Carbohydrates, Lipids and Nucleic Acids

Chapter 3 Biological Macromolecules Vocabulary

Functional Group

Small, reactive groups of atoms attached to organic molecules that confer specific chemical properties.

Hydrocarbon

A molecule consisting solely of carbon and hydrogen atoms, which forms a nonpolar structure that stores considerable energy in its covalent bonds.

Hydroxyl Group

A polar functional group (-OH) that forms hydrogen bonds with water, facilitates dissolving, and enables alcohol molecules to link via dehydration synthesis.

Carbonyl Group

A functional group consisting of a carbon atom double bonded to an oxygen atom (=C=O); found in aldehydes and ketones, it serves as a major building block of carbohydrates.

Carboxyl Group

A functional group (-COOH) that acts as an organic acid by readily releasing a hydrogen ion (H+) in aqueous solutions.

Amino Group

A functional group (-NH2) that acts as an organic base by accepting a proton (H+) in aqueous solutions.

Phosphate Group

A functional group (-PO42-) that acts as a weak acid, bridges organic building blocks (such as in DNA), and conserves or releases energy during biological reactions.

Sulfhydryl Group

A functional group (-SH) that can easily form a covalent disulfide linkage (-S-S-) to help stabilize protein and molecular structures.

Isomer

Molecules that share the same molecular or empirical formula but possess different structural arrangements.

Structural Isomers

Molecules with identical chemical formulas that differ in the actual arrangement or bonding pattern of their atoms (e.g., glucose vs. fructose).

Stereoisomers

Molecules that have the same chemical bonds but differ in how their attached groups are arranged three-dimensionally in space.

Enantiomers

A sub-type of stereoisomers that exist as mirror images of each other around a chiral carbon atom (e.g., D-sugars and L-sugars).

Monomer

A small, similar chemical subunit that serves as a building block for larger molecules.

Polymer

A large molecule constructed by covalently linking multiple monomers together.

Dehydration Synthesis

A chemical reaction that joins monomers into larger polymer molecules by removing the components of a water molecule.

Hydrolysis

A chemical reaction that breaks polymers down into smaller subunits through the addition of a water molecule.

Monosaccharide

The simplest form of carbohydrate, containing between 3 to 7 carbon atoms and following the empirical formula (CH2O)n.

Disaccharide

A carbohydrate molecule constructed from two monosaccharides covalently joined together by dehydration synthesis.

Polysaccharide

A long carbohydrate polymer composed of more than 10 linked monosaccharide subunits.

Glycosidic Bond

A covalent linkage formed between two sugar molecules during a dehydration synthesis reaction.

Starch (Amylose)

A polysaccharide consisting of alpha-glucose units that serves as the primary energy storage molecule in plants.

Glycogen

A highly branched polysaccharide made of alpha-glucose units used for short-term energy storage in animal tissues.

Cellulose

An unbranched structural polysaccharide built from beta-glucose units joined by beta (1->4) linkages that reinforces plant cell walls.

Chitin

A structural polysaccharide composed of modified glucose units containing nitrogen groups; forms the exoskeletons of arthropods and cell walls of fungi.

Lipids

Water-insoluble, nonpolar biological molecules composed primarily of hydrocarbons.

Neutral Lipids

Nonpolar energy-storage lipids that lack charged groups, existing as either liquid oils or solid fats.

Fatty Acid

A lipid subunit containing a single long hydrocarbon chain attached to a carboxyl group (-COOH) at one end.

Triglyceride

A lipid formed by linking three fatty acid chains to a three-carbon glycerol molecule via ester linkages.

Ester Linkage

A covalent bond formed between the carboxyl group (-COOH) of a fatty acid and the hydroxyl group (-OH) of glycerol.

Saturated Fatty Acid

A fatty acid chain that holds the maximum possible number of hydrogen atoms and contains only single bonds between carbon atoms.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double bonds between carbon atoms, introducing kinks in the chain structure.

Trans Fat

A type of unsaturated fat produced through industrial hydrogenation that converts liquid vegetable oil into a solid fat.

Phospholipid

An amphipathic lipid made of a glycerol backbone, two nonpolar fatty acid tails, and a polar phosphate head group.

Phospholipid Bilayer

A two-molecule-thick layer of phospholipids where hydrophobic tails face inward and hydrophilic heads face the surrounding water; forms the structural foundation of cell membranes.

Micelle

A spherical cluster of lipid molecules formed in liquid, where hydrophilic heads face outward toward water and hydrophobic tails face inward.

Steroid

A nonpolar lipid structure built on a core framework of four interconnected carbon rings.

Sterol

A common type of steroid featuring a single polar -OH group at one end and a nonpolar hydrocarbon chain at the other end (e.g., cholesterol).

Nucleic Acids

Polymeric macromolecules (DNA and RNA) built from nucleotide chains linked together by phosphodiester bonds.

Nucleoside

A structural unit consisting solely of a nitrogenous base attached to a five-carbon sugar.

Nucleotide

The fundamental monomer of nucleic acids, consisting of a nitrogenous base, a five-carbon sugar, and 1 to 3 phosphate groups.

Pyrimidines

Nitrogenous bases composed of a single carbon-nitrogen ring; includes Cytosine (C), Thymine (T), and Uracil (U).

Purines

Nitrogenous bases composed of two fused carbon-nitrogen rings; includes Adenine (A) and Guanine (G).

Deoxyribose

The five-carbon sugar found in DNA, which lacks an oxygen atom at the 2' carbon position (-H).

Ribose

The five-carbon sugar found in RNA, which contains a hydroxyl group at the 2' carbon position (-OH).

Phosphodiester Bond

The covalent bond linking individual nucleotides together, formed between the 5' phosphate group of one sugar and the 3' hydroxyl group of the next.

DNA (Deoxyribonucleic Acid)

A double-stranded, helical nucleic acid chain that encodes genetic information using Adenine, Thymine, Cytosine, and Guanine.

RNA (Ribonucleic Acid)

A single-stranded nucleic acid involved in protein synthesis that utilizes Uracil instead of Thymine.

Complementary Base Pairing

Specific hydrogen bonding between complementary nitrogenous base pairs.

Adenosine Triphosphate (ATP)

A nucleotide consisting of adenine, ribose, and three phosphate groups that serves as the primary energy currency of the cell.

Aldehydes

Carbonyl group is at the end of the molecule.

Ketones

Carbonyl group is in the middle of the molecule.

Phosphatidyl Serine, Phosphatidyl ethanolamine, Phosphatidyl Choline, Phosphatidyl Insoitol

Four types of phospholipids.

Waxes

Fatty acids combine with long-chain alcohols or hydrocarbon structures.

Chlorophylls & Carotenoids

Pigments that absorb light and help convert it to chemical energy in plants.

Glycolipids

Lipid groups combine with carbohydrates.

Lipoproteins

Lipid groups combine with proteins.

Number of hydrogen bonds between Adenine & Thymine/Uracil

2

Number of hydrogen bonds between Guanine & Cytosine

3

“Hybrid” Double Helices

RNA chain paired with DNA chain, occurs when RNA temporarily copies DNA.

NAD+ & FAD+

Electron carriers for many cellular reactions.

Maltose

2 Glucose molecules form an alpha (1 → 4) linkage.

Sucrose

1 Glucose molecule and 1 Fructose molecule form an alpha (1 → 2) linkage.

Lactose

1 Galactose molecule and 1 Glucose molecule form a beta (1 → 4) linkage.