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Biochemistry > Cell Membranes And Cytoskeleton > Flashcards

Cell Membranes And Cytoskeleton Flashcards

1
Q

Phospholipids

A

. Most prevalent type of lipid in biological membranes
. Synthesized in sER, transported to Golgi then to plasma/organelles
. Polic, ionic compounds
. Amphiphatic

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2
Q

Phospholipid structure

A

. Alcohol attached by phosphodiester bridge to carbon3 of glycerol backbone or to sphingosine
. Hydrophobic tail contains 2 fatty acid chains links to carbons 1 and 2 of glycerol backbone
. Number of carbon atoms in fatty acid chain is even
. 1 of the fatty acid chains is unsaturated (1 double bond)

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3
Q

Major membrane phospholipids

A 
. Phosphatidylserine (PS)
. Phosphatidylethanolamine (PE)
. Phosphatidylcholine (PC)
. Phosphatidylinositol (PI)
. Sphingomyeline (SM)
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4
Q

T/F membrane phospholipids cannot move

A

F, capable of many types of motion (rotation, flexion, lat. movement) contributing to membrane fluidity

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5
Q

Areas w/ most cholesterol synthesis

A

Liver, adrenal cortex, and reproductive tissues

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6
Q

T/F Every human tissue is capable of cholesterol synthesis

A

T

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7
Q

Cholesterol structure

A

Polar hydroxyl group and hydrophobic steroid ring and attached hydrocarbon
. Amphiphatic

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8
Q

Cholesterol interaction w/ phospholipid membrane

A

. Goes btw phospholipids w/ hydroxyl group near polar heads and steroid ring and hydrocarbon tail parallel to the fatty acid chains of phospholipids

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9
Q

Cholesterol function in membrane

A

Inc packing of phospholipids and slows their lat. mobility

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10
Q

Glycolipids

A

.minor lipid components in cell membranes
. Have acquired sugar groups in the non-cystolic half of lipid bilayer from golgi so sugar is always displayed on exterior of cell when in the membrane
. Important in cell-cell and cell-matrix interactions

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11
Q

T/F lipids important for membrane structure, protein important for membrane biological functions

A

T

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12
Q

Integral membrane proteins

A

. Embedded in phospholipid bilayer
. Can be transmembrane or lipid-anchored
. Rotate along their long axis (lat. movement) w/in membrane but can’t flip form one leaflet to another

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13
Q

Lipid anchored protein

A

Integral protein covalently attached to lipid w/o entering core of membrane bilayer

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14
Q

Integral membrane protein functions

A

. Ligand receptors
. Channels and transport proteins
. Cellular identity

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15
Q

Ligand receptors

A

. External signals (ligand) that bind to protein receptor on cell surface
. Specific receptors for specific ligand
. Cells w/o receptor can’t respond to ligand

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16
Q

Glycoproteins

A

. Integral proteins w/ carbs attached to them on exterior of cell
. Each cell type has different glycoproteins to give it individual identity
. Individual humans can have different glycoproteins

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17
Q

Peripheral membrane proteins

A

. Can be removed w/o disrupting bilayer
. Attach to membrane surface via ionic interactions w/ integral protein or via interaction w/ polar head groups of phospholipids

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18
Q

Peripheral membrane protein functions

A

. Constituents of cytoskeleton: maintain cell shape and form, move chromosomes during cell division, help w/ cell motion
. Signal transduction: enzymes that are active after ligand binding

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19
Q

Asymmetry in membrane

A

. Different proteins, phospholipids, and glycolipids are presented on the external and internal sides of membrane
. Proteins have specific orientations when embedded into membranes

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20
Q

because of the fluidity of biological membrane ____

A

. Proteins diffuse in plane of bilayer and interact
. Easy to distribute membrane lipids and proteins through diffusion
. Membranes can fuse w/ one another to allow mixing of molecules
. Insurance that membrane molecules are distributed evenly btw daughter cells during mitosis

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21
Q

Lipid rafts

A

. Specialized cholesterol-enriched microdomains w/in cell membrane
. Fatty acid chains of phospholipids are extended and more tightly packed
. Float independent w/in fluid created by less ordered lipids in surrounding portions of membrane

22
Q

Lipid raft function

A

. Cholesterol transport
. Endocytosis
. Signal transduction

23
Q

Types of lipid rafts

A

. Gycosphingolipid-enriched membranes (GEM)
. Polyphosphoinositol-rich
. Caveolae

24
Q

Caveolae

A

Flask-shaped invaginations of cell membrane

. Contains protein caveolin that causes local change in morphology of membrane

25
Q

Major factor in controlling fluidity of membrane and what does it do?

A

Cholesterol

. Inc. cholesterol: less fluid outer surface but more fluid in hydrophobic core

26
Q

Spur cell anemia

A

. Erythrocyte has inc. cholesterol and dec. membrane fluidity causing dec. ability to negotiate micocirculation
. Causes premature destruction of cells

27
Q

Intoxicating ethanol effects on nervous system from caused by ____

A

Modification of membrane fluidity and alteration of receptors and ion channels

28
Q

Abetalipoproteinemia

A

Altered phospholipids in membranes causing dec. membrane fluidity

29
Q

Reason RBC dies in 120 days

A

. Loss of membrane fluidity preventing them from negotiating microcirculation

30
Q

Hereditary spherocytosis

A

Reduction in erythrocytic spectrin content

. Creates spherical fragile rbcs and hemolytic anemia

31
Q

Hereditary elliptocytosis

A

. RBCs are elliptical and fragile

. Spectrin can’t bind protein 4.1 or form stable spectrin-4.1-actin complex

32
Q

Functions of actin in non-muscle cells

A

Regulation of physical state of cytoplasm, cell movement, formation of contractile rings in cell division

33
Q

Polymerization fo actin

A

. Actin filaments (F-actin) are polymers of actin monomers (G-actin)
. Each G-actin monomer has ATP bound to polymerize onto F-actin

34
Q

Diameter of actin filament

A

8nm

35
Q

Stages of actin filament formation

A

. Lag
. Polymerization
. Steady state

36
Q

Lag phase of actin filament formation

A

3 G-actin monomers w/ bound ATP join to form nucleation site
. ATP is hydrolyzed and G-actin is added to end of F-actin

37
Q

Steady state in actin formation

A

. Actin monomers added at one end at same rate as they are being removed from other end
. Treadmilling

38
Q

Actin-binding proteins

A

.regulate structure of actin by controlling polymerization and breakdown of actin
. Regulate gel-state of cytosol: more structured actin more firm gel, less structured (more fragmented) more soluble
. Spectrin and dystrophin important ones

39
Q

Muscular dystrophy diseases

A

. Deletion in dystrophin gene
. X-linked recessive
. Duchene: no functional dystrophin, rapid severe muscle degeneration
. Becker: partially functional dystrophin, slowly progressive muscle weakness

40
Q

Intermediate filaments

A

. Intermediate in thickness btw actin and microfilaments (10nm)
. Rope-like appearance
. Fibrous protein subunits that form fibrous heteropolymers
. Structural function
. Assoc. w/ nuclear envelope and plasma membrane

41
Q

Types of intermediate filaments

A 
. Acidic and basic keratin 
. Desmin and vimentin
. Neurofilaments, synemin, syncollin
. Nuclear lamina
. Nestin
42
Q

Microtubule function

A

. Ciliary and flagella motility
. Mitotic and meiotic chromosomal movement,
. Intracellular vesicles transport and secretion

43
Q

Principle component of microtubules

A

Tubulin

44
Q

Tubulin structure

A

Globulin protein heterodimer w/ alpha and beta subunits

45
Q

T/F GTP not required for dynamic instability of microtubules

A

F, need GTP bound to tubulin for assembly and disassembly

46
Q

Assembly and disassembly process of microtubules

A

. GTP hydrolyzed to GDP after tubulin addition to microtubule
. Disassembly peels back protofilaments and begins once GTP cap is hydrolyzed to GDP from plus end (beta side)

47
Q

Microtubule-protein interaction

A

Motor proteins associate w/ them to position membrane-bound organelles w/in cell

48
Q

Spectrin

A

Actin-binding protein that strengthens and supported membranes
. Important in erythrocytes

49
Q

Dystrophin

A

. In Skeletal muscle cells

. Links actin to supporting structures w/in and strengthens muscle fibers

50
Q

FRAP experiment

A

Showed that phospholipids were mobile
. Bleach a spot of cell that has fluorescence and if it has lateral mobility the bleached part will regain it’s fluorescence

51
Q

Which phospholipids are on inner leaflet?

A

. Phosphatidylethanolamine
. Phosphatidlinositol
. Phosphatidylserine

52
Q

Phospholipids on outer leaflet

A

. Phosphatidylcholine

. Sphingomyelin

Biochemistry (64 decks)

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