Cell Transport Flashcards
cell membrane, passive, active
amphipathic
hydrophobic and hydrophilic sections
peripheral proteins
protein that temporarily attaches to membrane
how does cholesterol contribute to cell membrane
controls fluidity
transmembrane proteins
umbrella term
- protein that goes THROUGH the membrane allowing molecules to pass thru
diffusion
small molecules moving along their conc grad without expending energy
what factors affect rate of diffusion
- conc grad: low conc grad = less collisions = slower diffusion
- distance (thickness)
- SA:V ratio (area involved)
- barriers (polarity - likes dissolves likes, size - larger= harder to diffuse, state of transporters)
what properties would maximize diffusion across a cell
high S/A, low Volume
- more surface area = more collisions = more diffusion
- sphere shape is good
conc gradient
difference in conc
osmosis
movement of water
- water ALWAYS moves along its own conc grad
- water is solvent
how does water cross the cell membrane as a polar molecule
aquaporins
aquaporins: what are they and how do they work
specific to water
- non polar aa outside and middle and polar top and bottom to pull water in
- thru the interactions with a.a inside tube water is pushed/pulled thru
- 6 alpha-helixes in circle shapei
isotonic
equal amounts of solute and solvent
- no net movement
hypertonic
more solute OUTSIDE cell
- net movement OUT
hypotonic
more solute INSIDE cell
- net movement IN
how do really large molecules cross the cell membrane
facilitated diffusion
- diffusion thru transport proteins
general characteristics of active transport
- requires energy
- pumping sols AGAINST conc grad
- always involves carrier proteins
- proteins change conformation with ATP
what are the diff types of membrane transporters
- uniport
- symport
- antiport
what type of substances need to move across the membrane against their conc grad
ions, glucose, gastric acid
- critical for a cell to maintain certain concentrations for homeostasis
explain how the Na/K pump works
- pump is facing the intercellular side, 3 Na and ATP come in and bind to the pump
- PO4 from ATP attaches and changes shape (phosphorylated pump), making pump turn around and face the extracellular side
- 2 K ions bind while the 3 Na leave, PO4 detaches changing pump shape AGAIN
- the 2 K ions leave the pump and enter the intercellular membrane
coupled transport
active and passive transport combined
- use active transport to create conc grad the equals out thru diffusion
cotransport
piggybacking
- molecule piggy backs off another and gets free ride inside
- ex: glucose - H
endocytosis
bringing molecules in bulk
exocytosis
removing molecules by fusing it out membrane thru vesicles
phagcytosis
cell eating
- bringing in large solids
pinocytosis
cell drinking
- bringing in small amounts of fluid
what is the difference between channel proteins and carrier proteins
CHANNEL: continuous passage, passive transport (substances move along conc grad)
- can be pores (always open) or gated (opens and closes based on stimulus)
CARRIERS: not continuous, has at least 2 gates that dont open simultaneously (unlike gated channels)
- slower than channels
ionophores
transport ions
glycolipds/glycoproteins
Carbohydrate chains attached to lipids (glycolipids) or proteins (glycoproteins) often are involved in cell recognition and signalling processes
