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Biochem > Lecture 8: Biological Membranes > Flashcards

Lecture 8: Biological Membranes Flashcards

1
Q

Features: General structure

A

sheetlike structures - 2 molecules thick - that form closed boundaries between different compartments

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2
Q

Features: Makeup of membranes

A
  • lipids and proteins
  • mass ratio ranges from 1:4 and 4:1
  • never any higher/lower than this ratio
  • vary for different membranes
  • some also contain carbohydrates that are linked to lipids and or proteins
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3
Q

Features: spontaneous activity

A
  • hydrophilic and hydrophobic moieties
  • spontaneously form closed bimolecular sheets in aqueous media
  • barriers to the flow of polar molecules
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4
Q

Features: proteins

A
  • embedded in the lipid bilayer
  • mediate distinctive functions
  • serve as pumps, channels, recepctors, transducers and enzymes
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5
Q

Features: Interactions of membranes

A

noncovalent interactions, act cooperatively

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6
Q

Features: Symmetry of membranes

A
  • asymmetric
  • two faces (leaflets, layers) of biological membranes have different lipid compositions
  • individual peripheral membrane membrane proteins are only associated with one side of th emmebrane while integral membrane proteins have different domains on different sides of the membranes
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7
Q

Features: Fluidity

A
  • fluid structures
  • lipids diffuse rapidly in the phase of th emmebrane, as do proteins unless anchored
  • do not ROTATE across the membrane, can be considered as an oriented 2D solution

saturated vs unsaturated fatty acids

more unsaturated keep mem more fluid (lower temps)

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8
Q

Features: Polarized

A
  • electrically polarized
  • inside is -60mv
  • membrane potential a key role in transport, energy conversion, excitability
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9
Q

What are lipids?

A
  • consists mostly of hydrocarbons
  • serve as fuel molecules and energy stores
  • signal molecules and messengers
  • one of the two main components of membranes
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10
Q

Three major types of lipids

A
  • phospholipids
  • sphingolipids
  • steroids
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11
Q

Glycerol structure

A

3 alcohol groups

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12
Q

Sphingosine structure

A

sphingosine makes up backbone and tail

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13
Q

Fatty acids

A
  • feature of phospholipids and glycolipids
  • various lengths and degree of unsaturation
  • fatty acids in biological systems usually ocntain even number of carbon atoms (14-24)
  • unsaturated have at least one DB in cis
  • polyunsaturated are separated by at least 1 methylene group
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14
Q

Fatty acid numbering

A
  • start at carboxyl terminus
  • methyl at distal (far) end is thne w-carbon and double bond is represented by ►with superscript

Ex: nutritionists number from the omega/terminal

Omega 3-6-9 has DBs beginning on each of those carbons

chemists number in opposite direction

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15
Q

Linolenate

A

chemist: 9-12-15 (from carboxyl terminus)
nutritionist: 3-6-9 (from end)

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16
Q

What affects the fluidity of fatty acids?

A
  • decreasing chain length
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17
Q

Glycerophospholipids structure

A

Head group:

  • choline
  • phosphate
  • glycerol

1 saturated tail

1 unsaturated tail

*ester bonds (from joining alcohol and carboxylic acid)

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18
Q

Breakdown of glycerophospholipids via phospholipases

A
  • produces a variety of signal molecules such as diacylglycerol and inositol phosphates (including inositol 1,4,5 trisP)

phospholipases A1 and A2

phospholipases C and D

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19
Q

phospholipasesd A1 and A2

A

cleave fatty acids from a glycerophospholipid, producing lysophospholipids

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20
Q

C and D phospholipases

A

hydrolyze on either side of the phosphate in the polar head group

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21
Q

Sphingolipids

A

1 fatty acid chain

ester bond vs amide bond

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22
Q

ABO Blood type

A
  • blood genes exist in more than 2 alleles
  • three alleles for blood
  • attach different carbohydrates to membrane components
  • Ia and Ib both code glycotransferases with different substrate specificity
  • I gene is nonfunctional
23
Q

Ia allele

A
  • adds a-N-acetylgalactosamine to D galactose end of an oligosaccharide side chain of sphingolipid (H antigen
  • makes A antigen
24
Q

Ib allele

A
  • encodes glycosyltransferase that joins a-D galactose to the a-D-galactose end of H antigen
  • creates b antigen
25
Q

Resultant blood types

A

A (only AA or AO)

B (only BB or BO)

O (ii) –> do not produce

AB (AB)

26
Q

Sphingolipids and diseases

A
  • defect of lysosomal enzymes involved in sphingolipid degradation results int he acucmulation of partial breakdown products (storage substances) causeing serious diseases
  • dont properly degrade lipids
  • BUT these diseases still result in 70-80% functionality. If the pathway was totally destroyed the person wouldnt be alive
27
Q

Whata re steroids?

A
  • family of organic compoudns whose multiple (usually 4) fused rings share carbons
  • in most cases an -OH is attached to at least 1 ring
  • part of membranes or function as hormones to carry messages

-

28
Q

deficiency of 17b-hydroxysteroid dehydrogenase 3

A
  • reduces production of testosterone and can result in dev of male pseudohermaphroditism
  • male doesnt go through puberty completely
29
Q

Amphipathic membranes

A
  • polar, hydrophobic head and nonpolar, hydrophilic tail
30
Q

Basic forms of membrane

A
  • micelle
  • bilayer
  • vesicle
31
Q

micelle

A
  • spherical structure with limited amphipathic molecules arranged with its hydrophobic regions in interior
32
Q

bilayer

A

2D sheet with 2 lipid monolayers

33
Q

vesicle

A

open bilayer is relatively unstable and can spontaneously self-associate into a hollow vesivle, closed bilayer or liposome, enclosing aqueous activity

34
Q

steps of lipids to membrane

A

unfavorable (planar phospholipid bilayer with edges exposed to water)

favorable ( sealed compartment formed by phospholipid bilayer)

* no energy needed (favorable)

35
Q

Disrtibution of lipids a membrane

A
  • asymmetric
  • different lipids and proteins can be concentrated differently on either side
36
Q

Fluid mosaic model

A

biological membranes

  • consist of lipid bilayer in which membrane proteins are embedded
  • considered an oriented 2D liquid- in which lipids and proteins diffuse more or less freely within the plane
  • contain some defined structures or domains (protein complexes, lipid rafts)
37
Q

Lipid rafts

A

groups of lipids linked to/associated with proteins

38
Q

Types of membrane proteins

A

peripheral

integral

39
Q

peripheral proteins

A

membrane proteins that lack exposed hydrophobic groups and do not penetrate the bilayer

40
Q

integral proteins

A
  • membrane proteins are amphipathic - hydrophobic an dhydrophilic regions or domains
  • some extend across the lipid bilayer since they have 1 or mroe transmembrane proteins
  • some partially embedded
41
Q

interactions of proteins in the membrane

A
  • independednt and interact noncovalently
  • some have fattya cids or other lipids groups covalently attached and are referred to as anchored
  • membrane spanning structures including b-strands, a-helices
  • sequences of 20 consecutive nonpolar amino acids suggests a membrane spannins a -helical region of a protein
42
Q

a helix in membrane IDd by

A
  • 20 consecutive nonpolar amino acids
43
Q

Types of membrane proteins

A
  1. single span a helix
  2. multiple span a helix
  3. multiple b-span (b barrel)
  4. nonspannign a helix
  5. fatty acyl or prenyl anchor
  6. lipid anchor with oligosaccharaide linker
  7. peripheral mebrane
44
Q

6 major functions of membrane proteins

A
  • transport
  • enzymatic activity
  • signal transduction
  • cell-cell regognition
  • intercellular
  • attachment to cytoskeleton and extraellular matrix
45
Q

How are double bonds made in hydrocarbons?

A

oxidation aka dehydrogenation

46
Q

How many carbons must be in fatty acid chain to find DBs?

A
  • at least 16
47
Q

Allergic reactions

A
  • venom has phospholipases
  • they break down erythrocytes
  • immune reaction also occurs in response to degradation products

antivenom deactivated phospholipases

48
Q

phospholipase C products

A

diacylglycerol and inositol 1,4,5 trisphosphate

diacylglycerol: activation of protein kinases, phosph in signaling pathways
inositol: increases Cell Ca2+, binding and reg

49
Q

Determining blood type

A
  • agglutination –> molecules join/link together
  • add antibodies to blood sample
  • A blood produces anti B antibodies, reacts with anti A
  • B produces antiA, reacts with anti B antibodies
  • AB blood produces no antibodies, blood reacts with both anti a and B
  • O produces all antibodies, doesnt react with anti A or anti B antibodies
50
Q

Importance of cholesterol

A
  • NEED for cellular membranes
  • hydrophobic but must be transported through hydrophilic blood
  • carried in bowl like structure
  • too much can build up and cause heart disease or stroke (plaque)
51
Q

steroids and gender determination

A
  • activate hundreds of transcription factors
  • can change complete expression patters

male vs female

52
Q

where are lipids made?

A
  • golgi apparatus
  • “melt” into membranes
53
Q

membrane protein complexes

A
  • do not move, cannot free flow
  • like cytochrome C
54
Q

hydropathy index

A

certain types of proteins and aas more likely to be span membrane

Biochem (15 decks)

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