bio ch 2

Atoms

The basic building blocks of all matter, combining to form molecules.

Structure of an Atom

An atom consists of a nucleus containing protons and neutrons, with electrons orbiting around the nucleus.

Atom

The smallest unit of matter, consisting of protons, neutrons, and electrons.

Element

A pure substance made of only one type of atom (e.g., Oxygen (O), Hydrogen (H)).

Protons

Positively charged particles in the nucleus.

Neutrons

Neutral particles in the nucleus.

Electrons

Negatively charged particles that orbit the nucleus.

Atomic Number

The number of protons in an atom.

Mass Number

The sum of protons and neutrons in an atom's nucleus.

Ion

An atom that gains or loses electrons, acquiring a charge.

Cation

Positively charged ion (loses electrons).

Anion

Negatively charged ion (gains electrons).

Electronegativity

An atom's ability to attract electrons.

Chemical Bond

The force that holds atoms together.

Molecule

Two or more atoms bonded together (e.g., H₂O).

Compound

A molecule containing different elements (e.g., NaCl).

Mixture

A combination of substances that do not chemically bond.

Chemical Bonds

Atoms interact by forming chemical bonds through the sharing, gaining, or losing of electrons.

Ionic Bond

Transfer of electrons between atoms (e.g., NaCl).

Covalent Bond

Sharing of electrons (e.g., H₂O).

Hydrogen Bond

Weak attraction between polar molecules (e.g., DNA strands).

Nonpolar Covalent Bond

Equal sharing of electrons (e.g., O₂, CH₄).

Polar Covalent Bond

Unequal sharing of electrons, creating partial charges (e.g., H₂O).

Water

Vital because it regulates temperature, dissolves substances, provides cohesion and adhesion, and supports chemical reactions.

Polarity

Unequal sharing of electrons in a molecule (H₂O).

Hydrophilic

Water-attracting molecules (e.g., salt).

Hydrophobic

Water-repelling molecules (e.g., oil).

Solution

A homogeneous mixture of solute and solvent.

Solute

The substance dissolved (e.g., salt in water).

Solvent

The substance that dissolves the solute (e.g., water).

Cohesion

Water molecules stick together (surface tension).

Importance of Carbon Atoms

Carbon forms four bonds, allowing the creation of complex molecules like proteins, carbohydrates, lipids, and nucleic acids.

Hydroxyl Group

Found in alcohols.

Carboxyl Group

Found in amino acids.

Amino Group

Found in proteins.

Phosphate Group

Found in DNA and ATP.

Condensation (Dehydration Synthesis)

Forms bonds by removing water (e.g., making proteins).

Hydrolysis

Breaks bonds by adding water (e.g., digestion of food).

Carbohydrates

Sugars and starches.

Lipids

Fats and oils.

Proteins

Made of amino acids.

Nucleic Acids

DNA and RNA.

Carbohydrate Monomers and Polymers

Monomer: Monosaccharide | Polymer: Polysaccharide

Protein Monomers and Polymers

Monomer: Amino acid | Polymer: Polypeptide

Lipid Structure

No true polymer, but made of fatty acids & glycerol.

Nucleic Acid Monomers and Polymers

Monomer: Nucleotide | Polymer: DNA/RNA

Monosaccharides

Simple sugars (e.g., glucose).

Disaccharides

Two sugars linked (e.g., sucrose).

Polysaccharides

Long chains of sugars (e.g., starch).

Starch

Energy storage in plants.

Glycogen

Energy storage in animals.

Cellulose

Structural component in plants.

Fats

Energy storage.

Phospholipids

Make up cell membranes.

Steroids

Hormones and cholesterol.

Saturated Fatty Acids

No double bonds, solid at room temp (e.g., butter).

Monounsaturated Fatty Acids

One double bond (e.g., olive oil).

Polyunsaturated Fatty Acids

Multiple double bonds (e.g., fish oil).

Phospholipids Structure

Consisting of hydrophilic heads and hydrophobic tails.

Steroids Definition

Lipid molecules with four rings, including cholesterol, testosterone, and estrogen.

Proteins Definition

Polymers of amino acids that perform structural and functional roles in cells.

Amino Acid Structure

Each amino acid has an amino group (-NH₂), carboxyl group (-COOH), and R-group (side chain, varies per amino acid).

Primary Protein Structure

Sequence of amino acids.

Secondary Protein Structure

Folding into alpha-helices and beta-sheets.

Tertiary Protein Structure

3D shape due to R-group interactions.

Quaternary Protein Structure

Multiple polypeptides forming a functional protein.

Peptide Bond Formation

A peptide bond forms when the amino group of one amino acid reacts with the carboxyl group of another, releasing water.

Nucleotide Components

Sugar (ribose or deoxyribose), phosphate group, nitrogenous base.

Types of Nucleic Acids

DNA (Deoxyribonucleic Acid) - Stores genetic information. RNA (Ribonucleic Acid) - Helps in protein synthesis.

Nitrogenous Bases in Nucleotides

Adenine (A), Thymine (T) [DNA only] / Uracil (U) [RNA only], Guanine (G), Cytosine (C).