|
Cell Membrane Proteins
general
not needed where simple diffusion possible (e.g. O2)
types of passive cross membrane activity
simple diffusion
diffusion through membrane
osmosis
water passing through a thin protein channel
facilitated difusion
large protein channel allows diffusion
types of active cross membrane activity
active transport
uses ATP via ATP Hydrolosis
energy sources
ATP
created through oxidative phosphorylation
oxidation-reduction reactions
in mitochondria
process
food
glycolysis, etc
krebs cycle
product of above 2 substrates
oxidative phosphorylation
ADP -> ATP
membrane pumps
use energy to move substances against the concentration gradient
move things in a low concentration to a high concentration
enzymatic activity that consumes energy (ATP)
primary active transport
can cause secondary active transport
example - leaking back in of same ion pumped out
most ATP in body is used as supply for pumps
most pumps move cations (positive ions, like NA+ K+ CA++)
types
ATP driven transport - ATPase pump
ATP -> via ATPase release phosphor -> ADP
subtypes
F0F1
made of 8 subunits
in mitochondria
used for moving H+
V0V1
made of 8 subunits
in lysosomes
used for moving H+
P-Type
subtypes
NA+K+Â ATPase
exchanges NA for K
muscle and nerve cells
H+K+Â ATPase
exchanges H for K
stomach and kidney membranes
SERCA CA++ ATPase
SERCA = smooth endoplasmic reticulum CA Pump
in sarcoplasmic reticulum (muscle cells)
actively remove calcium from cell
ABC-Transporters
as a family most diverse
subtypes
MDR
transports chemotherapy drugs in to cell
CFTR
found in respiratory and pancreatic cells
Cystic-fibrosis transporter
transports chloride
MDR2
in liver cell
bile secretion
membrane channels
integral membrane proteins
contain pores
sometimes open, some times closed
some cooperate with pumps
participate in regulating electrical potential of cell
main channels
sodium
potasium
calcium
some can be gated
can be one sided or two
active (all open) or inactive (all closed)Â state
stimulus to open can be
electrical
chemical
called ligans
channel then called receptors
photo
mechanical
memrane carriers
qualities
made of singe polypeptides
usually alpha helix shape
spiral
called a secondary structure
some beta sheet
flat squigal
called a secondary structure
if you combine 2 structures - tertiary structure
if you combine 2 tertiary structures you get a quatenary structure
these are "integral proteins" since they cross membrane
they do not change substrates in process
types
uniporter
facilitatated diffusion of one substrate
example Glucose Transporter (GLUT)
GLUT 1
most cells
in particular red blood celss
GLUT 2
liver cells
pancreas beta cells
hypothalmus
small intestine
GLUT 3
placenta
nerve cells
testies
GLUT 4
heart cells
skeleton
muscles
GLUT 5
small intestine
sperm
symporters
facilitates a primary and secondary substrate togetherÂ
SGLT1
Sodium + Glucose transporter
small intestines
NKC1
Sodium Potassium 2-Chlorides transporter
in kidney, intestines and lungs
antiporter
one substrate in one direction the other in the opposite direction
NHE1
NA+ / H+
acid base (PH) balance
kidney and intestines
Band 3
in red blood cells
HCO3- / CL-
acid base (PH) balance
| 
