Biomolecules, Cell Structure, and Membrane Dynamics Vocabulary

Vocabulary practice flashcards covering biomolecules, cellular structure, transport mechanisms, and cellular junctions based on lecture notes.

Hydrocarbon

An organic molecule consisting entirely of carbon and hydrogen atoms, which can vary in length, presence of single, double, or triple bonds, and ring structures.

Monomer

A single, small molecular subunit that can covalently bond to other identical or similar molecules to form a larger macromolecule.

Polymer

A large molecule composed of many repeating structural subunits (monomers) connected together by covalent bonds.

Dehydration Reaction

A chemical reaction that bonds two monomers together to form a polymer, accompanied by the loss of a water molecule.

Hydrolysis Reaction

A chemical reaction that utilizes water molecules to break down polymers into monomers, often accelerated by enzymatic catalysts.

Monosaccharide

The simplest monomer form of a carbohydrate, which can exist as a linear molecule or form ring structures in solution.

Disaccharide

A carbohydrate made of two monosaccharides joined by a covalent bond that resembles an ether bond ($\text{R--O--R}$).

$\alpha$-Glucose and $\beta$-Glucose

Isomeric forms of glucose differing in the spatial orientation of their hydroxyl group, which dictates whether they form digestible linkages (like starch) or structural linkages (like cellulose).

Starch

A storage polysaccharide produced by plants to store energy.

Glycogen

A highly branched storage polysaccharide synthesized and stored by animals for energy.

Cellulose

A structural carbohydrate polysaccharide synthesized by plants that groups into microfibrils and fibers to form cell walls.

Saturated Fatty Acid

A fatty acid tail containing no carbon-carbon double bonds, holding the maximum possible number of hydrogen atoms and forming straight chains.

Unsaturated Fatty Acid

A fatty acid tail containing one or more double or triple bonds between carbon atoms, resulting in a kinked structure.

Triglyceride

A lipid macromolecule composed of a glycerol molecule bonded to three fatty acid tails.

Steroid

A lipid characterized by a carbon backbone made of four fused rings, serving as hormones or membrane components based on specific functional side groups.

Phospholipid

An amphipathic lipid with a hydrophilic head and hydrophobic tails that spontaneously forms lipid bilayers or micelles in aqueous environments.

Selectively Permeable

A feature of lipid bilayers that allows small, nonpolar molecules to cross easily while restricting large, polar molecules or charged ions.

Integral Proteins

Transmembrane proteins embedded directly within the hydrophobic interior of the lipid bilayer.

Peripheral Proteins

Proteins that attach temporarily to the extracellular or intracellular surface of the membrane rather than embedding in the lipid core.

Purines

A category of double-ring nitrogenous bases in nucleic acids comprising adenine (A) and guanine (G).

Pyrimidines

A category of single-ring nitrogenous bases in nucleic acids comprising cytosine (C), thymine (T), and uracil (U).

Phosphodiester Linkage

The directional covalent bond that links nucleotide monomers together into a nucleic acid polymer.

Peptide Bond

The covalent bond formed between the carboxyl group of one amino acid and the amino group of another via a condensation reaction.

Secondary Structure

Localized structural patterns within a polypeptide, such as $\alpha$-helices and $\beta$-pleated sheets, stabilized by hydrogen bonds along the backbone.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide chain caused by interactions among R-groups/side chains.

Quaternary Structure

The overall protein structure that results from the assembly and interaction of two or more polypeptide subunits.

Denaturation

The unfolding or alteration of a protein's natural active shape due to disruption of its non-covalent bonds, leading to loss of function.

Isotopes

Forms of an element that share the same atomic number (protons) but differ in atomic mass due to varying numbers of neutrons (e.g., $^{12}\text{C}$ vs. $^{14}\text{C}$).

Emergent Properties

New, complex traits or features that arise at higher levels of biological organization that were not present in individual lower-level components.

Secretory Pathway

The intracellular pathway where proteins are synthesized in the Rough ER, modified in the Golgi apparatus, and transported via vesicles to the plasma membrane.

Sodium-Potassium Pump

An electrogenic active transport mechanism in animal cells that moves sodium ions out and potassium ions in against their concentration gradients.

Membrane Potential

The voltage or electrical charge difference across a plasma membrane established by the unequal distribution of positive and negative charges.

Electrogenic Pump

A membrane transport protein that generates a membrane potential while moving ions against their chemical concentration gradient (e.g., proton pumps in plants, fungi, and bacteria).

Cotransport

A process in which the movement of one solute down its concentration gradient is linked to the active transport of another solute against its gradient (e.g., Sucrose-$\text{H}^+$ cotransporter).

Kinases

Enzymes that add phosphate groups to target proteins, often turning on or driving signal transduction pathways.

Phosphatases

Enzymes that remove phosphate groups from target proteins, turning off or regulating signal transduction pathways.

G Protein-Coupled Receptors (GPCRs)

Transmembrane receptors that bind an extracellular ligand and utilize a G protein intermediate to initiate an intracellular signaling cascade.

Tight Junctions

Intercellular junction complexes that seal neighboring animal cells together tightly to prevent fluid leakage across cell layers.

Desmosomes

Anchoring cell junctions that fasten adjacent animal cells into strong structural sheets.

Gap Junctions

Intercellular channels between adjacent animal cells that allow direct cytoplasmic passage of ions, water, and small signaling molecules.

Plasmodesmata

Channels opening through plant cell walls that connect the cytoplasm of neighboring cells for direct transport and communication.

Nucleus

The membrane-bound organelle in eukaryotic cells that encloses the genetic material ($\text{DNA}$) and regulates gene expression and cell division.

Ribosomes

Non-membrane-bound cellular structures made of $\text{RNA}$ and proteins that catalyze protein synthesis during translation.

Rough Endoplasmic Reticulum (RER)

A network of interconnected membrane sacs studded with ribosomes that synthesizes and processes proteins destined for secretion, membranes, or organelles.

Smooth Endoplasmic Reticulum (SER)

A membranous network lacking ribosomes that synthesizes lipids, metabolizes carbohydrates, stores calcium ions, and detoxifies chemicals.

Golgi Apparatus

An organelle of flattened membranous sacs that receives, modifies, sorts, and packages proteins and lipids for secretion or delivery to intracellular destinations.

Lysosomes

Membrane-enclosed sacs of hydrolytic enzymes that break down macromolecules, worn-out organelles, and engulfed foreign material.

Vacuole

A membrane-bound vesicle present in plant and fungal cells that stores nutrients, wastes, and water while maintaining turgor pressure.

Peroxisomes

Specialized metabolic organelles containing enzymes that transfer hydrogen to oxygen, producing hydrogen peroxide ($\text{H}_2\text{O}_2$) and converting it to water.

Mitochondria

Double-membrane organelles that conduct cellular respiration to generate chemical energy in the form of $\text{ATP}$.

Chloroplasts

Double-membrane plant and algal organelles containing chlorophyll that conduct photosynthesis to convert light energy into