Synthesis: At interface between cytosolic face of Lipids are amphipathic -> self assemble into closed Can be overcome by transport proteins
ER membrane and the cytosol. Membrane bilayer structures in aqueous environment (channels)
bound enzymes link the produced water soluble
Can be measured using FRAP:
(acetate-CoA; 2C) to create larger hydrophobic Railroad track: polar headgroups
specific membrane lipids or prot Barrier: selective permeability that restricts
membrane PL facing outside (aqueous) and
are fluorescently labelled and a movement of hydrophilic molecules
Fatty acids laser will bleach a small area. The hydrocarbon tail facing inwards
Movement: to membrane extent and rate at which the toward each other -> forms
Different types of proteins present on the
systems that cannot Incorporation: into florescence is recovered is hydrophobic core
two sides -> distinctive functions
produce their own PL (PM) both leaflets: flippases measured
via FABs. They have a can flip membrane PL
hydrophobic pocket lined from cytosolic to
Lipid bilayer
2D fluids: lipids (and prot) can rotate along their 3 main classes of lipids: phosphoglycerides,
with β sheets -> account for exoplasmic face of the axes and move laterally within each leaflet (driven sphingolipids, and sterols
movement of FA in within ER membrane by thermal energy)
the cell
Synthesis: from multiple precursors: Degree of fluidity depends on the T,
length and saturation of the FA chains Differ in chemical structure, Are all amphipathic
Phospholipids sphingosine from ER and polar head
and the presence of specific lipids abundance and function
sphingolipids group (phosphorylcholine) from
Golgi
cholesterol
Sphingolipids Ionic: disrupt ionic and hydrogen bonds Non-ionic: do not denature
Biomembranes that hold the 2º and 3º structure (SDS) prot -> extract while
Synthesis: 2 Acetyl-CoA -> HMG-CoA -> mevalonate -> IPP -> maintaining native
cholesterol. Regulated by HMG-CoA reductase -> catalyses conformation; below CMC:
the rate-controlling step. The enzyme is subject to negative Can be removed with detergents: amphipathic
prevent hydrophobic regions
feedback by cholesterol. HMG-CoA reductase has eight molecules that disrupt membranes by intercalating
to aggregate (triton X-100)
transmembrane segments and five of these have a sterol- Lipid rafts: clusters of into PL bilayers → solubilize lipids and many
sensing domain -> triggers proteasomal degradation membrane proteins
cholesterol and sphingolipids,
have potential kinase activity
Integral: pass through the
Cholesterol
Atherosclerosis: clogging Membrane proteins
membrane (cyt, exopl and
of the arteries by
Peripheral: associate with lipid membrane-spanning domain)
deposition of cholesterol,
Movement: 3 possibilities bilayer through interactions with
lipids, and ECM material. Lipid anchor: have one or
1. Vesicles transfer lipids either integral proteins or with PL
Medication: statins -> more covalently attached Aquaporins: transport Porins: unlike other
between membranes heads of the membrane
block HMG-CoA -> lipid molecule which water, glycerol and integral proteins,
2. Transfer by direct contact other hydrophilic Contain membrane
cholesterol synthesis is embeds in one leaflet
between membranes, molecules; tetramer spanning β sheets
reduced, low-density Anchoring to exo face:
mediated by membrane- of identical subunits, that form barrel like
lipoprotein drops in the acetylation or prenylation
embedded proteins each with 6 channels
blood, and formation of
3. Transfer mediated by small, membrane-spanning α
atherosclerotic plaques is Anchoring to cyt face: GPI
soluble lipid-transfer
reduced. A: N-term glycine or (glycophosphatidylinositol) -> helices
molecules P: C-term cys
cysteine residue of binds proteoglycans
residue is bound
prot is attached to
w prenyl group
FA
, PM is organized in 2 discrete Parietal cells
Slower than channels because the
regions: apical facing the outside 1. H+/K+ ATPase (apic) -> K in, H from water) out The major contributor to the free-energy-
substrate causes conformational
(gut) and the basolateral side 2. CO2 + OH -> HCO3- -> antiporter with Cl (bas) = Cl in driving transport through a uniporter is the
changes in the uniporter -> one
facing the blood -> separated by 3. Cl out via channel -> K follows to make neutral entropy (ΔS) increase as a molecule moves
substrate at a time; in channels
tight junctions Bone remodelling: allows bone healing from a high concentration to a low
multiple molecules can pass through
concentration.
Transcellular and Ca2+ to be used elsewhere. Via simultaneously
Epithelial cells osteoclasts: form enclosed EXT space btw
1. Na+/K+ ATPase (baso) -> Na+ and K+ [ ]-gradients themselves and bone and secrete HCl -> Can be gated Uniporter GLUT1: exhibits Michaelis-Menten kinetics and
2. K out through non-gated channel -> inside (-) MP dissolving bone into Ca2+ and P (HCl (open upon
+
approaches saturation as the [glucose] is
3. Both [Na] and MP -> uptake glucose by symp (apic) formed same as parietal cells only V class signal) or non- increased. For any given substrate, GLUT1 displays
Facilitated
4. Glucose out via GLUT2 (baso) (water follows) pump <-> p class); Osteopetrosis: Cl- is gated (always a characteristic Km: concentration at which GLUT1
not able to be secreted in the space -> open) is transporting the substrate at 50% of Vmax.
Aerobic metabolism yields CO2 → combines Channel
dense bones
with water to form carbonic acid (H2CO2).
These weak acids dissociate ⇒ H+ -> pH↓ => 2 Both sym- and antiporters move organic molecules Aquaporins: molecule Changing Vmax can Without changing Vmax, liver
antiporters: Na+HCO3-/Cl- (import 1 Na+HCO3- against gradient by coupling E unfavourable move forms H-bonds with be done with insulin. and muscle cells increase the
;export 1 Cl- -> HCO - dissociated by CA -> OH to a E favourable move of a small inorganic ion.
3 N-H groups of aa When insulin is low, glc uptake by converting
binds with H+) and Na+/H+ (im Na+;export H+) RBC: transport CO2 in the form of HCO3- (OH lining the channel (e.g GLUT4 is stored in glucose into glycogen,
comes from water; Hb takes up H). AE1 H+ cannot pass but vesicles, insulin stim lowering the [glucose] and
Na+/gluc symporter:
transports HCO3- out of the cell in exchange of Cl- glycerol can ~ indep of fusion with membr -> maximizing the gradient.
Inward flow of 2 Na Cotransport (opposite happens in lungs; use CA to dissociate size) increase GLUT Tumor cells express more
can generate an []in >>
HCO3-) GLUT1.
[]ext;
ABC: first identified as multidrug-
Na+/Ca2+ antiporter: regulates strength of Membrane transport resistance protiens. Common
Important in ATP synthesis in
Na+/Aa symporter: 1 Na is heart contraction. Remain low Ca2+ in the chloroplasts and mitochondria ->
bound to the carboxyl group substrates are: toxins, drugs, PL,
cytosol. Can be problematic in certain Cystic fibrosis: caused by commonly called ATP synthases
of leucine = necessary. As the peptides, and proteins
diseases, digoxin will increase the Ca2+ mutation in gene for CFTR
Na lose their water in binding but limit the frequency by inhibiting the (member of ABC -> is chloride F-class: are reverse proton pumps: E released
to the transporter, they bind Na+/K+ pump so that the antiporter cant channel, reuptake of cl-). Active by energetically favoured movement of protons
to 6 O. This prevents other take advantage of the gradient anymore. from exo to cyto face of membrane down H+
P-class: generate and maintain PM electric
ions, such as K+ who keep electrochemical gradient is used to power E
potential in plant, fungal, and bacterial cells
their water coat when PM of animal cells contain many open unfavourable synthesis of ATP
+ +, -
binding, from binding in place K channels but few open Na Cl , or
of Na+
2+ +
Ca channels -> K out -> excess (-) on H+/K+ ATPase: Muscle relaxation: depends V-class: Generate low pH of acidic
cyt face ⇒ excess (+) charge on exo = acidification of on Ca2+ ATPases that pump compartments (e.g. lysosome) by
Pumps generate differences inside-negative membrane potential Pumping relatively
Ca2+ from the cytosol into pumping H+ from cyt to exopl face
in [ion], non-gated ion stomach lumen, few H+ is required
located in the SR: rise in cytosolic Ca - against gradient <-> P class
channels utilize the gradients to acidify intra-
Passive diffusion parietal cell that > binding to calmodulin ->
cellular vesicles
to generate membrane activation ATPase -> low
potentials (depolarization = P-segment in K+ channel forms secrete HCl
free Ca = relaxation Low pH of lysosome can be measured by
membrane potential less (-); selectivity filter (studied from
Can never acidify the lumen on their own. The more H+ in, the labeling particles with pH sensitive
hyper-polarization = more (-) bacteria -> highly conserved)
higher the (+) charge on the other side of the membrane, (-) fluorescent dye and modifying the DNA so it
With patch clamping, the in- or outward movement of ions across a patch charge is left behind. They will attract each other -> electric encodes a naturally fluorescent protein ->
of membrane is quantified from the amount of electric current needed to potential will work against pump, which makes it difficult to protein is targeted to the lysosomal lumen
maintain the membrane potential at a particular “clamped” value bring in more H+ and the process will stop before any lowering by a signal sequence. Now the emitted
of pH is done fluorescence can be measured (FRAP)
