뒤로General Biology: Macromolecules of Life
02:00
이 집합의 용어 (29)
Macromolecules are large molecules composed of thousands of covalently connected atoms, formed by joining small organic molecules.
A polymer is a long molecule consisting of many similar building blocks called monomers, such as proteins made of amino acids.
Carbohydrates, proteins, and nucleic acids are polymers. Lipids are large but not true polymers.
A dehydration reaction joins two monomers by removing a water molecule, forming a new covalent bond.
Hydrolysis is the breakdown of polymers into monomers by adding a water molecule, reversing dehydration synthesis.
Monosaccharides are the simplest carbohydrates or single sugars, usually with molecular formulas that are multiples of CH2O.
By the location of the carbonyl group (aldose or ketose) and the number of carbons in the skeleton (e.g., triose, pentose, hexose).
A glycosidic linkage is a covalent bond formed between two monosaccharides by a dehydration reaction.
Starch is a plant storage polysaccharide made of glucose monomers linked mainly by α-1,4 glycosidic bonds, with some α-1,6 branching.
Glycogen is an animal storage polysaccharide similar to amylopectin but more highly branched, stored mainly in liver and muscle cells.
Cellulose is a structural polysaccharide of β-glucose monomers linked by β-1,4 glycosidic bonds, forming straight chains that hydrogen bond to form microfibrils.
Humans lack enzymes to hydrolyze β-glycosidic linkages in cellulose, so it passes as insoluble fiber; some microbes can digest it.
Chitin is a structural polysaccharide with β linkages, found in arthropod exoskeletons and fungal cell walls, used also as surgical thread.
Lipids are hydrophobic molecules mostly made of hydrocarbons, not true polymers, including fats, phospholipids, and steroids.
Fats are made of glycerol (a 3-carbon alcohol) and three fatty acids joined by ester linkages, forming triacylglycerols.
Saturated fatty acids have no double bonds and maximum hydrogens, solid at room temperature; unsaturated have one or more double bonds causing kinks.
Phospholipids have two fatty acid tails (hydrophobic) and a phosphate-containing head (hydrophilic), forming bilayers that make up cell membranes.
Steroids are lipids with a carbon skeleton of four fused rings; cholesterol is a key steroid in animal cell membranes.
Proteins are polymers of amino acids linked by peptide bonds; amino acids have carboxyl and amino groups and variable R groups.
Amino acid properties depend on their side chains (R groups), which can be nonpolar, polar, or charged (acidic/basic).
Primary: amino acid sequence; Secondary: α-helices and β-sheets; Tertiary: 3D folding from R group interactions; Quaternary: multiple polypeptide chains.
Tertiary structure is stabilized by hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals forces, and disulfide bridges between R groups.
Denaturation is the loss of a protein’s native structure due to environmental changes, causing loss of biological activity.
Chaperonins are protein molecules that assist the proper folding of other proteins in a protected environment.
Nucleic acids are polymers of nucleotides that store and transmit hereditary information; DNA and RNA are the two types.
A nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group; without phosphate it is a nucleoside.
Nucleotides are linked by phosphodiester bonds between the 3′ hydroxyl of one sugar and the 5′ phosphate of the next, forming a sugar-phosphate backbone.
DNA has two antiparallel polynucleotide strands forming a double helix, with complementary base pairing: A with T, and G with C via hydrogen bonds.
RNA is usually single-stranded, uses ribose sugar, and substitutes uracil (U) for thymine (T), pairing A with U.