Chapter 5 - Membranes

Question 1

Explain how the body can be in osmotic equilibrium but electrical and chemical disequilibrium.

Answer 1

• Osmotic equilibrium does not mean that there are equal levels of molecules
• Electrical and chemical disequilibrium can mean that the levels of ions are disproportionate between ECF and ICF but in their own ‘equilibrium’

Question 2

Describe the distribution of body water among compartments.

Answer 2

ICF - fluid is 2/3 of total body water volume
ECF - 1/3 of the total body water volume

Question 3

How much water is in a “textbook normal” person.

Answer 3

42 L

Question 4

What percentage of the ECF is plasma?

Answer 4

25%

Question 5

what percentage of ECF is interstitial fluid?

Answer 5

75%

Question 6

what is the only difference between interstitial fluid and plasma?

Answer 6

plasma has more proteins

Question 7

Compare and contrast molarity, osmolarity, and osmotic pressure.

Answer 7

• molarity: moles solute/liter of solution
• osmolarity: osmoles/liter of solution
• osmotic pressure: minimum pressure that must be applied to prevent flow of solvent across membrane (osmosis)

Question 8

Compare bulk flow to solute movement across membranes.

Answer 8

• bulk flow: fluid movement in response to pressure gradients
• solute movement across membranes: solute movement in response to energy requirements of transport

Question 9

Explain the differences between diffusion in an open system and diffusion across biological membranes.

Answer 9

diffusion in an open system:
- does not require an outside energy source
- diffuse from high to low concentration
- diffusion continues until equilibrium

diffusion across membranes:
- requires energy
- rate of diffusion depends on the SA
- permeability depends on lipid composition

Question 10

What is Fick’s law of diffusion?

Answer 10

Diffusion of an uncharged solute across a membrane is proportional to the concentration gradient of the solute, the membrane surface area, and the membrane permeability to the solute.

(rate of diffusion) is proportional to (SA) x (concentration gradient) x (membrane permeability)

Question 11

What is the equation for membrane permeability?

Answer 11

lipid solubility / molecular size

Question 12

What subcategories fall under passive protein-mediated transport across membranes?

Answer 12

• facilitated diffusion
• ion channel
• aquaporin channel

Question 13

What subcategories fall under active protein-mediated transport across membranes?

Answer 13

• direct/primary transport
• indirect/secondary transport (concentration gradient created by ATP)

Question 14

What subcategories fall under vesicular transport across membranes?

Answer 14

• exocytosis
• endocytosis
• phagocytosis

Question 15

Compare movement through channels to movement on facilitated diffusion and active transport carriers.

Answer 15

channels:
- move ions (and water)
- passive transport
- transport down concentration gradients
- no energy input
- facilitated diffusion uses carrier molecules (GLUT transporters)
- always open to both ICF + ECF at the same time

active transport carriers:
- move different types of molecules
- change conformation
- transport against concentration gradients
-requires energy
- never open to both ICF + ECF at the same time

Question 16

Apply the principles of specificity, competition, and saturation to carrier-mediated transport.

Answer 16

specificity: molecule has to fit the “mold” of the transporter or else it won’t be carried across the membrane

competition: decreases transport rate when another molecule is fighting to be transported in the same transport as another molecule

saturation: when transport reaches a maximum rate + all the carrier binding sites are filled with substrate

Question 17

Give the 4 types of membrane proteins based on function.

Answer 17

1) membrane transport
2) structural proteins
3) membrane enzymes
4) membrane receptors

Question 18

what are uniport carriers?

Answer 18

move one molecule

Question 19

what are cotransporters?

Answer 19

move more than one type of molecule

Question 20

what are symport carriers?

Answer 20

move molecules in the same direction

Question 21

what are antiport carriers?

Answer 21

move molecules in opposite directions

Question 22

what is primary (direct) active transport?

Answer 22

uses ATP directly (ex: Na, K, ATPase)

Question 23

what is secondary (indirect) active transport?

Answer 23

Uses potential energy stored in concentration gradients of one molecule to push another molecule against its gradient (ex: SGLT)

Question 24

How many Na+ and K+ transported in the Na+-K+-ATPase?

Answer 24

3 Na+ out to ECF
2 K+ in to ICF

Question 25

Compare phagocytosis, endocytosis, and exocytosis.

Answer 25

Phagocytosis: uses actin microfilaments and myosin motor proteins to engulf particles in large vesicles

exocytosis: same as phagocytosis except it engulfs smaller things like fluid, ECF, and solutes

endocytosis: removes something from inside the cell (ex: membrane removed from the cell surface)

Question 26

Explain transcellular transport, paracellular transport, and transcytosis as they apply to epithelial transport.

Answer 26

transcellular transport: goes through the cell (by simple diffusion or transporters)
paracellular transport: goes between cells (have to be small to move)
transcytosis: use vesicles to cross cells

Question 27

what is the definition of absorption?

Answer 27

Transport from lumen to ECF

Question 28

what is the definition of secretion?

Answer 28

Transport from ECF to lumen

Question 29

Explain what it means for a cell to have a resting membrane potential difference.

Answer 29

• Resting is the steady state
• Potential energy stored in the electrochemical gradient
• Difference in electric charges inside and outside of the cell

Question 30

Explain how changes in ion permeability change membrane potential, giving examples.

Answer 30

Depolarization –> getting more positive
- ex:

Repolarization –> go from depolarization to RMP
-ex:

Hyperpolarization –> get more negative
- ex: