Primary And Secondary Active Transport Flashcards
Primary active transport
Driven directly by hydrolysis of ATP
ATP hydrolysis catalysed by transporter
Primary active transporter examples:
Ca2+ ATPase (plasma membrane, drives Ca out cell)
F1F0 ATPase (ATP synthetase, reverse mode, uses H ions from ETC chain to produce ATP)
Na+K+ ATPase
Co transport
More than one type of ion or molecule transported on a membrane per reaction
Types of transporter
UNIport - one molecule through
SYMport - 2 molecules same direction
ANTIport - two molecules opposite directions
Na+ K+ ATPase actions
3 Na out
2 K into cell
(Antiporter)
What is type of ATPase is Na+K+ATPase and why?
P-type
ATP phosphorylates aspartate and produces phosphoenzym
What percent of BMR is used for Na+K+ pump?
25%
Structure of sodium pump
A subunit - binding sites for Na, K and Ouabain (inhibitor)
B subunit - glycoprotein that directs the pump to surface
What is the sodium pump important for?
Generating ion gradients to allow secondary transport
Creates high intracellular K+ - when diffuses out of cell via channels contributes to membrane potential
How much does the sodium pump actually contribute to membrane potential?
Only -5 to -10 mV
SMALL
High intracellular K more important
Secondary active transport
Driven indirectly by energy released of hydrolysis of ATP
Dissipation of gradients formed by another ion or substance provides energy for secondary active transport
Secondary active transport example
Na+K+ATPase pumps sodium out of cell
High concentration of sodium outside cell
Na+Ca2+ exchanger allows 3Na+ in and 1 Ca2+ out
(Antiport)
Importance of Na+K+ ATPase and type
Maintain cellular concentrations of Na+ and K+
Antiporter
Na+Ca2+ importance and type
Inward flow of Na (from sodium pumping out to create gradient) drives OUTWARD flow of Ca2+ up concentration gradient
Antiport
Na+ H+ exchange importance and type
Inward flow of Na (from sodium pumping out to create gradient) leads to outward flow of H+
= alkalisation
Antiport
Na+glucose co transport importance and type
Small intestine and kidney
Inwards flow of Na provides energy for glucose to go against concentration gradient
Symport
Examples of transporters in medicine (CFTR)
Cystic fibrosis - sodium pump creates gradient
Na+, 2Cl-K+ transporter allows all into cell
Potassium and sodium re used in pumps
Cl leaves via CFTR
mutation = CFTR doesnt work so no Cl leaves so no water leaves
= thick non motile mucus
Diarrhoea transporters
Sodium pump creates gradient Na+Cl-K+ enters cell via transporter Na and K leave Cl leaves via CFTR Vibrio cholera activates protein kinase Phosphorylates CFTR Increased activity More Cl leaves so more water leaves