Macromolecules - AP Biology

A glycosidic linkage is defined as a covalent bond created by a dehydration reaction between two monosaccharides. The resulting product is called a disaccharide.

A saturated fat contains no double bonds in its fatty acid chain. Just remember that saturated means the fat is saturated with hydrogens. Double bonds eliminate two hydrogen atoms per occurrence, and are present in unsaturated fats.

Energy is stored in the form of glucose. Cells, in turn, tap into glucose reserves to fuel cellular respiration. The carbon in glucose also serves as raw materials for the synthesis of other molecules such as amino acids.

When two monosaccharides connected together by a glycosidic linkage into a single unit, the product is called a disaccharide. Strings of monosaccharides linked together are called polysaccharides.

Starch is a storage polysaccharide in plants. It is a polymer consisting solely of glucose. Glucose is a source of fuel for cells; therefore, starch is stored for energy.

Starch is a storage polysaccharide in plants. It is a polymer consisting solely of glucose. Glucose is a source of fuel for cells; therefore, starch is stored for energy.

Glycogen is a polysaccharide used as energy storage in animals. Glycogen is a polymer made up of glucose units and undergoes hydrolysis to release glucose when demand for sugar increases.

The polysaccharide cellulose is a major component of plant cell walls. Similar to starch, cellulose is made up of glucose though the linkages in the polymers are different.

Enzymes are not changed or consumed by the reactions they catalyze, but can be altered by environmental conditions. They work in three-dimensional active sites to bind specific substrates and lower the activation of certain reactions, subsequently increasing the reaction rate. Reaction rate can be further increased when enzymes react with cofactors or coenzymes, but decreased when enzymes are blocked from their specified active sites by competitive inhibitors.

Fats have an incredibly high potential to produce a lot of energy when broken down. This is because they are very saturated, which means they have a lot of bonded hydrogens. They also have a lot of carbon-carbon bonds, which have a lot of potential energy stored. When you break down a fat, especially one that has fourteen or more carbons in the chain, you release the energy from every carbon-carbon and carbon-hydrogen bond.

Comparing this to a sugar, alcohol, or protein (amino acids make up proteins), we can see that there aren't as many of these bonds to break. Proteins, in fact, require a lot of energy to break down because they have to be converted into other forms first.

Amphipathic molecules have both a polar and nonpolar region. This amphipathic quality allows phospholipids to create the plasma membrane in eukaryotic cells. The polar region is the phosphate head, which interacts with the aqueous cytosol and extracellular environment. The nonpolar region is the fatty acid tail, which is sequestered in the bilayer of the membrane and helps reduce the permeability to certain molecules.

Macromolecules, such as proteins, nucleic acids, and polysaccharides, are composed of monomers. Each polymer is made from at least two smaller monomers. Protein monomers are amino acids, nucleic acid monomers are nucleotides, and polysaccharide monomers are monosaccharides. In order to form polymers, the monomers must form covalent bonds with one another.

For proteins, these covalent bonds are peptide bonds, and for saccharides they are glycosidic linkages.

Nucleotides are the monomers that make up nucleic acids. They are composed of a five-carbon sugar, a nitrogenous base, and a phosphate group. In building the polymer nucleic acid chain, the sugar and phosphate of one nucleotide align with those of another to build the phosphate-sugar backbone, while the nitrogenous bases will form hydrogen bonds across the helix to link two chains of nucleotides together. Phosphate groups carry negative charge; this gives the cell nucleus an overall negative charge and can be used to generate electrochemical gradients across the nuclear membrane.

Carboxylic acids are found in amino acids, and are not present in nucleic acids.

Water is a very polar substance that will not interact well with nonpolar macromolecules. Enzymes (proteins), oligosaccharides (carbohydrates), and nucleic acids all contain polar regions that make them soluble in aqueous environments. Lipids, however, are hydrocarbons and generally lack a polar region. Lipids would not be soluble in water, but would be soluble in nonpolar organic solvents, like chloroform. We can conclude that cholesterol is a lipid.

Lipids are composed of hydrocarbon chains and are very nonpolar. Polar solvents interact well with polar solutes, but do not solvate nonpolar solutes. When lipids are placed in a polar solvent, they will group together to minimize surface contact with the solvent. These droplets of lipids, or micelles, act like containers for the lipid, keeping them grouped together instead of being distributed through the solvent.

The lipids do not precipitate as they are not necessarily in a solid form. Even lipids in the liquid state can form micelles.

Chargaff found that in double-stranded DNA, the number of guanine bases should be equal to the number of cytosine bases, and the number of adenine bases should equal the number of thymine bases. These rules proved to be important pieces of evidence for the idea of complementarity, the theory that each DNA base pairs only with a specific other base on its opposite strand.

According to Chargaff's rules, the statement regarding guanine and cytosine bases is correct. The two other statements that are similarly worded are not correct because they do not compare the frequencies of two bases that are complementary to each other (adenine will not bind cytosine and guanine will not bind thymine). Finally, guanine-cytosine bonds are more stable than adenine-thymine bonds.

To block a receptor protein, a molecule must structurally resemble the natural ligand. The active sites of proteins are highly specific, and will only bind certain molecules. The chemical formula, electrons, and bonding in the molecule can all influence small regions of the molecule's structure, but the overall shape must ultimately match the active site of the target protein.

G proteins are second messengers involved in cell signaling and propagation or effects within the cell. G protein receptors in the plasma membrane bind to extracellular ligands, causing them to recruit G proteins. Inactive G proteins carry ADP. Once they bind to G protein receptors in the membrane, this GDP molecule is removed, and a GTP molecule is substituted to activate the G protein.

The activated G protein then binds another protein and hydrolyzes GTP to GDP to activate this protein and stimulate cellular effects.

Triglycerides are made up of a glycerol backbone and three fatty acids. They are commonly used to store energy within cells.

A polar head group, a glycerol backbone, and three fatty acids very nearly describes a phospholipid (phospholipids only have two fatty acids). The other answers are not compounds that are readily observed in cells.