Lecture 6 Review Sheet: Passive and Active Transport and Secretory Pathways

Flashcards covering passive transport, active transport mechanisms (MFS, ABC), and the three types of secretory pathways based on Lecture 6 notes.

Facilitated diffusion

A form of passive transport for ions and polar molecules that always transports from highest to lowest concentration using channels or porins in the membrane.

Uniport

A secondary active transport mechanism that uses electrical potential from the PMF to pull cations into the cell or onions out.

Major facilitator superfamily (MFS)

A type of secondary active transport that uses energy from the $H^+$ gradient to move materials against the concentration gradient.

Symport

A transport mechanism where the direction of transport is the same, such as when $H^+$ and another material enter the cell at the same time.

Antiport

A transport mechanism where the transport direction of the materials is opposite.

Rocker-switch model

A three-step mechanism for secondary active transport: 1) binding a charged ion to lock the transporter; 2) binding another material to R-groups to point the transporter inwards; 3) the protein returns to its original tertiary structure.

Primary active transport

Transport that moves materials from lower to higher concentration using ATP as an energy source.

ATP binding Cassette (ABC)

A primary active transport system that uses ATP to bind a periplasmic binding protein (PPB) to open a transport channel for solutes.

Periplasmic binding protein (PPB)

A protein that, when bound in the ABC system, makes transport irreversible because of its use of ATP as an energy source.

General Secretory Pathway

A system designed to get proteins out of the cell by crossing the inner (cytoplasmic) membrane.

SecYEG (translocon)

A transport protein complex in which proteins must remain unfolded in their primary ($1^{\circ}$) structure to pass through.

TAT system

A secretion system that moves fully folded proteins across the inner membrane.

Type I secretory system

A class of export transporter that simultaneously crosses both membranes and is often used by bacteria as a pump for antibiotic resistance.

Type II secretory system

A two-step transport process that has a periplasmic intermediate and uses a complex protein to cross from the periplasmic membrane through the outer membrane.

Type III secretory system

A system that simultaneously crosses both membranes using a protein complex called a "Syringe needle" to transport proteins directly into a host cell's cytoplasmic membrane; typically associated with pathogens and flagella.