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Membrane Flashcards

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1
Q

The Functions of Membranes

A

define boundaries and serve as permeability barriers

are sites of specific functions
.
regulate the transport of solutes

detect and transmit electrical and chemical signals

mediate cell-to-cell communication

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2
Q

Composition of Plasma Membrane

A

lipids,

proteins

carbohydrates

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3
Q

most abundant lipids in membranes

A

phospholipids

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4
Q

types of Phospholipids in membrane

A

Glycerol-based phosphoglycerides
Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine
PhosphotidylEnositol (Not as abundant)

Sphingolipids
sphingomyelin

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5
Q

major classes of lipids in Membranes

A

Phospholipids (most abundant)

Glycolipids

Sterols

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6
Q

Cerebrosides

Gangliosides

A

Glycolipids

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7
Q

name the parts

A
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8
Q

effects of fatty acid composition

on membrane fluidity

A

Long-chain fatty acids: higher Tm than shorter-chain

unsaturated fatty acids: tend to have lower Tm and are more fluid

Fluidity is enhanced by increased temperature and a high degree of unsaturation of fatty acid tails

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9
Q

effects of sterols

on membrane fluidity

A

less fluid at higher temperatures

Increases fluidity at lower temperatures
prevents fatty acid chains from getting close

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10
Q
A
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11
Q
A
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12
Q

Lipid Rafts

A

Also called microdomains

localized regions of membrane lipids that are involved in cell signaling

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13
Q

Peripheral Membrane proteins

A

Associate through weak electrostatic forces and hydrogen bonding

change in pH or salt remove them

Lack discreet hydrophobic segments

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14
Q

Integral membrane proteins

A

Singlepass or multipass proteins

Hydrophobic transmembrane segments

Some are lipid-anchored proteins

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15
Q
A
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16
Q

Single-pass transmembrane protein

Key points

(Oligosaccharide chains disulfide bonds)

A

Oligosaccharide chains and disulfide bonds

are on the extracellular side

in the cytosolic domain do not form disulfide bonds because the reducing environment in the cytosol maintain these groups in their reduced (-SH) form

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17
Q

Glycocalyx

A

surface (sugary) coat of carbohydrates extending from

_glycoproteins _(integral membrane) and

_glycolipids (_oligosaccharide side chains)

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18
Q
A
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19
Q

Simple Diffusion

A

Unassisted movement down the gradient

moves solutes toward equilibrium

from regions of higher to lower free energy

limited to small, nonpolar molecules

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20
Q

Osmosis

A

diffusion of water across a

differentially permeable membrane

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21
Q

Hypertonic

A

a solution with a higher solute concentration

than inside the cell

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22
Q

Isotonic

A

a solution with an equal solute concentration

than inside the cell

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23
Q

Hypotonic

A

a solution with a lower solute concentration

than inside the cell

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24
Q

Osmosis

A
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25
Facilitated Diffusion | (clases)
Protein-mediated movement down the gradient not require input of energy 2 classes : Carriers and channels
26
Carrier proteins
transporters or permeases bind one or more solute molecules on one side of the membrane and undergo conformational change to deliver solute to the other side of membrane analogous to enzymes in their specificity and kinetics
27
Channel proteins | (examples)
form hydrophilic channels, often transport ions Ion channels Porins Aquaporins
28
Uniport
Carrier proteins transport single solute
29
Cotransport
Carrier proteins transport two solutes Symport and Antiport
30
31
Ion channels
only participate in passive transport transport inorganic ions Voltage-gated Ligand-gated Mechanosensitive
32
Porins
Transmembrane proteins that allow rapid passage of various solutes
33
Aquaporins
Transmembrane channels that allow rapid passage of water
34
Active transport
Protein-mediated movement up the gradient requires energy! has directionality
35
Three major functions of Active transport
Uptake of essential nutrients Removal of secretory products and waste Maintain nonequilibrium intracellular [] of ions
36
Direct active transport
the accumulation of solute molecules or ions on one side of the membrane is coupled directly to an exergonic chemical reaction (ATP hydrolysis) Na+/K+ Pump
37
Indirect active transport
depends on the cotransport of two solutes, with the movement of one solute down its gradient driving the movement of the other solute up its gradient Na+/glucose symporter
38
what is it?
Na+/K+ Pump
39
what is it and what kind?
Indirect Transport: Na+/glucose symporter
40
Wha is it? Name the parts
Transcellular Transport of Glucose
41
explain the process involve
Glucose is pumped into cell by a Na+ powered _glucose symporter._ Glucose passes out of cell (down its conc. gradient) by _passive movement_ through a different GLUT in the basal and lateral membrane domains. The Na+ gradient driving the glucose symport is maintained by the Na+ pump in the basal and lateral plasma membrane domains, which keeps the internal concentration of Na+ low
42
Four types of Transport ATPases
P-type ATPases (P for phosphorylation) F-type ATPases (F= factor) V-type ATPases (V=vesicle) ABC-type ATPases (ATP-binding cassette)
43
P-type ATPases
(P for phosphorylation): Reversibly phosphorylated by ATP as part of the transport mechanism. responsible for maintaining an ion gradient across the membrane Example: Na/K pump and proton pump in stomach
44
F-type ATPases
(F=factor): ATP synthases. Proton transporter found in bacteria, chloroplasts and in mitochondria.. Not only can ATP be used as an energy source to generate and maintain electrochemical gradients, but such gradients can be used as an energy source to synthesize ATP
45
V-type ATPases
(V=vesicle): Pump protons into such organelles as: vesicles, vacuoles, lysosomes, endosomes, and the Golgi complex in a phosphorylation independent manner Structurally related to F-type ATPases
46
ABC-type ATPases
(ATP-binding cassette): Large superfamily. Handles a wide variety of solutes. (ions, sugars, AA, peptides and polysaccharides) Example: Multidrug resistance transport protein found in tumor cells, may help these cells evade drug therapy.
47
Cystic fibrosis transporter gene | (CFTR)
encodes for a chloride transporter. Mutation in this gene causes cystic fibrosis ABC Transporter Superfamily
48
Cystic Fibrosis
inability of cells to transport chloride and water to body secretions increased frequency of respiratory infections pancreatic insufficiency Males often are sterile progressive lung disease is the principle cause of death
49
what is happening and which disease is it?
dehydrated mucus Cystic fibrosis
50
Endocytosis and what types (3)
Uptake of macromolecules from the extracelluar surroundings by localized regions of plasma membrane Phagocytosis Pinocytosis Receptor-mediated – binding of ligands to receptors triggers vesicle formation
51
Phagocytosis
endocytosis of large particulate substances
52
Pinocytosis
endocytosis of fluid and dissolved solutes
53
Exocytosis
secretion of macromolecules by transport vesicles
54
Signal transduction
Detection of specific signals at the cell surface and the mechanism by which such signals are transmitted into the cell’s interior, resulting in changes in cell behavior and/or gene expression
55
Primary messenger Second messenger
1-A molecule that binds to a receptor, thereby beginning the process of transmitting a signal to the cell 2-substances that transmit signals from extracellular signaling ligands to the cell interior
56
chemical signals that can be received by cells
57
types of Extracellular Signal Molecules
Endocrines Paracrines Autocrines
58
Endocrines hormone
exerts its actions on specific target cells, which may be some distance away
59
Paracrines actions
those performed on nearby cells, and the location of the cells plays a role in the specificity of the response Very important in limiting immune response to a specific location in the body
60
Autocrine actions
messenger that acts on the cell from which is secreted, or on nearby cells that are the same type as the secreting cells.
61
If deprived of appropriate survival signals, a cell will undergo a form of cell suicide known as
apoptosis
62
3 SIGNALING PATHWAYS BY WHICH EXTRACELLULAR LIGANDS INFLUENCE GENE EXPRESSION
63
use intracellular gene-specific trancription factors (Receptors)
lipophilic hormones steroid hormones, thyroid hormones, retinoic acid and vitamin D
64
3 largest classes of cell-surface receptor proteins
Ion-channeled coupled receptors G-protein-coupled receptors Enzyme-coupled receptors
65
Ion-channeled coupled receptors
rapid synaptic signaling between nerve cells and other electrically excitable target cells such as muscle cells. Mediated by neurotransmitters that transiently open or close and ion channel formed by the protein to which they bind
66
G-protein-coupled receptors
**_indirectl_**y regulate the activity of a separate plasma-membrane-bound target protein, which is generally either an enzyme or an ion channel A trimeric _GTP-binding protein_ mediates the interaction between the activated receptor and this target protein
67
Enzyme-coupled receptors
Either function directly as enzymes or associate directly with enzymes that they activate
68
which cell-surface receptor proteins
Ion-channeled coupled receptors
69
which cell-surface receptor proteins
G-protein-coupled receptors
70
which cell-surface receptor proteins:
Enzyme-coupled receptors

Cell bio (3 decks)

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