Cell Transport Flashcards
passive transport
diffusion of a substances across a membrane with NO energy investment
- diffuse down the concentration gradient, high to low
- 3 types
Simple diffusion
- a type of passive transport
- through membrane with no transport or carrier protein necessary
- ex. O2, CO2, lipids
Osmosis
- passive transport
- diffusion of water
- water moves from [high]=> [low]; moves toward side with more solute
Facilitated diffusion
- for larger polar or charged molecules that can not pass through the membrane
- needs a transport protein, but still NO energy
- ex. glucose, Na+
Active transport
- requires energy
- moves against the concentration gradient using ATP hydrolysis
- use carrier proteins
Primary active transport
uses ATP directly
-ex. Na+/K+ pump
Secondary active transport (cotransport)
energy does not directly come from ATP, active transport of a solute INDIRECTLY drives transport of other substances
- diffusion of actively transported solute down its concentration gradient coupled with transport of 2nd substance against its own concentration gradient
ex. Proton pump uses ATP and indirectly powers the H+/sucrose cotransporter
Exocytosis
transport vesicles migrate to membrane, fuse with it, and release contents outside of the cell
-export products
Endocyctosis
cells take in macromolecules by forming vesicles from plasma membrance
Phagocytosis
Cell eating, engulfs a particle in a vacuole
-fuses with a lysosome to digest
pinocytosis
molecules dissolves in droplets are taken up; cell drinking= invagination
receptor-mediated endocytosis
bind specific solutes to receptors to trigger vesicle formation
-receptor proteins, receptors, molecules from extracellular fluid are transported in vesicles
Effects of cholesterol on fluidity
- at warm temperatures cholesterol restrains movement of phospholipids
- at cool temp it maintains fluidity by preventing tight packing
- acts as a buffer
peripheral proteins
bound to surface of the membrane
integral proteins
penetrate hydrophobic core
