Unit 1: Introduction to Cell Biochemistry

Flashcards covering atomic structure, chemical bonding, electronegativity, water properties, reactions, and biological macromolecules based on lecture notes.

Why are atoms typically electrically neutral?

They have an equal number of positively charged protons and negatively charged electrons.

What is electronegativity?

An atom's tendency to attract electrons, which is determined by factors including the positive charge of the nucleus and the distance of electrons from the nucleus.

How is a nonpolar covalent bond defined by electronegativity difference and electron sharing?

It occurs when two atoms have an electronegativity difference less than 0.4–0.5, resulting in equal sharing of the electron pair halfway between the atoms.

How is a polar covalent bond defined in terms of electronegativity difference and charge distribution?

It occurs with a moderate electronegativity difference (0.5–1.7), causing the shared electron pair to be closer to the more electronegative atom and creating partial negative ($\delta^-$) and partial positive ($\delta^+$) charges.

What occurs during ionic bonding between two atoms?

An electron is transferred from one atom to another due to a large electronegativity difference (>1.7), creating a positively charged cation and a negatively charged anion held together by opposite charge attraction.

Why is a solid line not drawn between sodium and chloride ions in Sodium chloride (NaCl)?

A solid line represents shared electron pairs in covalent bonds, whereas sodium and chloride ions are held together solely by opposite charge attraction after electron transfer.

How many electrons do Carbon, Oxygen, Nitrogen, and Hydrogen each need to fill their valence orbitals and become most stable?

Carbon needs 4, Oxygen needs 2, Nitrogen needs 3, and Hydrogen needs 1.

What structural characteristics make water a polar molecule?

Water contains polar covalent bonds between oxygen and hydrogen and has an asymmetrical, bent geometry.

What defines a hydrogen bond?

An interaction involving the partial positive charge ($\delta^+$) of a hydrogen atom and the partial negative charge ($\delta^-$) of another atom.

Why are nonpolar molecules hydrophobic and insoluble in water?

They contain mostly or all nonpolar bonds that lack partial charges, providing no partial charge for water molecules to interact with.

What is the difference between a condensation reaction and a hydrolysis reaction?

A condensation reaction builds a polymer by adding monomers and removing water, whereas a hydrolysis reaction breaks down a polymer into monomers by adding water.

Which class of cellular macromolecules does NOT form a polymer structure?

Lipids.

What are the monomers of Nucleic Acids, Proteins, and Carbohydrates?

Nucleic Acids have Nucleotides, Proteins have Amino acids, and Carbohydrates have Monosaccharides.

What electron shell and orbital structure is shown in this atomic diagram of Neon?

Neon has 2 electron shells: the 1st shell has 1 orbital filled with 2 electrons, and the 2nd shell has 4 orbitals filled with 8 electrons total, making it stable and unreactive.