Chapter 5: Cell Membranes and Signaling Flashcards Preview

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Flashcards in Chapter 5: Cell Membranes and Signaling Deck (54):
1

fluid mosaic model

The general design of the phospholipid bilayer serves as a lipid lake in which proteins float in

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domains

the hydrophobic regions of phospholipids

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Hydrophilic region of a phospholipid

Phosphorous containing head
electrically charged
gets along really well with polar water molecules

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Hydrophobic regions of a phospholipid

associate with other hydrophobic substances
Long, non polar fatty acid tails

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Phospholipid bilayer

the tails interact on the inside while the heads are on the outside

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lipid composition

the kinds of lipids that make up the membrane/their proportion

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Lipid Composition

One of the two factors that affects membrane fluidity
Cholestorl and saturated fats pack together and are less fluid
Unsaturated fats or ones with short chains increase membrane fluidity

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Temperature

One of the two factors that affects membrane fluidity
Fluidity declines under cold temperatures
some animals change lipid composition to get through this problem by replacing saturated with unsaturated

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Peripheral membrane proteins

lack exposed hydrophobic groups and are not embedded in the bilayer
Instead, had polar or charged regions that interacted with exposed parts of the integral membrane proteins or with the polar heads of the phospholipids

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Integral membrane proteins

at least partly embedded in the phospholipid bilayer
have hyrophobic and hydrophilic regions

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anchored membrane proteins

have fatty acids or lipid groups covanlently attached to them
hydrophobic lipid components that anchor them in the phospholipid bilayer

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transmembrane protein

an integral membrane protein that extends all the way through the phospholipid bilayer and protrudes on both sides
always oriented the same way

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Transmembrane domains

extend through the bilayer
transmembrane proteins have them

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glycolipid

carbohydrate covalently bonded to a lipid
carb goes out of cell surface and may serve as a recognition signal

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glycoprotein

carbohydrate covalently bonded to a protein
The carbohydrate is an oligosaccharide of 15 or fewer monosaccharide units
often function as signaling units

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selective permeability

biological membranes allow some sometimes, but not others to pass through
like the bachelor (not everyone gets a rose)

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Passive transport

direct input of metabolic energy is NOT required to drive these processes
kind of just happens
gradients though

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Active transport

requires the input of metabolic energy from an outside source

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diffusion

process of random movement toward a state of equilibrium
net movement from greater concentration to lower
very slow process in living tissues

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equilibrium

the state in which a solution in which solute molecules are evenly distributed is in

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Factors that determine how fast a substance diffuses

diameter of molecules or ions: smaller diffuses faster
temperature of the solution: higher temperature, more movement, faster diffusion
concentration gradient: change in solute concentration with distance in a given direction
greater concentration gradient, the more rapidly it diffuses

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simple diffusion

just passes through
in membranes, must be teeny weeny, hydrophobic, and lipid solubles

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Osmosis

the movement of water across membranes

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signal transduction pathway

a sequence of molecular events and chemical reactions that lead to a cell's response to that signal

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Autocrine signals

affect the same cells that release them
ex. many tumor cells make their own division singles

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Paracrine signals

diffuse to and affect nearby cells
ex. neurotransmitter made by one cell stimulates an adjacent one

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hormones

signals to distant cells that travel through the circulatory system

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Can any cells respond to any stimulus?

NOPE!
Only the cells with the necessary receptors can respond

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allosteric regulation

involves an alteration in the three dimensional shape of a protein as a result of the binding of another molecule at a site other than the active site
ex. gated channel

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law of mass action

binding is reversible (noncovalent bonding)
generally favored though

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Inhibitor or antagonist

binds to receptor protein and prevents the binding of the normal ligand
Girlfriend by Avril Lavigne
like competitive inhibition

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Cytoplasmic receptors

small or nonpolar ligands can diffuse across the phospholipid bilayer of the plasma membrane and enter the cell
ex. estrogen
many regulate gene expression

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Membrane receptors

Large or polar ligands cannot cross the lipid bilayer
ex. Insulin
binds to transmembrane receptor with an extracellular binding domain

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Protein kinases

catalyze this reaction:
ATP + protein ----> ADP + phosphorylated protein

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simple diffusion

to use this to pass through the bilayer, a molecule must be small, hydrophobic, and lipid soluble

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osmosis

diffusion of water across a membrane

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If the total solute concentration is high, then the the concentration of water molecules is....?

lower

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hypertonic solution

higher solute concentration than the other solution

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Isotonic solution

equal solute concentrations

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Hypotonic

Lower solute concentration than the other one

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turgor pressure

The pressure within a cell with a cell wall that comes from the limited amount of water the cell can take in, building up internal pressure and preventing water from entering

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channel proteins

integral membrane proteins that form channels actoss the membrane through which certain substances can pass

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carrier proteins

Membrane proteins that speed up diffusion rate through the bilayer

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Facilitated diffusion

Diffuse according to gradients, but made easier by channel or carrier proteins

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Ion Channels

famous
specific

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Gated channel

opens when a stimulus causes a change in the three-dimensional shape of the channel

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Ligand

binding of a chemical signal
can be the stimulus of a gated channel

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Ligand-gated channels

channels controlled by ligands

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Voltage-gated channels

Opens or closes based on changes in the voltage across the membrane

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Aquaporins

Water is special and gets its own super cool channel to use to diffuse
allow large amounts of water to follow concentration gradients

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saturated

increases in concentration gradient are no longer accopmanied by increased diffusion rates

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Primary active transport

uses ATP directly

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Secondary Active transport

does not use ATP directly
energy comes from electron or ion concentration gradient

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