Carbon and Biological Macromolecules

Flashcards covering carbon chemistry, organic isomers, functional groups, and the four major biological macromolecules: carbohydrates, proteins, nucleic acids, and lipids.

Carbon Valence

The chemical property of carbon having four valence electrons, enabling it to form covalent bonds with up to four other atoms to construct macromolecular backbones.

Hydrocarbon

An organic molecule composed entirely of carbon and hydrogen atoms, such as methane ($CH_4$) or ethane ($C_2H_6$).

Structural Isomer

Molecules that share the same chemical formula but differ in the covalent arrangements of their atoms, such as glucose, galactose, and fructose ($C_6H_{12}O_6$).

Stereoisomers (Enantiomers)

Molecules with identical chemical formulas and bonding connections that are non-superimposable mirror images of each other, such as D-lactic acid and L-lactic acid.

Geometric Isomer

Isomers that have the same covalent bonds but differ in spatial arrangement around a double bond, categorized as cis (same side) or trans (opposite side).

Oleic Acid

A cis-unsaturated fatty acid containing a double bond that introduces a kink in the hydrocarbon chain, rendering it liquid at room temperature.

Elaidic Acid

A trans-unsaturated fatty acid with a straight hydrocarbon chain configuration around its double bond, rendering it solid at room temperature.

Functional Group

Specific arrangements of atoms (containing elements like H, N, O, P, or S) attached to carbon skeletons that dictate the chemical reactions and behavior of organic molecules.

Condensation Reaction (Dehydration)

A chemical process that covalently links two monomers together by removing a molecule of water ($H_2O$).

Hydrolysis Reaction

A chemical reaction that breaks covalent bonds in polymers into smaller monomers through the addition of a water molecule ($H_2O$).

Monosaccharide

The simplest carbohydrate monomer, generally represented by the formula $C_n(H_2O)_n$, which cells use directly for energy (e.g., glucose, fructose, galactose).

Disaccharide

A carbohydrate composed of two monosaccharide units covalently linked together by a glycosidic bond, such as sucrose or maltose.

Glycosidic Linkage

The covalent bond formed between two monosaccharides through a condensation reaction.

Starch

An energy-storage polysaccharide in plant cells composed of ̑\alpha--glucose monomers, existing as unbranched amylose or branched amylopectin.

Glycogen

A highly branched energy-storage polysaccharide composed of $\alpha$--glucose units, stored in animal liver and muscle cells.

Cellulose

A structural polysaccharide in plant and algal cell walls consisting of $\beta$--glucose monomers linked by $\beta-1,4$--glycosidic bonds in parallel strands joined by hydrogen bonds.

Chitin

A structural polysaccharide found in fungal cell walls and arthropod exoskeletons, made of $\beta$--NAG monomers joined by $\beta-1,4$--glycosidic linkages.

Peptidoglycan

A structural polymer in bacterial cell walls made of alternating $\beta$--NAM and $\beta$--NAG monosaccharide chains cross-linked by peptide bonds between amino acid chains.

Oligosaccharide

A short carbohydrate chain of 3 to 10 monosaccharides that attaches to cell membrane proteins or lipids, acting as molecular ID tags for recognition.

Amino Acid

The monomer of proteins, consisting of a central $\alpha$--carbon bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R-group).

Peptide Bond

The covalent bond formed between the carboxyl group of one amino acid and the amino group of another via a dehydration reaction.

Primary Protein Structure

The linear sequence of amino acids in a polypeptide chain, held together by covalent peptide bonds.

Secondary Protein Structure

Local structural shapes like $\alpha$--helices and $\beta$--pleated sheets formed by hydrogen bonding along the polypeptide backbone.

Tertiary Protein Structure

The overall three-dimensional conformation of a polypeptide, stabilized by R-group interactions including hydrogen bonds, ionic bonds, hydrophobic forces, van der Waals forces, and disulfide bonds.

Quaternary Protein Structure

The overall protein structure formed by the combination and bonding of two or more distinct polypeptide subunits (e.g., dimers or tetramers).

Disulfide Bond

A covalent bond formed between sulfhydryl groups ($-SH$) on cysteine side chains that helps stabilize tertiary protein structure.

Nucleotide

The monomer building block of nucleic acids, comprising a phosphate group, a 5-carbon pentose sugar (ribose or deoxyribose), and a nitrogenous base.

Phosphodiester Linkage

The covalent linkage joining nucleotides together in a nucleic acid chain, formed between the 3' carbon hydroxyl of one sugar and the 5' carbon phosphate of the next.

Triglyceride

A lipid energy-storage molecule composed of one glycerol backbone attached to three fatty acid chains via carboxylic ester linkages.

Saturated Fatty Acid

A fatty acid with no carbon-carbon double bonds in its hydrocarbon chain, containing the maximum possible number of hydrogen atoms.

Unsaturated Fatty Acid

A fatty acid containing one or more double bonds in its hydrocarbon chain, which reduces hydrogen saturation and often introduces structural kinks.

Phospholipid

An amphipathic lipid consisting of a glycerol molecule attached to two nonpolar fatty acid tails and one polar/charged phosphate head.

Amphipathic

Having both hydrophilic (water-loving, polar) and hydrophobic (water-fearing, nonpolar) regions within the same molecule.

Steroid

A class of nonpolar lipids characterized by a structure of four fused carbon rings, such as cholesterol, testosterone, and estrogen.

Wax

A highly hydrophobic lipid composed of long hydrocarbon chains connected by wax ester bonds, functioning as protective or water-repellent coatings.