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Terms in this set (82)
Pleural, pericardium, peritoneum
Extracellular, intracellular, plasma membrane
- A structure that lines a cavity
- A phospholipid bilayer that forms the outer boundary of an organelle or a cell
AKA plasma membrane, plasmalemma, sarcolemma, neurolemma.
Cell Membrane Functions
- Permeable molecules
- Impermeable molecules
Lipids in Cell Membranes
Proteins in Cell Membranes
- Integral proteins
- Peripheral proteins
- Lipids-anchored proteins
Cell Membrane Components
Hydrophilic and hydrophobic.
The major lipid of membranes.
Slightly larger than phospholipids.
Have fatty acid tails, but their heads may be either phospholipids or glycolipids.
Significant part of many cell membranes.
Insert themselves between the hydrophilic heads of phospholipids.
Helps make membranes impermeable to small water-soluble molecules and keeps membranes flexible over a wide range of temperatures.
Tightly bound to the membrane and the only way they can be removed is by disrupting the membrane structure with detergents or other harsh methods that destroy the membrane's integrity.
Attach to other membrane proteins by non-covalent interactions and can be separated from the membrane by chemical methods that do not disrupt the integrity of the membrane.
Some of these proteins are covalently bonded to lipid tails that insert themselves into the phospholipid bilayer.
A membrane allows a substance to pass through it.
A membrane that does not allow a substance to pass through it.
Does not require the input of energy other than the potential energy stored in a concentration gradient.
Requires the input of energy from some outside source, such as the high-energy phosphate bond of ATP.
The movement of molecules from an area of higher concentration of the molecules to an area of lower concentration of the molecules.
Properties of Diffusion
1. Is a passive process.
2. Molecules move from an area of higher concentration to an area of lower concentration.
3. Net movement of molecules occurs until the concentration is equal everywhere.
4. Rapid over short distances but much slower over long distances.
5. Directly related to temperature.
6. Rate is inversely related to molecular weight and size.
7. Can take place in an open system or across a partition that separates two compartments.
A difference in the concentration of a substance between two places.
- Docking-marker acceptors
- Membrane bound enzymes
- Cell adhesion molecules (CAMs)
- Self recognition
Create water-filled passageways that directly link the intracellular and extracellular compartments.
Named based on:
- The molecule that passes through
- Type of gate
Also called 'transporters'.
Bind to the substrates that they carry but never form a direct connection between the intracellular and extracellular fluid.
Spend most of their time with their gate open, allowing ions to move back and forth across the membrane without regulation.
Sometimes called 'leak channels'.
Spend most of their time in a closed state, which allows these channels to regulate the movement of ions through them.
When open, allows for movement of ions.
Chemically Gated Channels
The gating is controlled by intracellular messenger molecules or extracellular ligands that bind to the channel protein.
Voltage Gated Channels
Open and close when the electrical state of the cell changes.
Mechanically Gated Channels
Respond to physical forces, such as increased temperature or pressure that puts tension on the membrane and pops the channel gate open.
- Interstitial fluid
Only uses the energy of molecular motion.
- Passive process
- From high to low concentration
- Continues to equilibrium
--- With higher concentration differences
--- Over short distances
--- At higher temps
--- For smaller molecules
Water is able to move freely between cells and the extracellular fluid and distributes itself until water concentrations are equal throughout the body.
Most solutes are concentrated in either one compartment or the other.
Cations and anions are not distributed equally between the body compartments.
Rate of Diffusion
- Depends on the permeability of the membrane for a particular substance.
- Directly proportional to the surface area.
- Inversely proportional to the membrane thickness.
Fick's Law of Diffusion
Diffusion rate increases when surface area, the concentration gradient, or the membrane permeability increase.
- the size and shape of molecules
- the lipid-solubility of the molecule
- the composition of the lipid bilayer across which it is diffusing
Fick's Law of Diffusion
diffusion rate/surface area = concentration gradient x membrane permeability
The diffusion of water through a semi-permeable membrane down its concentration gradient.
The pressure that exactly opposes the osmotic movement of water into the other compartment.
A measure of solute concentration - given in terms of the # of particles.
Does not provide information about the type of particle.
(OsM = osmoses/liter)
280-296 mOsM (~300 mOsM)
Same osmotic pressure.
When extracellular fluid osmolarity is greater than that of the intracellular fluid.
Characterized by having a lower osmotic pressure than a surrounding fluid.
Affect a solution has on a cell.
Cell doesn't swell or shrink.
Assisted Membrane Transport
2 main mechanisms for transport of molecules that cannot simply diffuse across the plasma membrane.
Protein Mediated Transport
- Passive (facilitated diffusion)
- Active (primary active and secondary active)
- Channel proteins
- Carrier proteins
Same properties as simple diffusion.
Protein channels and carriers mediate the diffusion of lipophobic molecules.
No outside energy required.
Molecules travel according to their concentration gradient, toward equilibrium.
Primary Active Transport
Moves molecules against their concentration gradient and requires an outside source of energy.
ATP being directly consumed.
Secondary Active Transport
Uses the potential energy stored in a concentration gradient and is indirectly driven by energy from ATP.
ATP removed from active comsumption.
Carrying a single ligand or substrate at a time.
Carrying more than one ligand or substrate at a time.
Type of co-transporter.
Carrying ligands/substrates in the same direction.
Type of co-transporter.
Carrying ligands/substrates in opposite directions.
1 ATP to pump 3 Na out and 2 K in.
Both ions moving low > high against concentration gradient.
Low Na inside. (saltwater)
Low K outside.
Cell eating; grow around something foreign.
A form of active transport in which a cell transports molecules (such as proteins) into the cell by engulfing them in an energy-using process.
The ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.
A process by which cells absorb metabolites, hormones, other proteins - and in some cases viruses - by the inward budding of plasma membrane vesicles containing proteins with receptor sites specific to the molecules being absorbed.
A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
Molecules entering the body through an epithelium need to cross 2 cell membranes.
Uses vesicular transport to move something through the epithelium.
Resting Membrane Potential
A 'steady state' phenomenon.
A barrier to the 'free' movement of charged ions.
Separated charges have the ability to do work.
100% impermeable, needs a channel.
Moves according to concentration gradient or charge.
Resting Membrane Potential Factors
1. Differences in concentrations on ions on either side of the cell membrane
2. Selective permeability of the cell membrane
3. Separation of charges on either side of the cell membrane
Differences in concentration of ions on either side of the cell membrane.
Separation of charges on either side of the cell membrane.
The electrical potential at which there is balance between the chemical force and the electrical force.
Ions responsible for RMP are Na+, K+ and A-
Differences in Na+ and K+ are produced and maintained by Na/K pump
K moving down ________ = inside becomes -
Na moving down _______ = inside becomes +
K+ more influence on RMP
E ion = 61/z log [ion] out/[ion] in
Determines equilibrium potential
Equilibrium Potential of K
Equilibrium Potential of Na
A modified Nerst equation that considers relative permeabilities of the ions that contribute to membrane potential.
Ion Permeability Changes
The membrane potential changes when permeability to Na+, K+, Ca++, or Cl- changes.
From resting state to more positive.
From resting state to more negative.
Back to rest from either positive or negative.
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