Chapter 3: Biological Molecules

Vocabulary flashcards covering key terms and definitions from Chapter 3: Biological Molecules.

Organic chemistry

The chemistry of carbon-containing compounds; ‘organic’ means carbon; exception: CO2, CO, CO3, CN.

Carbon

Element with 4 electrons in the outer shell; can form up to 4 covalent bonds.

Hydroxyl group

An -OH group; characterizes alcohols and enables hydrogen bonding.

Carboxyl group

A -COOH group; acts as an acid and is common in amino acids and fatty acids.

Amino group

An -NH2 group; basic, key component of amino acids.

Phosphate group

A -PO4^3− group; involved in energy transfer and nucleotides; adds polarity.

Methyl group

An -CH3 group; affects hydrophobicity and gene expression in some contexts.

Monomer

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

Polymer

A large molecule made of repeating monomer units.

Dehydration synthesis

A reaction that links monomers by removing water.

Hydrolysis

A reaction that breaks polymers apart by adding water.

Carbohydrates

Molecules with the formula (CH2O)n; includes sugars and starches.

Monosaccharide

Simple sugar; examples include glucose, fructose, galactose, ribose, deoxyribose.

Disaccharide

Two monosaccharides linked together; examples: sucrose, lactose, maltose.

Polysaccharide

Complex carbohydrates; many sugar units; examples: starch, glycogen, cellulose, chitin.

Glucose

A common hexose sugar; principal energy source in many organisms.

Fructose

A hexose sugar found in fruits; isomer of glucose.

Ribose

Five-carbon sugar in RNA.

Deoxyribose

Five-carbon sugar in DNA lacking one oxygen.

Sucrose

Glucose + fructose; common table sugar.

Starch

Plant storage polysaccharide; generally branched.

Glycogen

Animal storage polysaccharide; highly branched.

Cellulose

Plant cell wall polysaccharide with different bond orientation (beta linkages).

Protein

Macromolecule made of amino acids; performs enzymes, structure, signaling, defense, and more.

Amino acid

Monomer of proteins; contains an amino group, a carboxyl group, and a variable R group.

Peptide bond

Bond between two amino acids formed by dehydration synthesis.

Hydrophilic

Water-loving; typically polar or charged side chains.

Hydrophobic

Water-fearing; typically nonpolar side chains.

R group

The side chain of an amino acid that determines its properties.

Cysteine

Amino acid containing a thiol group that can form disulfide bonds.

Disulfide bond

Covalent bond between two cysteine residues; helps stabilize proteins.

Nucleic acids

Polymers of nucleotides that store and transmit genetic information.

Nucleotide

Monomer of nucleic acids; sugar, phosphate, and base component.

Phosphodiester bond

Bond linking nucleotides between the 5’ phosphate and 3’ sugar.

DNA bases

Adenine (A), Guanine (G), Cytosine (C), Thymine (T).

RNA bases

Adenine (A), Guanine (G), Cytosine (C), Uracil (U).

Lipids

Hydrophobic molecules composed mainly of carbon and hydrogen; include fats, oils, waxes, phospholipids, steroids.

Triglycerides

Glycerol backbone with three fatty acids; storage form of fat.

Glycerol

Three-carbon alcohol that forms triglycerides.

Fatty acids

Long hydrocarbon chains; can be saturated or unsaturated.

Saturated fats

Fats with no double bonds; typically solid at room temperature; often animal fats.

Unsaturated fats

Fats with one or more double bonds; typically liquid at room temperature; often plant fats.

Phospholipids

Lipids with two fatty acids and a phosphate group; form cell membranes; amphipathic.

Steroids

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

Cholesterol

Vital membrane component; precursor to other steroids; modulates membrane fluidity.

Denaturation

Unfolding of a protein due to heat, salts, acids, etc.; often destroys function.

Membranes

Phospholipid bilayers that form barriers and compartments in cells.