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Plant Phy > Chapter 11 > Flashcards

Chapter 11 Flashcards

1
Q

Micelle

A

An aggregate of amphipathic molecules in water, with the nonpolar portions in the interior and the polar portions at the exterior surface, exposed to water.

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2
Q

Bilayer

A

A double layer of oriented amphipathic lipid molecules, forming the basic structure of biological membranes. The hydrocarbon tails face inward to form a continuous nonpolar phase.

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3
Q

Vesicle

A

A small, spherical, membrane-bounded particle with an internal aqueous compartment that contains components such as hormones or neurotransmitters to be moved within or out of a cell.

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4
Q

Fluid mosaic model

A

The model describing biological membranes as a fluid lipid bilayer with embedded proteins; the bilayer exhibits both structural and functional asymmetry.

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5
Q

Lipid transfer protein

A

A family of proteins that transfer membrane lipids between parts of the endomembrane system at contact points.

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6
Q

Integral proteins

A

Proteins firmly bound to a membrane by interactions resulting from the hydrophobic effect; as distinct from peripheral proteins.

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7
Q

Peripheral proteins

A

Proteins loosely bound to a membrane by hydrogen bonds or electrostatic forces; generally water-soluble once released from the membrane. Compare integral proteins.

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7
Q

Amphitropic protein

A

Proteins that associate reversibly with the membrane and thus can be found in the cytosol, in the membrane, or in both places.

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8
Q

Monotopic

A

integral proteins have small hydrophobic domains that interact with only a single leaflet of the membrane

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9
Q

Bitopic

A

proteins span the bilayer once, extending on either surface.

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10
Q

Polytopic

A

proteins cross the membrane several times.

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11
Q

Hydropathy index

A
  • free energy of transfer
  • ranges from highly exergonic for charged or polar residues to highly endergonic for amino acids with aromatic or aliphatic hydrocarbon side chains.
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12
Q

B barrel

A

Another structural motif common in bacterial and mitochondrial membrane proteins is the barrel, in which 20 or more transmembrane segments form sheets that line a cylinder

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13
Q

Porins

A

proteins that allow certain polar solutes to cross the outer membrane of gram-negative bacteria such as E. coli, have many-stranded barrels lining the polar transmembrane passage

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14
Q

Positive-inside rule

A

The general observation that most plasma membrane proteins are oriented so that most of their positively charged residues (Lys and Arg) are on the cytosolic face.

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15
Q

GPI-anchored protein

A

A protein held to the outer monolayer of the plasma membrane by its covalent attachment through a short oligosaccharide chain to a phosphatidylinositol molecule in the membrane.

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16
Q

Flippases:

A

Membrane proteins in the ABC transporter family that catalyze movement of phospholipids from the extracellular leaflet (monolayer) to the cytosolic leaflet of a membrane bilayer.

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17
Q

Floppases

A

Membrane proteins in the ABC transporter family that catalyze movement of phospholipids from the cytosolic leaflet (monolayer) to the extracellular leaflet of a membrane bilayer.

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18
Q

Scramblases

A

are proteins that move any membrane phospholipid across the bilayer down its concentration gradient (from the leaflet where it has a higher concentration to the leaflet where it has a lower concentration); their activity is not dependent on ATP, although some require Ca2+

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19
Q

FRAP (fluorescence recovery after photobleaching)

A

A technique used to quantify the diffusion of membrane components (lipids or proteins) in the plane of the bilayer.

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20
Q

Microdomains

A

cholesterol-sphingolipid microdomains of the plasma membrane make the bilayer slightly thicker and more ordered (less fluid) than neighboring regions, which are rich in phospholipids.
- microdomains are more difficult to dissolve with nonionic detergents; they behave like liquid-ordered sphingolipid ra s adri on an ocean of liquid-disordered phospholipids

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21
Q

Rafts

A

adri ft on an ocean of liquid-disordered phospholipids

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22
Q

Caveolin

A

an integral protein with two globular domains connected by a hairpin-shaped hydrophobic domain that binds the protein to the cytoplasmic leaflet of the plasma membrane

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23
Q

BAR domains

A

superfamily of proteins containing BAR domains (named for the first three members of the family that were identified: BIN1, amphiphysin, and RVS167) can assemble into a crescent-shaped scaffold that binds to the membrane surface, forcing or favoring membrane curvature.
- BAR domains have coiled coils that form long, thin, curved dimers with a positively charged concave surface that tends to form ionic interactions with the negatively charged head groups of membrane lipids PIP2 and PIP3.

24
Q

Septins

A

A family of highly conserved GTP-binding proteins that act in processes that involve membrane bending, such as cytokinesis, exocytosis, phagocytosis, and apoptosis.

25
Q

Fusion protein

A

(1) One of a family of proteins that facilitate membrane fusion.
(2) The protein product of a gene created by the fusion of two distinct genes or portions of genes.

26
Q

v-SNAREs

A

Protein receptors in the membrane of a secretory vesicle that bind to t-SNAREs in a targeted membrane (typically the plasma membrane) and mediate fusion of the vesicle and target membranes.

27
Q

t-SNAREs

A

Protein receptors in a targeted membrane (typically the plasma membrane) that bind to v-SNAREs in the membrane of a secretory vesicle, mediating fusion of the vesicle and target membranes.

28
Q

Integrin

A

One of a large family of heterodimeric transmembrane proteins that mediate adhesion of cells to other cells or to the extracellular matrix.

29
Q

selectins

A

A large family of membrane proteins that bind oligosaccharides on other cells tightly and specifically and carry signals across the plasma membrane.

30
Q

simple diffusion

A

Movement of solute molecules across a membrane to a region of lower concentration, unassisted by a protein transporter.

31
Q

membrane potential

A

The difference in electrical potential across a biological membrane, commonly measured by insertion of a microelectrode; typical values range from -25 mV
(by convention, the negative sign indicates that the inside is negative relative to the outside) to more than across some plant vacuolar membranes.

32
Q

electrochemical gradient/ electrochemical potential

A

The resultant of the gradients of concentration and of electric charge of an ion across a membrane; the driving force for oxidative phosphorylation and photophosphorylation.

33
Q

passive transporter

A

A membrane protein that increases the rate of movement of a solute across the membrane along its electrochemical gradient without the input of energy.
- simply facilitate movement down a
concentration gradient, increasing the transport rate. This process is called passive transport or facilitated diffusion.

34
Q

Active transporters

A

Membrane protein that moves a solute across a membrane against an electrochemical gradient in an energy-requiring reaction.
- (sometimes called pumps) can move substrates across a membrane against a concentration gradient or an electrical potential, a process called active transport.

35
Q

ion channels:

A

Integral proteins that provide for the regulated transport of a specific ion, or ions, across a membrane.
- use a different mechanism than transporters to move inorganic ions across membranes

36
Q

amphipathic:

A

Containing both polar and nonpolar domains.

36
Q

K transaport / Transaport constant

A

is a constant analogous to the Michaelis constant, a combination of rate constants that is characteristic of each transport system.
- A kinetic parameter for a membrane transporter, analogous to the Michaelis constant, Km , for an enzymatic reaction. The rate of substrate uptake is half- maximal when the substrate concentration equals Kt.

37
Q

electroneutral

A

This protein mediates the simultaneous movement of two anions: for every HCO3- ion that moves in one direction, one Cl- moves in the opposite direction, with no net transfer of charge: the exchange is electroneutral

38
Q

cotransport

A

The simultaneous transport, by a single transporter, of two solutes across a membrane. See also antiport; symport; uniport.

39
Q

antiport

A

Cotransport of two solutes across a membrane in opposite directions.

40
Q

symport

A

Cotransport of solutes across a membrane in the same direction.

41
Q

uniport

A

A transport system that carries only one solute, as distinct from cotransport.

42
Q

electrogenic

A

Contributing to an electrical potential across a membrane.

43
Q

P-type ATPases

A

Catalytic cycles :
The family of active transporters called P-type ATPases are cation transporters that are reversibly phosphorylated by ATP (thus the name P-type) as part of the transport cycle.

43
Q

SERCA pump

A

Animal tissue: sarcoplasmic/ER Ca2+ ATPase (SERCA) pump and the plasma membrane Ca2+ ATPase pump, which are uniporters for Ca2+ ions, together maintain the cytosolic level of Ca2+ below 1 μM.

44
Q

Na+ K+ ATPases

A

The electrogenic ATP-driven active transporter in the plasma membrane of most animal cells that pumps three outward for every two moved inward.

45
Q

ATP synthase

A

An enzyme complex that forms ATP from ADP and phosphate during oxidative phosphorylation in the inner mitochondrial membrane or the bacterial plasma membrane, and during photophosphorylation in chloroplasts

45
Q

V-type ATPases

A

a class of proton-transporting ATPases, are responsible for acidifying intracellular compartments in many organisms (thus, V for vacuolar).

46
Q

F-type ATPases

A

transporters catalyze the uphill transmembrane passage of protons, driven by ATP hydrolysis.

47
Q

ABC transporters

A

Plasma membrane proteins with sequences that make up ATP-binding cassettes; serve to transport a large variety of substrates, including inorganic ions, lipids, and nonpolar drugs, out of the cell, using ATP as the energy source.

48
Q

Na+ -glucose symporter

A

in the apical plasma membrane takes up glucose from the intestine in a process driven by the downhill flow of
(2Naout+ + glucoseout -> 2Nain+ + glucosein)

49
Q

multidrug transporters

A

Plasma membrane transporters in the ABC transporter family that expel several commonly used antitumor drugs, thereby interfering with antitumor therapy.

50
Q

ionophore

A

A compound that binds one or more metal ions and is capable of diffusing across a membrane, carrying the bound ion.

51
Q

aquaporins (AQPs)

A

A family of integral membrane proteins that mediate the flow of water across membranes.

52
Q

ligand-gated channel

A

(which are generally oligomeric), binding of an extracellular or intracellular small molecule forces an allosteric transition in the protein, which opens or closes the channel.

53
Q

voltage-gated ion channel

A

a change in transmembrane electrical potential (Vm) causes a charged protein domain to move relative to the membrane, opening or closing the channel.

54
Q

patch-clamping

A

very small currents are measured through a tiny region of the membrane surface containing only one or a few ion- channel molecules

Plant Phy (2 decks)

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