SAT II Biology E : Molecular Biology

Study concepts, example questions & explanations for SAT II Biology E

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Example Questions

Example Question #1 : Lipids

The phospholipid bilayer is critically important to the separation of the internal and external environment of the cell.

What drives the formation of the phospholipid bilayer?

Possible Answers:

The external environment pushes non-polar hydrophobic fatty acid tails to form the inner layer and the polar hydrophilic head groups to form the outer layer.

The external environment pushes non-polar hydrophilic fatty acid tails to form the inner layer and the polar hydrophobic head groups to form the outer layer.

The external environment pushes non-polar hydrophobic fatty acid tails to form the inner layer and the polar hydrophobic head groups to form the outer layer.

The external environment pushes non-polar hydrophilic fatty acid tails to form the inner layer and the polar hydrophilic head groups to form the outer layer.

None of these

Correct answer:

The external environment pushes non-polar hydrophobic fatty acid tails to form the inner layer and the polar hydrophilic head groups to form the outer layer.

Explanation:

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.

Example Question #2 : Lipids

Lipids are made up of hydrocarbons linked to each other. 

A hydrocarbon involves an atom of carbon with how many hydrogen atoms bonded to it?

Possible Answers:

One

Three

Two

Five

Four

Correct answer:

Two

Explanation:

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

Example Question #1 : Lipids

Which of the following macromolecules are composed of long chains of amino acids?

Possible Answers:

Proteins

Lipids

Fats

Nucleic acids

Carbohydrates

Correct answer:

Proteins

Explanation:

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. 

Example Question #11 : Molecular Biology

Nucleic acids carry the information of what your cells will do. An example of a nucleic acid would be which of the following?

Possible Answers:

Cellulose

RNA

Carbon 

Asparagine

Correct answer:

RNA

Explanation:

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. 

Example Question #12 : Molecular Biology

Which of the following is not involved in DNA synthesis?

Possible Answers:

Thymine

Guanine

Uracil

Cytosine

Adenine

Correct answer:

Uracil

Explanation:

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

Example Question #1 : Dna, Rna, And Proteins

What type of mutation will code for an amino acid but not the correct or desired amino acid?

Possible Answers:

Deletion mutation

Nonsense mutation

Silent mutation

Insertion mutation

Missense mutation

Correct answer:

Missense mutation

Explanation:

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.

Example Question #2 : Dna, Rna, And Proteins

Given the partial sequence of a single DNA strand shown below, what will be the sequence of the complementary strand that is produced during DNA replication? 

3' - ATCGAAGTGC - 5'

Possible Answers:

3' - UAGCUUCACG - 5'

5' - TAGCTTCACG - 3'

3' - TAGCTTCACG - 5'

5' - ATCGAAGTGC - 3'

5' - UAGCUUCACG - 3'

Correct answer:

5' - TAGCTTCACG - 3'

Explanation:

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'

Example Question #3 : Dna, Rna, And Proteins

What is the dividing structure that separates transcription from translation in a eukaryotic cell?

Possible Answers:

Nuclear envelope

Mitochondrial matrix

Rough endoplasmic reticulum membrane

Smooth endoplasmic reticulum membrane

Cell membrane

Correct answer:

Nuclear envelope

Explanation:

The nuclear envelope separates transcription from translation in a eukaryotic cell. Translation cannot occur until transcription is finished, which is the opposite of what occurs in a prokaryotic cell. In eukaryotic cells, transcription occurs in the nucleus where mRNA will be produced. Once mRNA is produced, it will exit the nucleus through pores and then proceed to be translated into protein in the cytoplasm.

Example Question #4 : Dna, Rna, And Proteins

The trp operon is a repressible operon. Which of the following best describes this type of operon?

Possible Answers:

The operon is usually off and has an active repressor

The operon is usually on and has an inactive repressor

The operon is usually off and has an inactive repressor

None are correct

The operon is usually on and has an active repressor

Correct answer:

The operon is usually on and has an inactive repressor

Explanation:

With a repressible system, the operon is on, meaning the repressor is inactive. Repressible operons are the opposite of inducible operons, which are always off until their repressor is inactivated.

Example Question #5 : Dna, Rna, And Proteins

The lac operon is an inducible operon. Which of the following best describes this type of operon?

Possible Answers:

The operon is usually on and has an active repressor

The operon is usually off and has an inactive repressor

None of these

The operon is usually on and has an inactive repressor

The operon is usually off and has an active repressor

Correct answer:

The operon is usually off and has an active repressor

Explanation:

With an inducible system, the operon is off, meaning its repressor is active, or actively repressing the system from turning on. Inducible operons are opposite to a repressible operon, which is always on until it is repressed.

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