BIOL 115 Exam 2 Study Guide: Cell Biology and Large Biological Molecules

Practice vocabulary flashcards covering cell structures, organelles, and the structures and functions of large biological molecules (lipids, nucleic acids, and proteins) for BIOL 115 Exam 2.

Amphipathic

Possessing both a polar (hydrophilic) head and a non-polar (hydrophobic) long tail, a property of lipids that leads to the spontaneous formation of bilayers and membranes.

Central Dogma of Biology

The biological framework stating that genetic information flows from DNA to RNA, and from RNA to protein.

Four main classes of large biological molecules

Carbohydrates, lipids, proteins, and nucleic acids.

Monomer

A single molecular subunit that serves as the repeating building block for larger biological macromolecules.

Polymer

A large molecule composed of repeating monomer subunits linked together by covalent bonds.

Dehydration reaction

A chemical reaction that synthesizes a polymer by joining monomers together with the removal of a water molecule ($H_2O$).

Hydrolysis

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

Nucleotide

The monomer subunit of nucleic acids, chemically composed of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Deoxyribonucleic acid (DNA)

A double-stranded nucleic acid containing deoxyribose sugar and the nitrogenous bases Adenine, Thymine, Guanine, and Cytosine ($A, T, G, C$) that stores hereditary instructions.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid containing ribose sugar and the nitrogenous bases Adenine, Uracil, Guanine, and Cytosine ($A, U, G, C$) that carries instructions from the nucleus to ribosomes to direct protein synthesis.

DNA Nitrogenous Bases

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

RNA Nitrogenous Bases

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

Amino acid

The monomer subunit of polypeptides, consisting of an amino group, a carboxyl group, and a variable side chain; $20$ distinct types exist in biological systems.

R group

The variable side chain portion of an amino acid structure that imparts specific chemical properties (non-polar, polar, or charged).

Peptide bond

The covalent linkage formed between the carboxyl group of one amino acid and the amino group of an adjacent amino acid via dehydration synthesis.

Primary protein structure

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

Secondary protein structure

Local repetitive folding patterns in the polypeptide backbone, such as alpha helices and beta pleated sheets, stabilized by hydrogen bonding.

Tertiary protein structure

The overall three-dimensional conformation of a single polypeptide chain formed by interactions among side chain R groups.

Quaternary protein structure

The functional macromolecular structure resulting from the assembly and aggregation of two or more independent polypeptide chains.

Hydrophilic

Having an affinity for water; characteristic of polar or charged molecules.

Hydrophobic

Lacking an affinity for water; characteristic of non-polar molecules such as hydrocarbon chains.

Phospholipids

Membrane lipids composed of a glycerol backbone, two non-polar fatty acid tails, and a polar phosphate head group.

Triglycerides

Fats composed of three fatty acids joined to a glycerol molecule via ester bonds, functioning primarily as concentrated energy storage.

Hydrocarbon tail

The non-polar, hydrophobic fatty acid chain portion of lipid molecules such as triglycerides and phospholipids.

Saturated fatty acid

A hydrocarbon tail with no carbon-carbon double bonds, maximizing hydrogen atoms and packing tightly together into a viscous or solid state.

Unsaturated fatty acid

A hydrocarbon tail containing one or more cis double bonds that create kinks, preventing compact packing and increasing membrane fluidity.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings, functioning as hormones or structural membrane components.

Cholesterol

A four-ring steroid within animal membranes that acts as a fluidity buffer, reducing phospholipid movement at moderate temperatures and preventing tight packing at low temperatures.

Plasma membrane

A selectively permeable phospholipid bilayer embedded with proteins that regulates nutrient import, waste export, and cellular communication.

Surface area-to-volume ratio

The geometric relationship that limits maximum cell size because internal cell volume increases faster than surface area, restricting metabolic exchange.

Nucleus

A double-membrane-bound eukaryotic organelle that encloses and protects genomic DNA.

Nucleolus

A dense non-membrane-bound region within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.

Ribosome

A non-membrane-bound cellular complex composed of RNA and protein that synthesizes polypeptides by translating messenger RNA.

Rough Endoplasmic Reticulum

A eukaryotic membrane network studded with ribosomes that synthesizes, modifies, and packages secretory and membrane proteins.

Smooth Endoplasmic Reticulum

A eukaryotic tubular membrane network lacking ribosomes that catalyzes lipid synthesis, carbohydrate metabolism, and detoxification.

Golgi apparatus

A series of flattened membranous sacs (cisternae) that modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum.

Lysosome

A membrane-bound animal organelle maintaining an acidic environment ($pH \to 4$) with hydrolytic enzymes to digest macromolecules and cellular debris.

Mitochondrion

A double-membrane eukaryotic organelle that generates cellular ATP through cellular respiration and oxidative phosphorylation.

Chloroplast

A double-membrane photosynthetic organelle in plants and algae that captures light energy to produce organic sugars.

Central vacuole

A large fluid-filled plant organelle that stores organic compounds, retains water, and provides turgor pressure for structural support.

Cytoskeleton

An intracellular network of protein fibers that provides mechanical support, maintains cell shape, and facilitates internal transport and locomotion.

Cell wall

An extracellular protective structure found in plant cells composed primarily of cellulose that maintains shape and prevents excess water uptake.