Chapter 5: Membrane Dynamics Flashcards Preview

Physiology 1 > Chapter 5: Membrane Dynamics > Flashcards

Flashcards in Chapter 5: Membrane Dynamics Deck (17):

Explain body fluid compartments and name the two types in regards to cells. 

  • Body fluid compartments are filled primarily with water and are separated by membranes
  • Intracellular: area inside cells
  • Extracellular: area outside cells

A image thumb

What is passive transport?

Passive transport: molecules move high  low concentration without using energy

  • Simple diffusion
    Lipid-soluble molecules
    Ions through nonspecific channels


  • Facilitated diffusion

A image thumb

What is active transport?

Active Transport: molecules move from low to high concentration using ATP

A image thumb

What is osmosis? 

Net movement of water across a semi-permeable membrane from side with more water to less water
Aided by channels in membrane

A image thumb

WHat is used to measure the the concentration of a solution?

  • Osmolarity (OsM) is a measure of solution concentration
    OsM = total # solute particles/L solution
  • In the body solute concentrations are usually expressed in milliosmoles = mOsM
  • Plasma and most cells are 300mOsM


How is the osmolarity of blood regulated?

  • Osmoreceptors in the hypothalamus detect increases in solutes (due to dehydration, etc)
  • Concentration of particles must constantly be maintained, or cells are damaged (e.g. neurons) 


What is the difference between non penetrating and  penetrating solutes?

  • Solution: consists of a solvent (water) and a solute (molecules dissolved in water)
  • Molecules in a solution are in constant motion
  • If there is a concentration difference between two regions, random motion will establish equilibrium
    Solutes that can cross membrane = penetrating
    Solutes that cannot cross membrane =non penetrating


What is tonicity? How does it work?

  • Tonicity is the effect of a solution’s solute concentration on the osmosis of water
  • Tonicity takes into account permeability of membrane to solutes
    Penetrating vs nonpenetrating solutes
  • If solute crosses membrane, tonicity will change
  • Solutions with a higher solute concentration than cell are hypertonic
  • Water leaves cell- crenation
  • Solutions with a lower solute concentration than cell arehypotonic
  • Water enters cell - lysis


A image thumb

Using Jerry's shit as an example, explain the the phenomena of diffusion?

  • Jk! XD
  • Net diffusion: Due to random movement, the net direction of diffusion is from high to low

A image thumb

What molecules can diffuse through the plasma membrane?

  • Nonpolar lipid soluble molecules and small uncharged polar molecules – permeable
    Steroid hormones, water, gases
    Net O2 into cells, CO2 out of cells

A image thumb

How do ions diffuse through the plasma membrane?

Charged ions can cross the plasma membrane by passing through ion channels

  • Some channels may always be open, others gated

A image thumb

Explain the various types of membrane transporters. 

  1. Channel proteins: create a water filled pore.
    Gated channels: open and close in response to signals
    Open channel: usually open (pore)
  2. Carrier proteins: never form an open channel between the two sides of the membrane
    Uniport carriers: transport only one kind of substrate
    Symport carrier: move two or more substances in the same direction across the membrane
    Antiport carrier: move substrate in the opposite direction


Explain facilitated diffusion.

  • Most molecules too large and polar to cross
  • Instead, specific carrier proteins within the membrane move these molecules across
  • Random movement of molecules
    No ATP
    High to low concentration
  • Transport proteins may be permanent in the plasma membrane or be inserted when needed
    Muscle cells insert carrier proteins to take in more glucose when needed as during exercise

A image thumb

What is primary active transport?

  • Move molecules from  low to high concentration
  • ATP hydrolysis directly provides energy
  • Pump is activated by phosphorylation using a Pi from ATP
    Na+/K+ pump
    Ca2+ pump

A image thumb

What is secondary active transport?

  • Energy from an ion gradient is used to move a second solute against its concentration gradient
  • Symport: 2nd molecule is moved in same direction
  • Antiport: 2nd molecule is moved opposite direction

A image thumb

How many transport proteins can be on a single epithelial cell?

  • Epithelial cells may have many different types of transport proteins on a single cell

Ex: movement of glucose across the intestinal wall

A image thumb

What is membrane potential?

  • There is a difference in charge on each side of the plasma membrane due to:

Permeability of the membrane
Action of Na+/K+ pumps
Negatively charged molecules inside the cell

  • Inside of cell is negative relative to outside

A image thumb