Molecular and Cellular Biology Exam 3

Lipid Bilayer

Membrane around cells made up of primarily amphipathic molecules and embedded proteins, arranged in multiple layers, essential for cell function.

Posphatidylcholine

Most abundant phospholipid in eukaryotic cells.

Cholesterol

Commonly found lipid in cell mebranes, a sterol.

Glycolipid

Commonly found class of lipids in cell mebranes.

Leaflet/Face

Commonly used termed for a monolayer within the lipid bilayer.

Smooth Endoplasmic Reticulum

Organelle that synthesizes lipids, cholesterol, and steroid hormones.

Breakdown drugs and metabolic waste.

Stores calcium

Scramblases

Enzymes that move necessary components to the lumenal leaflet.

Transmembrane proteins

Proteins that have a hydrophobic region extending through the bilayer and the hydrophilic regions are exposed on both sides of the membranes.

Monolayer-associated proteins

embedded in one face of the membrane but do not extend all the way through.

Membrane attached proteins.

Are linked to lipids or transmembrane proteins.

FRAP

Fluorescence Recovery After Photobleaching; a technique used to study lateral diffusion of membrane proteins using fluorescence and photobleaching.

Simple diffusion

net movement of something from a region of higher concentration to a region of lower concentration.

Concentration gradient

a difference in the concentration of a substance between two areas

Passive transport

Use of proteins to transport molecules or ions across the membrane. Does not require energy and is required by concentration gradient.

Channel proteins

Proteins that form a pore through the membrane that allows for free diffusion of appropriately charged molecules and direct connection across the cell membrane

Aquaporins

Water channels; selective filter, improves rate of water transport compared to simple diffusion.

Ion channels

Mediate passage of ions across membrane; allows for rapid transport and is highly selective.

Transport proteins

Bind to a specific molecule and undergoes a conformational change, allows molecules to move down their concentration gradient.

Active transport

Use of proteins to move a solute from a lower to higher concentration gradients. Requires an energy source.

Protein Pumps

Alternative name for proteins used in active transport

Symport

moving both solutes in the same direction.

Antiport

Moves each solute in a different direction.

Na+ glucose symport

Uses Na+ gradient to transport glucose

The diffusion of Na+ is coupled to the movement of glucose against its concentration.

Active transport with ATP Hydrolysis

Uses ATP as energy source

Active Transport using coupled gradients

Coupled transport

Gated ion channels

channels that switch between open and closed conformations in response to a specific signal.

Mechanically-gated channels

channels respond to movement

Ligand gated channels

channels respond to binding of a specific molecule (ligand)

Voltage Gated channels

channels respond to a change in the membrane potential

Action potentials

a rapid change in the voltage across a cell membrane that occurs when a cell is stimulated

Membrane Potential

the difference in electric charge across a cell membrane, crucial for the generation of action potentials.

Depolarization

the process by which the membrane potential becomes less negative, often leading to the initiation of an action potential.

Threshold Potential

the critical level of depolarization that must be reached for an action potential to be initiated.

Synapses

The places where neurons connect and communicate with each other

Synaptic Vesicles

organelles that store and release neurotransmitters in neurons, enabling nerve impulses to travel between neurons and facilitating communication at synapses.