Membrane Dynamics

(1)

Chapter 5c

(2)

Figure 5-25

The Body Is Mostly Water

• Distribution of

water volume in

the three body

fluid

compartments

• 1 liter water

weighs 1 kg or

2.2 lbs

(3)

Aquaporin

Moves freely through

cells by special

(4)

Figure 5-26

Osmosis and Osmotic Pressure

• Osmolarity

describes the

number of

particles in

solution

Volume s equal

Osmotic pressure is the pressure that must be applied to B to oppose osmosis. Volume increase d Volume decrease d

Two compartments are

separated by a membrane that is permeable to water but not glucose.

(5)

Table 5-5

Osmolarity: Comparing Solutions

Hyper / Hypo / Iso are relative terms

Osmolarity

is total particles in solution

(6)

Table 5-6

Tonicity

• Solute concentration = tonicity

(7)

Figure 5-27a

Tonicity

• Tonicity depends on the relative

(8)

Figure 5-27b

Tonicity

(9)

Figure 5-28

Tonicity

• Tonicity depends on

nonpenetrating

solutes

only

(a )

(b)

(c )

(d )

Cel l

Solution

(10)

Plasmolysis and Crenation

(11)

Table 5-7

(12)

Table 5-8

(13)

Electricity Review

1. Law of conservation of electrical charges

2. Opposite charges attract; like charges repel

each other

3. Separating positive charges from negative

charges requires energy

(14)

Figure 5-29b

Separation of Electrical Charges

• Resting membrane potential is the electrical

gradient between ECF and ICF

(b)_{Cell and solution in chemical and electrical}

disequilbrium.

Intracellular fluid

(15)

Figure 5-29c

Separation of Electrical Charges

(16)

Figure 5-30

Measuring Membrane Potential Difference

The voltmeter

Cel l

The chart recorder Saline

bath A recording electrode

Input

The ground ( ) or reference

electrode

(17)

Figure 5-31a

Potassium Equilibrium Potential

Artificial cell

(18)

Figure 5-31b

Potassium Equilibrium Potential

(b)

(19)

Figure 5-31c

Potassium Equilibrium Potential

• Resting membrane potential is due mostly

to potassium

• K

+

can exit due to [ ] gradient, but electrical gradient will

pull back; when equal resting membrane potential

Concentratio

n

gradient

Electrical

gradient

(20)

Figure 5-32

Sodium Equilibrium Potential

• Single ion can be calculated using the Nernst Equation

• E

ion

= 61/z log ([ion]

out

/ [ion]

in)

150 mM

0 mV

15 mM

(21)

Figure 5-33

Resting Membrane Potential

Extracellular

fluid

0 mV

Intracellular

fluid

(22)

Figure 5-34

Changes in Membrane Potential

• Terminology associated with changes in

membrane potential

PL

AY

Interactive Physiology

®

_Animation:

_{Nervous I:}

(23)

1

Low glucose levels in blood.

No insulin secretion Metabolism slows. ATP decreases. AT P Metabolism

Glucos

e

Cell at resting

membrane potential. No insulin is released. K_ATP

channels open.

Insulin in secretory vesicles

K+_leaks

out

of cell Voltage-gated _Ca2+_channel

closed

GLUT transporter

(a) Beta cell at rest

2 3 4 5

Figure 5-35a

(24)

1

Glucos

e

Figure 5-35a, step 1

(25)

1

Metabolism slows.

Metabolism

Glucos

e

(a) Beta cell at rest 2

Figure 5-35a, steps 1–2

(26)

1

Metabolism slows.

ATP

decreases.

AT P Metabolism

Glucos

e

2 3

(27)

1

Metabolism slows. ATP decreases. AT P Metabolism

Glucos

e

K_ATP channels open.

K+_leaks

out of cell

2 3 4

(28)

1

No insulin secretion Metabolism slows. ATP decreases. AT P Metabolism

Glucos

e

Cell at resting

membrane potential. No insulin is released. K_ATP

channels open.

Insulin in secretory vesicles

K+_leaks

out

of cell Voltage-gated _Ca2+_channel

closed

2 3 4 5

(29)

1

Glycolysis and citric acid cycle

ATP

Ca2+ signal triggers exocytosis and insulin is secreted. Ca2+ Ca2+ High glucose

levels in blood.

Metabolism increases. ATP increases. Glucos e

Cell depolarizes and calcium channels open.

K_ATP channels close.

Ca2+ entry acts as an intracellular signal.

(b) Beta cell secretes insulin

2 3 4 5

6

7

Figure 5-35b

(30)

1

High glucose levels in blood.

Figure 5-35b, step 1

Insulin Secretion and Membrane Transport

Processes

(31)

1

Glycolysis and citric acid cycle High glucose

(b) Beta cell secretes insulin 2

Figure 5-35b, steps 1–2

Insulin Secretion and Membrane Transport

Processes

Glucos e

(32)

1

ATP High glucose

2 3

Insulin Secretion and Membrane Transport

Processes

Glucos e

Metabolism increases.

ATP

(33)

1 Glycolysis and citric acid cycle ATP High glucose

2 3 4

(34)

1 Glycolysis and citric acid cycle ATP Ca2+ High glucose levels in blood.

2 3 4 5

(35)

1 Glycolysis and citric acid cycle ATP Ca2+ Ca2+ High glucose

2 3 4 5

6

(36)

1

ATP

Ca2+ signal triggers exocytosis and insulin is secreted. Ca2+ Ca2+ High glucose