Lecture 16: Cell Processes and Transport Across Cell Membranes

Flashcards to review transmembrane transport, channel and carrier mediated transport, and osmosis.

__ transport does not directly use a transport protein.

Non-mediated

__ transport moves materials with the help of a transport protein.

Mediated

__ transport moves substances down their concentration or electrochemical gradients with only their kinetic energy.

Passive

__ transport uses energy to drive substances against their concentration or electrochemical gradients.

Active

__ transport moves materials across membranes in small vesicles either by exocytosis or endocytosis.

Vesicular

Nonpolar, hydrophobic molecules like oxygen, carbon dioxide, nitrogen, fatty acids, steroids, small alcohols, ammonia and fat-soluble vitamins (A, E, D and K) are examples of __ transport.

Non-mediated

Ions do not bind to the __ pore, so transport is very rapid.

channel

The channel forms a __ filled pore that shields the ions from the hydrophobic core of the lipid bilayer.

water

The __ amino acids lining the pore determine the selectivity of the channel to ions.

specific

__ contain gates that control opening and closing of the pore

Channels

Stimuli that can control (gate) channel opening and closing include: voltage, ligand binding, cell volume (stretch), pH, __.

phosphorylation

The substrate to be transported directly interacts with the __ protein.

transporter

Transport proteins exhibit __ , inhibition, competition, saturation (transport maximum).

specificity

Mediated transport can be passive (__ ) or active

facilitated

During facilitated diffusion of glucose, glucose binds to transport protein (__ ).

GLUT

During facilitated diffusion of glucose, kinase enzyme reduces glucose concentration inside the cell by transforming glucose into __.

glucose-6-phosphate

__ active transport: energy is directly derived from the hydrolysis of ATP.

Primary

A typical cell uses __ % of its energy (ATP) on primary active transport.

30

__ active transport: energy stored in an ionic concentration gradient is used to drive the active transport of a molecule against its gradient.

Secondary

3 Na+ ions are __ from cell as 2 K+ brought into cell by the Na/KATPase.

removed

The Na pump maintains a __ concentration of Na+ and a high concentration of K+ in the cytosol

low

Na+ __ or exchangers: Na+ ions rush inward, Ca2+ or H+ pushed out

antiporter

Na+ __ or cotransporters: Glucose or amino acids rush inward together with Na+ ions

symporters

__ - diffusion of H2O across membranes.

Membrane Osmosis

__ is mediated by the aquaporins (9 isoforms).

Pf