Lecture 1: Body Fluid Compartments and Transport across cell membranes

Question 1

What is total body water?

Answer 1

Total water in the body

Question 2

The amount of water in the body is __________ related to fat.

Answer 2

Inversely

Question 3

What are the two major fluid compartments and what percentage of body weight do they comprise?

Answer 3

Intracellular fluid (ICF)- inside cells, 40% BW
Extracellular fluid (ECF)- outside cells, 20% BW

Question 4

There are two types of extracellular fluid. What are they and what percentage of total body weight do they comprise?

Answer 4

Plasma (inside capillaries)- ~4% total body weight
Interstitial Fluid (bathes cells & tissues)- ~16% total body weight

Question 5

Total body water is what percentage of body weight?

Answer 5

On average 60%
range of 50-70% depending on species

Question 6

What is the average blood volume? Important number*

Answer 6

70mL/kg BW

Question 7

When measuring the AMOUNT of solutes in fluid compartments, you can measure amounts in _________, __________, or _________.

Answer 7

moles, equivalents or osmoles

Question 8

what is an equivalent?

Answer 8

amount of charged solute that has participated in a chemical reaction or electrical process (ex: 2 Eq of Ca and 2 Eq of Cl)

Question 9

what is an Osmole?

Answer 9

number of particles into which a solute dissociates in solution (NaCl= 2 osmoles in solution)

Question 10

What is osmolarity?

Answer 10

osmoles/L

Question 11

What is electroneutrality?

Answer 11

each body fluid compartment must have the same concentration of cations as of anions

Question 12

What are the major ions in the ECF?

Answer 12

Cation: Na+
Anions: Cl- and HCO3- (bicarb)

Question 13

What are the major ions in the ICF?

Answer 13

Cation: K+
Anions: proteins and organic phosphates

Question 14

What is the normal range of osmolarity?

Answer 14

290-300 mOsm/L

Question 15

What are the two types of Ca in ICF and ECF?

Answer 15

Total Ca: bound and ionized Ca
Ionized Ca: Free Ca & active form

Question 16

Cell membranes are selectively permeable, meaning what?

Answer 16

Cell membranes are not freely soluble to all solutes

Question 17

What are the two transport mechanisms in the cell membrane?

Answer 17

Na+/K+ ATPase pump: pumps Na= out of the cell, K+ pumped into cells (because K+ concentration is higher in cells)
Ca2+/ATPase pump: pumps Ca2+ out of cells (pumps Ca2+ out of cells)
both mechanisms directly use ATP*

Question 18

Why are ion concentration differences important?

Answer 18

-Allows nerve and muscle cells to have resting membrane potentials (due to K+ difference)
- Upstroke of action potentials in nerve and muscle cells and absorption of nutrients due to Na+ difference
- excitation-contraction coupling in muscle cells depends on Ca2+ difference

Question 19

Cell membranes are composed of lipids and proteins. What are the three types of lipids that are in cell membranes?

Answer 19

phospholipids
cholesterol
glycolipids

Question 20

What is the function of lipids in cell membranes?

Answer 20

-allow membrane to be permeable to lipid soluble substances (CO2, O2, fatty acids, steroid hormones
low permeability to H2O soluble substances)
- transporters, enzymes, hormone receptors, antigens, ion& H2O channels

Question 21

What is the function of proteins in cell membranes?

Answer 21

• transporters, enzymes, hormone receptors, antigens, ion& H2O channels

Question 22

What is the function of the phospholipid component in cell membranes?

Answer 22

Glycerol backbone (water-soluble) + FA tails (lipid-soluble= amphipathic*
*has both polar and non-polar components in its structure

Question 23

Cell membranes can contain peripheral proteins. Where can these proteins be found?

Answer 23

Only on one side of the membranes

Question 24

Transport across cell membranes can occur down an electrochemical gradient. What are these types of transport called?

Answer 24

Simple Diffusion
Facilitated Diffusion (needs a carrier protein to grab and move)
***No input of energy

Question 25

Transport across cell membranes can occur against an electrochemical gradient. What are these types of transport called?

Answer 25

Primary transport- direct input of energy Secondary transport- use energy to establish the Na+ gradient, then use Na+ to move other substances

Question 26

True or False: Simple Diffusion is NOT carrier-mediated.

Answer 26

TRUE ***this is important

Question 27

When two solutions are separated by a membrane permeable to the solute, the solute will ____________ across the membrane.

Answer 27

equilibrate

Question 28

What are two additional consequences of charge on an ion that is diffusing?

Answer 28

1) A potential difference across a membrane will alter the rate of diffusion of a charged solute (diffusion of a positively-charged ion will slow down if diffusing to an area with positive charge) 2) A diffusion potential can be created when a charged solute diffuses down its concentration gradient

Question 28

Movement of solute depends on several factors. Name these factors.

Answer 28

1) Concentration gradient: driving force, the larger the difference in the concentration gradient, the larger the driving force 2) Partition coefficient: based on the lipid solubility of the solvent (greater the solute's solubility in oil, the higher the partition coefficient, the more easily it can diffise) 3) Diffusion coefficient: based on the size of the solute and the viscosity of solution ( small solutes in non-viscous solution have a higher diffusion coefficient) 4) Thickness of membrane: thicker the membrane, the lower the diffusion 5) Surface area: greater surface area=higher diffusion rate

Question 28

Facilitated Diffusion: Does it use a carrier protein yes or no? Is there an input of energy yes or no?

Answer 28

Yes, uses a carrier protein No, no input of energy

Question 29

Facilitated diffusion will proceed faster or slower at relatively low solute concentrations? Why?

Answer 29

Facilitated diffusion will proceed FASTER at low solute concentrations because there are more carrier proteins available

Question 29

There are 3 features of carrier-mediated transport. Name the 3 and describe them.

Answer 29

1) Saturation: carrier proteins have a limited number of binding sites for a solute, therefore: the RATE of transport increases at a higher rate at lower solute concentrations 2) Stereospecificity: binding sites for solute on carrier proteins are specific 3) Competition: Although binding sites are specific, carriers may recognize and bind chemically-related solutes

Question 29

Which type of transport directly uses energy and is carrier-mediated? A) Primary active transport B) Secondary active transport C) Simple Diffusion D) Facilitated Diffusion

Answer 29

A) Primary Active Transport

Question 30

Give the definition of primary active transport.

Answer 30

One or more solutes moved AGAINST a concentration gradient directly using ATP

Question 31

What is the Na+/K+ ATPase pump?

Answer 31

-Present in membranes of ALL cells - 3 Na+ pumped to ECF and 2 K+ pumped to ICF, this creates a charge separation and potential difference - Cardiac glycosides inhibit this protein transporter

Question 32

There are two examples of the Ca2+ ATPase pump. What are they?

Answer 32

1) Plasma-Membrane Ca2+ ATPase (PMCA): one Ca is pumped out of the cell for every ATP consumed 2) Sarcoplasmic and Endoplasmic reticulum Ca2+ATPase (SERCA): takes 2 Ca from ICF into SR or ER for every 1 ATP used

Question 33

What is the action of the H+/K+ ATPase pump?

Answer 33

Parietal cells of gastric mucosa- pumps H+ into lumen of the stomach

Question 34

What is the definition of secondary active transport?

Answer 34

Indirectly uses energy by utilizing the Na+ gradient to transport solutes against their concentration gradient

Question 35

Co-transport (aka symport) is an example of secondary active transport. What does this mean?

Answer 35

- all solutes are transported in the same direction - Na+/Glucose co-transporter (SGLT 1) - Na+/Amino acid co-transporter - Na+/K+/2Cl- co-transporter in renal tube

Question 36

Counter-Transport (aka antiport) is an example of secondary active transport.

Answer 36

- Solutes move in opposite directions- Na+ moves INTO the cell and other solute moves OUT of the cell - Ca2+/Na+ exchange - Na+/H+ exchange