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biochemistry > test 2 > Flashcards

test 2 Flashcards

1
Q

define lipid

A

water insoluble biomolecules that are highly soluble in organic solvents

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2
Q

what are the hydrophobic properties of lipids due to

A

fatty acids

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3
Q

what are some examples of derivatives of fatty acids

A

hormones
signal molecules
intracellular messengers

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4
Q

what is the range of C atoms in fatty acids

A

14-24 (even numbers)

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5
Q

what are the most common numbers of carbon for fatty acids

A

16 and 18

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6
Q

what configuration of double bonds is most common in unsaturated fatty acids

A

cis

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7
Q

what determines the properties of fatty acids

A

length of the chain and degree of saturation

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8
Q

what occurs to the melting points of saturated fatty acids as the chain length increases

A

melting point increases

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9
Q

do unsaturated or saturated fatty acids of same length of lower melting point

A

unsaturated

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10
Q

what fatty acids fall into NEFA

A

laurate, myristate, palmitate, stearate, arachidate, behenate, lignocerate, palmitoleate, oleate

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11
Q

what fatty acids are w-6 EFA

A

linoleate

arachidonate

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12
Q

what fatty acids are w-3 EFA

A

linoleate

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13
Q

what are the major membrane components of lipids

A

phospholipids
glycolipids
cholesterol

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14
Q

what are the 4 components of phospholipids

A

fatty acid
backbone to which fatty acids are attached
phosphate
alcohol attached to phosphate

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15
Q

what is phosphatidylserine important for

A

memory and cognition

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16
Q

what is phosphatidylcholine important for

A

major constituent of cell membrane and pulmonary surfactant

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17
Q

what is phosphatidylethanolamine important for

A

composing 25% of all phospholipids

found particularly in nervous tissue (white matter of brain)

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18
Q

what is phosphatidylinositol important for

A

signalling and other functional activities in eukaryotic cell

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19
Q

what is diphosphatidylglycerol important for

A

important component of inner mitochondrial membrane

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20
Q

define sphingosine

A

amino alcohol that contains a long, unsaturated hydrocarbon chain

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21
Q

how is the amino group of the sphingosine backbone linked to a fatty acid

A

amide bond

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22
Q

what are glycolipids derived form

A

sphingosine

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23
Q

what is the difference between sphingomyelin and glycolipids

A

identify of the unit that is linked to the primary hydroxyl group of the sphingosine backbone

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24
Q

how is the sugar residue oriented in glycolipids

A

on the extracellular side of the membrane

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25
Q

what is cerebroside

A

simples glycolipid
contains a sugar residue (glucose or galactose)
important component in animal muscle and nerve cell membrane

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26
Q

what is cholesterol built from

A

4 fused saturated hydrocarbon rings

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27
Q

what is the metabolic precursor of steroid hormones

A

cholesterol

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28
Q

what are common features of biological membranes

A 
sheetlike structure
mainly consists of lipids and proteins
hydrophilic and hydrophobic unit
specific proteins are embedded in lipid bilayers and mediate distinct functions
form non-covalent assemblies
asymmetric
fluid structure (both lipid and protein diffuse rapidly in the plane of the membrane but do not rotate across the membrane)
electrically polarized (inside negative)
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29
Q

what are characteristics of micelle

A

limited structure
usually less than 20 nm
formed when a variety of molecules including soaps and detergents are added to water

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30
Q

why are phospholipids and related molecules important membrane consituents

A

they readily form extensive bilayers

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31
Q

what type of process is the formation of lipid bilayers

A

self-assembly

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32
Q

what are the major driving forces for lipid bilayer assembly

A 
hydrophobic interaction (major)
van der waals (attractive forces between hydrocarbon tails)
electrostatic and hydrogen-bonding: attractions between polar head groups and water molecules
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33
Q

what are the 3 significant consequences of the hydrophobic interactions of the lipid bilayer

A

lipid bilayers have inherent tendency to be extensive, close on themselves so that there are no edges with exposed hydrocarbon chains (form compartment), and are self-sealig

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34
Q

how are peripheral membrane proteins primary bound to membranes

A

electrostatic and hydrogen bond interactions with the head group of lipids

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35
Q

how are peripheral membrane proteins dissociated

A

adding salt or pH changes

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36
Q

where are peripheral membrane proteins bound to the surfaces of integral proteins

A

cytosolic or extracellular side of membrane

anchored to the lipid bilayer by a covalently attached hydrophobic chain (i.e.: fatty acid)

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37
Q

what is the most common structure motif in membrane proteins

A

membrane-spanning alpha helices

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38
Q

what are the kinds of modification in lipid-linked proteins

A

palmitoylation of cysteine residues by a thirster bond
fernesylation of cysteine residues at the C-terminus
Glycosylphosphatidylinositol-link to the carboxyl terminus

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39
Q

what are the functions of farnesylation of the C-terminus

A

anchoring the protein to the membrane and facilitating the protein-protein interaction

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40
Q

what does glycosyl phosphatidylinositol (GPI) do

A

anchors the proteins to the outer leaflet of the plasma membrane

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41
Q

what is the site of most TCA cycle and fatty acid oxidation

A

mitochondrial matrix

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42
Q

what Is membrane fluidity controlled by

A

fatty acid composition

cholesterol content

43
Q

what are major contributors to fatty acid composition

A 
length of fatty acid chain
saturation levels (Tm, rigidity)
position of double bands, (cis position produces bend), effects Tm, provides more fluidity
44
Q

what type of environment does membrane fluidity provide

A

environment where signal transduction and molecule transportation takes place

45
Q

how do lipid and many membrane proteins move

A

laterally (lateral diffusion)

46
Q

what does FRAP do

A

tests the dynamics of membrane molecules

47
Q

what does the rate of recovery of fluorescence depend on (FRAP)

A

lateral mobility of the fluorescent labeled components

48
Q

what are the main components of plasma membranes

A

carbs
glycoproteins
glycolipids

49
Q

where does glycosylation occur

A

extracellular surface of the plasma membrane

50
Q

what does glycocalyx participate in

A

cell adhesion, lymphocyte homing, and many others

51
Q

how do antibodies recognize blood cell types

A

extracellular carbohydrates

52
Q

define nuclear pores

A

located in the nuclear envelope; closed membranes that come together

53
Q

why must membranes be able to separate and join together

A

so that cells and compartments can take up, transport, and release molecules

54
Q

what does SNARE do

A

it is a protein that gathers the appropriate membranes to initiate fusion process

55
Q

what is an analogy to describe fission

A

it is like pinching a balloon (making 2 balloons from one)

56
Q

what is mitochondrial fission particularly used for

A

mitochondrial proliferation

57
Q

why is fission harder in mitochondria than many sign payer organisms

A

because the inner membrane will be very hard to divide (must get electron transport chain component as well) even though the outer will not be that difficult

58
Q

explain why mitochondria fusion is a salvage process

A

when a mitochondria is sick,healthy ones will try to fuse with the unhealthy to make them healthy. if they are beyond repair, mitophagic mitochondria will break down sick mitochondria and re-used usable components (recycle)

59
Q

what are requirements for inner membrane fusion in mitochondria

A

sufficiently large electrochemical gradient

elevated GTP levels must be available for hydrolysis

60
Q

what are the vast majority of mitochondrial proteins encoded by

A

the nuclear genome

61
Q

what does Tim do in mitochondria

A

it mediates transport across the inner mitochondrial membrane

62
Q

what is HSP 70 crucial for

A

driving polypeptide translocation

63
Q

what is considered the matrix targeting signal

A

N-terminal signal

64
Q

what must be true for a protein to be imported into the mitochondria

A

it must first be unfolded and it is refolded once the protein enters inside

65
Q

what do membrane transport proteins facilitate

A

the movement of specific molecules across the PM

66
Q

what is the plasma membrane very permeable to

A

lipophilic molecules

67
Q

what determines the ionic composition of the cell (membrane transporters)

A

activity and protein levels of specific transporters

68
Q

what governs the biochemical/metabolic characteristics of a cell

A

expression of specific transporters

69
Q

what type of bond does the transporter form in P type ATPases

A

covalent bond with the phosphate to form an enzyme-phosphate intermediate

70
Q

where does phosphorylation occur in P type ATPases

A

conserved asparate residue

71
Q

what is a potential inhibitor of the Na pump

A

plant steroids

72
Q

what does the PMCA do

A

transports calcium from cytosol to extracellular side

73
Q

what stimulates PMCA

A

calcium binding protein calmodulin (CaM)

74
Q

what does SERCA do

A

transports calcium from cytosol to ER

75
Q

what is the mechanism of action of ABC transporters

A
  1. protein free of substrate and ATP
  2. channels face intracellular side
    3, substrate binds
  3. conformational changes in ATP binding cassettes
  4. increase affinity for ATP
  5. ATP binds
  6. conformational change in ATP binding cassette
  7. reorientation of the membrane spanning domains
  8. expulsion of substrate to extracellular side
  9. ATP hydrolysis resets transporter to original state
76
Q

what is lactose permease

A

symporter
uses proton gradient generation by oxidation of fuel molecules to drive lactose and other sugars against concentration gradient

77
Q

what do ion channels mediate

A

facilitated passive transport

78
Q

what are the 3 types of ion channels and describe them

A

voltage-gated: respond to change in membrane potential
chemically gated; respond to ligands such as neurotransmitters
mechanically gated: respond to mechanical stimuli, found in sensory neurons

79
Q

what is the model of voltage gated (how is it set up)

A

sensors include segments S1-S4

pore is S5 and S6

80
Q

explain the ball and chain model

A

when the port is closed, the domain is free flowing. as it opens, the peptide gets pulled toward the base of the pore causing the pore to close (blocks the pore)
*this causes the inactivation of voltage-gated ion channels

81
Q

where is AcH located

A

post-synaptic side

82
Q

what is the structure of the Ach receptor

A

pentamer of 4 kinds of membrane spanning subunits (2 alpha, 1, beta, 1 game, 1 delta) arranged in the form of a ring that creates a pore through the membrane

83
Q

what is the most important manifestation of membrane transport

A

basis for communication in the nervous system

84
Q

what is a nerve impulse

A

electrical signal produced by the flow of current across the plasma membrane of a neuron

85
Q

what are the steps of an action potential

A
  1. AP arises form large transient changes in the permeability of the axonal membrane to ions
  2. conductance for Na+ changes first due to opening of sodium channels
  3. depolarization increases permeability to Na+ which begin to flow in via the Na+ channel due to high concentration outside
  4. depolarization then opens the K+ channels and K+ moves out
86
Q

what are the steps of synaptic transmission

A
  1. AP reaches presynaptic terminal
  2. depolarization opens up the VGCC
  3. calcium enters cell
  4. causes fusion of synaptic vesicles
  5. exocytosis: release of NT in synaptic cleft
  6. NT bind to its receptor on post-synaptic side
  7. opens up a ligand-gated channel
87
Q

how are gap junctions packed

A

hexagonal array

88
Q

what kind of molecules can pass through gap junctions

A

small hydrophilic molecules and ions can pass through these channels

89
Q

what is the structure of a gap junction

A

each channel made of 12 connexin
six connexin molecules arrange hexagonally to form a half channel called connexon
2 connexon join end to end in the intracellular space to form a functional channel

90
Q

what do gap junctions ensure in cardiac tissue

A

synchronous response to stimuli

91
Q

how are gap junctions sealed and why

A

sealed by high Ca++ and H+ to protect normal cells from injured or dying cells

92
Q

how are gap junctions regulated

A

by membrane potential and hormone-induced phosphorylation

93
Q

what do gap junctions connect

A

cytoplasm to cytoplasm

94
Q

what are characteristics of aquaporins

A

increase rate of water flow across membranes
found in RBC, kidney, cornea
have 6 transmembrane alpha helical domains

95
Q

what are the steps of solid phase peptide synthesis

A
  1. anchoring of the C terminus aa to a solid resin
  2. deprotection of the amino terminus
  3. coupling of the free amino terminus with the DCC-activated carboxyl group of the next aa (2 and 3 repeated for each added aa)
  4. completed peptide is released from the resin
96
Q

how are fatty acids stored as fuel molecules

A

triacylglycerols

97
Q

how can the dynamics of mitochondria effect neurodegenerative diseases

A

both inefficient mitochondrial fission and fusion could contribute to progression of neurodegenerative dieseas

98
Q

what occurs if something goes about the Tm

A

it transitions from the rigid state to the fluid state

99
Q

what state does the presence of saturation in fatty acids favor

A

rigid state because their straight hydrocarbon chains interact very favorably with one another

100
Q

what occurs with a cis double bond in fatty acids

A

a bend occurs, which interferes with highly ordered packing of fatty acid chains and Tm is lowered

101
Q

how do bacteria regulate fluidity of their membranes

A

by varying the number of double bonds and the length of their fatty acid chains

102
Q

what is the key regulator of membrane fluidity in animals

A

cholesterol

103
Q

what are the 2 main roles of the lipid bilayer

A

solvent for integral membranes and permeability barrier

104
Q

what are the main components of the outer and inner leaflets of the lipid bilayer:

A

outer: sphingomyelin and phosphatidylcholine
inner: phosphatidylethanolamine and phosphatidylserine
both: cholesterol

biochemistry (6 decks)

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