Chapter 2: Chemical Basis for Life

VTHT 1413 Fall 2026

These elements make up 96% of matter in all living creatures

• hydrogen

• oxygen

• carbon

Matter (definition)

Anything that occupies space and takes up mass

States of matter

• gas

• liquid

• solid

Element

A pure substance that cannot be broken down into simpler substances by chemical means, made up of atoms with the same number of protons.

Major elements in the animal body

• oxygen

• carbon

• hydrogen

• nitrogen

Minor elements in the animal body

• calcium

• phosphorus

• potassium

• sulfur

• sodium

• chlorine

• magnesium

Trace elements in the animal body

• silicone

• aluminum

• iron

• manganese

• fluorine

• vanadium

• chromium

• copper

• boron

• cobalt

• zinc

• selenium

• molybdenum

• tin

• iodine

Atom

The smallest unit of matter that retains the unique properties of an element.

Ion

An atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

Isotope

Atoms of the same element that have different numbers of neutrons, resulting in varying atomic masses.

Electron shell

A region surrounding an atom's nucleus where electrons are likely to be found, determining the atom's reactivity and bonding properties.

Molecule

A group of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound that retains its chemical properties.

Compound

A substance formed when two or more different elements are chemically bonded together, exhibiting properties different from the individual elements.

Solution

A homogeneous mixture of two or more substances, typically involving a solvent and a solute, where the solute is evenly distributed within the solvent.

Colloid

A mixture in which fine particles of one substance are dispersed within another but do not settle out. Colloids can exhibit properties of both solutions and suspensions.

Suspension

A heterogeneous mixture in which solid particles are suspended in a liquid or gas, where the particles can settle over time.

Covalent bond

A type of chemical bond formed when two atoms share one or more pairs of electrons, allowing them to achieve stability.

Ionic bond

A type of chemical bond formed through the electrostatic attraction between oppositely charged ions, typically involving the transfer of electrons from one atom to another.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Hydrogen bond

A weak bond formed when a hydrogen atom covalently bonded to an electronegative atom experiences attraction to another electronegative atom.

Synthesis reaction

A chemical reaction in which two or more reactants combine to form a single product.

Decomposition reaction

A chemical reaction in which a single compound breaks down into two or more simpler products.

Exchange reaction

A chemical reaction where elements from two different compounds exchange places, forming two new compounds.

Endergonic reaction

A chemical reaction that requires an input of energy to proceed, resulting in products with higher energy than the reactants.

Exergonic reaction

A chemical reaction that releases energy, resulting in products with lower energy than the reactants.

Factors that affect the rate of a reaction

• concentration of reactants

• temperature of environment

• activation energy

• presence of a catalyst

Activation energy

The minimum amount of energy required to start a chemical reaction, enabling the reactants to reach the transition state and form products.

Catalyst

A substance that increases the rate of a chemical reaction by lowering the activation energy without being consumed in the process.

Unique properties of water

• universal solvent

• ideal transport medium

• high heat capacity

• high heat of vaporization

• lubrication

Organic compounds

Compounds primarily composed of carbon and hydrogen, often containing oxygen, nitrogen, and other elements, that are essential for life.

Four categories of organic compounds

• proteins

• carbohydrates

• lipids

• nucleic acids

Examples of inorganic compounds

• water

• salts

• acids

• bases

Functional groups

Specific groups of atoms within molecules that determine the characteristics and reactivity of organic compounds.

Hydroxyl

Functional group (-OH) that increases solubility in water and is found in alcohols and sugars.

Carbonyl

Functional group (C=O) found in ketones and aldehydes, influencing the properties of sugars and organic compounds.

Carboxyl

Functional group (-COOH) that acts as an acid and is found in amino acids and fatty acids.

Methyl

Functional group (-CH₃) that acts as a nonpolar hydrocarbon chain, affecting the solubility and structure of organic molecules.

Amino

Functional group (-NH₂) that acts as a base, found in amino acids and contributing to protein structure.

Sulfhydryl

Functional group (-SH) that can form covalent bonds, particularly in protein structure, contributing to the stability of protein shape.

Phosphate

Functional group (-PO₄) that plays a crucial role in energy transfer and is a key component of nucleotides and phospholipids.

Acetyl

A functional group (-COCH₃) that is a derivative of acetic acid, often involved in the structure and metabolism of various biomolecules.

Hydrophilic

Describes molecules or functional groups that are attracted to water, typically polar and capable of forming hydrogen bonds, enhancing their solubility in aqueous environments.

Hydrophobic

Describes molecules that do not interact well with water and tend to be nonpolar, making them insoluble in aqueous environments.

Salts

Mineral compounds that have ionic bonds

Electrolytes

Salts in their ionic form, capable of transmitting an electric charge

Acid

a substance that donates protons (H+) in a chemical reaction, resulting in an increase in hydrogen ion concentration in solution.

Base

A substance that release -OH when added to water (proton acceptors)

Buffer

A solution that resists changes in pH when small amounts of acid or base are added, maintaining a stable hydrogen ion concentration. (Weak acids and bases)

Carbohydrates

Organic compounds made up of carbon, hydrogen, and oxygen, typically in a ratio of 1:2:1. They serve as a primary energy source and structural components in cells.

Monosaccharide

Simple sugar unit, basic building block of carbohydrates.

Disaccharide

A carbohydrate formed from two monosaccharide molecules linked by a glycosidic bond, serving as an important energy source.

Dehydration synthesis

A chemical reaction in which two molecules combine to form a larger molecule, with the loss of water, commonly used in the formation of polymers such as carbohydrates.

Hydrolysis

The process of breaking down a compound by addition of water, often used to dismantle polymers into their monomer units, such as carbohydrates into monosaccharides.

Anabolism

The metabolic process that builds larger molecules from smaller units, often requiring energy, and is essential for growth and repair.

Catabolism

The metabolic process that involves the breakdown of larger molecules into smaller units, often releasing energy in the process, such as the conversion of carbohydrates into glucose.

Polysaccharide

A complex carbohydrate formed from long chains of monosaccharides linked together, serving as a significant energy storage and structural component in organisms.

Lipids

A group of hydrophobic molecules that include fats, oils, and hormones, primarily used for energy storage, insulation, and cellular membrane structure.

Four types of lipids

• neutral fats (trigylcerides)

• phospholipids

• steroids

• eicosanoids

Neutral fats

trigylcerides

• glycerol head with 3 fatty acid chain “legs”

  • saturated: all single bonds

  • unsaturated: 1⁺ double bond

Phospholipids

A class of lipids that are a major component of cell membranes, consisting of fatty acids, a glycerol backbone, and a phosphate group.

Steroids

Lipids that take the form of four interlocking carbon rings; often associated with hormones and metabolic functions.

Eicosanoids

Lipids formed from a 20-carbon fatty acid and a ring structure

• prostaglandins

• thromboxanes

• leukotrienes

Proteins

Large, complex molecules made up of amino acids that perform a variety of functions in the body, including catalyzing reactions as enzymes, providing structural support, and regulating bodily processes.

Amino acids

Building blocks of proteins, consisting of an amino group, a carboxyl group, and a unique side chain.

Peptide bond

A covalent bond formed between two amino acids, linking the carboxyl group of one amino acid to the amino group of another, releasing a molecule of water.

Primary protein structure

The unique sequence of amino acids in a polypeptide chain, determining the overall shape and function of the protein.

Secondary protein structure

The second level of protein structure, characterized by the folding or coiling of the polypeptide chain into alpha helices or beta-pleated sheets, stabilized by hydrogen bonds.

Tertiary protein structure

The third level of protein structure, formed by the further folding and three-dimensional arrangement of a polypeptide chain, determined by interactions between the side chains of amino acids.

Quarternary protein structure

The fourth level of protein structure, formed by the assembly of multiple polypeptide chains into a functional protein complex, stabilized by various interactions.

Structural proteins

Proteins that provide support and shape to cells and tissues, such as collagen, fibrin, and keratin, playing critical roles in maintaining structural integrity.

Functional proteins

Proteins that play critical roles in biochemical processes, including enzymes, antibodies, and hormones, often participating in metabolic functions and regulation.

Enzymes

Proteins that act as biological catalysts, speeding up chemical reactions in the body by lowering activation energy. They are highly specific for their substrates and can be regulated by various factors, including temperature and pH.

Substrates

The reactants upon which enzymes act, specifically binding to the enzyme's active site to form an enzyme-substrate complex during a biochemical reaction.

Nucleid Acids

Biopolymers essential for storing and transmitting genetic information, comprising sequences of nucleotides that form DNA and RNA.

Nucleotides

The building blocks of nucleic acids, consisting of a nitrogenous base, a five-carbon sugar, and one or more phosphate groups, which link together to form DNA and RNA.

Nucleotides in DNA and RNA

• adenine

• guanine

• cytosine

Nucleotide found only in DNA

• thymine

Nucleotide found only in RNA

• uracil

Gene

A segment of DNA that contains coding information for a protein or functional RNA molecule, serving as a hereditary unit.

Chromosomes

Longs chains of genes combined with proteins.

ATP

An RNA nucleotide that acts as the main energy carrier in cells, consisting of adenine, ribose, and three phosphate groups.

NH_4⁺

Ammonium

Ca⁺²

Calcium

Fe⁺²

Ferrous

• Iron(II)

Fe⁺³

Ferric

• Iron(III)

H⁺

Hydrogen

Mg⁺²

Magnesium

K⁺

Potassium

Na⁺

Sodium

Cl^-

Chloride

PO_4^3-

Phosphate

HCO_3^-

Bicarbonate

OH^-

Hydroxide