2. Review
Cell membrane has selective permeability.
_________CAN across membrane
_________CANNOT across membrane.
TO MAINTAIN
HOMEOSTASIS,
WHAT TO DO?
TRANSPORT
5. Passive Transport
No energy required
Movement is due to gradient
differences in concentration, charge
Move to equalize gradient
High moves toward low
6.
7. Simple Diffusion
Does not require energy.
Move from high to low cont.
Until evenly distributed.
Example: O2,CO2,fatty acids, steroids,
glycerol.
8. Facilitated Diffusion
A type of passive transport that does not
require energy to move molecules.
Direction depends on conc. gradient.
Use transport proteins to move molecules
that are large or charged(ions).
Large polar: glucose and amino acids
Ions: Na+, Cl-
Carrier proteins & ion channels.
9.
10. Ion Channel Proteins
Form hydrophilic pores to transport
inorganic ions across the membrane.
Ion channels are selective and gated
11. Types of Ion Channels
leak channel: always open
Based on stimulus that can open/close
gates:
I. Voltage-gated ion channels
II. Ligand-gated ion channels
III. Mechanically-gated ion channels
16. Aquaporin
Water channel proteins
Embedded in the
membrane.
Increases the
permeability to water
No energy is required
(passive)
Kidney distal and
collecting tubules
19. Cont’d
Carrier-mediated transport exhibits the
properties of specificity, competition,
and saturation.
Saturation: rate of transport limited by
number of carrier proteins.
Blood-brain barrier, GIT mocusa.
20.
21. Classification
Carrier proteins transport either one or
two types of molecules:
Uniport: one type, bidirectionally
Two types (couple)
I. Symport: both in same direction (co-)
II. Antiport: in opposite direction
(counter-)
24. Active Transport
Molecular movement against gradient
Requires energy
Function:
1. Maintain the chemical and electrical
charge at rest.
2. Intake of nutrient substances.
3. Remove waste and secretory products.
25. Active Transport
Large molecules(non-lipid soluble), ions
Based on the source of energy used for
transport:
I. Primary active transport
(pump/ATPase)
II. Secondary active transport
26. Primary Active Transport
Transmembrane carrier protein.
Use the energy directly from hydrolysis of ATP
Conformational change
Examples:
1. Na+/K+ pump
2. Ca2+ pump
3. H+/K+ ATPase
28. Sodium Potassium Pump
Present in all eukaryotic cells
Functions:
1. Maintain sodium potassium cont.
difference across the cell membrane.
2. Maintain volume of the cell.
3. Causes negative electrical charge inside the
cell.
4. Active the carrier protein.
29. Inhibition of Na+/K+ Pump
The pump requires binding of Na+ and K+
and ATP for its operation. If cont. of any
substances is low Dysfunction.
Metabolic poisons -----ATP
Cardiac drugs: ouabain and digitalis
Low temp.
Less O2
30.
31. Calcium Pump
Ca2+ is extremely low
in cytosol
Function:
1. Maintain high cont. in
ECF
2. Helps in storage of Ca2+
in sarcoplasmic
reticulum needed for
instant muscle
contraction.
34. Hydrogen Potassium ATPase
Gastric glands- parietal cells- HCl secretion-
pumps H+ into the gastric lumen, meantime
K+ inside the cell.
Renal tubules- intercalated cells in the late
distal tubules and cortical collecting ducts-
secretion of H+ & reabsorption of K+
35. Secondary Active Transport
ATP provides the
energy for transport
indirectly.
Uses energy of an
electrochemical
gradient produced
originally by primary
active transport
44. Vesicular Transport
Transport of membrane bounded
substances moving across plasma
membrane.
Require energy.
Classification:
I. Exocytosis
II. Endocytosis
45. Endocytosis
Movement of large material
Particles ; Organisms ; Large molecules
Movement is into cells
Types of endocytosis
I. Phagocytosis— “Cell eating”
II. Pinocytosis– “Cell drinking”
III. Receptor-mediated endocytosis- specific
particles, recognition.
48. Exocytosis
Reverse of endocytosis
Cellular secretion
Process:
I. Vesicle moves to
cell surface
II. Membrane of
vesicle fuses
III. Materials expelled
49. Cont’d
Substances and processes involved:
I. Secretion of proteins like enzymes,
hormones, antibodies from cells
II. Release of neurotransmitter from
presynaptic neurons
III. Recycling of plasma membrane
50. Associated Diseases
Mutations affecting membrane proteins can
cause diseases:
1. Familial hypercholesterolemia is due to
mutations in the gene encoding the LDL
receptor.
2. Cystic fibrosis is due to mutation in the
gene encoding CFTR, a chloride
transporter.
51.
52. References :
oAlberts B, Johnson A, Lewis J, et al: Molecular Biology of
the Cell,5th ed. Garland Science, 2008.
ohttps://www.slideshare.net/biochem/membrane-
transport-ppt-biochemistry
oVance DE, Vance J (editors): Biochemistry of Lipids,
Lipoproteins and Membranes, 5th ed. Elsevier, 2008.
oSakai, Hideki; Fujii, Takuto; Takeguchi, Noriaki (2016).
"Chapter 13. Proton-Potassium (H+/K+) ATPases:
Properties and Roles in Health and Diseases.
oDoherty GJ, McMahon HT: Mechanisms of endocytosis.
Annu Rev Biochem 2009;78:857.
oLodish H, Berk A, Kaiser CA,Guyton, Arthur C – Hall,
John E. Textbook of Medical Physiology. 11th
edition. 2006. ISBN 0-7216-0240-1.
