M2P 1 Flashcards by Christian Kassicieh

Individual units of membrane are

cylindrical

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When was fluid mosiac model proposed

1972

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Integral proteins

span, sym or asym, association, removal, movement in memb

Span the bilayer, have assymetry like membrane, tightly associated w membrane, and removed by detergents that disrupt membrane. Can move laterally in membrane

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Peripheral Proteins

association, removal, polar or non

weakly associated, easily removed, associate w polar head groups of memb, removed by disrupting ionic interactions with high salt or change in pH

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Some peripheral proteins are

non-covalently attached, or linked to membrane lipids

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Glycerophospholipids

made of glycerol backbone + 2 FA chains

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Sphingophospholipids

made of sphingosine backbone + long chain FA

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Niemann-Pick disease is caused by

deficiency in sphingomyelinase ( that breaks down sphingomyelin)

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Niemann-Pick disease presents as:

mental retardation, seizures, ataxia, cherry red spot in eye

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Cholesterol (3 things)

embedded in lipid layer, maintains membrane fluidity, unsat FA chains are “cis”

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Membrane Lipids that face EC envi

Phosphotidylcholine, Sphingomyelin, Glycolipids

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Membrane Lipids that face IC envi`

Phosphotidyl-

-inositol,-serine,-ethanolamine

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Amphitropic proteins

sometimes associated w memb and sometimes not

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Type I

single helix, amino terminal (NH3+) OUT of cell

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Type II

single helix, amino terminal ( NH3+) INSIDE of cell

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Type III

multiple helices, but single polypeptide (connected together)

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Type IV

transmembrane domains of different polypeptides assembled in a channel through memb

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Type V

held to bilayer w covalently linked lipids

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Type VI

Both transmemb helices and lipid anchors

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Lipid Anchors

Some are lipoproteins w covalently linked lipid molecule that can become part of memb.

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Lipid Anchoring can be

reversed

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Lipid anchoring of proteins allows

targeting of proteins

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Opsin

detects light from outside

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Insulin receptor

detects hormones

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Acetylcholine receptor

detects NTs

Taste and smell receptors

detects Pheromones

Enzymes in membrane do:

Lipid biosynth( acyltransferase), ATP synth (F0F1 ATPase/ATP synthase)

Physical Properies of Memb:

Rapid rotational diffusion, slow flip-flop, rapid lateral diffusion, rapid flec of hydrocarbon chains

Memb is permeable to and not permeable to

Permeable to small polar solutes and nonpolar compounds, not to large polar solutes and ions

Transition Temp (Tm)

temp at which membs switch from fluid to semi-crystalline state

Temp >>>Tm

too fluid

Temp> Tm

optimal fluidity

Temp < Tm

rigid, semi-crystalline

Sat Lipids vs Unsat Lipids

Sat-Less fluid | Unsat-more fluid

Cholesterol in fluid membrane does what to fluidity

Decrease

Cholesterol in rigid membrane does what to fluidity

Increase

Gel phase vs Fluid phase

Can only move around in fluid ( fluid=proper function)

What causes trans from gel to fluid?

Heating until phase transition

Under normal conditions, are membranes more gel or fluid-like?

Fluid is for proper function

Lateral Diffusion of individual lipid in memb happens:

uncatalyzed and rapidly (1 micrometer/sec)

Transverse diffusion: in memb happens:

uncatalyzed and very slowly

membrane fluidity is determined by

FA composition

Unsaturated FAs and shorter chains make the memb more

Fluid

To maintain integrity at high temps, cells need

more Saturated FAs (Warm Socks)

To maintain integrity at low temps, cells need

more Short, Unsaturated FAs (Cold Stuff Up there)

It's so cold, what do I do for membs

Replace sat w unsat, use shorter FA tails

Flippase

P-type ATPase moves PE and PS from Outer to Cytosolic (Flip it in)

Floppase

ABC transporter moves phospholipids from Cyt to Outer (Flop it out)

Scramblase

Moves lipids in either direction, toward equilibrium

Membrane Fusion occurs

without losing continuity, spontaneous or protein mediated

Membrane Fusion examples

Entry of Influenza Virus into host, or release of NTs at synapse

Spur Cell Anemia is caused by

high cholesterol in erythrocyte (RBC) membrane, which lowers fluidity , then break/lyse as pass through spleen capillaries

Spur Cell anemia is associated with

beta lipoproteinemia and advanced alcoholic cirrhosis

Spur Cell Anemia makes erythrocytes

have Acanthocytes, Thorny and Rough projections

Gaucher disease , rare and genetic(deficiency and build up of)

Def in Glucocerebrosidase, build up of Glucocerebroside in bones, liver and spleen

Nieman-Pick (deficiency and build up)

Def of Sphingomyelinase, Builds Sphingomyelin | "Nah man pick up your sphingomyelin"

Tay-Sachs (deficiency and build up)

Def of Hexominidase A, Builds GM2 Ganglioside Def in tiny 6s (hexomini) and builds a gang(lioside)

Nucleotides and Nucleic Acids are composed of:

5-C Sugar (pentose), Nitrogenous base, 1 or more Phosphate groups (Nucleoside, NMP, NDP, NTP)

Nucleic Acids: Two classes of base are

Purine (Pure As Gold) and Pyrimidine (CUT the pie)

Nucleotides are involved in:

DNA and RNA biosynthesis

Purines

Adenine and Guanine

Pyrimidine

Cytosine, Uracil, Thymine

Adenine, Guanine, Cytosine, Uracil, Thymine w Ribose are called:

Adenosine, Guanosine, Cytidine, Uridine, Thymidine (With monophosphate on end if ribose phosphate)

DNA:Thymine:: RNA:?

Uracil

DNA vs RNA strands

DNA-Double strand helix with base pair | RNA-single strand doesn't form helix

DNA and RNA are linear sequences of nucleotides linked by :

phosphodiester bonds between 3' sugar of nucleotide and 5' sugar of next nucleotide

Histones interact with DNA by

ionic interactions, neg DNA spools around positive histone octamer

Histone octamer is formed with:

2 copies of H2A, H2B, H3 and H4

10nm vs 30nm chromatin

absence of Histone 1