Biological Molecules: Lipids, Proteins, and Nucleic Acids

Flashcards covering the vocabulary and definitions for lipids, proteins, and nucleic acids as presented in the Chapter 4 Biological Molecules lecture.

Lipids

Greasy or oily compounds consisting mainly of carbon, hydrogen, and few oxygen-containing functional groups, which tend to be hydrophobic and insoluble in water.

Hydrophobic

A property of molecules that are insoluble in water and dominated by nonpolar covalent bonds, often referred to as water-fearing behavior.

Triacylglycerol

Also known as a triglyceride, it is a large molecule formed from one glycerol and three fatty acids through a series of three condensation processes.

Ester linkage

A specific bond created by a condensation process that joins a fatty acid to a glycerol molecule in a lipid.

Saturated Fatty Acids

Fatty acids with straight hydrocarbon chains, no carbon-carbon double bonds, and the maximum number of hydrogen atoms; they are typically solid at room temperature.

Unsaturated Fatty Acids

Fatty acids containing one or more carbon-carbon double bonds that cause a kink in the chain, making them liquid at room temperature.

Phospholipid

A molecule consisting of two fatty acid tails (hydrophobic) and a phosphate group with a glycerol (hydrophilic head), serving as a major component of cell membranes.

Amphipathic

A term describing a molecule like a phospholipid that contains both a hydrophobic tail and a hydrophilic head.

Steroids

A class of lipids identified by a carbon skeleton consisting of four fused rings; examples include cholesterol, estrogen, and testosterone.

Waxes

Insoluble, difficult-to-hydrolyze lipids consisting of long fatty acids connected to alcohol by ester linkages, often forming protective waterproof coatings.

Proteins

Macromolecules composed of carbon, hydrogen, oxygen, and nitrogen that consist of one or more polypeptide chains folded into a specific conformation.

Amino Acids

The monomers of proteins, consisting of a central carbon ($\alpha$ carbon) attached to a basic amino group ($-NH_2$), an acidic carboxyl group ($-COOH$), a hydrogen atom, and a variable R group.

Essential amino acids

Amino acids that cannot be synthesized within the body and must be consumed through food.

Amphoteric

A characteristic of amino acids allowing them to act as both an acid (donating a proton from the carboxyl group) and a base (accepting a proton via the amino group).

Peptide bond

A covalent bond formed by a condensation reaction between the carboxyl group of one amino acid and the amino group of another.

Primary Protein Structure

The unique linear sequence of a chain of amino acids joined by peptide bonds in a polypeptide.

Secondary Protein Structure

The local folding of a polypeptide chain into $\alpha$-helices or $\beta$-pleated sheets, held together by hydrogen bonds.

Tertiary Protein Structure

The overall three-dimensional folding pattern of a protein maintained by interactions among side chains, such as disulfide bridges and hydrophobic interactions.

Quaternary Protein Structure

A complex protein level consisting of more than one amino acid chain or polypeptide subunit.

Denaturation

The alteration or modification of a protein's shape, resulting in the loss of its high-order 3-D structure due to external factors like heat, acid, or alkali.

Renaturation

The process by which denatured proteins fold back to their native conformations and restore biological function once denaturants are removed.

Nucleic Acids

Macromolecules composed of chains of monomer subunits called nucleotides, categorized into DNA and RNA.

Nucleotide

The building block of nucleic acids, consisting of a five-carbon (pentose) sugar, a phosphate group, and a nitrogenous base.

Deoxyribose

The five-carbon sugar found in DNA that lacks one oxygen atom at Carbon no 2 (replaced by a hydrogen atom).

Ribose

The normal five-carbon sugar found in RNA, characterized by a hydroxyl group ($-OH$) at Carbon no 2.

Purine

A nitrogenous base featuring a large double-ring structure, specifically Adenine ($A$) and Guanine ($G$).

Pyrimidine

A nitrogenous base featuring a single-ring structure, including Cytosine ($C$), Thymine ($T$), and Uracil ($U$).

Phosphodiester bond

The strong covalent bond that joins different nucleotides together by linking the phosphate group to the pentose sugar.

Watson-Crick DNA Model

A model proposed in 1953 describing DNA as a double-stranded helix where strands are anti-parallel and bases are paired via hydrogen bonds.

mRNA (Messenger RNA)

Long, single strands of RNA that transcript genetic code and carry instructions for amino acid sequences from the nucleus to the ribosome.

rRNA (Ribosomal RNA)

A structural component of the ribosome that provide the site for polypeptide assembly.

tRNA (Transfer RNA)

The smallest type of RNA that picks up amino acids in the cytoplasm and carries them to the ribosome surface to build polypeptides.