Biology Key Concepts: Ions, Bonds, and Nucleic Acids

What are cations and anions?

Cations are positively charged ions (more protons than electrons), while anions are negatively charged ions (more electrons than protons).

What are valence electrons?

Valence electrons are the electrons located in the outermost shell of an atom.

What is a covalent bond?

A covalent bond is formed when two atoms share electrons.

What distinguishes polar covalent bonds from nonpolar covalent bonds?

Polar covalent bonds occur when one atom is more electronegative than the other, while nonpolar covalent bonds occur when the atoms share electrons equally.

Give an example of a polar bond.

The bond between hydrogen and oxygen in water is a polar bond.

What is an ionic bond?

An ionic bond occurs when one atom steals an electron from another, resulting in one positive ion and one negative ion that attract each other.

What are hydrogen bonds?

Hydrogen bonds form when a molecule with a polar covalent bond has a partial negative charge and is attracted to a partial positive charge in another molecule.

What are Van der Waals interactions?

Van der Waals interactions occur when molecules interact with each other due to transient dipoles.

What is the difference between hydrophobic and hydrophilic substances?

Hydrophobic substances repel water, while hydrophilic substances are attracted to water.

What are proteins made of?

Proteins are made up of amino acids and contain the elements carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).

What is a dipeptide?

A dipeptide is a type of protein that consists of two amino acids connected by peptide bonds.

What are nucleic acids composed of?

Nucleic acids are made up of nucleotides, which consist of a nitrogenous base (A, T, G, C), a sugar, and a phosphate group.

What forms the backbone of DNA?

The backbone of DNA is formed by phosphodiester bonds between the phosphate group and the sugar group.

What is the significance of the 5' and 3' ends of DNA?

The 5' end has a phosphate group, while the 3' end has a sugar; this orientation is crucial for DNA replication and transcription.

What is the role of RNA polymerase?

RNA polymerase is the enzyme that transcribes DNA into RNA.

What is an operon?

An operon is a cluster of genes under the control of a promoter.

What happens during mRNA post-processing?

During post-processing, introns are removed, exons are retained, a poly-A tail is added, and a 5' cap is attached.

What is the purpose of the 5' cap and poly-A tail on mRNA?

The 5' cap and poly-A tail stabilize mRNA and assist in the binding of ribosomes for translation.

What is the untranslated region (UTR) of mRNA?

The UTR is the region of mRNA that is not translated into amino acids, located before the start codon and after the stop codon.