Chapter 7: Membranes (Exam 2)

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37 Terms

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Fluid Mosaic Model

Describes the structure of cell membranes as a dynamic mosaic of phospholipids, proteins, cholesterol, and carbohydrates. These components can move laterally, giving the membrane a fluid and flexible nature

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Phospholipid Bilayer

Proteins can travers the membrane; Hydrophobic tail, hydrophillic head

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How do things move in the plasma membrane?

Most laterally; Once a month flip flop (switch)

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What happens when membrane temps cool off?

Fluid state turns to a solid state

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What determines temperature function fo membranes?

Depends on the types of lipids present in membrane

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What restrains movement of phospholipids?

Cholesterol

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Diffusionq

The natural tendency of particles to move

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Proteins:

Determine most of the membranes specific functions

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Peripheral proteins

Proteins that are not embedded

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Integral proteins

Penetrate the hydrophobic core; span across the membrane.

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What are Transmembrane proteins?

Integral proteins that span the membrane

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<p>Hydrophobic regions of integral proteins:</p>

Hydrophobic regions of integral proteins:

Consist of one or more stretches of nonpolar a-acids; coiled into alpha helices

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Functions of membrane proteins:

  1. Transport

  2. Enzymatic Activity

  3. Signal Transduction

  4. Cell-cell recognition

  5. Interstellar joining

  6. Attachment to cytoskeleton and extracellular matrix (ECM)

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How do cells recognize each other?

Binding to surface molecules, often carbs, on plasma membrane

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Inside Membrane face:

Intracellular

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Outside Membrane face

Extracellular

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Selective Permeability

regulates what leaves and enters the cell membrane

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Hydrophobic Molecules:

Dissolve in the lipid bilayer and pass through the membrane rapidly

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Polar Molecules (Sugars):

Do not cross the membrane easily

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Transport Proteins

Allow passage of hydrophilic, polar substances across the membrane

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Channel Proteins

Hydrophilic channel that certain molecules or ions can use as a tunnel

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Carrier Proteins

Bind to molecules and change shape to shuttle them across membrane

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Dynamic Equilibrium

As many molecules cross one way cross in the other direction

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Which way do substances diffuse?

Down their concentration gradient

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Passive Transport

Requires no energy from cell to make it happen

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Osmosis

Diffusion of water across a selectively permeable membrane

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Direction of osmosis is determined by:

Difference in total solute concentration; goes from lower solute to higher solute.

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Tonicity

Ability of a solution to cause a cell to gain or lose weight

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Isotonic Solution

Solute concentration is the same as that inside the cell

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Hypertonic Solution

Solute concetration is greater thatn that inside the cell; cell loses water

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Hypotonic Solution

Solute concentration is less than that inside the cell; cell gains water

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Osmoregulation

The control of water balance

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Turgid

Plant cell in hypotonic solution until the wall opposes uptake

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Flaccid

Plant cell with 0 net movement

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Plasmolysis

contraction of the protoplast of a plant cell as a result of loss of water from the cell.


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Facilitated diffusion

Passive transport aided by proteins; Transport proteins speed movement of molecules across membranes

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