Unit 1: Biochemistry, Life’s Origins, and Chi-Square — Vocabulary Flashcards

Vocabulary flashcards covering key terms from Unit 1 topics: scientific methods and concepts, chemical bonds, properties of water, organic macromolecules, digestion and protein structure, and basic origins of life.

Hypothesis

A proposed explanation that is testable and falsifiable, forming the basis for experimentation.

Scientific theory

A well-tested explanation supported by a large body of evidence; explains broad ideas and has been repeatedly tested.

Model (scientific model)

A simplified representation of a system used to understand, predict, and test ideas; can be physical, mathematical, or computer-based.

Covalent bond

A chemical bond formed by sharing electrons between atoms.

Ionic bond

A bond formed by transfer of electrons, creating oppositely charged ions that attract.

Single bond

A covalent bond where one pair of electrons is shared between atoms.

Double bond

A covalent bond where two pairs of electrons are shared.

Triple bond

A covalent bond where three pairs of electrons are shared.

Polar covalent bond

A covalent bond in which electrons are shared unequally due to differences in electronegativity.

Nonpolar covalent bond

A covalent bond in which electrons are shared equally between atoms.

Electronegativity

The tendency of an atom to attract electrons toward itself in a chemical bond.

Water

A polar molecule (H2O) with two hydrogen atoms bonded to oxygen; highly cohesive and solvent for many substances.

Hydrogen bond

A weak attraction between a slightly positive hydrogen atom and a slightly negative atom (often O or N) in another molecule.

Cohesion

Attraction between like molecules (e.g., water molecules sticking to each other) due to hydrogen bonding.

Adhesion

Attraction between different substances (e.g., water to plant cell walls).

Surface tension

The cohesive forces at the surface of a liquid that create a 'skin' effect, due to hydrogen bonding.

Solvent

The substance that dissolves solutes (e.g., water in aqueous solutions).

Solute

The substance dissolved in a solvent.

Solution

A homogeneous mixture of solvent and solute.

Hydrophilic

Having an affinity for water; water-loving.

Hydrophobic

Repelling or failing to mix with water; water-fearing.

Colloid

A mixture with dispersed particles that do not settle out over time (e.g., milk).

Molarity

A measure of solute concentration: moles of solute per liter of solution.

Moles

A quantity used in chemistry to express amount of substance.

Buffer

A substance that resists changes in pH by absorbing or releasing H+ ions.

pH

A scale that measures how acidic or basic (alkaline) a solution is.

Acid

A substance that increases the H+ concentration in solution.

Base

A substance that either decreases H+ concentration or increases OH− concentration; pH > 7.

Acid precipitation

Acid rain caused by pollutants that lowers pH in lakes and soils, harming ecosystems.

Primordial soup (Oparin–Haldane)

Hypothesized early Earth environment where simple molecules formed into more complex organic compounds.

Miller–Urey experiment

Laboratory simulation of early Earth conditions that produced amino acids and other organics.

Protobiont

Early cell-like structures with membranes and simple metabolic-like processes; precursors to cells.

RNA

Ribonucleic acid; can store information and act as a catalyst; plausible early genetic material.

DNA

Deoxyribonucleic acid; stores genetic information; typically double-stranded and antiparallel.

Nucleotide

The monomer of nucleic acids, consisting of a sugar, a phosphate group, and a nitrogenous base.

Purine

Two-ring nitrogenous bases (Adenine, Guanine) found in DNA and RNA.

Pyrimidine

One-ring nitrogenous bases (Cytosine, Thymine, Uracil) found in DNA/RNA.

A–T base pairing

Adenine pairs with thymine via two hydrogen bonds in DNA.

G–C base pairing

Guanine pairs with cytosine via three hydrogen bonds in DNA.

Monosaccharide

A single sugar unit (e.g., glucose); the basic unit of carbohydrates.

Disaccharide

Two monosaccharides linked together (e.g., sucrose).

Polysaccharide

Many monosaccharides linked together (e.g., starch, glycogen, cellulose).

Glucose

A six-carbon monosaccharide; C6H12O6; primary energy source in cells.

Amylose

Unbranched (straight) form of starch (plant storage carbohydrate).

Amylopectin

Branched form of starch (plant storage carbohydrate).

Glycogen

Highly branched storage polysaccharide in animals.

Alpha linkage

Glycosidic bonds in starch and glycogen (alpha-1,4).

Beta linkage

Glycosidic bonds in cellulose (beta-1,4); beta linkages are not digestible by humans.

Triglyceride

Glycerol molecule bound to three fatty acids; primary storage lipid; hydrophobic.

Phospholipid

Lipid with glycerol, two fatty acids, and a phosphate group; amphipathic and forms cell membranes.

Amphipathic

Having both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Steroid

Lipids with four fused carbon rings; include hormones and cholesterol.

Cholesterol

A steroid essential for membrane structure and a precursor to other steroids.

Protein

Large biomolecule consisting of one or more polypeptides folded into a functional shape.

Amino acid

Organic molecule with an amino group, a carboxyl group, a hydrogen, and an R group; building blocks of proteins.

Peptide bond

Covalent bond linking amino acids to form proteins, formed by dehydration synthesis.

Primary structure

The linear sequence of amino acids in a protein.

Secondary structure

Local folding patterns (α-helix and β-pleated sheet) stabilized by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a protein due to R-group interactions.

Quaternary structure

Association of multiple polypeptides into a functional protein.

Denaturation

Loss of a protein’s shape and function due to heat, pH change, or chemicals.

Nucleotide components

A nucleotide contains a sugar, a phosphate group, and a nitrogenous base.

ATP

Adenosine triphosphate; the cell’s main energy currency, released energy upon hydrolysis.

Monomer

A small molecule that can join with others to form a polymer.

Polymer

A large molecule composed of many repeating monomer units.

Enzyme

A protein that acts as a biological catalyst to speed up chemical reactions.

Active site

The region of an enzyme where the substrate binds.

Induced fit

The flexible interaction where enzyme changes shape to accommodate the substrate.

Activation energy

The minimum energy required for a chemical reaction to occur; enzymes lower this barrier.

Substrate

The molecule or substance that binds to an enzyme’s active site and is transformed by the reaction.