lipid biochemistry: active lipids Flashcards
1
Q
what is the basic role of phosphoinositides
A
cell signaling and differentiating
2
Q
what is the head group of phosphoinositides
A
inositol
3
Q
at which positions can inositol be phosphorylated
A
3, 4, 5
4
Q
how many phosphates total can there be on a molecule of phosphatidylinositol
A
4 (PI already has a phosphate, and then 3 more can be added to the inositol head group)
5
Q
give the abbreviations for all the phosphorylated forms of phosphatidylinositol
A
PI, PIP, PIP2, PIP3
6
Q
what is the full name of PIP2
A
phosphatidylinositol 4,5-bisphosphate
7
Q
where is PIP2 found + in what orientation
A
clustered on the inner leaflet of plasma membranes
8
Q
what cleaves PIP2
A
phospholipase
9
Q
what activates the phospholipase that cleaves PIP2
A
extracellular signals
10
Q
give the full names + abbreviated names of the products of PIP2 cleavage
A
inositol 1,4,5-triphosphate (IP3)
diacylglycerol (DAG)
11
Q
once IP3 and DAG are made via PIP2 cleavage, where do they go
A
IP3: travels into the cytosol
DAG: stays embedded in the membrane
12
Q
why does IP3 travel to the cytosol but DAG stays embedded in the membrane once PIP2 is cleaved?
A
IP3 is water soluble while DAG is not water soluble
13
Q
which type of pathway is PIP2 cleavage involved in?
A
GPCRs and trimeric G proteins
14
Q
describe how PIP2 cleavage is involved in GPCR/trimeric G protein pathways
A
IP3 causes Ca2+ to exit the ER
DAG and Ca2+ activates protein kinase C
15
Q
what is the full name of PIP3
A
phosphatidylinositol-3,4,5-triphosphate
16
Q
how is PIP3 formed
A
phosphorylation of PIP2
17
Q
what phosphorylated PIP2 to create PIP3
A
phosphoinositide 3-kinase (PI3K)
18
Q
which carbon of PIP2 is phosphorylated to get PIP3
A
C3
19
Q
what is the charge of PIP3? which part of the molecule carries the charge?
A
negatively charged, inositol head carries the charge
20
Q
what is the outcome of the PIP3 signaling pathway
A
growth, proliferation, survival
21
Q
why is PIP3 a target for cancer treatment
A
PIP3 signaling pathways are related to growth, meaning it correlates with tumor progression
22
Q
what is the PIP3 signalling pathway initiated by
A
receptor tyrosine kinases (RTKs)
23
Q
describe how PIP3 is part of the cellular response to insulin
A
it activates glycogen synthesis (lowers blood glucose), brings GLUT4 to the PM so glucose can leave the bloodstream, and the insulin receptor is an RTK
24
Q
what can PIP3 do with adaptor or scaffold proteins?
A
it uses those proteins to help cluster together proteins that are involved in the same signaling pathway
25
give an example of an adaptor protein that PIP3 uses
AKAP5
26
using AKAP5 as an example, describe how PIP3 interacts with adaptor proteins
AKAP5 has binding sites for PIP3, which localizes the adaptor and its associated proteins into lipid rafts
27
what is a conjugated lipid
one with alternating double and single bonds
28
describe how conjugated dienes produce specific colors
the delocalized electrons (due to conjugation) can be excited by certain wavelengths of visible light, and so they will reflect a different wavelength = color
29
how do birds acquire different colors
by ingesting conjugated dienes via their diet
30
how do birds acquire sex-specific feather colors?
either by different diets between males and females, or by different metabolic processing of the conjugated dienes
31
what is the general function of eicosanoids
they are signalling hormones
32
what type of signalling do eicosanoids do
paracrine signalling
33
what is paracrine signalling
signalling over short distances
34
how many carbons are eicosanoids composed of
20
35
which fatty acid are all the eicosanoids derived from? give the shorthand name and the common name
20:4Δ(5,8,11,14)
arachidonate
36
list the 3 eicosanoids we cover in this course
prostaglandin, thromboxane, leukotriene
37
what structural characteristic defines a prostaglandin
5C ring
38
where were prostaglandins originally discovered
prostate gland
39
T or F: prostaglandins can be released by most tissues
true
40
when are prostaglandins released
when there is a site of injury or inflammation
41
list the roles of prostaglandin at a site of injury/inflammation
promote either vasodilation or vasoconstriction, promote tissue inflammation and pain, promote fever
42
describe how prostaglandins regulate the female reproduction system
they're required for ovarian follicle to rupture and release eggs during ovulation. They stimulate smooth muscle contraction in uterus during menstruation and childbirth
43
when are synthetic prostaglandins used
can be used to induce labour
44
what structural characteristic defines thromboxanes
a 6C ring
45
what produces thromboxanes
platelets (thrombocytes)
46
where in the body are thromboxanes released
released near damaged blood vessels
47
describe the roles of thromboxanes at damaged blood vessles
they promote local platelet aggregation to help form blood clots, promote formation of new platelets, vasoconstriction, and increases in blood pressure
48
what structural characteristics define leukotrienes
they have 3 conjugated double bonds in a row. They do not have any rings like the other eicosanoids do
49
which of the eicosanoids have rings in their structure? which doesn't?
prostaglandins and thromboxanes have rings, leukotrienes do not
50
what produces leukotrienes
leukocytes
51
when do leukocytes release leukotrienes
during allergies or asthma attacks
52
describe the roles of leukotrienes during allergies or asthma attacks
they promote inflammation, increase mucus production, and they can cause contraction of smooth muscle in bronchioles
53
how do some anti-asthma medications work? what do they target?
they target leukotriene synthesis
54
other than allergies and asthma, what else do leukotrienes play a role in
arthritis and inflammatory bowel disease
55
what is the full name for NSAIDs
nonsteroidal anti-inflammatory drugs
56
what do NSAIDs do
inhibit the enzymes that help from prostaglandins and thromboxanes from their precursor molecule (arachindonate)
57
give 3 examples of nonsteroidal anti-inflammatory drugs
aspirin, ibuprofen, motrin
58
how many rings do sterols have
4
59
describe the structure of the 4 sterol rings
three 6C rings and one 5C ring
60
are sterols rigid or fluid
rigid
61
are sterols planar or not planar
planar
62
describe C-C rotation in sterols
there is little rotation around C-C bonds in sterols, as they're rigid and planar
63
what are bile acids formed from
polar derivatives of cholesterol
64
where are bile acids secreted from
liver
65
where are bile acids stored
gall bladder
66
where are bile acids moved to from the gall bladder
moved into the small intestine
67
role of bile acids in the small intestine?
helps emulsify fats to allow digestion of fats by lipases
68
what are steroid hormones formed from
oxidized derivatives of cholesterol
69
describe the basic structure of steroid hormones
they have the sterol nucleus but lack the alkyl chain
70
where are sex (steroid) hormones synthesized
testes and ovaries
71
where are adrenocortical (steroid) hormones synthesized
in the adrenal gland
72
where do steroid hormones go once they're synthesized
they travel to target tissues in the blood bound by hydrophilic carriers
73
where do steroid hormones go once they're synthesized
they travel to target tissues in the blood bound by hydrophilic carriers
74
what do steroid hormones do once they reach their target tissue
they can trigger changes in gene expression
75
why might lipid signalling molecules in plants be fragranced
to attract pollinators or to repel herbivores
76
list 3 functions of lipid signalling molecules in plants (other than fragrance), and give examples
bending a shoot towards light (auxin), repairing insect damage (jasmonate), or ripening fruit (ethylene)
77
which plant lipid is responsible for bending shoots towards light
auxin
78
which plant lipid is responsible for repairing insect damage
jasmonate
79
which plant lipid is responsible for ripening fruit
ethylene
80
what are plant lipids often made from
fatty acids or sterol derivatives
81
most fragrant plant signalling molecules are generated from ____ units
isoprene
82
what are isoprenes? what is their basic structure?
isoprenes are lipids. 5C molecules joined via condensation reactions to build 10-40C molecules
83
isoprene units contribute to many other active lipids too, such as _________________
fat soluble vitamins
84
which isoprene-unit molecule produces geranium smell
geraniol
85
which isoprene-unit molecule produces pine smell
b-pinene
86
which isoprene-unit molecule produces lime smell
limonene
87
which isoprene-unit molecule produces mint smell
menthol
88
which isoprene-unit molecule produces spearmint smell
carvone
89
are vitamins essential?
yes
90
can vitamins be synthesized by the body?
no
91
describe the origins of the word "vitamin"
originally every vitamin was believed to have amine in it
vital + amine = vitamin
92
what are the two categories of vitamins?
water soluble and fat soluble
93
list the fat soluble vitamins
A, D, E, K
94
how are the fat soluble vitamins synthesized?
by isoprene condensation
95
what is the name of vitamin A1
retinol
96
list the main structural characteristics of vitamin A1
lipid with trans double bonds and a hydroxyl group
97
from which foods do we acquire vitamin A1
fish oils or dairy, or it can be formed from B-carotene precursor that's prevalent in carrots/sweet potatoes
98
what characteristics does vit A have due to the conjugated double bonds
it can absorb light
99
what two things are formed from retinol when it's oxidized
retinal or retinoic acid
100
by which process are retinal and retinoic acid formed from retinol
oxidation
101
T or F: B-carotene is comprised of isoprene units
true
102
what functional group does retinal have
aldehyde
103
what is the initial structure of retinal after the oxidation of retinol
a cis double bond on carbon 11
104
T or F: 11-cis-retinal is the final form of retinal
false; it undergoes a change
105
what happens to 11-cis-retinal (because this isn't its final form)
it binds to a protein (opsin) in rod cells of the retina to form rhodopsin pigment. Rhodopsin is excited by visible light and changes 11-cis-retinal to all-trans-retinal
106
what is the result of 11-cis-retinal changing to all-trans-retinal
a signal cascade that results in vision
107
what protein does 11-cis-retinal bind to on the way to converting to its new form
opsin
108
where do 11-cis-retinal and opsin bind
in rod cells of the retina
109
11-cis-retinal + opsin = ?
rhodopsin pigment
110
how does rhodopsin convert 11-cis-retinal to all-trans-retinal
it's excited by visible light
111
what are rods and cones
photoreceptors
112
where are rods and cones located
in the inner layer of the eyeball (retina)
113
what is the retina
the inner layer of the eyeball where rod and cone cell photoreceptors are located
114
what is a photoreceptor
a modified neuron
115
visual information captured by ____ is relayed by ____ to the ____ towards the brain
photoreceptors, neurons, optic nerve
116
in order for vision to occur, what must rods release
neurotransmitters
117
what do rods release neurotransmitters to
neurons
118
rods --> release NTs to neurons --> ? --> ?
optic nerve, brain
119
what type of vision do we get from rods
light (greyscale)
120
what type of vision do we get from cones
colors
121
describe the structures of rod and cone photoreceptors
the outer segment has many membranous disks filled with visual pigments
122
what is the visual pigment of rods
rhodopsin
123
retinal lipid + opsin protein = ?
rhodopsin pigment
124
? + ? = rhodopsin pigment
retinal lipid + opsin protein
125
what type of protein is opsin
a GPCR
126
how do the conformational changes of retinal affect vision
conformational changes of cis retinal to trans retinal = conformational changes in the opsin protein (a GPCR)
127
T or F: the trans state of retinal is permanent
false; it is not permanent and will eventually convert back to its cis form
128
what gets activated once light (photons) activate the visual pigment
transducin
129
what is transducin (what type of protein)
a G protein
130
once activated, what does transducin do
it activates phosphodiesterase (PDE)
131
what does PDE stand for
phosphodiesterase
132
what does PDE do once it's activated by transducin
it converts cGMP --> GMP (causing cGMP levels to fall)
133
as PDE forms GMP, what is the effect of cGMP levels falling
cGMP-gated cation channels close = hyperpolarization
134
how do Na+ channels close during the visual cascade
closed via light-induced signal transduction
135
what happens to the rod's membrane potential when a Na+ channel closes
Na is no longer coming in = membrane potential gets more negative = hyperpolarization
136
describe the behavior of hyperpolarized neurons
they're less likely to release neurotransmitters, so they're turned "off" when hyperpolarized
137
T or F: a rod is "off" in the presence of light
TRUE
138
when will rod cells be depolarized
in the DARK
139
T or F: the absence of a neurotransmitter release from the rod is what triggers vision
TRUE!!!
140
which neurotransmitter do rods release
glutamate
141
describe how the visual signal is ceased
when light isomerizes cis retinal to trans retinal, it causes opsin to expose its C-terminal. Because of this, rhodopsin kinase will phosphorylate residues on the C-term of opsin. Arrestin then binds to phosphorylated opsin and stops the GPCR from activating its G protein
142
during the cease of the visual signal, which enzyme phosphorylated opsin
rhodopsin kinase
143
during the cease of the visual signal, which part of opsin gets phosphorylated
C-terminal
144
during the cease of the visual signal, which protein binds to phosphorylated opsin to prevent it from activating its G protein
Arrestin
145
how is retinoic acid formed
via the oxidation of retinal
146
what functional group does retinoic acid have
carboxylic acid
147
what type of molecule is retinoic acid
a hormone
148
which form of retinoic acid is a hormone
all-trans
149
role of retinoic acid? (3)
it regulates gene activity in the early embryo to determine anterior/posterior axis patterning, cell differentiation, and organogenesis
150
T or F: excess or deficiency in vitamin A during pregnancy has no negative effects
false; it's correlated with increased risks of birth defects in many mammals
151
vitamin A deficiency is the leading cause of ___ ___ in children
preventable blindness
152
what is golden rice and why is it beneficial
rice that's enriched with beta carotene. Useful because it decreases the risk of childhood blindness (B-carotene is a precursor of retinol, which is involved with the visual signal)
153
exposure to __ __ causes a compound in the skin to be converted to vitamin D3
UV light
154
what disease does vit D prevent
rickets
155
what is rickets
a disease where bones soften in children
156
where is/was rickets common
in cold climates where heavy clothing blocked UV light
157
which form of vit D is produced in yeast and added to our milk and butter
D2
158
why is vit D2 added to our milk and butter
to mimic vit D3
159
T or F: vit D3 is biologically active
false; it needs to be converted to an active form
160
what is D3 converted to to become active? where does this take place?
D3 is converted to calcitriol (a hormone) via reactions in the kidney and liver
161
what type of molecule is calcitriol
a hormone
162
what does calcitriol do
it increases absorption of calcium from foods and deposits it into bones
163
describe the basic structure of vit E and K
aromatic rings with a long side chain formed from isoprenoids
164
T or F: humans are rarely deficient in vit E and vit K
true
165
what does vit E do
helps prevent oxidative damage to membranes
166
what does vit K do
assists with blood clotting
167
what does the drug Warfarin do? what vitamin does it mimic, but what sets it apart from this vitamin
Warfarin is a blood thinner that mimics vitamin K, but it actually prevents excess blood clotting (unlike K)
