Biological Macromolecules: Lipids, Proteins, and Nucleic Acids

Vocabulary practice flashcards covering lipids, protein structures and functions, nucleic acids, and functional groups based on lecture notes.

Lipids

A class of nonpolar biological molecules that do not mix well with water and are not considered true polymers or macromolecules.

Glycerol

An alcohol in which each of its three carbon atoms bears a hydroxyl group ($\text{-OH}$).

Fatty Acid

A molecule with a long carbon skeleton (typically $16\text{ to }18$ carbon atoms) with a carboxyl group at one end and the rest consisting of a hydrocarbon chain.

Triacylglycerol (Fat Synthesis)

A fat molecule consisting of three fatty acid molecules linked to one glycerol molecule through ester linkages formed by dehydration reactions.

Saturated Fatty Acid

A fatty acid with no double bonds between carbon atoms composing the chain, allowing as many hydrogen atoms as possible to bond to the carbon skeleton.

Unsaturated Fatty Acid

A fatty acid with one or more double bonds, resulting in one fewer hydrogen atom on each double-bonded carbon and causing a kink in the hydrocarbon chain.

Phospholipid Structure

A lipid molecule composed of a hydrophilic head (glycerol attached to a negatively charged phosphate group) and two hydrophobic fatty acid tails.

Phospholipid Bilayer

A double-layered arrangement formed by phospholipids in water, shielding the hydrophobic tails on the inside while exposing the hydrophilic heads outward.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings.

Cholesterol

A common component of animal cell membranes and the precursor from which other steroids, such as sex hormones, are derived.

Protein

A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.

Polypeptides

Unbranched polymers of amino acids linked together by peptide bonds.

Enzymes

Chemical catalysts that speed up chemical reactions selectively without being consumed.

Enzymatic Proteins

Proteins whose function is the selective acceleration of chemical reactions, such as digestive enzymes catalyzing the hydrolysis of food.

Storage Proteins

Proteins that store amino acids, such as ovalbumin in egg whites serving as an amino acid source for developing embryos.

Hormonal Proteins

Proteins that coordinate an organism's activities, such as insulin regulating blood sugar by causing tissues to take up glucose.

Contractile and Motor Proteins

Proteins responsible for movement, such as actin and myosin in muscle contraction, and motor proteins powering cilia and flagella undulations.

Defensive Proteins

Proteins that function in protection against disease, such as antibodies that help destroy viruses and bacteria.

Transport Proteins

Proteins that transport substances throughout the body or across cell membranes, such as hemoglobin carrying oxygen from the lungs to other body parts.

Receptor Proteins

Proteins that function in the response of a cell to chemical stimuli, such as membrane receptors detecting signaling molecules released by nerve cells.

Structural Proteins

Proteins that provide structural support, such as keratin found in hair, horns, feathers, and other appendages.

Amino Acid Structure

An organic molecule containing an $\alpha$ carbon bonded to four partners: an amino group ($\text{-NH}_2$), a carboxyl group ($\text{-COOH}$), a hydrogen atom, and a variable side chain ($\text{R}$ group).

Peptide Bond

A covalent bond formed between two amino acids when the carboxyl group of one is joined to the carboxyl/amino group of another via a dehydration reaction.

N-terminus and C-terminus

The two ends of a polypeptide chain, where the N-terminus has a free amino group and the C-terminus has a free carboxyl group.

Primary Structure

The unique linear sequence of amino acids in a protein, determined by genetic information, which dictates secondary and tertiary structure.

Secondary Structure

Coils and folds within segments of a polypeptide chain resulting from hydrogen bonds between repeating constituents of the polypeptide backbone.

$\alpha$ Helix

A secondary structure characterized by a delicate coil held together by hydrogen bonding between every 4th amino acid in the polypeptide backbone.

$\beta$ Pleated Sheet

A secondary structure formed when two or more parallel segments of a polypeptide chain lying side by side are connected by hydrogen bonds.

Tertiary Structure Interactions

The overall three-dimensional shape of a polypeptide formed by side chain ($\text{R}$ group) interactions, including hydrogen bonds, hydrophobic and van der Waals interactions, ionic bonds, and disulfide bridges.

Disulfide Bridges

Strong covalent links formed when the sulfhydryl groups ($\text{-SH}$) of two cysteine monomers are brought close together by protein folding.

Quaternary Structure

The overall protein structure that results from the aggregation of two or more polypeptide subunits.

Hemoglobin Structure

A quaternary protein composed of four polypeptide subunits ($\alpha_1$, $\alpha_2$, $\beta_1$, $\beta_2$), each containing a heme group with an iron atom that binds oxygen.

Sickle-Cell Disease

A genetic disorder caused by the substitution of valine for glutamine at a specific position in the primary structure of hemoglobin, causing molecules to crystallize into a sickle shape.

Denaturation and Renaturation

Denaturation is the unravelling and loss of shape/function of a protein due to changes in pH, salt concentration, temperature, or solvent nonpolarity; renaturation is the refolding back into its native shape.

X-ray Crystallography

A method used to study protein structure by analyzing the diffraction pattern of an X-ray beam directed through a crystallized molecule.

Nucleic Acids

Polymers made of nucleotide monomers, consisting of Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA), that enable organisms to reproduce and direct protein synthesis.

Gene Expression Process

The multi-step process in which DNA directs mRNA synthesis in the nucleus, mRNA moves to the cytoplasm via nuclear pores, and ribosomes use mRNA information to synthesize polypeptides.

Nucleotide Monomer

The monomer of nucleic acids consisting of three parts: a nitrogenous base, a five-carbon pentose sugar, and one or more phosphate groups.

Nucleoside

The portion of a nucleotide composed only of a nitrogenous base attached to a pentose sugar, lacking any phosphate group.

Pyrimidines and Purines

The two families of nitrogenous bases: Pyrimidines have a single 6-membered ring (Cytosine, Thymine, Uracil), while Purines have a 6-membered ring fused to a 5-membered ring (Adenine, Guanine).

Deoxyribose vs. Ribose

Deoxyribose is the pentose sugar in DNA that lacks an oxygen atom on its second carbon ($2'$ carbon), whereas Ribose is the pentose sugar found in RNA.

Phosphodiester Linkage

A covalent bond joining nucleotides in a polynucleotide, consisting of a phosphate group linking the $3'$ carbon of one sugar to the $5'$ carbon of the next sugar.

Antiparallel

The arrangement of the two sugar-phosphate backbones in a DNA double helix running in opposite $5' \rightarrow 3'$ directions.

Functional Groups Table

A collection of chemical groups attached to organic molecules, including Hydroxyl, Methyl, Carbonyl, Carboxyl, Amino, Phosphate, and Sulfhydryl, each imparting specific properties.