General Biology: Biomolecules, Cellular Organelles, and Membrane Transport

Comprehensive vocabulary flashcards covering macromolecule structure and function (Chapter 5), eukaryotic cellular organelles and cytoskeletal networks (Chapter 6), and membrane dynamics, tonicity, and transport mechanisms (Chapter 7).

Macromolecules

Large biological molecules composed of thousands of covalently bonded atoms, including carbohydrates, proteins, and nucleic acids.

Polymer

A long molecule consisting of many similar or identical building blocks linked by covalent bonds.

Monomers

Small repeating chemical units that serve as the building blocks of a polymer.

Hydrolysis

A chemical reaction that breaks the bond between monomers through the addition of a water molecule.

Dehydration Reaction

A condensation reaction that joins two monomers together by covalently bonding them with the loss of a water molecule.

Lipids

A diverse class of hydrophobic biological molecules consisting primarily of hydrocarbons with nonpolar covalent bonds, which do not mix well with water and do not form true polymers.

Fats (Triglycerides)

Lipids constructed from a single three-carbon glycerol molecule joined to three fatty acids by ester linkages.

Saturated Fatty Acids

Fatty acids that lack double bonds between carbon atoms, containing the maximum number of hydrogen atoms possible; they are typically solid at room temperature and common in animals.

Unsaturated Fatty Acids

Fatty acids that possess one or more double bonds in the hydrocarbon chain; they are typically liquid at room temperature and found in plants and fish.

Hydrogenation

The artificial process of converting unsaturated fats into saturated fats by adding hydrogen, which can also generate trans fats with trans double bonds.

Phospholipids

Amphipathic lipid molecules composed of two hydrophobic fatty acid tails and a hydrophilic head containing a phosphate group attached to glycerol.

Steroids

Lipids characterized by a carbon skeleton composed of four fused rings, including hormones and cholesterol.

Monosaccharides

The simplest carbohydrates (simple sugars) that typically have formulas that are multiples of $CH_2O$, serving as cellular nutrients and building blocks.

Glycosidic Linkage

A covalent bond formed between two monosaccharides by a dehydration reaction.

Starch

A plant storage polysaccharide composed of glucose monomers linked by $\alpha\text{-(1}\rightarrow\text{4)}$ glycosidic bonds, stored as granules in plastids and chloroplasts.

Glycogen

An extensively branched storage polysaccharide found in animals, primarily stored in liver and muscle cells to release glucose upon hydrolysis.

Cellulose

A structural polysaccharide made of glucose monomers connected by $\beta\text{-(1}\rightarrow\text{4)}$ linkages, forming the tough fibrous walls of plant cells.

Chitin

A structural polysaccharide found in the exoskeletons of arthropods and providing structural support in fungal cell walls.

Polypeptide

An unbranched polymer of amino acids covalently linked together by peptide bonds, possessing an N-terminus and a C-terminus.

Amino Acids

Organic molecules possessing both an amino group and a carboxyl group, along with a variable side chain ($R$ group) bonded to an $\alpha$-carbon.

Primary Structure

The specific linear sequence of amino acids in a polypeptide chain, determined by DNA and held together by peptide bonds.

Secondary Structure

Repetitive coiling or folding in a polypeptide backbone caused by hydrogen bonding between repeating constituents, forming an $\alpha$-helix or $\beta$-pleated sheet.

Tertiary Structure

The overall three-dimensional shape of a polypeptide resulting from interactions among the $R$ groups, including ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bridges.

Quaternary Structure

The overall protein conformation resulting from the aggregation of two or more polypeptide chains into a single functional macromolecule.

Denaturation

The process in which a protein unravels and loses its native functional structure due to changes in pH, salt concentration, or temperature.

Polynucleotides

Polymers of nucleic acids composed of nucleotide monomers, each containing a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Nucleoside

The structural portion of a nucleotide that consists only of a nitrogenous base and a pentose sugar, without any phosphate group.

Smooth Endoplasmic Reticulum

The ribosome-free section of the endoplasmic reticulum responsible for synthesizing lipids, metabolizing carbohydrates, detoxifying drugs and poisons, and storing calcium ions.

Rough Endoplasmic Reticulum

The portion of the endoplasmic reticulum studded with ribosomes that serves as a membrane protein factory and distributes transport vesicles.

Golgi Apparatus

An organelle consisting of flattened membranous sacs called cisternae with distinct polarity (cis and trans faces) that modifies, sorts, and packages macromolecules for delivery.

Lysosome

A single-membrane-bound sac containing hydrolytic enzymes in an acidic internal environment used to break down ingested macromolecules and recycle damaged cell parts.

Autophagy

A lysosomal degradation pathway through which a cell digests and recycles its own damaged organelles and macromolecules.

Peroxisome

A single-membrane metabolic sac containing oxidative enzymes, such as catalase, that generate hydrogen peroxide and convert it into water during cellular detoxification.

Central Vacuole

A large membrane-bound compartment in mature plant cells that stores water and organic compounds, contributing to cell turgor.

Mitochondria

Double-membrane powerhouses of the cell that possess folded inner cristae and an internal matrix where stages of cellular respiration and ATP generation occur.

Chloroplasts

Double-membrane photosynthetic organelles in plants and algae containing chlorophyll, stacks of thylakoids (grana), and fluid stroma that convert light energy into chemical energy.

Microtubules

Hollow rods composed of tubulin dimers that form the thickest elements of the cytoskeleton, guiding vesicle transport, forming cilia and flagella, and separating chromosomes.

Microfilaments (Actin Filaments)

Thin, solid cytoskeletal rods made of actin proteins that support cell shape and drive cell motility and muscle contraction.

Intermediate Filaments

Cytoskeletal fibers of middle diameter that specialize in bearing tension, anchoring organelles in place, and holding adjacent cells together.

Centrosome

The primary microtubule-organizing center near the nucleus in animal cells, containing a pair of centrioles arranged in nine triplets of microtubules.

Dynein

A large motor protein attached to the outer microtubule doublets that drives the bending motion of cilia and flagella.

Fluid Mosaic Model

A conceptual model describing biological membranes as a fluid bilayer of phospholipids with various embedded integral and peripheral proteins.

Selective Permeability

The characteristic of the plasma membrane that allows hydrophobic (nonpolar) substances to pass easily while blocking or restricting polar molecules and ions.

Diffusion

The passive movement of solute particles down their concentration gradient from a region of higher concentration to one of lower concentration until dynamic equilibrium is reached.

Osmosis

The passive transport of water across a selectively permeable membrane from a region of low solute (high water) concentration to a region of high solute (low water) concentration.

Tonicity

The capacity of an extracellular solution to cause a cell to gain or lose water, dependent on the nonpenetrating solute concentrations relative to inside the cell.

Isotonic Solution

An external environment whose solute concentration is equal to the solute concentration inside the cell, resulting in no net movement of water.

Hypertonic Solution

An external solution with a higher concentration of solutes than the cytoplasm, causing water to leave the cell and resulting in cell shrinkage or crenation.

Hypotonic Solution

An external solution having a lower solute concentration than the cytoplasm, causing water to enter the cell and leading to cell swelling or turgidity.

Plasmolysis

The phenomenon in walled plant cells placed in a hypertonic environment where the plasma membrane pulls away from the cell wall as water exits.

Aquaporins

Specialized channel proteins embedded in cellular membranes that facilitate the rapid passage of water molecules.

Carrier Proteins

Membrane transport proteins that specifically bind solute molecules, alter their three-dimensional conformation, and shuttle polar nutrients (like glucose) across the bilayer.

Active Transport

The energy-requiring movement of a solute against its electrochemical or concentration gradient, mediated by specific carrier proteins using ATP.

Sodium-Potassium Pump

The primary electrogenic transport pump in animal cells that expends ATP to pump $3\text{ Na}^+$ out of the cell for every $2\text{ K}^+$ brought into the cell.

Proton Pump

The main electrogenic pump in plants, fungi, and bacteria that actively expels hydrogen ions ($H^+$) from the cytoplasm using ATP.

Endocytosis

The active cellular uptake of macromolecules and particulate substances by forming transport vesicles from invaginations of the plasma membrane.

Phagocytosis

A form of endocytosis known as 'cellular eating,' where a cell extends pseudopodia to engulf large particles or cells into a food vacuole.

Pinocytosis

A form of endocytosis known as 'cellular drinking,' in which the cell non-specifically gulps droplets of extracellular fluid into coated vesicles.

Receptor-Mediated Endocytosis

A selective bulk import mechanism in which specific ligands bind to outer membrane receptor proteins, triggering vesicle formation in coated pits.

Exocytosis

The active cellular export of materials out of the cell through the fusion of transport vesicles with the plasma membrane.