Proteins and Nucleic Acids - Lecture Review

Comprehensive flashcards covering the structure and function of proteins and nucleic acids, including amino acid properties, peptide and phosphodiester bonds, protein folding, DNA double helix, and the RNA world hypothesis.

What percentage of a cell's dry weight is made up of proteins?

Proteins make up approximately $50\%$ of a cell's dry weight.

What functions do proteins perform in living organisms?

Proteins function in structural support, defense, transport, communication, catalysis, and movement.

How do the amino group and carboxyl group of an amino acid behave in solution?

In solution, amino acids are ionized: the amino group gains an $H^+$ and the carboxyl group loses an $H^+$.

How many common amino acids exist across all life, and how many are essential in the human diet?

There are 20 common amino acids; 9 are essential (must be ingested), and 11 can be synthesized by cells.

How is a peptide bond in proteins formed between two amino acids?

A peptide bond is a strong covalent C-N bond formed via a dehydration reaction between the carboxyl group of one amino acid and the amino group of another.

Calculate the total number of possible polypeptide sequence combinations?

The formula is $20^n$, where $n$ represents the number of amino acids in the polypeptide chain.

What are two specific examples of protein shapes and their functional roles?

1. Keratin (fibrous protein) providing structure in hair and nails

2. Hemoglobin (globular protein) that carries oxygen in red blood cells.

What is protein denaturation, and what conditions can cause it?

Denaturation - loss of a protein's shape and function. Factors such as heat or chemicals that break hydrogen bonds and disulfide bonds.

What three components form a generic nucleotide monomer?

A 5-carbon sugar, a phosphate group attached to the 5' carbon, and a nitrogenous base attached to the 1' carbon.

Which nitrogenous bases are found in DNA versus RNA?

DNA contains Cytosine, Thymine, Guanine, and Adenine (C, T, G, A).

RNA contains Cytosine, Uracil, Guanine, and Adenine (C, U, G, A).

How does a phosphodiester linkage form during nucleotides polymerization?

It forms via a dehydration reaction between the 3' carbon of one nucleotide's sugar and the phosphate group on the 5' carbon of the next nucleotide.

In which direction does a polynucleotide chain grow, and why?

5' to 3' direction, because incoming nucleotides must bind to an available $-OH$ group on the 3' carbon.

What complementary base pairing rules define the DNA double helix?

Adenine pairs with Thymine (A with T) and Guanine pairs with Cytosine (G with C) between two antiparallel strands running in opposite directions.

What structural features distinguish RNA from DNA?

RNA contains ribose sugar instead of deoxyribose, uses Uracil instead of Thymine, and is single-stranded, often folding into secondary structures like hairpins.

What is the primary proposal of the RNA World Hypothesis?

It proposes that early RNA served as both the genetic material and the catalyst (via ribozymes) for its own polymerization before DNA and proteins evolved.

Nucleic acids….

store and pass on genetic info, the body needs to live, grow, and build proteins

DNA and RNA are….

made up of nucleotide monomers, a long chain forms called polynucleotides that are linked by phosphodiester bonds

All proteins are made up of….

amino acid polymers

Amino acids are distinguished by

their side chain (R-group) being polar or non-polar and -/+ charge. The size and shape and charge can affect reactivity and solubility.

Types of proteins includes…

hormones and enzymes

Which of the following is not a function of proteins?

store information

Nucleic acids are polymers, made up of which of the following monomers?

nucleotides