Upload
lillie-stansberry
View
215
Download
2
Embed Size (px)
Citation preview
Chapter 5c
Membrane Dynamics
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
• 70 kg X 60% = 42 liters for avg 154 lb male
Aquaporin
Moves freely through cells by special channels of aquaporin
Figure 5-26
Osmosis and Osmotic Pressure
• Osmolarity describes the number of particles in solution
Volumesequal
Osmotic pressure isthe pressure that must beapplied to B to oppose osmosis.
Volumeincreased
Volumedecreased
Two compartments areseparated by a membrane that is permeable to water but not glucose.
Water moves byosmosis into the moreconcentrated solution.
Glucosemolecules
Selectivelypermeablemembrane
A B
1
3
2
Table 5-5
Osmolarity: Comparing Solutions
Hyper / Hypo / Iso are relative termsOsmolarity is total particles in solution
Normal Human body around 280 – 300 mOsM
Table 5-6
Tonicity
• Solute concentration = tonicity• Tonicity describes the volume change of a
cell placed in a solution
Figure 5-27a
Tonicity
• Tonicity depends on the relative concentrations of nonpenetrating solutes
Figure 5-27b
Tonicity
• Tonicity depends on nonpenetrating solutes only
Figure 5-28
Tonicity
• Tonicity depends on nonpenetrating solutes only
(a)
(b)
(c)
(d)
Cell
Solution
H2O
Plasmolysis and Crenation
• RBC’s
Table 5-7
Osmolarity and Tonicity
Table 5-8
Intravenous Solutions
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
4. Conductor versus insulator
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 Extracellular fluid
Figure 5-29c
Separation of Electrical Charges
• Resting membrane potential is the electrical gradient between ECF and ICF
Figure 5-30
Measuring Membrane Potential Difference
The voltmeter
Cell
The chart recorder
Saline bath
A recording electrode
Input
The ground ( ) or referenceelectrode
Output
Figure 5-31a
Potassium Equilibrium Potential
Artificial cell
(a)
Figure 5-31b
Potassium Equilibrium Potential
(b)
K+ leak channel
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
Concentrationgradient
Electricalgradient
(c)
Figure 5-32
Sodium Equilibrium Potential• Single ion can be calculated using the Nernst Equation
• Eion = 61/z log ([ion] out / [ion] in)
150 mM0 mV
15 mM+60 mV
Figure 5-33
Resting Membrane Potential
Extracellular fluid0 mV
Intracellular fluid-70 mV
Figure 5-34
Changes in Membrane Potential
• Terminology associated with changes in membrane potential
PLAY Interactive Physiology® Animation: Nervous I: The Membrane Potential
1
Low glucose levels in blood.
No insulinsecretion
Metabolismslows.
ATPdecreases.
ATPMetabolismGlucose
Cell at restingmembrane potential.No insulin is released.
KATP
channels open.
Insulin in secretory vesicles
K+ leaks out
of cellVoltage-gated Ca2+ channel closed
GLUT transporter
(a) Beta cell at rest
2 3 4 5
Figure 5-35a
Insulin Secretion and Membrane Transport Processes
1
Low glucose levels in blood.
Glucose
(a) Beta cell at restFigure 5-35a, step 1
Insulin Secretion and Membrane Transport Processes
1
Low glucose levels in blood.
Metabolismslows.
MetabolismGlucose
GLUT transporter
(a) Beta cell at rest
2
Figure 5-35a, steps 1–2
Insulin Secretion and Membrane Transport Processes
1
Low glucose levels in blood.
Metabolismslows.
ATPdecreases.
ATPMetabolismGlucose
GLUT transporter
(a) Beta cell at rest
2 3
Figure 5-35a, steps 1–3
Insulin Secretion and Membrane Transport Processes
1
Low glucose levels in blood.
Metabolismslows.
ATPdecreases.
ATPMetabolismGlucose
KATP
channels open.
K+ leaks out
of cell
GLUT transporter
(a) Beta cell at rest
2 3 4
Figure 5-35a, steps 1–4
Insulin Secretion and Membrane Transport Processes
1
Low glucose levels in blood.
No insulinsecretion
Metabolismslows.
ATPdecreases.
ATPMetabolismGlucose
Cell at restingmembrane potential.No insulin is released.
KATP
channels open.
Insulin in secretory vesicles
K+ leaks out
of cellVoltage-gated Ca2+ channel closed
GLUT transporter
(a) Beta cell at rest
2 3 4 5
Figure 5-35a, steps 1–5
Insulin Secretion and Membrane Transport Processes
1
Glycolysisand citric acid cycle
ATP
Ca2+ signal triggersexocytosis and insulin is secreted.
Ca2+
Ca2+
High glucose levels in blood.
Metabolismincreases.
ATPincreases.
Glucose
Cell depolarizes andcalcium channelsopen.
KATP channels close.
Ca2+ entry acts as anintracellularsignal.
GLUT transporter
(b) Beta cell secretes insulin
2 3 4 5
6
7
Figure 5-35b
Insulin Secretion and Membrane Transport Processes
1
High glucose levels in blood.
(b) Beta cell secretes insulinFigure 5-35b, step 1
Insulin Secretion and Membrane Transport Processes
Glucose
1
Glycolysisand citric acid cycle
High glucose levels in blood.
GLUT transporter
(b) Beta cell secretes insulin
2
Figure 5-35b, steps 1–2
Insulin Secretion and Membrane Transport Processes
Glucose
Metabolismincreases.
1
Glycolysisand citric acid cycle
ATP
High glucose levels in blood.
GLUT transporter
(b) Beta cell secretes insulin
2 3
Figure 5-35b, steps 1–3
Insulin Secretion and Membrane Transport Processes
Glucose
Metabolismincreases.
ATPincreases.
1
Glycolysisand citric acid cycle
ATP
High glucose levels in blood.
KATP channels close.
GLUT transporter
(b) Beta cell secretes insulin
2 3 4
Figure 5-35b, steps 1–4
Insulin Secretion and Membrane Transport Processes
Glucose
Metabolismincreases.
ATPincreases.
1
Glycolysisand citric acid cycle
ATP
Ca2+
High glucose levels in blood.
Cell depolarizes andcalcium channelsopen.
KATP channels close.
GLUT transporter
(b) Beta cell secretes insulin
2 3 4 5
Figure 5-35b, steps 1–5
Insulin Secretion and Membrane Transport Processes
Glucose
Metabolismincreases.
ATPincreases.
1
Glycolysisand citric acid cycle
ATP
Ca2+
Ca2+
High glucose levels in blood.
Cell depolarizes andcalcium channelsopen.
KATP channels close.
Ca2+ entry acts as anintracellularsignal.
GLUT transporter
(b) Beta cell secretes insulin
2 3 4 5
6
Figure 5-35b, steps 1–6
Insulin Secretion and Membrane Transport Processes
Glucose
Metabolismincreases.
ATPincreases.
1
Glycolysisand citric acid cycle
ATP
Ca2+ signal triggersexocytosis and insulin is secreted.
Ca2+
Ca2+
High glucose levels in blood.
Cell depolarizes andcalcium channelsopen.
KATP channels close.
Ca2+ entry acts as anintracellularsignal.
GLUT transporter
(b) Beta cell secretes insulin
2 3 4 5
6
7
Figure 5-35b, steps 1–7
Insulin Secretion and Membrane Transport Processes
Glucose
Metabolismincreases.
ATPincreases.
Summary
• Mass balance and homeostasis• Law of mass balance• Excretion• Metabolism• Clearance• Chemical disequilibrium• Electrical disequilibrium• Osmotic equilibrium
Summary
• Diffusion• Protein-mediated transport• Roles of membrane proteins• Channel proteins• Carrier proteins• Active transport
Summary
• Vesicular transport• Phagocytosis• Endocytosis• Exocytosis
• Transepithelial transport
Summary
• Osmosis and tonicity• Osmolarity• Nonpenetrating solutes • Tonicity
• The resting membrane potential• Insulin secretion