Composition and volume regulation of cells

Question 1

Volume of extracellular fluid

Answer 1

14 liters; 1/3 total body fluid

Question 2

Volume of intracellular fluid

Answer 2

28 liters; 2/3 total body fluid

Question 3

Volume of plasma compartments

Answer 3

2.8 liters; 20% of ECF

Question 4

What are the major differences in ionic composition between ECF and ICF?

Answer 4

ECF - mostly Na+ and Cl-

ICF - mostly K+ cations and a variety of anions

Question 5

What is one of the most functional properties of lipids in membranes?

Answer 5

resistance to charge diffusion. They can withstand the large amount of electric force imposed by the charge differentiation across the membrane

Question 6

True or False: Transporters allow passive diffusion

Answer 6

false - channels allow passive diffusion. Transporters actively pump ions across the membrane

Question 7

Are channels selective for particular ions?

Answer 7

Yes

Question 8

What are some of the forces that control channels?

Answer 8

• electric field (membrane potential)
• mechanical stimulation
• chemical (synaptic receptors for a neurotransmitter)
• temperature (cutaneous thermal receptor)

Question 9

Where does the energy come for primary active transport?

Answer 9

ATP

Question 10

Where does the energy come from for secondary active transport?

Answer 10

not ATP, ex - when Na+ ions leak into the cell

Question 11

Osmosis

Answer 11

the net inward movement of water across a semi-permeable membrane

Question 12

What are three mechanisms that have evolved to solve the problem of volume control?

Answer 12

• build a strong wall around the cell (plant cells)
• balance the osmotic force osmotically, bu having solute molecules in the ECF, in order to balance those in the ICF (animal cells)
• contractile vacuole that takes up excess water from the cytoplasm and periodically contract to expel the water out of the cell (some prokaryotes)

Question 13

Is a solution with the same starting solute concentration as the cell isomotic (same osmolarity) with the cell?

Answer 13

yes

Question 14

Tonicity

Answer 14

whether the cell shrinks (hypertonic) or swells (hypotonic)

Question 15

What is the reflection coefficient?

Answer 15

how permeable the cell membrane is to a substance (1= impermeable)

• some things can pass into cells more quickly and some things can’t come into cells at all
• balance of solute will not be balanced throughout the diffusion process