BIOL 105: Fundamentals of Biology - Vocabulary Flashcards

Vocabulary flashcards covering key terms and concepts across chemical foundations of life, biological macromolecules, cell organization, thermodynamics, and the origin of life from BIOL 105.

Homeostasis

The process by which living organisms regulate their internal environment to maintain stable, constant conditions necessary for survival.

Cell Theory

The fundamental biological principle stating that all living organisms are composed of cells, cells are the fundamental units of life, and all cells arise from preexisting cells.

Independent Variable

The variable in an experiment that is intentionally changed or manipulated by the researcher to observe its effect.

Dependent Variable

The variable in an experiment that is measured or observed to evaluate the effect of changing the independent variable.

Positive Control

An experimental control sample expected to produce a positive result, confirming that the experimental procedure and reagents are functioning properly.

Negative Control

An experimental control sample expected to give a negative result, ensuring that external or unconditioned factors do not interfere with the test outcome.

Covalent Bond

A strong chemical bond formed when two nonmetal atoms share one or more pairs of valence electrons.

Ionic Bond

A chemical bond formed through electrostatic attraction between oppositely charged ions resulting from the complete transfer of electrons.

Electronegativity

A measure of the relative attraction or pulling power an atom exerts on shared bonding electrons within a covalent bond.

Hydrogen Bond

A weak noncovalent electrical attraction between a hydrogen atom covalently bound to an electronegative atom (such as $\text{O}$ or $\text{N}$) and another electronegative atom.

Van der Waals Forces

Weak, short-range noncovalent interactions between nonpolar molecules resulting from brief, temporary fluctuations in electron distribution.

Endergonic Reaction

A non-spontaneous chemical reaction that absorbs free energy from its surroundings, characterized by a positive change in Gibbs free energy ($\Delta G > 0$).

Exergonic Reaction

A spontaneous chemical reaction that releases free energy into its surroundings, characterized by a negative change in Gibbs free energy ($\Delta G < 0$).

Activation Energy

The minimum amount of energy required to destabilize existing chemical bonds and initiate a reaction by reaching the transition state.

Hydrophilic

Having an affinity for water; describes polar or charged molecules that readily interact with or dissolve in water.

Hydrophobic

Lacking an affinity for water; describes nonpolar molecules that tend to aggregate together and exclude water molecules.

Amphiphilic

Describing a molecule (such as a phospholipid or fatty acid) that possesses both hydrophilic (polar) and hydrophobic (nonpolar) regions; also known as amphipathic.

Buffer Solution

A solution containing a mixture of a weak acid and its conjugate base that resists significant changes in $\text{pH}$ when small amounts of acid or base are added.

Structural Isomers

Molecules that share the same molecular formula but differ in the covalent arrangements and connectivity of their atoms.

Optical Isomers

Isomers that are non-superimposable mirror images of one another due to the presence of an asymmetric carbon atom (chirality); also called enantiomers.

Condensation Reaction

A chemical reaction in which two monomers are covalently linked together with the concomitant loss of a water molecule; also called dehydration synthesis.

Hydrolysis Reaction

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

Primary Structure

The specific linear sequence of amino acids in a polypeptide chain joined by covalent peptide bonds.

Secondary Structure

Regular, localized patterns of polypeptide backbone folding (such as $\alpha$ helices and $\beta$ pleated sheets) stabilized by hydrogen bonds.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide chain, maintained by side-chain (R group) interactions including ionic bonds, hydrophobic interactions, hydrogen bonds, and disulfide bridges.

Quaternary Structure

The specific spatial arrangement and assembly of two or more polypeptide subunits into a functional multi-subunit protein complex.

Peptide Bond

The covalent amide linkage formed between the carboxyl group of one amino acid and the amino group of another during protein synthesis.

Disulfide Bridge

A strong covalent bond formed between the sulfhydryl ($-\text{SH}$) groups of two cysteine amino acid side chains within or between polypeptide chains.

Molecular Chaperones

Specialized proteins (such as the HSP60 family) that assist newly synthesized or denatured proteins in folding into their correct functional three-dimensional conformations.

Allostery

A mechanism of protein regulation in which ligand binding at a regulatory site induces a conformational change that alters functional activity at a distant active site.

Glycosidic Bond

A covalent bond formed between a monosaccharide and another molecule via a condensation reaction.

Cellulose

An unbranched polysaccharide polymer consisting of glucose monomers linked by $\beta\text{-1,4}$ glycosidic bonds, serving as a primary structural component of plant cell walls.

Glycogen

A highly branched storage polysaccharide composed of glucose monomers joined by $\alpha\text{-1,4}$ and $\alpha\text{-1,6}$ glycosidic bonds, stored in animal liver and muscle cells.

Saturated Fatty Acid

A fatty acid chain containing only single bonds between carbon atoms, producing a straight hydrocarbon chain that packs tightly.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double bonds between carbon atoms, creating kinks in the hydrocarbon chain that prevent dense packing.

Triacylglycerol

A lipid storage molecule consisting of a glycerol backbone esterified to three fatty acid chains; also known as a triglyceride.

Phospholipid

An amphiphilic lipid composed of a glycerol backbone attached to two nonpolar fatty acid tails and a polar phosphate head group, forming biological membranes.

Steroids

A class of lipids characterized by a carbon skeleton composed of four fused rings (containing 17 carbon atoms), functioning as structural membrane components and signaling molecules.

Nucleoside

A compound consisting of a nitrogenous base covalently linked to a pentose sugar (ribose or deoxyribose), lacking a phosphate group.

Nucleotide

The monomeric building block of nucleic acids, consisting of a nitrogenous base, a five-carbon sugar, and one to three phosphate groups.

Purines

Double-ring nitrogenous bases found in nucleic acids, specifically Adenine (A) and Guanine (G).

Pyrimidines

Single-ring nitrogenous bases found in nucleic acids, specifically Cytosine (C), Thymine (T), and Uracil (U).

Phosphodiester Bond

The covalent linkage formed between the $3'\text{-OH}$ group of one sugar and the $5'\text{-phosphate}$ group of an adjacent nucleotide in DNA or RNA chains.

Miller-Urey Experiment

A landmark 1950s experiment simulating prebiotic Earth atmospheric conditions ($\text{CH}_4$, $\text{NH}_3$, $\text{H}_2$, $\text{H}_2\text{O}$) with electrical discharge, proving that organic molecules like amino acids form spontaneously under prebiotic conditions.

RNA World Hypothesis

The hypothesis proposing that primordial life forms relied on RNA for both storing genetic information and catalyzing chemical reactions (ribozymes) before DNA and proteins evolved.

Protocell

A self-assembled, membrane-bound spherical structure composed of fatty acid bilayers enclosing catalytic and genetic molecules, considered an evolutionary precursor to modern cells.