Cell Membrane and Energy Concepts (VOCABULARY)

Vocabulary flashcards covering membrane structure and function, diffusion/osmosis, transport, energy transformations, enzymes, and basic thermodynamics as presented in the notes.

Prostaglandin pathway enzyme (cyclooxygenase / COX)

the enzyme inhibited by NSAIDs that catalyzes prostaglandin production; inhibition reduces inflammation but can impair stomach protection and blood clotting.

Prostaglandins

lipid signaling molecules involved in inflammation and protective mucous lining of the stomach; produced via the COX pathway.

NSAIDs (nonsteroidal anti-inflammatory drugs)

drugs that reduce inflammation by inhibiting cyclooxygenase (COX) enzymes, with potential side effects on stomach lining and clotting.

Cyclooxygenase (COX)

the enzyme in prostaglandin synthesis targeted by NSAIDs.

Membrane proteins

proteins embedded in the plasma membrane that mediate transport, signaling, and enzymatic activities.

Receptor

a membrane protein that binds signaling molecules to initiate a cellular response.

Cell junction

protein complexes that connect adjacent cells, enabling communication and adhesion.

Signal transduction

the relay of a signal from a membrane receptor to intracellular targets via a cascade.

Plasma membrane

the phospholipid bilayer that encloses the cell and regulates entry/exit of substances; selectively permeable.

Selective permeability

property of the plasma membrane allowing some substances to cross more easily than others.

Signaling molecule

a molecule (e.g., hormone) that binds to a receptor to initiate a cellular response.

Boundary (cell boundary)

the plasma membrane forms the outer boundary of the cell.

Lipid bilayer

the foundational structure of cell membranes, formed by phospholipid tails and heads.

Spontaneous self-assembly

lipids can spontaneously form bilayers due to amphipathic nature, creating membranes without external energy.

Amphipathic

having both hydrophobic and hydrophilic regions, enabling formation of lipid bilayers.

Phospholipid bilayer

the basic structure of cell membranes composed of two layers of phospholipids.

Simple diffusion

the passive movement of small nonpolar molecules across the lipid bilayer down their concentration gradient.

Small non-polar molecules

molecules that diffuse readily through the lipid bilayer (e.g., O2, CO2).

Diffusion

net movement of molecules from high to low concentration; a type of passive transport that requires no energy.

Passive transport

transport that occurs without cellular energy input, including diffusion and facilitated diffusion.

Osmosis

diffusion of water across a semipermeable membrane.

Hypertonic solution

a solution with a higher solute concentration than the interior; water tends to move out of the cell or balloon.

Hypotonic solution

a solution with a lower solute concentration than the interior; water tends to move into the cell or balloon.

Isotonic solution

a solution with equal solute concentration to the cell interior; no net water movement.

Contractile vacuoles

organelles in some protozoa that expel excess water; indicate a hypotonic environment.

Osmotic lysis

rupture of a cell due to an influx of water in a hypotonic environment.

Turgor pressure

the rigidity in plant cells caused by water uptake creating pressure against the cell wall.

Dehydration

a state of reduced body water; can result from drinking saline water and net water loss.

Facilitated diffusion

diffusion of a substance across a membrane with the help of transport proteins; still passive (no energy).

Transport proteins

proteins in the membrane that assist in moving substances across via channels or carriers.

Concentration gradient

the difference in the concentration of a substance across a space; the driving force for diffusion.

Aquaporins

water channel proteins that allow rapid movement of water across membranes.

Active transport

movement of substances against their concentration gradient, requiring energy.

ATP-driven active transport

active transport powered by energy from ATP hydrolysis to move substances against their gradient.

Exocytosis

bulk release of materials from the cell when vesicles fuse with the plasma membrane.

Endocytosis

bulk uptake of material into the cell via vesicle formation.

Phagocytosis

a form of endocytosis where a cell engulfs large particles or bacteria.

Endocytosis of LDLs

cells uptake low-density lipoproteins through receptor-mediated endocytosis.

Kinetic energy

energy of motion.

Chemical energy

energy stored in chemical bonds, available to drive reactions.

Endothermic reaction

a reaction that absorbs heat/energy from the surroundings.

Open thermodynamic system

a system that can exchange both energy and matter with its surroundings.

Closed system

a system that does not exchange matter with its surroundings; may exchange energy.

Energy transfer

the conversion of one form of energy to another within living systems (e.g., light to chemical; chemical to kinetic).

Entropy

a measure of disorder; living systems locally decrease entropy using energy, while the universe's entropy increases.

Endergonic

an energy-absorbing (non-spontaneous) reaction.

Exergonic

an energy-releasing (spontaneous) reaction.

Metabolic pathway

a series of interconnected biochemical reactions catalyzed by enzymes.

ATP hydrolysis

the reaction of ATP breaking down to ADP and Pi, releasing energy.

Phosphorylation

the transfer of a phosphate group to a molecule.

Energy coupling

the use of energy released by exergonic reactions to drive endergonic reactions, often via ATP.

Enzymes

proteins that act as biological catalysts to speed up chemical reactions.

Activation energy

the energy barrier that must be overcome for a reaction to proceed.

Active site

the region of an enzyme where substrates bind.

Enzyme specificity

enzymes catalyze specific reactions with specific substrates.

Denaturation

the loss of an enzyme's 3-D structure and function due to heat, pH change, or other factors.

Coenzyme

organic non-protein helpers that assist enzymes in catalysis.

Competitive inhibition

inhibitor competes with the substrate for binding at the active site.

Noncompetitive (allosteric) inhibition

inhibitor binds to a site other than the active site, altering enzyme shape and activity.

Negative feedback inhibition

the final product inhibits an earlier enzyme in its pathway to regulate production.

Irreversible inhibition

inhibitor forms covalent bonds with the enzyme, permanently inactivating it.

Antiseptic

a chemical substance that can prevent infection by killing or inhibiting microorganisms on living tissue.

Osmotic shock

cell damage due to rapid osmosis, often from drastic changes in solute concentration.