Identify structure and purpose of carbohydrates, lipids, proteins, and nucleic acids - AP Biology

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.

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.

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.

The backbone of DNA is made up of deoxyribose sugars linked to phosphate groups. These units are joined by phosphodiester bonds into chains. Nitrogenous bases are bound to the sugars of these groups and join DNA strands together by hydrogen bonds with their complementary base pairs.

Amino acids are the building blocks of proteins, and are not found in DNA. Alpha-linked glucose residues describe a type of polysaccharide, namely glycogen. Glycerol and fatty acids describe a type of lipid known as a triglyceride. Triglycerides and glycogen are primarily used in energy storage.

Peptide bonds form between the amine group of one amino acid and the carboxylic acid of another via a covalent linkage. The formation of a polypeptide chain from amino acid residues constitutes the protein primary structure.

Secondary structure is formed by hydrogen bonding between the amino and carboxyl backbone units of the polypeptide. Tertiary structure is formed by disulfide covalent bonds, hydrophobic interactions, and R-group hydrogen bonding. Quaternary structure is the joining of multiple polypeptide subunits.

Lipids are primarily found in membranes. This includes both the plasma membrane and membranes surrounding particular organelles. Lipids are very useful in membranes because their nonpolar nature helps them act as a barrier between the cell and the outside environment.

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.

An amino acid is the monomer unit of the polymer known as a polypeptide. Polypeptide chains form the primary structure of proteins.

A monosaccharide is the simplest unit of a carbohydrate; a monosaccharide dimer is a disaccharide. Triglycerides are a simple form of lipid and nucleic acids are primarily composed of nucleotide monomers.

An amino acid may be represented by multiple different codon sequences of base pairs of DNA. This codon degeneracy is what allows for the greater variability of DNA as compared to amino acid sequences.

For example, a DNA sequence may show variability without affecting the variability of the coded amino acids.

Organism 1 DNA: 5'-AAAGCAGGC-3' // Organism 2 DNA: 5'-AAGGCTGGT-3' // Differences: 3

Organism 1 RNA: 3'-UUU-CGU-CCG-5' // Organism 2 RNA: 3'-UUC-CGA-CCA-5' // Differences: 3

Organisms 1 Amino Acids: Phe-Arg-Pro // Organism 2 Amino Acids: Phe-Arg-Pro // Differences: 0

Peptide nuerohormones are synthesized in the rough endoplasmic reticulum of the cell body of the neuron. They are then packaged in the Golgi complex and transported along the axon to the nerve endings. Since peptide hormones must be transported out of the cell in vesicles, they are not likely to be synthesized by cytoplasmic ribosomes. These ribosomes are primarily involved in synthesizing cytoplasmic proteins that do not leave the cell.

The nucleus houses DNA and is the site of transcription. The nucleolus is the site of ribosomal submit synthesis. The smooth endoplasmic reticulum is responsible for certain waste disposal and other functions.

Euchromatin is the most active part of the genome and is almost always in active transcriptional mode. mRNA is formed via transcription from DNA in the nucleus, in the form of euchromatin, as opposed to heterochromatin. Heterochromatin is characterized by tight winding of DNA around histones, such that it cannot easily be accessed by RNA polymerase and transcription proteins. Most DNA resembles euchromatin during interphase, when transcription is most active, and condenses to heterochromatin during mitosis.

Note that assembly of eukaryotic ribosomal subunits takes place in the nucleolus, but mRNA is always transcribed directly from DNA within the greater nuclear structure.

Plasma membranes are mostly made up of phospholipids. Phospholipids are lipid molecules that contain both polar and nonpolar regions. This amphipathic nature of phospholipids is very important in plasma membranes. Several hormones of the endocrine system are derived from steroids (a type of lipid). Some examples of steroid derived hormones include testosterone, estrogen, and cortisol; therefore, lipids are precursors to molecules in the endocrine system. By definition, unsaturated fatty acids contain carbon-carbon double bonds.

Glycerol is a three-carbon molecule and forms the backbone of triglycerides and phospholipids. Triglycerides have three fatty acids, one attached to each of the carbons in glycerol. Phospholipids use two glycerol carbons to bind fatty acids, and the third to bind a phosphate group.