composition of cells

Question 1

volumes of plasma

Answer 1

3 liters

Question 2

volume extracellular fluid (ECF) ___ L

Answer 2

about 13 liters plus another 5 for the ‘third space’)

Question 3

volume intracellular fluid (ICF) ____ L

Answer 3

27 liters

Question 4

__% of all the chemical particles in the __ liters of body fluids are water molecules.

Answer 4

99%

45L

Question 5

Of the remaining 1%, about 5 out of every 6 are simple

Answer 5

inorganic ions, principally Na+, K+, and Cl-. All of the rest – all carbohydrates, proteins, nucleic acids, lipids, and so forth – constitute a very small fraction of the total.

Question 6

the fluids in the various body compartments _________;

Answer 6

do not have the same composition

the ion content of cells, for example, is vastly different from that of blood plasma.

Question 7

The boundary between the intra- and extracellular fluids is

Answer 7

plasma membrane

Question 8

extracellular fluid (ECF) comprises

Answer 8

plasma (~3 liters – plasma is whole blood without the cells), lymph, and interstitial fluid, all of which have nearly identical inorganic ion and water compositions.

Question 9

ECF we will mean the

Answer 9

interstitial fluid.

Question 10

Intracellular fluid (ICF) comprises

Answer 10

mitochondrial, vesicular, nuclear, and other subcompartments.

Question 11

ICF

Na+

Answer 11

14

Question 12

ICF K+

Answer 12

145

Question 13

ICF

Cl-

Answer 13

5

Question 14

ICF

A-n

Answer 14

126

Question 15

ICF

H2O

Answer 15

~55,000

Question 16

ECF

Na+

Answer 16

140

Question 17

ECF K+

Answer 17

5

Question 18

ECF

Cl-

Answer 18

145

Question 19

ECF

A-n

Answer 19

~0

Question 20

ECF H2O

Answer 20

~55,000

Question 21

membrane permeability

Na+

Answer 21

• (no)

Question 22

membrane permeability

K+

Answer 22

+ (yes)

Question 23

membrane permeability

Cl-

Answer 23

+ (yes)

Question 24

membrane permeability

A-n

Answer 24

• (no)

Question 25

membrane permeability | H2O

Answer 25

+ (yes)

Question 26

A note on the word permeable: _____ are permeable (or impermeable) to solute, while a _____ is permeant (or impermeant) or permeating (or nonpermeating)

Answer 26

membranes solute

Question 27

Membranes are mostly _____, which are_______ to water and charged substance

Answer 27

lipid molecules impermeable

Question 28

Lipids are also 'strong', in an _______. they can keep opposite _______.

Answer 28

electric sense. electric charges separated, without collapsing

Question 29

he cytoplasm of nearly all cells is electrically ______, compared to the ECF, because:

Answer 29

negative because cells contain a few more negative than positive ions.

Question 30

membrane potential, is caused by:

Answer 30

The excess anions create an electrical potential difference between the inside and the outside of the cell

Question 31

Membrane potential governs some:

Answer 31

vital cell processes, is wholly dependent on the integrity of the plasma membrane

Question 32

The ability of the membrane to withstand the imposed electric force (which has a whopping strength of about 100,000 volts/cm) is due to its_______

Answer 32

lipid composition.

Question 33

Many charged and polar molecules can cross membranes. Through:

Answer 33

1. channels | 2. transporters

Question 34

channels are ______ for particular ions

Answer 34

selective

Question 35

Sodium channels will pass ___________.

Answer 35

Na+ ions, but not K+, or Cl-, or other ions

Question 36

voltage gated channels depend on _____ The gate open when the membrane is _____

Answer 36

electric field across the membrane or membrane potential. the gates open when the membrane is depolarized

Question 37

depolarized means

Answer 37

cell is less negative inside

Question 38

aquaporins

Answer 38

channel that has no gate,

Question 39

pumping means work, energy can come from

Answer 39

1. directly from metabolism: primary active transport | 2. other sources: secondary

Question 40

active transport

Answer 40

pump molecules across a membrane to concentrate them on one side against their energy gradient.

Question 41

primary active transport example

Answer 41

Na+ pump, which extrudes Na+ from the cell and requires ATP

Question 42

secondary active transport,

Answer 42

use the energy released when Na+ ions leak into cells, and the energy released is captured and used to pump another ion across the membrane.

Question 43

Transporters work ______ than channels, usually not exceeding _____

Answer 43

thousands of times slower usually not exceeding several hundred transport cycles per second.

Question 44

by mutating only a few amino acid residues, a transporter of chloride and hydrogen ions, which pumps only about a hundred ions per second, can be turned into a _______

Answer 44

chloride-selective ion channel that allows the passage of tens of thousands of ions per second.

Question 45

From a functional standpoint, there are two kinds of proteins that mediate the transmembrane movements of charged substances:

Answer 45

channels and transporters.

Question 46

Understand the routes by which a given substance can traverse a membrane.

Answer 46

1. diffusion 2. passive transport: channels 3. active transport: transporters

Question 47

Diffusion:

Answer 47

This is primarily for water, which crosses membranes through special channels called aquaporins. Water always diffuses down its concentration gradient – there is no active transport for water.

Question 48

Passive transport: Channels

Answer 48

* Charged and polar substances can cross membranes through these * passive pores/tunnels through the membrane * selective for specific ions/substances * Some are gated, and substances can only pass when the gate is open

Question 49

Active transport: Transporters

Answer 49

• substances cross membranes by binding to proteins and being escorted across • big molecules, like glucose • selective • needed to pump molecules across a membrane, concentrating them on one side against their energy gradient – requires ATP

Question 50

dentify physical forces that can determine the gating properties of ion channels.

Answer 50

* Electric field (membrane potential) across the membrane * Mechanical stimulation (stretching of the membrane) * Binding of a particular chemical * Temperature

Question 51

in secondary active transport, the transporter uses

Answer 51

the energy released when Na+ ions leak | into cells: the energy released is captured and used to pump another ion across the membrane

Question 52

Ultimately, secondary active transport also depends on

Answer 52

metabolism.