Lecture 3: Organic Molecules (Chapter 3)

Vocabulary-style flashcards covering key terms and their definitions from the notes on organic molecules, including carbohydrates, proteins, nucleic acids, and lipids.

Organic molecule

A molecule that contains both carbon and hydrogen.

Monomer

Small building-block molecules from which larger molecules are built.

Polymer

A long molecule consisting of many similar building blocks (monomers) joined together.

Dehydration synthesis

A chemical reaction that joins monomers with the removal of a water molecule to form a polymer.

Hydrolysis

A reaction that breaks polymers into monomers by adding water.

Monosaccharides

Carbohydrate monomers; simple sugars such as glucose and fructose.

Polysaccharides

Carbohydrate polymers such as glycogen, starch, cellulose, and chitin.

Oligosaccharides

Carbohydrates consisting of three to ten monosaccharide units.

Di-

Prefix meaning two.

Oligo-

Prefix meaning few or a small number.

Simple sugars

Monosaccharides and disaccharides together; also called simple sugars.

Monosaccharide formula

General formula (CH2O)n; ratio of carbon, hydrogen, and oxygen is 1:2:1.

Ribose

A five-carbon sugar (pentose) found in RNA.

Glucose

A common hexose monosaccharide with formula C6H12O6.

Fructose

A hexose monosaccharide found in fruits; isomer of glucose.

Galactose

A hexose monosaccharide that is part of lactose.

Disaccharides

Carbohydrates formed from two monosaccharides (e.g., lactose, sucrose).

Glycosidic bond

Covalent bond between monosaccharides linking them into polysaccharides.

Amylose

A linear form of starch made of glucose units.

Starch

Main energy storage carbohydrate in plants; stored in plastids.

Plastids

Organelles in plant cells where starch is stored.

Glycogen

Storage form of glucose in animals and fungi; highly branched carbohydrate.

Lipids (fat storage)

Another form of long-term energy storage in animals and fungi (fats).

Cellulose

Structural carbohydrate; major component of plant cell walls.

Chitin

Structural polysaccharide in exoskeletons and fungal cell walls.

Fiber

Indigestible cellulose; passes through digestive tract; some microbes digest it.

Proteins

Macromolecules that perform most cellular functions; proteins’ function depends on their structure.

Enzymes

Proteins that speed up chemical reactions.

Amino acids

Monomers of proteins; 20 different amino acids with common structure.

R groups (side chains)

Variable side chains that determine amino acid properties (polar, nonpolar, charged).

Peptide bond

Covalent bond formed between amino acids during dehydration synthesis.

Polypeptide

A long chain of amino acids linked by peptide bonds.

Protein

A biologically functional molecule made of one or more folded polypeptides.

N-terminus

End of a protein with a free amino group.

C-terminus

End of a protein with a free carboxyl group.

Primary structure

Linear sequence of amino acids; determined by peptide bonds (covalent).

Secondary structure

Local folded structures (alpha helix, beta pleated sheet) stabilized mainly by hydrogen bonds.

Tertiary structure

Overall three-dimensional shape of a single polypeptide, stabilized by various weak bonds and interactions.

Quaternary structure

Arrangements of multiple polypeptides in a protein complex.

Denaturation

Loss of protein structure and function due to disruption of bonds; heat, pH changes, or chemicals can cause it.

Sickle-cell disease

A disease caused by a single amino acid substitution in hemoglobin, altering cell shape and function.

Nucleic acids

Information-storage and transmission molecules (DNA and RNA).

Nucleotides

Monomers of nucleic acids.

Phosphodiester bond

Bond between nucleotides linking the sugar of one nucleotide to the phosphate of the next.

Coenzyme A (CoA)

A coenzyme formed from nucleotides that participates in metabolic reactions.

ATP

Adenosine triphosphate; primary energy currency of the cell; energy stored in high-energy phosphate bonds.

ADP

Adenosine diphosphate; lower-energy form after one phosphate is released.

DNA

Deoxyribonucleic acid; stores, expresses, and transmits genetic information.

RNA

Ribonucleic acid; involved in gene expression; two major types introduced later.

Nucleotides energy bonds

Nucleotides can store chemical energy in their bonds (as in ATP).

Lipids

A diverse group of hydrophobic molecules; do not form true polymers; predominantly nonpolar; include fats, phospholipids, steroids, and waxes.

Fatty acids

Hydrocarbon chains with a terminal carboxyl group; can be saturated or unsaturated.

Saturated fats

Fatty acids with only single C-C bonds; pack tightly; solid at room temperature; common in animals.

Unsaturated fats

Fatty acids with one or more C=C double bonds; kinked chains; liquid at room temp; common in plants and fish.

Triglycerides

Fats composed of glycerol bound to three fatty acids; primary energy storage molecule in animals.

Glycerol

Three-carbon backbone to which fatty acids are attached in triglycerides.

Phospholipids

Lipids with a hydrophilic head and hydrophobic tails; amphipathic; form lipid bilayers in water.

Phospholipid bilayer

Two-layer membrane structure with hydrophobic tails inward and hydrophilic heads outward; forms cell membranes.

Cholesterol

Steroid lipid important in cell membranes; precursor to steroid hormones.

Steroids

Lipids with four interlinked carbon rings; include cholesterol and hormone precursors.

Steroid hormones

Hormones derived from cholesterol (e.g., aldosterone, testosterone, estrogen, progesterone, cortisol).

Waxes

Hydrophobic lipids that form water-repellent protective coatings; provide waterproofing.

Structural Isomers

The two molecules differ in the covalent bond relationships among their atoms.

Cis-Trans isomers (geometric isomers)

These molecules differ in how their atoms are arranged about a double bond.

Enantiomers

These molecules are mirror images.