Biology Chps. 3 & 4

A chemical process in which two molecules become covalently bonded to each other with the removal of a water molecule. Also called condensation.

A double membrane, perforated with pores, which encloses the nucleus and separates it from the rest of the eukaryotic cell.

A steroid that is an important component of animal cell membranes and that acts as a precursor molecule for the synthesis of other steroids such as hormones.

A digestive organelle in eukaryotic cells; contains hydrolytic enzymes that digest the cell's food and wastes.

A dense region of DNA in a prokaryotic cell.

In an organic molecule, a functional group consisting of an oxygen atom double-bonded to a crabon atom that is also bonded to a hydroxyl group.

The second level of protein structure; the regular local patterns of coils or folds of a polypeptide chain.

The covalent linkage between two amino acid units in a polypeptide; formed by a dehydration reaction.

An assemblage of atoms commonly attached to the carbon skeletons of organic molecules and usually involved in chemical reactions.

Member of the class of biological molecules consisting of simple single-monomer sugars (monosaccharides), two-monomer sugars (disaccharides), and other multiunit sugars (polysaccharides)

The chain of carbon atoms that forms the structural backbone of an organic molecule.

An organic compound consisting mainly of carbon and hydrogen atoms linked by nonpolar covalent bonds, making the compound mostly hydrophobic. Lipids include fats, phospholipids, and steroids and are insoluble in water.

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). Most of the genes of a eukaryote are located in its chromosomal DNA; a few are carried by the DNA of mitochondria and chloroplasts.

The spiral shape resulting from the coiling of a polypeptide in a protein's secondary structure.

Pertaining to fats and fatty acids whose hydrocarbon chains contain the maximum number of hydrogens and therefore have no double covalent bonds. Saturated fats and fatty acids solidify at room temperature.

An instrument that focuses an electron beam through, or onto the surface of, a specimen. An electron microscope achieves a hundredfold greater resolution than a light microscope.

(plural, grana) A stak of hollow disks formed of thylakoid membrane in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.

An organelle containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.

A membrane-enclosed sac that is part of the endomembrane system of a eukaryotic cell, having diverse functions.

An intermediate-sized protein fiber that is one of the three main kinds of fibers making up the cytoskeleton of eukaryotic cells. Intermediate filaments are ropelike, made of fibrous proteins.

A chemical process in which polymers are broken down by the chemical addition of water molecules to the bonds linking their monomers; an essentail part of digestion.

A structure in an animal cell composed of cylinders of microtubule triplets arranged in a 9 and 0 pattern. AN animal usually has a centrosome with a pair of centrioles involved in cell division.

A functional group consisting of a phosphorus atom covalently bonded to four oxygen atoms.

In an organic molecule, a functional group consisting of a nitrogen atom bonded to two hydrogen atoms.

A double-stranded helical nucleic acid molecule consisting of nucleotide monomers with deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T). Capable of replicating, is an organism's genetic material. See also gene.

Pertaining to fats and fatty acids whose hydrocarbon chains lack the maximum number of hydrogen atoms and therefore have one ore more double covalent bonds. nsaturated fats and fatty acids do not solidify at room temperature.

An organic monomer consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. Nucleotides are the building blocks of nucleic acids.

The third level of protein structure; the overall, three-dimensional shape of a polypeptide due to interactions of the R groups of the amino acids making up the chain.

A structure within the nucleus of a eukaryotic cell where ribosomal RNA is made and assembled with proteins imported from the cytoplasm to make ribosomal subunits.

An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.

A chemical subunit that serves as a building block of a polymer.

A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses.

A synthetic variant of the male hormone testosterone that mimics some of its effects.

A structural polysaccharide found in many fungal cell walls and in the exoskeletons of arthropods.

A sac made of membrane in the cytoplasm of a eukaryotic cell.

In an organic molecule, a carbon bonded to three hydrogens.

The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.

A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. Chromosomes consist of chromatin, a combination of DNA and protein.

An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic molecules (sugars) from carbon dioxide and water.

A protein (or RNA molecule) that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process.

A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.

A lipid made up of glycerol joined to two fatty acids and a phosphate group, giving the molecule a nonpolar hydrophobic tail and a polar hydrophilic head. Phospholipids form bilayers that function as biological membranes.

A sugar molecule consisting of two monosaccharides linked by a dehydration reaction.

A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists; protects the cell and helps maintain its shape.

The complex of DNA and proteins that constitutes eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.

The chemical activities of cells.

A short cellular appendage specialized for locomotion formed from a core of nine outer doublet microtubules and two single microtubules covered by the cell's plasma membrane.

A microscope that uses an electron beam to study the surface architecture of a cell or other specimen.

(plural, plasmodesmata) An open channel in a plant cell wall through which strands of cytoplasm connect from adjacent cells.

A chemical compound composed only of the elements carbon and hydrogen.

A network of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.

The simplest carbohydrate; a simple sugar with a molecular formula that is generally some multiple of CH2O. Monosaccharides are the building blocks of disaccharides and polysaccharides.