Biology 2e - Chapter 3: Biomolecules

Flashcards covering the synthesis, structure, and function of the four major classes of biomolecules: carbohydrates, lipids, proteins, and nucleic acids.

Macromolecules

Large molecules consisting of individual subunits called monomers linked together via covalent bonds into polymers.

Dehydration synthesis

A reaction where two molecules are linked by a covalent bond to form a larger molecule, resulting in the formation of a water molecule.

Hydrolysis

The process of breaking polymers down into individual monomers where water serves as a reactant, with one monomer receiving an $H^+$ and the other receiving an $OH^-$.

Enzymes

Biological molecules that catalyze or speed up reactions by reducing the energy of activation; specific enzymes exist for each macromolecule class.

Carbohydrates

Biomolecules represented by the general formula $(CH_2O)_n$ with a carbon:hydrogen:oxygen ratio of $1:2:1$, providing energy to the body in the form of glucose.

Monosaccharides

Simple sugars usually containing $3-7$ carbons and ending with the suffix -ose, categorized as aldoses or ketoses based on the position of the carbonyl group ($C=O$).

Aldoses

Monosaccharides that have a carbonyl group at the end of the carbon chain.

Ketoses

Monosaccharides that have a carbonyl group in the middle of the carbon chain.

Structural isomers

Molecules with the same chemical formula, such as glucose, galactose, and fructose ($C_6H_{12}O_6$), but different arrangements of atoms.

Glycosidic bond

A covalent bond formed between two monosaccharides during a dehydration reaction.

Polysaccharides

Long chains of monosaccharides joined by glycosidic linkages, which may be branched or unbranched and have a molecular weight exceeding $10,000$ daltons.

Cellulose

An organic compound composed of linear chains of glucose molecules that form hydrogen bonds to create strong microfibrils, providing structural rigidity to plant cell walls.

Chitin

A nitrogen-containing polysaccharide that forms the hard exoskeleton of arthropods and the cell walls of fungi.

Triacylglycerol

A lipid formed by joining three fatty acids to a glycerol backbone through ester linkages, releasing three molecules of water.

Saturated fatty acid

A fatty acid with no carbon-carbon double bonds in the backbone, typically solid at room temperature, such as stearic acid.

Unsaturated fatty acid

A fatty acid containing at least one carbon-carbon double bond, typically liquid at room temperature; includes oleic acid.

Trans-fats

Unsaturated fats with hydrogens on opposite sides of the double bond chain (trans configuration), which have no kink and may increase LDL cholesterol.

Phospholipid

A molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone; it is the major component of all cellular membranes.

Steroids

Hydrophobic lipids characterized by a closed ring structure consisting of four linked carbon rings, such as cholesterol.

Amino acids

The monomers that make up proteins, consisting of a central carbon, an amino group ($-NH_2$), a carboxyl group ($-COOH$), a hydrogen, and a variable side chain (R-group).

Peptide bond

A covalent bond formed via dehydration synthesis that links the carboxyl group of one amino acid to the amino group of another.

Primary protein structure

The unique sequence of amino acids in a polypeptide chain determine by the gene encoding the protein.

Secondary protein structure

The local folding of a polypeptide, such as the $\alpha\text{-helix}$ or $\beta\text{-pleated sheet}$, stabilized by hydrogen bonding in the peptide backbone.

Tertiary protein structure

The unique three-dimensional structure of a polypeptide determined by chemical interactions between R-groups, such as hydrophobic interactions, ionic bonding, and disulfide bridges.

Quaternary protein structure

The structure resulting from interactions and weak bonds between several polypeptides that make up a functional protein.

Denaturation

Changes in protein structure, often caused by alterations in pH or temperature, that lead to a loss of function.

Nucleic acids

Biological molecules, specifically DNA and RNA, that constitute the genetic material of living organisms.

Nucleotide

The monomer of nucleic acids composed of a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Transcription

The process of synthesizing RNA from a DNA template, where the RNA sequence is complementary to the DNA sequence.

Translation

The process of protein synthesis where the bases of mRNA are read in sets of three (codons) and tRNA delivers the corresponding amino acids at the ribosome.