active and vesicular transport by dr nazish. a four-year-old boy severely dehydrated child presented...
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Active and vesicular Transport
By Dr Nazish
A four-year-old boy severely dehydrated child presented with one day history of severe diarrhea and vomiting and a temperature up to 40°C (104°F).
Over the previous 12 hours the child had watery, bowel movements every 20 Minutes .
Mother gave the history that vommitting is now settled but diarrhea is still there.
On physical examination, the patient's temperature was 39.6°C , his respiratory rate was 28 and his pulse rate was 140 .
The patient weighed 15 kg (33 lb) and had a blood pressure measurement of 90/60 mm Hg. He was alert but irritable, with a dry mouth . Bowel sounds were
increased, and the abdominal examination was otherwise normal.The child was admitted to the peadriatic OPD and was given an intravenous
antibiotic as well as intravenous saline.
Condition of the child improved and was discharged in the morning. Along with an oral antibiotic cover for 5 days the doctor also advised that the child
should be continued with ORS for atleast 2 days.
Active transport
• It is the movement of the molecules against the electrical, concentration or the pressure gradient with the use of energy.
Active transport is a type of assisted transport.• A substance moves against its concentration
gradient.
• It requires a carrier molecule.
• Primary active transport requires the direct use of ATP to drive a sodium-potassium pump.
• Secondary active transport is driven by a concentration gradient of ions established by primary active transport.
PRIMARY ACTIVE TRANSPORT
ICF
ECF
(Passive)Na+–K+
pump (Active)
(Active)(Passive)K+ channelNa+ channel
Figure 3.29 Page 92
= Sodium (Na+) = Potassium (K+) = Phosphate
When open to the ECF, the carrier drops off Na+ on its high-concentration side and picks up K+ from its low-concentration side
Phosphorylated conformation Yof Na+–K+ pump has high affinityfor Na+ and low affinity for K+ when exposed to ICF
When open to the ICF, the carrier picks up Na+ from its low-concentration side and drops off K+ on its high-concentration side
Dephosphorylatedconformation X of Na+–K+ pump has high affinity forK+ and low affinity for Na+when exposed to ECF
ICF
ECF
Figure 3.22Page 82
Importance of Na+-K+ Pump
• Establish Na+-K+ concentration gradient across membrane generation of membrane potential.
• Regulate cell volume by controlling concentration of solutes inside the cells
• Pump energy is used indirectly for co-transport of other materials, i.e., glucose, amino acids
What would be the effect on cell volume, if the sodium
pottasium pump is damaged?
SECONDARY ACTIVE TRANSPORT
Secondary active transport
• Energy is required in the entire process but not directly
• Transportation against conc gradient
• Using carrier with more than one binding site
Lumen ofintestine
No energyrequired
Cotransport carrier Luminal border
Epithelial cell liningsmall intestine
Basolateralborder
Energyrequired
Tightjunction
Na+–K+ pump
Blood vessel
= Sodium = Potassium = Glucose = Phosphate
Figure 3.23
Page 84
No energyrequired Glucose
carrier
CO TRANSPORT
• Sodium glucose co transport in intestinal and renal cells
COUNTER TRANSPORT
SODIUM HYDROGEN COUNTER TRANSPORT
SODIUM CALCIUM COUNTER TRANSPORT
A four-year-old boy severely dehydrated child presented with one day history of severe diarrhea and vomiting and a temperature up to 40°C (104°F).
Over the previous 12 hours the child had watery, bowel movements every 20 Minutes .
Mother gave the history that vommitting is now settled but diarrhea is still there.
On physical examination, the patient's temperature was 39.6°C , his respiratory rate was 28 and his pulse rate was 140 .
The patient weighed 15 kg (33 lb) and had a blood pressure measurement of 90/60 mm Hg. He was alert but irritable, with a dry mouth . Bowel sounds were
increased, and the abdominal examination was otherwise normal.The child was admitted to the peadriatic OPD and was given an intravenous
antibiotic as well as intravenous saline.
Condition of the child improved and was discharged in the morning. Along with an oral antibiotic cover for 5 days the doctor also advised that the child
should be continued with ORS for atleast 2 days. What would be the effects on tonicity of the body fluids of this child?Explain the effects of change of tonicity on the size and shape of body cells.What type of IV fluid is given to the child and why?
How does ORS therapy works? Explain the physiological basis of mechanism of action of ORS in treatment of dehydration..
VESICULAR TRANSPORT
Other kinds of assisted transport are:
• Vesicular transport - Materials move in or out of the cell wrapped in a membrane.
• Need energy
• Examples of vesicular transport are endocytosis and exocytosis.
• By endocytosis substances move into the cell.
• Exocytosis is the reverse process.
Particularprotein
Nucleusof cell
Surface receptor site
Endocytoticpouch
Endocytoticvesicle
Receptor-mediated endocytosis
White blood cell
Pseudopod Bacterium
Phagocytic vesicle
Lysosome
Phagocytosis
Click to view animation.
Phagocytosis
Animation
Click to view animation.
Secretion
Animation
Exocytosis
Characteristics of methods of membrane transport: DIFFUSION
Until Steady state, or stopped by opposing hydrostatic pressure, or cell dies
Passive Water onlySpecial case of osmosis
Until Steady state reached
Passive Specific small ions, Na,K,Cl
Through protein
Continues until gradient is abolished
Passive Nonpolar molecules of any size
O2, CO2, FA
Through lipid bilayer
Limits to transport
Energy requirements & force producing movements
Substances involved
Method of transport
Characteristics of methods of membrane transport: CARRIER MEDIATED TRANSPORT
Transport maximum Cotransport carrier saturation
Active Specific polar molecules and ions for which cotransport carriers available
Secondary ACTIVE TRANSPORT
Transport maximum. Saturation
Active Specific small ions, Na,K,Cl
PRIMARY ACTIVE TRANSPORT
Displays a Transport maximum (Tm). Saturation
Passive Specific polar molecules
glucose
Facilitated DIFFUSION
Limits to transport
Energy requirements & force producing movements
Substances involved
Method of transport
Characteristics of methods of membrane transport: VESICULAR TRANSPORT
Secretion triggered by neural or hormonal stimuli
ATP required Increase in cytosolic Ca induces fusion
Secretory products Large molecules passing through Membrane recycling
EXOCYTOSIS
Necessitates binding to specific receptor site
ATP required
Active
Multimolecular particles
Phagocytosis
Control poorly understood
ATP requiredSmall volume of ECF may be bound with proteins
ENDOCYTOSIS
Pinocytosis
Limits to transport
Energy requirements & force producing movements
Substances involved
Method of transport