unit 3 flashcards

Lipid Bilayer

A membrane structure consisting of two layers of phospholipids, which creates a barrier between the interior of a cell and the external environment.

Phospholipid

A type of lipid molecule that consists of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails, forming a bilayer in cellular membranes.

Amphipathic

Referring to a molecule that has both hydrophilic and hydrophobic parts, enabling it to interact with both water and fats.

Bilayer Sphere Formation

The process by which lipid bilayers spontaneously form spherical shapes to minimize hydrophobic interactions with water.

Fluidity

The degree of movement and flexibility of lipids within a membrane; affected by temperature and lipid composition.

Transmembrane Proteins

Proteins that span across the lipid bilayer of a membrane, crucial for transport and communication across the membrane.

Flippases

Enzymes that facilitate the transfer of phospholipids from one leaflet of a membrane bilayer to another, maintaining membrane asymmetry.

Glycocalyx

A sugar-rich coating on the extracellular surface of membranes formed by glycolipids and glycoproteins.

Apoptosis

The process of programmed cell death, often indicated by the flipping of phosphatidylserine to the outer leaflet of the plasma membrane.

Scramblase

An enzyme that randomizes the distribution of phospholipids between the inner and outer leaflets of a bilayer during membrane assembly.

Membrane Proteins

Proteins that perform multiple functions including transporters, anchors, receptors, and enzymes associated with cell membranes.

Hydrophobic Residues

Amino acid side chains that do not interact favorably with water; key for membrane protein insertion.

Aqueous Pore Proteins

Proteins that create hydrophilic spans across membranes allowing the passage of hydrophilic molecules.

Amphipathic Detergents

Detergents like SDS and Triton X-100 that can release membrane proteins by covering hydrophobic regions.

X-ray Crystallography

Classic method for determining protein structure requiring ordered crystal formation for X-ray scattering.

Cryo-Electron Microscopy

Modern proteomics method revealing the structure of membrane proteins, allowing visualization without the need for crystallization.

Cell Cortex

A network of proteins that supports cell shape by interacting with the cytoskeleton and membrane proteins.

Glycosylation

The process where sugars are attached to proteins and lipids on the plasma membrane.

Lectins

Proteins that bind specific sugar patterns, playing a role in cell recognition and immune response.

Fluorescence Recovery After Photobleaching (FRAP)

Method to measure protein diffusion by observing the recovery of fluorescence in bleached membrane areas.

Epithelial Cells

Cells that form sheets attached to a basal lamina and exhibit polarity with restricted protein regions.

Diffusion Barriers

Structural features that restrict protein movement in the plasma membrane, forming specialized functional domains.

Bacteriorhodopsin

A light-driven proton transporter found in Halobacterium halobium, important for understanding membrane protein function.

Integral Membrane Proteins

Proteins that are directly associated with the membrane, either spanning it completely or partially.

Peripheral Membrane Proteins

Proteins that are indirectly associated with the membrane, often through interactions with integral proteins.

Transmembrane Transport

Movement of substances across biological membranes.

Concentration Gradient

A difference in concentration of a substance across a space, driving the movement of solutes.

Passive Transport

Movement of solutes across a membrane without the use of energy, following their concentration gradient.

Active Transport

The process of moving molecules against their concentration gradient, requiring energy input (usually from ATP).

Aquaporins

Specialized water channels that facilitate rapid transport of water across cell membranes.

Sodium-Potassium Pump

An ATP-powered pump that moves sodium out of and potassium into cells, maintaining electrochemical gradients.

Symporter

A type of transporter that moves two different solutes in the same direction across a membrane.

Antiporter

A transporter that moves two different solutes in opposite directions across a membrane.

Facilitated Diffusion

The process of spontaneous passive transport of molecules across a membrane via specific transmembrane integral proteins.

Gradient-Driven Pumps

Pumps that use the energy from the movement of one solute down its gradient to move another solute against its gradient.

Osmosis

The movement of water across a membrane from an area of low solute concentration to an area of high solute concentration.

Ion Channels

Proteins that facilitate the passage of ions across a cellular membrane, often selective for specific ions.

Membrane Potential

The electrical potential difference across a cell membrane due to the distribution of ions.

Nernst Equation

A mathematical formula used to calculate the equilibrium potential for a specific ion based on its concentration gradient.

Potassium Leak Channels

Ion channels that open randomly, allowing K+ ions to move out of the cell, contributing to resting membrane potential.

Electrochemical Equilibrium

The state where the electrical gradient and concentration gradient for a specific ion balance each other, resulting in no net movement of that ion.

Selectivity Filter

A narrow region within an ion channel that determines which ions can pass based on their size and charge.

Ligand-Gated Channels

Ion channels that open in response to the binding of a specific molecule (ligand), allowing ions to flow through.

Mechanically-Gated Channels

Ion channels that open or close in response to mechanical forces or pressure, commonly found in sensory cells.

Na+-K+ ATPase

A pump that actively transports Na+ out of and K+ into cells, crucial for maintaining the membrane potential.

Depolarization

A decrease in the membrane potential, making the inside of the cell less negative relative to the outside.

Hyperpolarization

An increase in the membrane potential, making the inside of the cell more negative relative to the outside.

Cation

A positively charged ion, such as Na+ or K+.

Anion

A negatively charged ion, such as Cl-.

Hydration Shell

The sphere of water molecules surrounding an ion in solution, affecting its ability to pass through ion channels.

Turgor Pressure

The pressure exerted by fluid in the central vacuole of plant cells, contributing to cell rigidity and support.

Threshold Potential

The membrane potential that must be reached for an action potential to be generated in a neuron. The level of depolarization required to initiate an action potential.

Patch Clamp Method

An experimental technique used to study the ionic currents that flow through individual ion channels.

Resting Membrane Potential

The membrane potential of a cell at rest, typically around -70mV for neurons, determined mainly by potassium ion concentration.

Equilibrium Potential

The membrane potential at which the net movement of a specific ion across the membrane is zero.

Electrolyte Bath

A solution used in patch clamp experiments that allows for the measurement of ionic currents through channels.

Neurons

Cells responsible for rapid electrochemical communication in the nervous system.

Dendrites

Input zones of a neuron that receive stimulatory or inhibitory signals.

Axon

Part of the neuron that propagates electrical signals down its length.

Action Potential

A transient change in membrane potential that is an all-or-nothing response.

Depolarization

A reduction in the charge difference across the plasma membrane of a neuron.

Hyperpolarization

An increase in the charge difference across the plasma membrane, making it more negative.

Voltage-gated Sodium Channels

Ion channels that open at threshold potential to allow Na+ influx, leading to depolarization.

Giant Axons

Thick axons found in species like the longfin inshore squid, allowing for rapid signal transmission.

Neurotransmitter

Chemical substances released by neurons to communicate with target cells.

Ligand-gated Ion Channels

Ion channels that open in response to the binding of a neurotransmitter.

Inactivation Gate

Part of the voltage-gated sodium channel that blocks sodium flow after an action potential.

Synapse

The space between an axon terminal of one neuron and a target cell, where communication occurs.

Optogenetics

A method that uses light to control neurons genetically modified to express light-sensitive ion channels.

Calcium Channels

Channels that open in response to an action potential, allowing Ca2+ influx and neurotransmitter release.

Psychotropic Drugs

Drugs that alter synaptic signaling and can affect neuronal communication.

Integration of Neuron Signaling

The process by which a neuron combines all incoming signals to decide whether to fire an action potential.

Free energy

The energy available to do work in a system, which can change based on reactions and conditions.

Macronutrients

Nutrients that must be consumed in large amounts, used as energy and raw materials for macromolecule synthesis.

Micronutrients

Nutrients required in smaller amounts, often functioning as coenzymes.

Anaerobic

Processes that occur without the presence of oxygen.

ATP

Adenosine triphosphate, the primary energy carrier in cells.

Kinase

An enzyme that catalyzes the addition of a phosphate group to a molecule.

Isomerase

An enzyme that catalyzes the rearrangement of bonds within a single molecule.

Dehydrogenase

An enzyme that catalyzes the oxidation of a molecule by removing hydrogen and electrons.

Mutase

An enzyme that catalyzes the shifting of a chemical group from one position to another within a molecule.

Phosphorylation

The addition of a phosphate group to a molecule, generally increasing its energy potential.

Fermentation

An anaerobic process that converts sugars to acids, gases, or alcohol in the absence of oxygen.

Acetyl CoA

A key intermediate in metabolism that links glycolysis and fatty acid oxidation to the citric acid cycle.

Phase 1 of Glycolysis

Energy investment phase requiring ATP to phosphorylate glucose.

Phase 2 of Glycolysis

3-carbon sugar generation phase where fructose 1,6-bisphosphate splits into two GAP molecules.

Phase 3 of Glycolysis

Energy payoff phase where ATP is produced through substrate-level phosphorylation.

Exergonic reaction

A spontaneous reaction that releases energy.

Endergonic reaction

A non-spontaneous reaction that requires energy input.

Oxidation

The process of losing electrons or hydrogen in a chemical reaction.

Reduction

The gain of electrons or hydrogen in a chemical reaction.

Substrate-level phosphorylation

The direct transfer of a phosphate group from a substrate to ADP to form ATP.

Hydroxyl group

-OH functional group that may participate in reactions, especially in organic compounds.

Citric Acid Cycle

Also known as the tricarboxylic acid (TCA) cycle and the Krebs cycle; a series of reactions that extracts energy from pyruvate and other molecules.

Oxaloacetate

A four-carbon molecule that is a crucial intermediate in the citric acid cycle.

Glycolysis

The metabolic process that converts glucose into pyruvate, producing a small amount of ATP and NADH.

Isomerization

A chemical reaction that rearranges the molecular structure of a compound, such as the conversion of citrate to isocitrate.

Decarboxylation

The process of removing a carboxyl group from a molecule, releasing CO2, as seen in isocitrate to alpha-ketoglutarate.

GTP

Guanosine triphosphate; a high-energy molecule synthesized in the citric acid cycle.

NAD+

Oxidized form of nicotinamide adenine dinucleotide, acts as an electron acceptor in metabolic reactions.