Molecular Biology - SAT Subject Test in Biology

Glucose and fructose are monomeric saccharides, or monosaccharides. The carbon to hydrogen to oxygen ratio exists in a 1:2:1 pattern indicative of a monomeric saccharide. The molecular formula of glucose and fructose is . Maltose is a disaccharide composed of two molecules of glucose.

The disaccharide maltose is formed by the dehydration synthesis reaction of two glucose monomers. When simply adding the two glucose monomers together, it may be thought that the summation of the two will be the chemical formula of maltose. However, this does not account for the dehydration synthesis reaction in which one oxygen atom and two hydrogen atoms disappear. After accounting for these molecules the chemical formula for maltose will be represented by .

Glycogen, starch, and cellulose are all polysaccharides composed of many glucose monomers linked together.

The sugar polymer form in which plants store energy is starch, whereas with animals, it is glycogen. While the other answers may in fact be sugar molecules involved in energy metabolism, they do not represent the primary sugar polymer storage molecule. Therefore the correct form of storage for plants is starch. And the correct form of storage for animals is glycogen.

Both lipids (fat) and glycogen (made up of glucose molecules) store energy in animals. Lipids are used for long-term energy storage while glycogen, found in the liver and muscles, is used for short-term energy storage. Peptidoglycan is the molecule that makes up the bacterial cell walls.

A phospholipid generally consists of a phosphate head (polar) and a fatty acid tail (non-polar).

The external hydrophilic environment attracts polar hydrophilic phosphate head groups to the exterior, while allowing non-polar hydrophobic fatty acids to remain shielded in the interior of what becomes the phospholipid bilayer.

A hydrocarbon is made up of a carbon and two hydrogen atoms attached to it.

Lipids make up the bulk of fat in animal tissues and thus stores energy.

Major lipid groups include fats, steroids, and waxes. Because the question references a "waxy covering," we know that the plant covering must be composed of lipids.

By process of elimination, lipids and fats cannot be the correct answer-they are synonymous (lipids are also known as fats). Carbohydrates, eg sugars and starches are composed only of carbon, hydrogen, and oxygen. Nucleic acids contribute to DNA and RNA structure and function. The correct answer is proteins, made of long chains of amino acids-amino acids are sometimes called the "building blocks" of proteins.

Uracil is a base utilized in RNA synthesis, whereas adenine, cytosine, guanine, and thymine are utilized in DNA synthesis.

Examples of nucleic acids include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Because DNA is not an answer choice, we know that the correct answer in this problem must be RNA. Cellulose is a carbohydrate, asparagine is an amino acid, and carbon is an element.

Amino acids are the building blocks of proteins, so when they are put together in a chain, you will get a protein.

A macromolecule made of amino acids is a protein. Lactase, the enzyme that aids in lactose digestion, is the only protein on the list. Sucrose and glucose are carbohydrates. Deoxyribonucleic acid is DNA, a nucleic acid. Triglycerides are a type of lipid.

Note: You can identify an enzyme (which is a protein) by the fact that its name ends in "-ase."

By definition, a missense mutation will still code for an amino acid, but not the desired amino acid. Silent mutations will have a different base pair, but due to the redundancy of genetic code, it will still code for the desired mutation. Nonsense mutations code for an amino acid that leads to a stop codon, which terminates the translation of mRNA into protein. Insertions and deletions result in a shifted reading frame and typically are detrimental.

The question specifies that this is DNA replication. U (uracil) is found only in RNA and T (thymine) is found only in DNA. In DNA, A (adenine) pairs with T (thymine) and G (guanine) pairs with C (cytosine) so the complementary strand will have "A" where the original has "T," "G" where the original has "C," "C" where the original has "G" and "T" where the original has "A."

DNA strands run antiparallel, so the 3' end on the new strand will go opposite the 5' end on the original and vice versa. In this case, that means the complementary strand will run from 5' to 3' to read 5' - TAGCTTCACG - 3'. This sequence is shown in bold below:

5' - TAGCTTCACG - 3'

3' - ATCGAAGTGC - 5'

According to Chargaff's rule, DNA nucleotides pair in a 1:1 ratio. Therefore, if we know how much of the particular gene is made up of one nucleotide, we can extrapolate that known variable to find the other three unknown variables.

To do so, you must remember that adenine pairs with thymine, and cytosine pairs with guanine (A-T, C-G), and that since the ratio between each pair is 1:1 then a gene with 33% adenine must also have 33% thymine. Combine these numbers and subtract from 100: the number leftover is the % of total cytosine and guanine in the gene.

100% - 66% = 34%

Finally, since we know that 34% of the DNA is both C and G, and that the ratio between C-G is 1:1, C and G must both be 17%.

This question is designed to catch a) students who are not reading the question carefully, and b) students unsure of which nucleotides pair with which.

The correct answer is 29%, because cytosine pairs with guanine in a 1:1 ratio. If you answered 21%, then you likely thought the question was more complex than it was.

The correct answer is hydrogen bonding, and each nucleotide attracts its pairing mate because they have corresponding number of hydrogen bonds. Adenine is attracted to thymine to create two hydrogen bonds, and cytosine is attracted to guanine to form three hydrogen bonds. While phosphodiester bonds are very important in creating the strand of DNA, they are not the bond that keeps the two strands in the double helix structure.