Chapter 6 - Body Fluids and Membrane Potentials

What does the extracellular environment consist of?

Consists of a fluid compartment in which molecules are dissolved and a matrix of polysaccharides and proteins that give form to the tissues

Where is the extracellular environment located?

Surrounds/outside of cells

What makes the extracellular environment important?

Cells must receive nourishment from and release their waste products into the extra cellular environment.

Cells interact with each other through the extracellular environment as well.

Extracellular Matrix is ___________

Extracellular matrix is extracellular material of connective tissue

What is the connective tissues made up of

Consists of protein fibers collagen and elastin and gel-like ground substance

What is gel composed of? Where does it extend to?

Gel is composed of glycoproteins and proteoglycans (water-bound sugars).

Some glycoproteins - integrins extend from cytoskeleton within the cell, through the plasma membrane, and into the extracellular matrix.

What acts like adhesions between cells and extracellular matrix?

glycoproteins

What does collagen do?

Collagen provides strength.

• Some collagen provides the basement membrane which allows epithelium to attach to underlying connective tissues.

What provides stretch and recoil

Elastin

How are the body’s fluids set up?

They are divided into two compartments:

Intracellular compartment

Extracellular compartment

What is the difference between intracellular compartment and extracellular compartment?

Intracellular compartment: 67% of total body water is inside cells

Extracellular compartment: 33% of total body water is outside of cells

• Includes blood plasma, interstitial fluid, lymph, humors of eye

What is interstitial fluid?

Is the extracellular fluid within the tissues - formed from filtered blood plasma

What is the permeability of the plasma membrane?

The plasma membrane is selectively permeable.

• Permeable to lipids and lipid-soluble molecules, gases

What is not permeable to the plasma membrane?

Proteins, nucleic acids, sugars, ions through the phospholipid bilayer

• need help with carriers or channels

What are the carrier-mediated transport types through the plasma membrane?

Facilitated diffusion

Active transport

What are the non-carrier-mediated transport options for the plasma membrane

• Simple diffusion of lipid-soluble molecules through phospholipid layers

• Osmosis of water molecules through aquaporin channels

• Simple diffusion of ions through channel proteins

List the three passive transports that do not require energy

• Simple diffusion

  • nonpolar small molecules. O2, CO2, lipid soluble, steroid hormone, vitamins A D E and K

• Osmosis

• Facilitated

  • Protein carrier or channel ions Na, K, Cl

Ion channels are either gated or leakage, which is which?

Gated: open and close

Leakage: Stay open

What is diffusion of a solute?

The movement of materials from high to low concentration

When will no net diffusion occur?

When there is no concentration gradient

What are the four factors that affect the rate of diffusion?

1) Magnitude of concentration difference across the membrane

2) The permeability of the membrane to the diffusing substances. Different membranes have different permeabilities

3) The temperature of the solution

4) The surface area of the membrane through which the substances are diffusing. Smaller molecules can move faster in and out.

What happens to ions to help them pass the membrane?

They become charged and pass through channels

How does water move?

Water moves from high concentration of water to low concentration of water. Or, towards the higher solute concentration.

What must happen for osmosis to occur?

• The membrane must be more permeable to water than to at least one type of solute.

• There must be a difference in the concentration of a solute on the two sides of a selectively permeable membrane

• The membrane must be relatively impermeable to the solute

What is osmotic pressure?

Osmotic pressure indicates how strongly a solution “draws” water by osmosis.

The greater the solute concentration of a solution, the greater its osmotic pressure.

Osmotic pressure is more like a “pull” - a solution with high osmotic pressure pulls water towards it.

What is tonicity?

Tonicity describes the effect of a solution on the osmotic movement of water

Isotonic solution

has the same concentration as a cell

Hypertonic solution

Has a higher concentration of solutes than the cell.

• Water will move towards a hypertonic solution and shrink the cell (crenation)

hypotonic solutions

Have a lower concentration of solutes than the cell.

• Water will move into the cell and the cell will swell and could burst (lyse)

Characteristics of carrier-mediated transport proteins:

They are within the membrane.

Specificity

Competition

Saturation

What is unique about facilitated diffusion

Involves net transport from higher concentration to lower concentration using carrier proteins.

Active transport -

Generally moves from low to high and needs ATP.

Primary active transport

secondary active transport/coupled transport

bulk transport/vesicular transport

Primary active transport -

Uses pumps.

The carrier hydrolyzes ATP (splits ATP) directly and creates/maintains a concentration gradient.

The Na+/K+ pump pumps:

• 3 Na+ out of the cell

• 2 K+ into the cell per ATP

Secondary active transport (coupled transport)

Uses the concentration gradient created by primary active transporters.

Generally the secondary active transports uses the Na+ concentration gradient created by the Na/K pumps.

Na+ moves down the gradient and another molecule comes along with it.

Vesicular transport or Bulk Transport

Moves molecules across the membrane with vesiculas.

• Endocytosis brings in

• Exocytosis brings out

What is the charge difference that exists at the plasma membrane?

Cells are slightly negative inside and slightly positive outside

What is the human body’s charge?

We are electrically neutral overall

Potential difference and membrane potential

Is the magnitude of difference in charge across the plasma membrane

Voltage

is how you measure potential difference

Resting membrane poteneial

The voltage or charge difference across the membrane at rest is known as resting membrane poteneial.

Where are there more Na+ and K+?

There are more Na+ ions outside of cells

There are more K+ ions inside of cells

What ion is the plasma membrane more permeable to?

K+ leaks out.

What is the resting membrane potential?

-70 mV in a neuron

The resting membrane potential value depends on two factors:

• The resting membrane is more permeable to K+ than to Na+

• The ratio of the concentration of each ion on the two sides of the plasma membrane

  • Meaning - if the concentration of an ion changes on either the inside or outside of the membrane, the resting membrane potential will change

What is the RMP in nerves and muscles?

• It is negative.

• Fixed anions stuck inside cell

• More K leaking out