one another by function/side groups attached to diff carbons in rings
- ex; estrogen, testosterone, cholesterol
- role as hormone; cell signaling

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12
Q

Cholesterol

A

important component of plasma membranes in many organisms

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13
Q

Fats

A

class of lipids that are nonpolar molecules composed of 3 fatty acids joined by ester linkages to a glycerol (3-carbon) molecule
- aka triacylglycerolol aka triglyceride
- primary energy storage in organisms
- form via dehydration reaction

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14
Q

Ester linkage

A

Covalent bond formed by a condensation reaction when 2 atoms (carboxyl & hydroxyl) are linked together by an oxygen
- join fatty acids to glycerol to form a fat or phospholipid

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15
Q

Are fatty acids monomers? what does that conclude

A

No, therefore fats are not polymers

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16
Q

How do fats differ from amino acids, nucleotides, & monosaccharides?

A

they are not polymers

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17
Q

Phospholipids

A

class of lipid that consists of a glycerol that is linked to a phosphate group (bonded to small organic molecule that is charged or polar) & 2 hydrocarbon chains of either isoprenoids or fatty acids
- hydrophilic head & hydrophobic tail
- major component of plasma membrane & organelle membranes
- ones w/fatty acid tails found in domains Bacteria & Eukarya
- ones w/isoprenoid tails are found in domain Archaea
- amphipathic

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18
Q

amphipathic

A

containing hydrophilic & hydrophobic regions
- responsible for plasma membrane

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19
Q

Micelles

A

tiny spherical aggregates created when the hydrophilic heads of a set of lipids face outward & interact w/water, while the hydrophobic tails interact w/each other in the interior, away from water

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19
Q

Micelles

A

tiny spherical aggregates created when the hydrophilic heads of a set of lipids face outward & interact w/water, while the hydrophobic tails interact w/each other in the interior, away from water
- tend to form from free fatty acids or other simple amphipathic lipids w/single hydrocarbon chains
- form spontaneously in water

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20
Q

Lipid bilayer

A
  • created when lipid molecules align in paired sheets
  • hydrophilic heads in each layer face surrounding solution while hydrophobic tails face one another inside
  • tend to form from phospholipids
  • form spontaneously in water
  • highly selective
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21
Q

what does it mean for something to form spontaneously

A

no input of energy is required

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22
Q

Lipids have ____ entropy as micelles & phospholipid bilayers form

A

less, so they are less disordered

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23
Q

vesicles

A

membrane-enclosed compartment w/aq interior that is often used in cells to transport cargo btwn organelles or to plasma membrane for secretion
- small bubble-like structures consisting of lipid bilayers surrounding a small amount small amount of aqueous solution

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23
vesicles
membrane-enclosed compartment w/aq interior that is often used in cells to transport cargo btwn organelles or to plasma membrane for secretion - small bubble-like structures consisting of lipid bilayers surrounding a small amount small amount of aqueous solution
24
liposome
artificial vesicle formed by mixing amphipathic lipids, such as phospholipids, together in an aq sol'n
25
planar bilayer
artificial membrane where lipid bilayer is constructed across a hole in a glass or plastic wall separating 2 aq sol'ns
26
permeability
the tendency of a structure to allow a given substane to diffuse across it
27
selective permeability
the property of a membrane that allows some substances to diffuse across it much more readily than other substances
28
high permeability molecules
small, nonpolar molecules - e.g. O2, CO2, N2
29
moderate permeability molecules
small, uncharged polar molecules - h2o, glycerol
30
low permeability molecules
large, polar molecules - glucose, sucrose
31
very little permeability molecules
small ions - Cl-, K+, Na+
32
hypothesis explaining pattern of permeability
charged substances and polar molecules above a certain size are more stable dissolved in water-- a polar environment-- than they would be in the nonpolar interior of membranes
33
factors of a phospholipid that affect membrane permeability
bond saturation & hydrocarbon chain length
34
bond saturation effect on membrane permeability
- when UNSATURATED hydrocarbon tails are packed into a lipid bilayer, kinks created by 2x bonds PRODUCE SPACES among the tails, REDUCING the # of van der Waals INTERACTIONS that help hold the hydrophobic tails together, WEAKENING the barrier to solutes - packed SATURATED hydrocarbon tails have FEWER SPACES & MORE van der Waals INTERACTIONS. As LENGTH of saturated hydrocarbon tails INCREASES, the forces that hold them together also INCREASE, making the membrane even DENSER
35
Lipid bilayers are more permeable when they contain many _______, ________, _______ hydrocarbon tails
short; kinked; unsaturated
36
Cholesterol affect on membrane permeability
- reduces permeability dramatically when added to artificial membranes - bc it orients in the membrane w/its hydrophobic steroid rings buried deeply in the hydrocarbon tails of phospholipids. Bulky cholesterol RINGS force tails CLOSER to each other, increasing their packing DENSITY
37
Temperature affect on permeability
- as temp DROPS, molecules in bilaryer move more slowly & LESS FLUID. - hydrophobic tails in interior of membranes are packed together more tightly - lipid bilayers SOLIDIFY
38
2nd law of thermodynamics
in an isolated system, entropy always increases
39
dissolved solutes are in constant random motion due to....
their thermal energy
40
diffusion
spontaneous movement of molecules & ions, often from high conc to low conc
41
concentration gradient
difference in solute concentrations across a space
42
entropy
randomness, disorder in a system
43
diffusion down a concentration gradient is a spontaneous process because...
it results in an increase in entropy
44
passive transport
diffusion of a substance across a membrane in the absence of an outside energy source
45
osmosis
diffusion of water across a SELECTIVELY PERMEABLE membrane from a region of lower SOLUTE conc to higher conc - spontaneous
46
only ______ water molecules are able to diffuse across the membrane during osmosis
unbound
47
Hypertonic
high in concentration - only for effect of water movement
48
hypotonic
low in concentration - only for effect of water movement
49
isotonic
equal concentrations on both sides - only for effect of water movement
50
what do diffusion & osmosis have to do with the first membranes floating in the prebiotic oceans of early Earth?
both processes tend to reduce differences in chemical composition btwn inside & outside of membrane-bound compartments
51
primary importance of first lipid bilayers
provide a container for replicating the first "living" molecule
52
protocell
hypothetical pre-cell structure consisting of a membrane compartment that encloses replicating macromolecules - simple vesicle-like structures that harbor nucleic acids
53
what sort of molecule could become incorporated into a lipid bilayer & influence the bilayer's permeability?
proteins
54
Can proteins be amphipathic
yes
55
fluid-mosaic model
- Singer & Nicolson - hypothesis that cellular membranes consist of proteins embedded in a fluid phospholipid bilayer - suggested membranes are dynamic
56
freeze-fracture electron microscopy
method used to visualize the surfaces of plasma membranes - freeze & fracture the membrane before examining it w/a scanning electron microscope - allow split of cell membrane & view the middle of the structure
57
scanning electron microscope
microscope that produces surfaces images by reflecting electrons off a specimen coated w/layer of metal atoms
58
transmembrane protein
- aka integral membrane protein - any membrane protein that spans the entire lipid bilayer - segments face both interior & exterior of cell
59
peripheral membrane proteins
Proteins that bind to membrane lipids or integral membrane proteins without passing through it
60
detergent
a small amphipathic molecule that can form micelles - water soluble - break up plasma membrane & isolate membrane protein
61
ion channel
type of channel protein that allows certain ions to diffuse across a plasma membrane down an electrochemical gradient - form pores/openings in membrane - diffuse from high to low conc & from areas of like charge to areas of unlike charge - down the EC gradient
62
channel protein
a transmembrane protein that forms a pore in a cell membrane, which may open or close in response to a signal - key side chains in the interior of the pore function as a filter - passive - ions or small, polar molecules
63
aquaproin
type of channel protein that facilitates the movement of water (osmosis) across a plasma membrane - gated
64
gated channel
channel protein that opens & closes in response to a specific stimulus, such as the binding of a particular substance or a change in voltage across the membrane - ions - flow of ions & small molecules through is carefully controlled
65
facilitated diffusion
passive diffusion of a substance across a membrane with the assistance of transmembrane carrier proteins or channel proteins
66
carrier proteins
transmembrane protein that facilitates diffusion of a small molecule (e.g. glucose) across a membrane by a process involving a REVERSIBLE change in the SHAPE of the protein - aka carrier or transporter
66
carrier proteins
transmembrane protein that facilitates diffusion of a small molecule (e.g. glucose) across a membrane by a process involving a REVERSIBLE change in the SHAPE of the protein - aka carrier or transporter
67
primary difference btwn channels & carrier proteins
mechanism of transport - channels allow movement through selective pore, like bridges - carrier proteins selectively pick up a solute on one side of membrane, then drop it off on the other side
68
GLUT-1
responsible for transporting glucose across plasma membranes - changes the shape of the protein in a way that moves the sugar through the hydrophobic region of the membrane & releases it on the other side - diffuses by its conc gradient
69
active transport
movement of ions/moelcules across a membrane, across a gradient. requires energy (e.g. from hydrolysis of ATP) & assistance of transport protein (e.g. pump) - counteract decrease in entropy
70
how does atp provide energy for active transport
transferring a phosphate group to an active transport protein called a pump - negative charges of phosphate group interact w/charged amino acid residues in the protein - pump's potential energy increase & shape changes
71
pump
any membrane protein that uses energy to change shape & power the active transport of a specific ion or molecule against its gradient
72
sodium-potassium pump
transmembrane protein that uses the energy of ATP to move sodium ions out of the cell & potassium ions into the cell, against their EC gradients - Na+/K+-ATPase - 3 Na+ ions out - 2 K+ ions in
73
How would pumps react if gradients were to reverse
they would continue to use the same energy source to transport he solutes in the same direction, even if it's not against the existing gradient
74
Sodium-potassium pump conversion of energy
converts ATP to an EC gradient across the membrane that favors the flow of ANIONS OUT of the cell & flow of CATIONS INTO the cell
75
secondary active transport
transport of an ion or molecule in a defined direction (often against gradient), made possible by the transport of another ion or molecule being moved along its gradient - aka cotransport - ATP not directly use to power transport, but instead ATP pump provides the energy in the form of a gradient that is used to power the movement of a diff solute against its gradient

BIOL 1306 (7 decks)

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