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BIOL 213 > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Fluid mosaic model

A

The general structure of membranes is known as the fluid mosaic model

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2
Q

Cholesterol

A

-is a flat hydrophobic molecule
-Cholesterol in eukaryotic cell membranes prevents “close packing” of phospholipids
-at colder temperatures membrane still maintains fluid-like motion
-conversely, at high temperatures the hydrophobic cholesterol helps hold membrane together
-temperature adaptation in some animals involves adjusting the amount of cholesterol in their membranes

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3
Q

Fluidity depends on

A

-temperature, lipid composition (saturated vs unsaturated), ad cholesterol percentage

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4
Q

Peripheral membrane proteins

A

Lack exposed hydrophobic groups and do not penetrate the bilayer. They may be anchored to lipid groups however

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5
Q

Integral membrane protiens

A

have hydrophobic and hydrophilic regions or domains. Some extend across the lipid bilayer (transmembrane); others are partially embedded

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6
Q

Transmembrane proteins

A

extend all the way through the phospholipid bilayer

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7
Q

domain

A

different parts of the protein that have different functions

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8
Q

anchored membrane proteins

A

membrane proteins that have fatty acids or other lipid groups covalently attached

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9
Q

Lipid-rafts

A

While some membrane proteins can move freely within the bilayer, others are anchored to a specific region
-Free diffusion is limited by the cytoskeleton and protein-protein interactions

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10
Q

Freeze-fracturing

A

a technique that reveals proteins that are embedded in the phospholipid bilayers of cellular membranes. Electron microscopy is then used to examine the structure

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11
Q

fluorescent microscopy

A

can be used to visualize “tagged” membrane proteins and lipids

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12
Q

Patch-Clamp

A

experimentation creates membrane “plugs”

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13
Q

Functions of membrane proteins

A

-Process information (signals and signaling receptors)
-Organize chemical reactions
-Transform energy
-Cell recognition and adhesion
-Transport into and out of the cell

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14
Q

Information processing

A

Binding of a specific ligand can initiate, stop, or modify cell functions.

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15
Q

Organizing chemical reactions

A

-Many cellular processes involve a series of enzyme-catalyzed reactions- all the molecules must come together for these to occur. Forms an “assembly line” of enzymes

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16
Q

Some transform energy…

A

Inner mitochondrial membranes-energy from fuel molecules is transformed to ATP
-Thylakoid membranes of chloroplasts transform light energy to chemical bonds

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17
Q

Cell recognition and adhesion

A

-Membranes also have carbohydrates on the outer surface that serve as recognition sites for other cells and molecules
-Glycolipids- carbohydrate+lipid
-Glycoproteins-carbohydrate+protein

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18
Q

Homotypic

A

The same molecule sticks out from both cells and forms a bond

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19
Q

Heterotypic

A

the cells have different protiens

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20
Q

Cell junctions

A

specialized structures that hold cells together

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21
Q

Tight junctions

A

help ensure directional movement of materials
-a quilted seal, air and water tight

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22
Q

Desmosomes

A

link adjacent cells tightly but permit materials to move around them in the intercellular space, similar to “spot welds”

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23
Q

Gap junctions

A

let adjacent cells communicate

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24
Q

apical membrane

A

faces the lumen or “outside” the body

25
Basolateral membrane
base and lateral membranes. Those membranes that face other cells or the interstitial compartment, the "inside" of the body
26
Extracellular Matrix (ECM)
-Composed of collagen, hyaline, proteoglycans and cellulose -For example; bone, cartilage, and the cellulose of plant walls
27
Integrin
transmembrane protein that binds to the matrix outside epithelial cells and to actin filaments inside the cells -binding can be noncovalent and reversible. This allows signaling between intracellular (inside) and intercellular (outside) environments
28
Selective permeability
some substances can pass through but not others
29
Passive transport
No outside energy required (diffusion)
30
Active transport
energy required
31
Diffusioin
The process of random movement from an area of high concentration to an area of low concentration until equilibrium is reached
32
Equilibrium
particles continue to move but there is no net change in distribution
33
Diffusion rate depends on...
-diameter of the molecules or ions -Temperature of the solution -concentration gradient
34
Because of diffusion...
a concentration gradient is a form of potential energy
35
Simple diffusion
small molecules pass through the lipid bilayer -water and lipid-soluble molecules can diffuse across the membrane -electrically charged and polar molecules can not pass through easily
36
Osmosis
-The diffusion of water -Water diffuses slowly, is the most abundant molecules in a living cell, universal solvent -depends on the number of solute particles present not the type of particles
37
Water follows salt...
Water will diffuse from the region of higher water concentration (lower solute concentration) to the region of lower water concentration (higher solute concentration)
38
Isotonic
Equal solute concentration (equal water concentration)
39
Hypertonic
higher solute concentration
40
Hypotonic
lower solute concentration
41
osmotic lysis
Animal cells may burst when placed in a hypotonic solution
42
Turgor pressure
Plant cells with rigid cell walls build up internal pressure that keeps more water from entering
43
Facilitated diffusion
-a form of passive transport, no cellular energy required but cellular protein(s) and a concentration gradient necessary
44
Carrier proteins
membrane proteins that bind some substances and speed their diffusion through the bilayer
45
Channel proteins
have a central pore lined with polar amino acids
46
Aquaporins
Water can cross a membrane by "hitchhiking" with hydrated ions or moving through the special water channels (aquaporins) -Function of these proteins was determined by injecting the aquaporin mRNA into an oocyte
47
Ion channels
-Specific channel proteins with hydrophilic pores -Most are gated-can be closed or open to ion passage -Gate opens when protein is stimulated to change shape. Stimulus can be a molecule (ligand-gated) or electrical charge resulting from many ions (voltage-gated)
48
Active transport
moves substances against a concentration and/or electrical gradient-requires energy -Energy source is often ATP
49
Three kinds of proteins in active transport
-Uniporters -Symporters -Antiporters
50
Primary active transport
requires direct hydrolysis of ATP
51
Secondary active transport
energy comes from an ion concentration gradient that is established by primary active transport -aids in uptake of amino acids and sugars -uses symporters and antiporters
52
Membrane potential
-A charge imbalance across a membrane -measured membrane potential of animal cells; -70mV -Membrane potential is mainly related to the concentration imbalance of Na+ and K+
53
Endocytosis
processes that bring molecules and cells into a eukaryotic cell -plasma membrane folds in or invaginates around the material forming a vesicle
54
Exocytosis
Material in vesicles is expelled from a cell
55
Why endo/exocytosis
-Macromolecules are too large to cross the membrane -Large amounts of fluid may need to be taken in or expelled -membranes need to be regenerated
56
phagocytosis
molecules or entire cells are engulfed -A food vacuole or phagosome forms which fuses with a lysosome -some protists feed in this way -Some white blood cells engulf foreign substances such as bacteria and viruses
57
Pinocytosis
A vesicle forms to bring small dissolved substances or fluids into a cell. Vesicles are much smaller than in phagocytosis -Pinocytosis is constant in endothelial cells
58
Receptor mediated endocytosis
-High specific -depends on receptor proteins to bind specific substances -Sites are called clathrin coated pits coated with the protein clathrin
59
Why exocytosis
-material in vesicles is expelled from a cell -Indigestible materials are expelled -other materials leave cells such as digestive enzymes and neurotransmitters -Plasma membrane components (lipids, proteins, etc) replaced

BIOL 213 (13 decks)

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