Lecture 8 - Movement Against the gradient Flashcards
What is ATP (function and structure)
adenosine triphosphate
function: source of energy for use and storage at the cellular level
structure: nucleoside triphosphate, consists of a nitrogenous base (adenine), a ribose sugar, and 3 serially bonded phosphate groups
What molecule is required to move solutes against their electrochemical gradient?
ATP
What is direct active transport?
transport that involved ATP to directly pump a solute across a membrane against its gradient
What is indirect active transport?
transporting a solute against its electrochemical gradient by coupling its transport to the facilitated diffusion of a second solute (usually an ion)
ex: symporters and antiporters
How does amino acid absorption require both direct and indirect active transport?
indirect: amino acid symporters move amino acids into enterocytes
direct: ATPase pumps maintain ion gradients
enterocytes want to keep:
- high concentration of H+ and Na+ in gut lumen
- low concentration of AAs in gut lumen
Why are ATP-driven pumps also called transport ATPases?
because they hydrolyze ATP to ADP and a phosphate and use this released energy to pump ions or other solutes across a membrane
What are the 4 types of ATPases?
- P-type pump
- ABC transporter
- V-type proton pump
- F-type ATP synthase
Why are p-type ATPases called that?
they phosphorylate themselves during the pumping cycle => this induces a conformational change
What are the 4 types of p-ATPases?
P1: transport heavy metals
P2: maintain electrochemical gradients
P3: membrane potential, plants and fungi
P4: a flippase, moves phospholipids
What do proton pump inhibitors do?
they prevent excess stomach acidification
What are the important P2-ATPases?
Ca2+/H+: in sarcoplasmic reticulum or plasma membrane, found in muscles of eukaryotes, keep [Ca+] low in cytosol
Na+/K+: in plasma membrane of animals, maintain membrane potential (-60mV)
H+/K+: in plasma membrane of animals, pumps H+ to acidify stomach
Ca2+ pump/ Ca2+ ATPase
located in SR membrane of muscle cells
- SR is a specialized type of ER that forms a network of tubular sacs in the muscle cell cytoplasm; serves as intracellular store of Ca2+
Na+/K+ ATPase
- maintains electrochemical ion gradients in all cells by continually pumping Na+ ions out of cell and K+ ions into cell
- has 2 conformations => E1 and E2
- binds 3 Na+ ions and 2 K+ ions
- potassium binding site made of oxygen
Vacuolar-ATPase
- two rotary motors
- ATP-driven motor turns an axle => turns a second motor that pumps protons across the membrane
- linkers hold complex together
- pumps H+ to increase acidity in specific organelles (i.e., vacuoles, lysosomes)
- not phosphorylated
- V-ATPase is regulated by separating the ATP-powered motor from the proton pumping motor
F-type ATPases (= ATP synthases)
- move H+
- located in inner mitochondrial membrane of eukaryotes
- uses H+ gradient to drive ATP synthesis
- F0 is an electric motor powered by the flow of H+
- F1 motor is a chemical motor powered by ATP
- F1 motor joins ADP to Pi by force - 2 motors are connected by a stator
