CVM 711 Lecture 1: Body Fluid Compartments and Transport Across Cell Membranes

What percentage of body weight (BW) is total body water?

60% of BW

What percentage of body weight (BW) is intracellular fluid (ICF)?

40% of BW

What percentage of body weight (BW) is extracellular fluid (ECF)?

20% of BW

What percentage of body weight (BW) is plasma (part of the ECF)?

4% of BW

What percentage of body weight (BW) is interstitial fluid (part of the ECF)?

16% of BW

What percentage of body weight (BW) is blood?

6-8% of BW

What is the average blood volume in animals?

70 mL/kg BW

What is the conversion rate of liters to kilograms?

1:1

Do lean animals have a higher or lower percentage of body water compared to obese animals?

Higher

What component of ECF bathes cells?

Interstitial fluid

What describes the amount of a substance in a fluid?

Mole

What describes the amount of electrical charge in a fluid?

Equivalent

What describes the number of dissolved particles in a fluid?

Osmole

What determines water movement between compartments?

Osmolarity

How do we expressed the relatively low concentration of hydrogen (H) ions in the body?

Logarithmic term (pH)

What happens to pH if hydrogen ions increased?

pH lowers (more acidic)

What describes the fact that within each body fluid compartment, total positive charges must equal total negative charges?

Electroneutrality

Are cations usually positively or negatively charged?

Positive

Are anions usually positively or negatively charged?

Negative

What is the major cation in ECF?

Na+

What are the major anions in ECF?

Cl- and HCO3-

What is the major cation in ICF?

K+

What are the major anions in ICF?

Proteins and organic phosphates

What is more acidic: ECF or ICF?

ICF

Is calcium (Ca2+) low or high in ICF?

Low

What prevents inappropriate cell signaling or muscle contractions?

Low intracellular Ca2+

What do you call free (unbound) calcium?

Ionized calcium

What do you call calcium that is bound to minerals or proteins (not available)?

Bound calcium

What is maintained since ECF and ICF have the same osmolarity?

Electroneutrality

What is the range of osmolarity for both ECF and ICF?

290-300 mOsm/L

Who has the higher concentration in ECF: Cl- or HCO3- ?

Cl-

What is the permeability of cell membranes?

Selectively permeable

Do transport mechanisms create or do they maintain the selective permeability of membranes?

Maintain

What does the Na+/K+ ATPase pump (sodium-potassium pump) do?

Directly uses ATP to pump Na+ out of the cell and K+ into the cell

What does the Ca2+/ATPase pump do?

Directly uses ATP to pump Ca2+ out of cells

What transporters utilize Na+ gradients but not direct energy?

Secondary transporters

Which compounds/ions use secondary transporters that utilize the Na+ gradient?

Glucose, amino acids, Ca2+, H+

What allows nerve and muscle cells to have resting membrane potentials?

K+ difference

What causes the upstroke of action potentials in nerve and muscle cells, as well as the absorption of nutrients?

Na+ difference

What does excitation-contraction coupling in muscle cells depend on?

Ca2+ difference

What are cell membranes composed of?

Lipids and proteins

What are included in the lipid portions of cell membranes?

Phospholipids, cholesterol, glycolipids

What do the proteins of the cell membrane function as?

Transporters, receptors, enzymes, channels

What do water soluble substances need to enter cells?

Power and proteins

What does it mean to have both hydrophilic and hydrophobic parts?

Amphipathic

What makes up the phospholipid bilayer?

Hydrophilic heads and hydrophobic fatty acid tails

What are hydrophilic heads made out of?

Glycerol

Which proteins can span the membrane once or can be transmembrane proteins (span more than once)?

Integral proteins

Which proteins are only on one side of the membrane?

Peripheral proteins

Which forms of transport can occur down an electrochemical gradient with no input of energy?

Simple diffusion and facilitated diffusion

Which forms of transportation can occur against an electrochemical gradient?

Primary transport and secondary transport

Which form of transport directly uses energy and uses a carrier?

Primary transport

Which form of transport indirectly uses energy and uses a carrier?

Secondary transport

Which form of transport is not carrier-mediated and does not require energy?

Simple diffusion

Which form of transport uses a carrier but does not required energy?

Facilitated diffusion

What form of transport is passive (downhill), is not carrier-mediated, does not use energy, and does not depend on the Na+ gradient?

Simple diffusion

What form of transport is passive (downhill), is carrier-mediated, does not use energy, and does not depend on the Na+ gradient?

Facilitated diffusion

What form of transport is active (uphill), is carrier-mediated, directly uses energy, and does not depend on the Na+ gradient?

Primary active transport

What form of transport is secondarily active, is carrier-mediated, indirectly uses energy, and depends on the Na+ gradient by moving solutes in the same direction as Na+ across the cell membrane?

Cotransport

What form of transport is secondarily active, is carrier-mediated, indirectly uses energy, and depends on the Na+ gradient by moving solutes in the opposite direction as Na+ across the cell membrane?

Countertransport

What five variables determine diffusion rate (Fick’s Law)?

Concentration gradient, partition coefficient, diffusion coefficient, thickness of membrane, and surface area

What determines permeability?

Partition coefficient, diffusion coefficient, thickness of membrane, and surface area (everything but concentration gradient)

What depends on driving force?

Concentration gradient

Does a larger concentration gradient have a greater or less driving force?

Greater

What is based on lipid solubility of solute?

Partition coefficient

Does something with a high lipid solubility have a higher or lower partition coefficient?

Higher

Does a higher partition coefficient make moving across the membrane harder or easier?

Easier

What is based on size of solute and viscosity of solution?

Diffusion coefficient

Will a non-viscous solution and smaller solutes have a higher or lower diffusion coefficient?

Higher

Will a thicker membrane make diffusion faster or slower?

Slower

Does a greater surface area have a higher or lower diffusion rate?

Higher

Potential difference created across a membrane because of an ion concentration difference?

Diffusion potential

Electrical forces + concentration forces =

electrochemical gradient

Why does facilitated diffusion proceed faster at relatively low solute concentrations?

Limited number of carriers

Where is the GLUT4 transporter located?

Skeletal and adipose tissue

What does GLUT4 respond to?

Insulin

What does GLUT4 transport into the cell?

Glucose

Why does glucose need a carrier to be transported into the cell?

Glucose is water soluble

What competes with glucose to bind the GLUT4 transporter?

D-galactose

What are the features of carrier-mediated transport?

Saturation, stereospecificity, and competition

What describes the fact that carrier proteins have a limited number of binding sites for solutes?

Saturation

Does the rate of carrier-mediated transport increase at a greater rate in lower or higher solute concentrations?

Lower

What does Tm/Tmax stand for in carrier-mediated transport?

When all carriers are saturated

What type of growth does the rate of carrier-mediated transport have?

Logarithmic

What type of growth does the rate of simple diffusion have?

Linear

What describes how binding sites for solute on carrier proteins are specific?

Stereospecificity

The fact that transporters for D-glucose won’t transport L-glucose is what?

Stereospecificity

What describes how although binding sites are specific, carriers may recognize and bind chemically-related solutes?

Competition

The fact that D-galactose can bind carriers for D-glucose is what?

Competition

What type of transport moves one or more solutes against a concentration gradient directly using ATP?

Primary active transport

What primary active transport pump is present in the membranes of ALL cells?

Na+/K+ ATPase pump

What primary active transport pump uses 20-40% of cellular ATP in many tissues?

Na+/K+ ATPase pump

How many Na+ does the Na+/K+ ATPase pump remove from the cell?

3 Na+

How many K+ does the Na+/K+ ATPase pump bring into the cell?

2 K+

What inhibits the Na+/K+ ATPase pump?

Cardiac glycosides (digoxin, ouabain, oleandrin)

What are the two Ca2+ ATPase pumps?

PMCA (plasma membrane) and SERCA (sarcoplasmic and endoplasmic reticulum)

What is the common goal of PMCA and SERCA?

Keep Ca2+ low in ICF

What does the PMCA do?

Pump one Ca2+ out of the cell (ICF to ECF)

What does the SERCA do?

Take two Ca2+ from the ICF and pump them into the sarcoplasmic reticulum

Where is the H+/K+ ATPase pump located?

Parietal cells of gastric mucosa