Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MBB 231 > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

can you see plasma membrane with light microscope

A

no, too small

need electron microscope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what lead them to find out that membranes are mostly comprised of lipids

A

dissolving power corresponded to that of oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is most energetically favourable orientation for polar head groups in plasma membrane

A

polar head groups facing the aqueous components outside the bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what stabilizes bilayers

A

van der Waals interactions in the fatty acyl chains

also there are h-bonds and ionic bonds between the polar head groups and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how are proteins present in lipid bilayer

A

as individual protein molecules and protein complexes that penetrate bilayer and extend out into the surrounding aqueous environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what makes membranes dynamic

A

membrane fluidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the functions of plasma membranes

A
  1. compartmentalization (define boundaries of cell organelles)
  2. scaffolding for biological activities (provides framework that organizes enzymes for effective interactions)
  3. selective permeability barrier (allows regulated exchange of substances between compartments)
  4. solute transport (membrane proteins facilitate the movement of substances between compartments)
  5. response to external stimuli (membrane receptors transduce signals from outside the cell in response to specific ligands)
  6. cell-cell communication ( mediate recognition and interactions between adjacent cells)
  7. energy transduction (membranes transduce photosynthetic energy, convert chemical energy to ATP, store energy)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how are membranes and lipid-protein assemblies held together

A

non-covalent bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the two components of membranes and their function

A
  • lipid bilayer: structural backbone and barrier to prevent random movement in/out of cell
  • membrane proteins: carryout the more specialized functions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

does the lipid-to-protein ration vary and what does it depend on

A

yes

depends on: type of cellular membrane, type of organism, type of cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the three types of lipids that mammalian membranes are primarily composed of

A
  • phosphoglycerides
  • sphingolipids

-cholesterol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what do phosphoglycerides contain (at a minimum)

A

2 fatty acids (usually one saturated and one unsaturated), a glycerol, and a phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what do all phosphoglycerides exhibit

A

a distinct amphipathic character

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are sphingolipids derived from / composed from

A

derivatives from ceramides
(sphingosine + a fatty acid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is a glycolipid

A

singolipid with an added carbohydrate group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is a ganglioside

A

sphingolipid with multiple sugars added

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

where are glycolipids found exclusively

A

ectoplasmic face of plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

where are sugar groups added to glycolipids

A

in lumen of the Golgi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

why is cholesterol amphipathic

A

the hydroxly group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is cholesterol used for

A

used to stabilize and maintain membranes

important for fluidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what can membrane lipids be precursors for

A

highly active chemical messengers that regulate cellular function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what do the hydrophobicnature of chains in membranes result in

A

they cannot be exposed to aqueous environment

membranes always continuous unbroken structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

can lipid bilayers self assemble

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what do in vitro phospholipids self assemble spontaneously into

A

spherical vesicles called liposomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

do leaflets in same lipid bilayer have different lipid compositions

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what cab lipid bilayers be thought of as

A

2 independent monolayers with different physical and chemical properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what side of bilayer are glycolpids always on and why

A

they are aways on the extracellular side and they serve as ligand receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what side of the lipid bilayer is negatively charged

A

cytosol side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

when can proteins bind to cytosolic side

A

when they require negatively charged PS for activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what way to all membrane carbohydrates face

A

away from the cytosol (extracellular space, ER lumen, etc..)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is glycosylation

A

addition of carbohydrates to proteins

most complex post translational modifications

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what are the 3 classes of proteins associated with membranes

A

integral monotonic proteins
single pass proteins
multi-pass proteins

(single and multi pass are transmembrane proteins)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What are lipid-anchored membrane proteins

A

located outside the membrane (either side), but are covalently “anchored” to a membrane lipid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what do the hydrophobic regions embedded into the membrane function as

A

transporters: moving ions across the membrane

anchors: binding intra/extracellular components to membrane

receptors: binding ligands to initiate signal transduction pathways

electron transporters: transfer e- during photosynthesis and respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what are integral membrane proteins (in terms of hydrophobic/hydrophillic)

A

amphipathic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what arrangement are transmembrane segments normally

A

alpha helices (sometimes beta barrels)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

how are the alpha helices held in place in membrane

A

by van der waals between hydrophobic amino acid side chain and lipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

why are integral membranes hard to isolate in a soluble form

A

they aggregate in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what is a glycophorin A

A

major integral protein of the erythrocyte plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

in glycophorin A what direction do most of the hydrophobic side chains of the amino acids in the a-helix face

A

lipid layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what does a hydropathy plot do

A

measures the hydrophobicity of amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what does + and - mean in hydropathy plots

A

+ hydrophobic

  • hydrophilic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what provide a transmembrane proton pathway

A

seven helices that are clustered together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

do peripheral membrane proteins interact with the hydrophobic core of the lipid bilayer

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

how are the peripheral membrane proteins associated with the membrane

A

interactions with lipid’s polar head groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

are peripheral membrane proteins removed easier/harder remove from membrane than integral membrane proteins

A

easier to remove

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what does removing peripheral membrane proteins do

A

changes pH
changes ionic strength

since it disrupts electrostatic interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what are the 3 lipid anchored membrane proteins and where are they synthesized

A
  • fatty acid anchored membrane proteins: in cytosol
  • isoprenylated membrane proteins: in cytosol

GPI-anchored membrane proteins: in ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what is the fluid mosaic model

A

membranes consist of a mosaic of proteins/lipids in a fluidic state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

why is membrane fluidity important

A

nearly every function involving a membrane is dependent on this phenomenon ex:

  • vesicle formation, cell division, muscle contractions, cell migration, signalling mechanisms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

what is the central dogma of membrane biology

A

fluid-mosaic model

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what state do membranes function properly in

A

only in the fluid state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what happens if a fluid membrane is too rigid

A

membrane components can’t organize properly as proteins can’t move and interact with binding partners

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what happens if a fluid membrane is too viscous

A

lose mechanical support (ability to orientate properly) with excessive fluidity resulting in an increase in membrane permeability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

how does membrane fluidity change with temperature

A

low temp: fluidity decreases

high temp: fluidity increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

what is the transition temperature (Tm)

A

temperature at which membrane becomes fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

how is fluidity affected by tail length

A

fluidity increases with shorter C tails

fluidity decreases with longer tails

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

what kind of fatty acids pack together better in a membrane

A

saturated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

what kind of fatty acids are more fluid

A

saturated fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

do saturated or unsaturated fatty acids have a lower Tm

A

unsaturated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

what temperature are high fluidity (more unsaturated fatty acids, shorter tails) at a fluid state

A

lower temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

what temperature are low fluidity (more saturated fatty acids, longer tails) at a fluid state

A

higher temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what layers of plasma membrane is cholesterol found in

A

both

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

what way does cholesterol orient itself in membrane

A

with hydroxyl group close to the polar head groups of phospholipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

what are the two roles of cholesterol in membranes

A
  • sterols decrease the permeability of membranes to ions and small polar molecules

-cholesterol acts as a fluidity buffer (broadens the temperature range of transition)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

how does cholesterol decreases the membrane’s permeability to ions

A

cholesterol fills spaces between hydrocarbon chains of phospholipids and block routes that ions and small molecules could take through the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

hoe does cholesterol alter the fluidity of lipid bilayers

A

with unsaturated fatty acids, cholesterol decrease fluidity (more packed)

with saturated fatty acids, cholesterols increase fluidity
(less packed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

what do most membranes vary in and why

A

chain length and degree of saturation

helps ensure that membranes are fluid at physiological temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

what do cells use to alter fatty acids in response to needs

A

enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

what are homeoviscous adaptations

A

the ability of a cell to regulate membrane fluidity in response to temperature changes by altering lipid composition and maintain fluidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

what are lipid rafts

A

localized regios of membrane lipids in association with specific proteins

dynamic structures that change compositions as lipids and proteins move into and out of them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

what are the functions of lipid rafts

A
  • believed to serve as floating platforms that concentrate proteins into compartments on the membrane
  • thought to have roles in deterring and responding to extracellular signals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

what do lipid rafts have elevated levels of in outer monolayer in animal cells

A

cholesterol and sphingolipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

are lipid rafts more/less fluid than rest of membrane

A

less fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

are lipids mobile in their monolayer

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

what are the two rapid and random movements in plasma membrane

A
  • rotation of phospholipids about their axis

-phospholipids can also move within monolayer via lateral diffusion (very fast)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

how do lipids “flip flop”

A

hydrophilic head of the lipids must pass though the internal hydrophobic sheet of membrane

(slow)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

what are flippases

A

enzymes that move certain phospholipids from one leaflet to he other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

what are flippases essential for

A

establishing membrane asymmetry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

does protein mobility vary within a membrane

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

what is fluorescence recovery after photobleaching (FRAP)

A

cell surface molecules are labeled with a fluorescent dye

laser beam bleaches an area on the cell surface

fluorescent labeled molecules diffuse into bleached area and bleached area disappear as lipids move laterally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

what did frap studies show

A

proteins move slower in living cell membranes than pure lipid bilayers

the mobility of many proteins was limited ( not free to diffuse back into bleached area)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

what is passive transport

A

down a concentration gradient

no energy is expended

transported proteins may or may not be needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

what is active transport

A

against a concentration gradient

requires input of energy (ATP)

transport protein pumps are required

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

what does simple diffusion require

A

membrane permeability and favourable gradient conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

what is permeability determines by

A

properties of the solute:

  • molecular size
  • partition coefficient
  • charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

do small or big molecules penetrate lipid bilayer more rapidly faster

A

small

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

are membranes impermeable to ions

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

how does moving down a concentration gradient affect entropy

A

increases entropy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

how does an electric potential gradient work

A

charged molecules want to move towards the compartment with the opposite charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

what is the thermodynamically favourable transport direction for molecules determined by:

A

no net charge: by concentration gradient

ions: by electrochemical gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

what is the electrochemical gradient

A

the combined effect of concentration gradient and the electrical potential gradient across the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

what is simple diffusion only possible for (typically)

A

gases

non-polar molecules

small polar molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

what direction does diffusion move towards

A

equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

what is passive/simple diffusion

A

unassisted movement of a molecule across a membrane, down its concentration gradient at a rate proportional to the gradient and the permeability of the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

is simple diffusion reversible

A

yes

97
Q

what is osmosis

A

diffusion of water through a semi-permeable membrane where water moves from an area of lower solute concentration to an area higher solute concentrations

98
Q

what happens in a hypotonic solution

A

cell swells

(more solutes in cell)

99
Q

what happens in a hypertonic solution

A

cell shrinks

(less solutes in cell)

100
Q

what happens in an isotonic solution

A

no net loss/gain of water

101
Q

what is facilitated transport

A

requires a protein to help get the molecule across the membrane

102
Q

how are transport molecules classified

A

carriers: bind one or more solute molecules, undergoes a conformational change that transfers the solutes to the other side

channels: form hydrophilic channels through the membrane that allow passage of solutes without a major conformational change

103
Q

what are the three types of transmembrane channel proteins (involved with facilitated diffusion)

A

ion channels: highly specific channel (often for kind of 1 ion) that can conduct a million ions a second

porins: passage of a variety of hydrophilic solutes, determined by pore size

aquaporins: water flows through and amino acid residues discriminate against other ions of similar size

104
Q

what direction do ion channels move in and what determines it

A

bidirectional

determined by electrochemical gradient

105
Q

what does ion specificity result from

A

ion specific associations and from constriction in centre (size filter)

106
Q

are most ion channels gated and do they require conformational changes

A

most have gates

no need to undergo conformational changes

107
Q

what are the types of ion channel gates

A

voltage gated: open and close in response to change in membrane potential

ligand gated: triggered by the binding of specific substances to the channel protein

mechxnosensitive gated: respond to mechanical forces that act on the membrane

108
Q

how do porins work

A

allow for rapid passage of various solutes (low specificity)

109
Q

where are porins found

A

outer membrane of mitochondria, chloroplasts, and bacteria

110
Q

what is the structure of a porin

A

beta barrel with water pore at its centre

polar side chains line the inside

nonpolar side chains point into the membrane

111
Q

how does water diffuse across membranes

A

slowly (through simple diffusion)

flows single file through aquaporins

112
Q

why do kidneys have a high density of aquaporins

A

reabsorption of water

113
Q

what is the alternate conformation model

A

how transport with carrier proteins work

where the membrane protein can adopt 2 conformational states to transport solute

114
Q

what are the similarities between carrier proteins and enzymes

A

carrier proteins are very specific for their target

carrier proteins have their activity regulated

exhibit saturation kinetics

115
Q

what is a uniporter

A

transports a single solute

116
Q

what is a symporter

A

transports 2 solutes in the same direction across the membrane

117
Q

what is an anti-porter

A

transports two solutes in opposite directions across the membrane

118
Q

how does glucose transporter GLUT1 work

A

facilitated diffusion of glucose by a uniport carrier protein

119
Q

how does chloride bicarbonate exchange work

A

facilitated diffusion via an antiport protein

(anion exchange protein, facilitates the reciprocal exchange of chloride and bicarbonate in opposite directions)

120
Q

what is a typical membrane potential in a mammalian cell

A

-60mV to -70mV

121
Q

what side of the membrane is negative with respect to the other side

A

cytosolic side

122
Q

what direction does active transport move

A

away from equilibrium

123
Q

what are the membrane proteins involved in active transport called

A

pumps since they require enegery

124
Q

what direction is active transport

A

unidirectional, has an intrinsic directionality

125
Q

what are the functions of active transport

A

uptake of essential nutrients

removal of wastes (even if concentration is higher outside the cell)

creation of gradients and maintenance of non-equilibrium concentration

126
Q

what is direct (primary) active transport

A

solute accumulation is coupled directly to an exergonic chemical reaction (ATP hydrolysis)

ATP hydrolysis drives the outward transport of protons, thereby establishing an electrochemical potential for protons across the membrane

127
Q

what is indirect (secondary) active transport

A

an endergonic (uphill against a concentration gradient) is coupled to the exergonic (downhill down a concentration gradient) (may have been pumped uphill by primary active transport)

simultaneous transport of 2 solutes. exergonic inward movement of protons provides energy to move the transported solute against its concentration gradient or electrochemical potential

128
Q

what is the difference between indirect and direct active transport

A

source of the energy

129
Q

what do ATPases do

A

harness the energy of ATP hydrolysis to perform active transport

130
Q

what are the similarities and differences between the 4 classes at ATPases

A

differ in structure, mechanism, localization, and physiological roles

all have one or more ATP binding sites on the cystolic membrane leaflet

131
Q

what are P-type ATPases

A

members of a large family of ATPases that are reversibly phosphorylated by ATP

132
Q

where are most types of P-type ATPases found

A

on the plasma membrane

133
Q

what do V type ATPases do

A

pump protons (H+) into organelles such as vacuoles, vesicles. lysosomes, endosomes, and the Golgi complex

134
Q

where are V type ATPases only found

A

eukaryotes

135
Q

what is the structure of V type ATPases

A

have 2 multi-subunit components: an integral component embedded in the membrane and a peripheral component that juts out from membrane surface

136
Q

what do F-type ATPases transport

A

protons in bacteria, mitochondria, and chloroplasts

137
Q

What does primary active transport maintain

A

intracellular sodium and potassium concentrations, which maintain osmotic balance and stabilize cell volume

138
Q

what are ABC-type ATPases

A

ATP binding casette transporterts

involved in uptake of nutrients

139
Q

what do all ABC-type ATPases have

A

2 nucleotide (ATP) binding domains

2 transmembrane domains

140
Q

what is secondary active transport:

A

indirect active transport

is not powered by ATP hydrolysis, but instead by potential energy stored in ionic gradients

141
Q

are there indirect active uriporters

A

no

142
Q

why does indirect transport rely on ATP

A

because the Na+ and H+ concentration gradient is generated by an ATPase pump

143
Q

what mediates transport of most molecules and ions across biomolecules

A

membrane proteins

144
Q

what can energy be loosely defined as

A

the capacity to cause a specific physical or chemical changes

145
Q

what is a chemotroph

A

no net fixation of carbon into organic compounds

(energy from food)

146
Q

what are the laws of thermodynamics

A

1st: total energy in universe remains the same

2nd: universe goes towards greater disorder (entropy increases)

147
Q

in a spontaneous rxn does delta S (entropy) - or +

A

positive

148
Q

does entropy increase or decrease when monomers are ordered into complex molecules

A

decrease

149
Q

what does enthalpy (H) tell us

A

heat content (energy) of a system

150
Q

hat are changed I’m enthalpy and entropy related by

A

Gibbs free energy (G)

151
Q

what does it mean if delta G (Gibbs free energy) is negative

A

process is exergonic

rxn releases energy

thermodynamically favourable

152
Q

what does it mean if delta G (Gibbs free energy) is positive

A

process is endergonic

input of energy is needed to drive the rxn forward

thermodynamically unflavoured

153
Q

what does it mean if delta G (Gibbs free energy) is 0

A

at equilibrium

no net flow in forward or reverse direction

neither direction is favoured

enthalpy and entropy changes are exactly balanced

154
Q

what has a significant effect on delta G of an rxn

A

concentration of products and reactions

155
Q

what is the equilibrium constant (Keq)

A

ratio of product concentration to reactant concentration at equilibrium

156
Q

is homeostasis equilibrium

A

no

living cells are characterized by continuous rxns and maintain themselves in states far from equilibrium

157
Q

what is homeostasis

A

the maintenance of dynamic steady state by regulatory mechanisms that compensate for external changes

158
Q

what charge does delta G have if its spontaneous

A

negative

159
Q

what is the metastable state

A

a result of the activation barrier

for most biologically important rxns (at normal temps) the activation energy is high enough that the number of molecules possessing sufficient energy to react is extremely small

160
Q

what must be overcome before a chemical rxn can occur

A

activation energy (Ea)

161
Q

what is the transition state

A

precise point at which weak chemical rxns between substrate and enzyme are at the stage where the rxn has an equal chance of going to product or back to substrate

162
Q

how do enzymes reduce the activation energy

A
  • maintaining precise substrate orientation (substrates can be brought closer together in the current orientation to allow the rxn to occur )
  • changing the substrate reactivity ( R-groups of the amino acids in the enzyme can influence the distribution of electrons within the substrate )
  • exerting physical stress. (conformational changes can exert a physical force on certain bonds destabilizing the substrate)

all of these help strategies allow substrates to reach the transition state more efficiently

163
Q

what is the active site

A

region of the enzyme that binds substrate (and cofactor)

complimentary groove that accommodates the substrate with high affinity

every enzyme contains a characteristic cluster of amino acid)

164
Q

what amino acids comprise active site

A

cysteine, serine, aspartat, glutamate, histidine and lysine

165
Q

Since active site takes up small portion of enzyme, what are the other parts of the enzyme

A
  • support structures
  • regulatory sites
  • sites of interaction with other properties
  • substrate channel
166
Q

how are enzymes characterized

A

by their sensitivity to temperature and pH

167
Q

how does enzyme activity change with temperature

A

increases since more kinetic energy

168
Q

are enzymes activated at different pHs

A

yes

169
Q

how are enzymes sensitive to ionic strength of environment

A

affects H bonding and ionic interactions needed to maintain tertiary conformations

170
Q

what do enzyme kinetics describe

A

the quantitative aspects of enzymes catalysis and the rate of substrate conversion into products

171
Q

what are the rxn rates of enzymes influenced by

A

concentrations of substrates, products, and inhibitors

172
Q

what is allosteric regulation

A

regulation of enzyme by binding an effector molecule at a site other than the active site

173
Q

where is allosteric regulation common

A

multi-subunit proteins and enzymes

174
Q

when enzymes are inactive what kind of modification activate them and vice versa

A

covalent modification

175
Q

how does phosphorylation work

A

changes a proteins charge and generally leads to conformational change, which can alter ligand binding

results in increase/decrease od activity

176
Q

what 3 elements are always needed for imaging (microscopy)

A
  • source of illumination

-specimen to examine

-system of lenses to focus illumination

177
Q

how does light microscopy work

A

use visible light and glass lenses to form an image

178
Q

what is a condenser lens

A

placed in front of the light source to focus the light at desired point on specimen

179
Q

what is the objective lens

A

forms primary image

closest to the object of interest

180
Q

what is the occult lens

A

magnifies the primary image produced by objective lens

181
Q

what is resolution

A

minimum distance that 2 points can be apart can be part and remain apart

182
Q

what is empty magnification

A

magnification without resolution

at a certain point the resolution is fixed no matter how much magnification

183
Q

what is the refractive index

A

measure of the change in velocity of light as it passes from one medium to another

184
Q

what does resolution consider

A

wavelength of illumination

refraction index

angular aperture

185
Q

what does magnification consider

A

refraction of index of the lens and medium the sample is immersed in

the focal length of the lens

186
Q

what are the different types of light microscopy

A

bright field (stained/unstained)

phase contrast

fluorescence

differential inference

confocal

187
Q

what is bright field microscopy

A

visualizing white light passed through a specimen

188
Q

what is phase contrast

A

takes advantages of differences in refractive index and thickness to image living cells without need to section and stain

189
Q

what is phase contrast most useful for

A

examination of dynamic events

  • since doesn’t use fix cells
190
Q

what is differential interference contrast

A

the technique has a shadow-casting effect that makes cells appear dark on one side and light on the other

  • results in an image with a 3D effect
191
Q

what do fluorescence and confocal microscopy detect

A

fluorescent proteins or dyes to show location of substances in the cell

192
Q

what is immunofluoresence microscopy

A

uses antibodies to locate specific molecules

193
Q

what are the advantages of immunofluoresence microscopy

A

high specificity

strong signal

identifies endogenous proteins in their native environment

194
Q

what are the disadvantages immunofluoresence microscopy

A

experiments are done on dead cells (samples require fixation)

there might not be an available antibody

195
Q

what is green fluorescent protein (GFP) used for

A

to visualize patterns of gene expression proteins in living cells and organisms

  • proteins can be tagged with GFP
196
Q

what are the advantages of GFP

A

cellular events can be observed in living cells

197
Q

what are the disadvantages of GFP

A

GFP protein that might negatively affect your target protein

introducing the GFP tagged proteins into the cells

198
Q

what does confocal fluorescence microscopy do

A

has ability to produce in-focus images of thick specimens, a process known as optical sectioning

images are acquired point by point, allowing a 3D reconstruction

199
Q

what are the advantages of viewing a fixed cell

A

organisms/organs can be viewed by sectioning thick tissue

easier to manage samples (can look at them anytime)

don’t need to introduce a recombinant protein (can disrupt cellular function)

200
Q

what are the advantages of viewing a live cell

A

can observe the movement of biomolecules within a cell

provides critical context to your observtaios

201
Q

what can live focal microscopy be used to visualize

A

the location of molecules but also to study dynamic movements and properties of biological molecules

202
Q

what do electron microscopy use

A

a beam of electrons rather than light and glass lenses

203
Q

what are the 2 types of electron microscopy

A

scanning electron microscopy (SEM): the surface tension of a specimen is scanned by detecting electrons deflected from outer surface

transmission electron microscopy (TEM): electrons are transmitted through the specimen

204
Q

what is cryo-electron tomography

A

take multiple 2D images at different angles and using computers, create a 3D image

used for high resolution structure determination of biomolecules in solution

205
Q

what are the 2 membranes the the nuclear envelope consists of

A
  • inner membrane defines the nucleus
  • the outer membrane is continuous with the ER
206
Q

what are the nuclear pores for

A

fuse the 2 membranes together and serve as a conduit for transport between the cystoplasm and nucleoplasm

207
Q

what does the nucleus contain

A

molecules of DNA organized into chromosomes

208
Q

what do nuclei serve as

A

info centres for the cell

DNA replication, transcription, and RNA processing occurring here

209
Q

where is rRNA transcribed

A

nucleus

210
Q

where are ribosome assembled

A

nucleus

211
Q

what is the structure of ER

A

consists of tubular membranes and flattened sacs called cisternae

internal space of the ER is the lumen

212
Q

what is the rough ER a critical starting point for

A

protein biosynthetic pathways

213
Q

where are most membrane lipids synthesized

A

rough ER

214
Q

what side of rough ER are the ribosomes on

A

cytoplasmic side

215
Q

what do ribosomes synthesize

A

polypeptides

216
Q

does the smooth ER have a role in protein synthesis

A

no

217
Q

what does the smooth ER synthesize

A

lipids and steroid hormones

218
Q

what is the sarcoplasmic reticulum

A

type of smooth ER

critical for the storage and release of calcium ions during muscle contraction

219
Q

what is closely related to the ER in proximity and function

A

Golgi apparatus

220
Q

what is the function of the Golgi apparatus

A

plays important role in processing and packaging secretory proteins and in complex polysaccharide synthesis

221
Q

what is TGN

A

vesicle sorting station

segregating proteins into vesicles headed to plasma membrane or other intracellular destinations

222
Q

what is CGN

A

transition vesicle sorting station

sorting proteins to be sent back to the ER or on to the Golgi

223
Q

what do lysosomes do

A

digestive organelle

224
Q

what is the structure of a lysosome

A

have a single membrane and store about 50 hydrolyses (digestive enzyme)

225
Q

what are the 3 degradation pathways utilizing the lysosome

A

endocytosis

phagocytosis

autophagy (mechanism for degrading intracellular organelles)

226
Q

what make up the endomembrane system

A

ER, golgi, vesicles, lysosomes

227
Q

what is the endomembrane system responsible for

A

trafficking substances through the cell

228
Q

are peroxisomes part of the endomembrane system

A

no

229
Q

what do peroxisomes do

A

detoxify harmful compounds and catabolize unusual substances

in animals, play a vital role in oxidative breakdown of fatty acids, especially longer chain fatty acids

230
Q

what is the structure of mitochondria

A

2 membranes creating 3 regions

outer membrane: relatively permeable, contains porins which allow free movement of small molecules and ions

inner membrane: high impermeable, acts as a permeability barrier to most solutes

regions:

matrix: within the inner membrane, contains most of the enzymes associated with mitochondrial function as well as DNA and ribosomes

intermembrane space: area between the inner and outer membranes

intracristal space: localized regions where protons can accumulate during the electron transport process

231
Q

where os the principle site of ATP production in non-photosynthetic cells

A

mitochondria

232
Q

what kind of cells have more mitochondrias

A

ones with high energy needs

233
Q

what is a tonoplast

A

the single membrane of a vacuole

contains numbers of active transporters

234
Q

what do vacuoles store

A

ions, amino acids, proteins, and polysaccharides

235
Q

are ribosomes organelles and why

A

no since they aren’t enclosed by a membrane

236
Q

what is a cytoskeleton

A

3D array of interconnected filaments, microtubules, and intermediate filaments

237
Q

what is the extracellular matrix (ECM) composed of

A

mainly of proteins and glycoproteins

238
Q

what are the functions of ECM (extracellular matrix )

A

support for cells to form tissues

substrate for attachment, motility

growth promoting signals

righty in plants

MBB 231 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions