Chapter 6: plasma member and lipids Flashcards
(100 cards)
1
Q
what was the defining point in evolution of life?
A
the formation of plasma member
2
Q
plasma membrane
A
protective barrier for cells that consists of lipids (fats and oils), carbohydrates, and proteins
A LIPID BILAYER IN CELL
3
Q
why is the plasma membrane important?
A
protect cells interior environment from the influence of the exterior environment
4
Q
the plasma membrane also acts as a what?
A
fence/gatewat that regulates entry and exit of material in and out of the cell
5
Q
lipids
A
class of macromolecule that includes fats, oils, and waxes
Do not consist of monomers
6
Q
why are lipids hydrocarbons
A
consist of a high proportion of C-C and C-H bonds (non polar)
7
Q
why are hydrocarbons non polar
A
due to the equal negativites that exist between C and H
so it has high pe
8
Q
are hydrocarbons insoluble or soluble
A
insoluble in water (due to nonpolar nature hence it is hydrophobic) BUTT only soluble in nonpolar solvents
9
Q
fatty acids
A
simple lipids that have long nonpolar(hydrophobic) hydrocarbon tail bonded to a polar (hydrophilic) carboxyl group
10
Q
how many carbon atoms does a hydrocarbon chain of a fatty acid have?
A
14-20 carbon atoms
11
Q
saturated fatty acids
A
bonds formed between carbon atoms consist entirely of single bonds resulting in this
12
Q
when do unsaturated fatty acids/ polyunsaturated fatty acids result?
A
whens bonds form between carbon atoms of a fatty acid are double bonded
13
Q
steroids
A
have four ring structure and unique chemical group attached to it
- these chemical groups distinguish different steroids
14
Q
what is cholesterol?
A
a steroid made by our livers and obtained from our diets
- aids with rigidity
- allows vein to be more flexible
15
Q
why is cholesterol important?
A
important constituent of cell membranes
16
Q
what is a precursor molecule for production of testosterone and estrogen?
A
Cholesterol
17
Q
Fats
A
have a glycerol molecule joined to 3 fatty acids
- have high pe
- a macromolecule with no monomers
18
Q
are fats a polymer?
A
NO bc they are not made of monomers
19
Q
how are fats formed?
A
Condensation reaction/dehy./ polymerization between hydroxyl group on glycerol and carboxyl group on fatty acid
- resulting bond is an ester linkage
20
Q
glycerol is covalently bound to 3 fatty acids so fats can be called
A
triacylglycerols or triacylglycerides
21
Q
why do fats have high pe
A
due to # of C-H and C-O bonds in fatty acid tails so it acts as an energy reservoir (like carbs!)
22
Q
Do carbohydrates or fats have higher potential energy?
A
fats!
23
Q
are fatty acids linked into chains like amino acids, nucleotides, carbohydrates?
A
no
24
Q
phospholipids
A
core component of plasma membrane (mesh of lipids)
25
what are phospholipids made of?
glycerol molecule covalently bound to 2 fatty acid (hydrophobic) tails via the ester linkage, along with a phosphate group (hydrophilic)
26
note that the phosphate group can also...
bind to an additional small charged or polar molecule
27
why are phospholipids unique?
bc they are amphipathic
28
amphipathic
both polar and nonpolar regions/properties
29
why is the phosphate functional group in a phospholipid structure hydrophilic?
Due to the negative electric charge
30
why are the 2 fatty acids in a phospholipid structure hydrophobic?
bc they are nonpolar
31
in water, phospholipids _____ arrange themselves so that their polar/hydrophilic heads face toward water molecules and hydrophobic tails face away from them
spontaneously
32
in water phospholipids are able to turn into either a...
1. micelle
2. lipid bilayer
33
micelle
spherical aggregate of lipids (single layer of phospholipids)
hydrophilic head interacts w. water and hydrophobic tails interact w. 1 another
34
lipid bilayer
paired sheets of phospholipids (2 layers of phospholipids) that is permeable (must know that it is permeable)
35
permeability
ability of certain substances to pass through it (in and out the cell)
36
lipid bilayers are highly ____
selective (in terms of permeability meaning some substances are able to pass through them easily than others)
37
what can cross the bilayer easily?
Small nonpolar (hydrophobic and soluble in lipids) and polar molecules (H2O and O2)
38
in the case of charged ions and large polar molecules, it needs ____ to cross the membrances
assistance!!
if not it cant cross
39
charged and polar molecules are what
hydrophilic and not rlly soluble in hydrophobic interior of bilayer
40
lipid structure affects...
membrane permeability
41
length of fatty acid tails and composition of saturated vs unsaturated fatty acids affect
permeability
42
bilayers with unsaturated fatty acids produce
kinks in the bilayer due to the presence of double bonds
43
what do these kinks do?
create space in between hydrophobic tails of the bilayer that increases permeability
44
since bilayers with saturated fatty acids do not have double bonds they produce...
more tightly packed membranes, having less space ----- decreasing permeability
this is what saturated fatty acids within the bilayers do^
45
hydrocarbon tail length affects _____
permeability
46
longer hydrocarbon tail
less permeable the membrane
47
shorter hydrocarbon tail
more permeable the membrane
48
presence of cholesterol in membrane
reduces permeability
49
how does cholesterol orient itself?
hydrophilic hydroxyl group faces water and hydrophobic isoprenoid tail embeds in membrane
50
why does cholesterol reduce membrane permeability?
fused rings of it rings phospholipid tails closer tg, reducing it
51
membranes have fluidity and movement of that fluid is correlated to
temperature
meaning temp. affects permeability
52
higher temp
faster lipids move, more permeable
(liquid-like membrane)
53
lower temp
slower lipids move, more impermeable or less permeable
(stronger/rigid membrane)
54
diffusion
spontaneous movement or spreading of ions and molecules
55
how do molecules move across membrane?
by diffusion
56
when do concentration gradients come into play?
when theres a difference in the amount / concentration of a solute in one area relative to another
57
when a concentration gradient exist, solutes natural tendency is to
move from an area of high concentration to an area of low concentration... diffuse down their concentration gradient
58
when there is no concentration gradient solutes....
move randomly in all directions in a solution
59
tonicity
ability of a solution surrounding a cell to cause a gain/loss of water
- cells react to these changes in solute concentrations in their environment
60
changes in tonicity affect...
sell structure
61
hypertonic
solution surrounding a cell has higher concentration of solutes than the inside of the cell
- water exits cell and cell shrivels
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hypotonic
solution surrounding a cell has lower concentration of solutes than the inside of the cell
- more water outside than inside
- water enters cell and cell swells and burstttt
63
isotonic
solution surrounding the cell has an equal concentration of solutes as inside of the cell
- no net movement of water (cells remain normal)
- solute in and out of cell
64
cell membranes are a fluid mosaic of....
lipids and proteins
65
_____ are another critical component of plasma membranes
proteins!!
66
fluid mosaic model
current model for the arrangement of molecules in the plasma membrane
membrane is a mosaic of protein + lipid molecules moving in motion
67
since proteins have polar to nonpolar r groups/ side chains, they are
amphipathic
68
amphipathic
polar (charged) portions proteins face the cell exterior (water) whileeee nonpolar (no charge) face cell interior
69
2 groups of proteins that play important role in stability + function of plasma membrane
1. transmembrane/integral proteins
2. peripheral proteins
70
transmembrane/integral proteins
proteins that embed within lipid bilayer (plasma membrane) bc of their hydrophobic core
ex: ion channels/protein channels and carrier proteins
71
peripheral proteins
proteins that lie on inner/ outer surface of lipid bilayer
- exterior is polar
- interior is nonpolar
72
channel and carrier proteins regulate...
diffusion
73
how are ions able to enter + exit the cell?
via ion channels or channel proteins (specialized transmembrane/ integral proteins)
74
due to ion having charge, what exists across membranes??
electrical gradients/ voltage (diff. in electrical charge)
75
unequal distribution of ions on each side of membrane causes...
cytoplasmic side of membrane to have overall negative charge
extracellular side has overall positive charge
76
2 forces drive diffusion of ions across a membrane
1. chemical force (ions concentration gradient)
2. electrical force (electrical gradient created by differences in electrical charge across membrane)
77
both forces combined acting on an ion =
electrochemical gradient
78
structure of channel (transmembrane/integral proteins) determines
specificity of ion/molecule that passes through it
and its selective (in what enters/exits through them)
which is important to keep organism alive and to relieve disfunction
ex: aquaporin allows water to cross plasma membrane but not other molecules/ions
mediated by amino acids in channel that interact w. only water
79
many ion channels are considered
voltage-gated ion channels (response to signal/stimulus like electrical stimulus) ... open or close allowing molecules to enter cell
80
example of voltage gated ion channels...
under normal cellular conditions K+ channels stay closed.
in response to electrical changes across plasma membrane, K+ channels open allowing these ions to passively exit the cell
81
diffusion is ______ bc energy is not requires to push K+ atoms out of cell, these ions are following electrochemical gradient
passive
(solute moves from high to low so it doesn't need energy)
82
carrier proteins
regulate diffusion of molecules across membranes through conformational change
BINDSSS to solute on 1 side of membrane, changing the conformation then substrate is released on opposite side of membrane.
- specialized transmembrane/integral proteins
83
conformational change is to
hold a substrate/reactant while binding
84
difference between channel proteins and carrier proteins
channel proteins have pores allowing molecules to enter/exit cell
carrier proteins bind to solute on one side of the membrane, changing their conformation resulting release of solute in the opposite side of the membrane due to the conformational change
85
GLUT-1
a glucose transporter which is an example of carrier protein
86
depending on glucoses concentration gradient, GLUT-1 can
bind to glucose on either side of the membrane.
as a result of a conformation change in its structure, promote the passive transport of glucose across membrane
87
passive diffusion of ions across a plasma membrane with the help of a carrier protein/channel protein is also called
facilitated diffusion
88
protein pumps regulate
active transport
89
cells also have the ability to move ions/molecules against....
concentration gradient so LOW to HIGH AKA ACTIVE TRANSPORT
90
active transport
type of transport when substancees are moved against concentration gradient of a membrane, going low to high
requires energy so it is not passive
91
protein pumps
proteins that facilitate active transport
ex: Sodium potassium pump
92
sodium-potassium pump uses ________ to exchange Na+ for K+ across the plasma membrane of animal cells
ATP Hydrolysis (energy)
93
interior of cell has
high concentration of K+ ions and low concentration of Na+ ions
where K+ stays in and Na+ stays out
94
how does the sodium-potassium pump maintain concentration gradient?
pumps 3 Na+ ions out of cell and pumps 2 K+ ions into cell
(ions are being transported against their concentration gradient)
95
sodium-potassium pump converts energy from ATP and creates
electrochemical gradient across membrane-----creates potential energy for the cell
96
cotransport is coupled transport by a membrane protein
coupled meaning 2 diff pumps
97
cell can use the potential energy created by the sodium potassium pump to ..
transport additional molecules across plasma membrane (aka cotransport/secondary transport)
98
example of cotransport/secondary transport is the sodium-glucose cotransporter where
gut cells use the Na+ gradient created by the sodium-potassium pump to import glucose into cells against its gradient
99
significance of active transport is that
ions + molecules can be concentrated/ diluted inside a cell depending on the needs of the cell
100
solutes reach equilibrium when
the concentration of solute is constant throughout a system
