Composition of Cells

Question 1

Intracell fluids

Answer 1

27L inside cells (bag of cytoplasm) (makes sense b/c 10x more mem in cells).

Question 2

Extracell fluids

Answer 2

13L, interstitital fluid (blood plasma (3L) lymph)

Question 3

Membrane permeable to?

Answer 3

K (~30x higher inside), Cl, H20.

Not permeable to Na or anions.

Question 4

Membrane composition

Answer 4

1. ) Made of lipid. Impermeable to anything charged, electrically strong (electric potential on either side of mem. created b/c of the neg anions inside)
2. ) Have holes (channels- selective or non-selective, may be gated (voltage, mechanical, chemical synapse) or (carriers- big mlc transport (too big) pumps against energy gradient), spend energy

Question 5

What can change the volume of a cell?

Answer 5

Movement of H20 ONLY

Question 6

How to prevent H20 from entering cells?

Answer 6

1. ) membrane impermeable to H20, not ideal b/c daughter cells are smaller and how will they get up to size if impermeable?
2. ) Cell wall (prevents swelling, 360lbs/sq. inch)
3. ) Osmotic pressure (US): dilute h20 outside cell to same as inside

Question 7

Patch Clamp Tecnique

Answer 7

See indiv ion channels at work.
Lower glass micropipette onto a cell, suck mem bleb into pipette. Tight seal. When channel gate opens can record electric current through the channel.

Question 8

Ion channel structure

Answer 8

x-ray crystallography.

Important for understanding certain disease. Can mutate a single AA with molecular biological tools.

Question 9

Channels

Answer 9

selective and gated (electric..mem potential, voltage…open whend depolarized (Cell less neg on inside), chemical…synaptic receptors for NT, temp… cutaneous thermal receptors, mechanical…stretching, like hair cells in cochlea or touch in skin).
Some have no gate (aquaporins)
Studied with patch clamp technique and x-ray crystallography.

Question 10

Transporters

Answer 10

cross membrane by binding to proteins and being escorted/carried across. Big molecules.
Also nec for pump things against gradient. (need energy)
Primary active= use ATP (ex: na pump to put Na out)
Secondary active= often use energy from Na leaking into cell to pump something else out.

Question 11

Typical ICF/ECF compostions

Answer 11

Na in 14, out 140
K in 145 out 5
Cl in 5 out 145
A in 126 out 0
H20 in 55,000 out same