Questions and Answers
What is the primary focus of studying life at the molecular level?
What are the two non-standard amino acids that use tRNAs that can base pair with stop codons in the mRNA during translation?
What is the underlying principle of all science, according to Linus Pauling?
What category do ornithine and citrulline fall under?
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What is characteristic of the first three major classes of biomolecules?
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What is the relationship between the structures of biomolecules and their functions?
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What is the reason for classification of amino acids into essential and non-essential groups?
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What type of molecules are nucleic acids, carbohydrates, and lipids?
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What is citrulline a metabolic byproduct of?
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According to Mark Twain, what is the difference between a person who does not read good books and a person who cannot read them?
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What is the importance of nitric oxide produced in the breakdown of arginine?
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What is characteristic of lipids, unlike the other major classes of biomolecules?
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Why do essential amino acids vary considerably from one organism to another?
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What is the purpose of studying the structures of biomolecules?
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What is the difference between essential and non-essential amino acids in humans?
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Why do essential amino acids differ in children and adults?
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What is the name of the bond formed between the carboxyl group of one amino acid and the amino group of another?
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What is the term for a short chain of amino acids?
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What is the name of the end of a peptide chain with a free amino group?
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What are the three types of molecules that can be derived from the amino acid tyrosine?
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What is the process by which amino acids are added to a growing peptide chain?
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What is the term for a long chain of amino acids?
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What is the name of the process by which the carboxyl group of one amino acid is joined to the amino group of another?
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What is the name of the end of a peptide chain with a free carboxyl group?
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Which amino acid is not coded for in the genetic code?
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What is the most abundant amino acid in circulating blood?
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Which of these amino acids can cross the blood-brain barrier?
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Which amino acid is a component of methane-producing enzymes?
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Which of the following amino acids has a carboxyamide side chain?
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What is the pKa value of the R-group carboxyl found in aspartic acid when free in solution?
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Which of the following amino acids is essential for humans undergoing intensive athletic training?
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What is the process of making glutamine from glutamate called?
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What modification occurs to the first methionine in prokaryotic cells?
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Which amino acid is unique for forming a secondary amine structure?
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Which of the following amino acids directly stimulates protein synthesis in muscle?
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What type of amino acid is proline categorized as?
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Which codons are used to code for proline?
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Which of the following amino acids is NOT found in proteins with an R-group that joins with its own α-amino group?
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Which characteristic is true for proline compared to other amino acids?
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What general category does proline fall under based on essentiality?
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Study Notes
Structure & Function
- The structures of biological molecules are inseparable from their functions.
- Molecular interactions that underlie life are dependent on the structures of the molecules we are made of.
Biomolecules
- There are four major classes of biomolecules: nucleic acids, carbohydrates, lipids, and proteins.
- The first three of these major groups are macromolecules built as long polymers made up of smaller subunits or monomers, like strings of beads.
- Lipids, while not polymer chains, also have smaller subunits that are assembled in various ways to make the lipid components of cells, including membranes.
Amino Acids
- Amino acids can be classified into two groups: essential and non-essential.
- Essential amino acids must be in the diet because cells can't synthesize them, while non-essential amino acids can be made by cells.
- There are 20 amino acids, each with a unique R-group that determines its properties.
Essential and Non-Essential Amino Acids
- Table 2.1 shows the classification of amino acids into essential and non-essential.
- Essential amino acids vary considerably from one organism to another and even differ in humans, depending on whether they are adults or children.
Amino Acid Categories
- Amino acids can be categorized based on the properties of their R-groups.
- Table 2.2 shows the categories: non-polar, carboxyl, amine, aromatic, hydroxyl, and other.
Non-Protein Amino Acids
- There are amino acids found in cells that are not incorporated into proteins.
- Examples include ornithine and citrulline, which are intermediates in the urea cycle.
Proline
- Proline is the only amino acid found in proteins with an R-group that joins with its own α-amino group, making a secondary amine and a ring.
- Proline is a non-essential amino acid and is coded by CCU, CCC, CCA, and CCG.
Glutamine
- Glutamine is an amino acid that is not normally essential in humans, but may be in individuals undergoing intensive athletic training or with gastrointestinal disorders.
- Glutamine has a carboxyamide side chain that does not normally ionize under physiological pHs, but which gives polarity to the side chain.
- Glutamine is coded for by CAA and CAG and is readily made by amidation of glutamate.
Selenocysteine
- Selenocysteine is a component of selenoproteins found in all kingdoms of life.
- It is a component in several enzymes, including glutathione peroxidases and thioredoxin reductases.
- Selenocysteine is incorporated into proteins in an unusual way.
Pyrrolysine
- Pyrrolysine is found in methanogenic archaeal organisms and at least one methane-producing bacterium.
- It is a component of methane-producing enzymes.
- Pyrrolysine is not coded for in the genetic code and must be incorporated by unusual means.
Ionizing Groups
- pKa values for amino acid side chains are very dependent upon the chemical environment in which they are present.
- Each amino acid has at least one ionizable amine group (α-amine) and one ionizable carboxyl group (α-carboxyl).
Building Polypeptides
- Amino acids serve as constituents of proteins, which are polymers of amino acids.
- Amino acids are linked to each other by peptide bonds, in which the carboxyl group of one amino acid is joined to the amino group of the next, with the loss of a molecule of water.
- A protein, which is made up of many amino acids, is called a polypeptide (poly=many).
- The end of the peptide that has a free amino group is called the N-terminus (for NH2), while the end with the free carboxyl is termed the C-terminus (for carboxyl).
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Description
This quiz covers the introduction to molecular biology, highlighting the importance of structure and function in understanding life at the molecular level.
