BIOL 105/106 Lecture Notes - Practice Flashcards (Question and Answer)

A set of Q&A flashcards covering key topics from the provided biology lecture notes, suitable for exam review.

What are the basic chemical components common to life?

Carbohydrates, fatty acids, nucleic acids, amino acids

What encloses all cells?

A plasma (cell) membrane

What uses a universal code to specify proteins?

Genetic information (DNA)

Do living organisms evolve?

Yes, through changes in frequencies of genetic variants over time

What is the biological hierarchy of organization from cells upward?

Cells → Tissues → Organs → Organ systems

Which six elements make up about 98% of living tissue?

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur (C, H, N, O, P, S)

What determines the identity of an atom?

The number of protons (atomic number)

What are isotopes?

Variations in the number of neutrons

What are radioisotopes?

Unstable isotopes

How much empty space is in an atom?

About 99.99% of the atom is empty space

How many electrons can the first electron shell hold?

2 electrons

How many electrons can the second and third shells hold?

8 electrons in each shell

What determines an atom’s reactivity?

The number of electrons in the outer (valence) shell

What is electronegativity?

The attractive force that a nucleus exerts on electrons; higher to the right of the periodic table

What is a polar covalent bond?

A covalent bond with unequal sharing of electrons due to electronegativity differences

What is a hydrogen bond?

Electrical attraction between a covalently bonded hydrogen and an electronegative atom

What is a hydrophobic interaction?

Interaction of nonpolar substances in the presence of polar substances (especially water)

What are van der Waals forces?

Weak attractions between nonpolar molecules that can be substantial when summed over a large molecule

What is an ionic bond?

Attraction between ions of opposite charges due to transfer of electrons

What happens when Na and Cl form an ionic bond?

Sodium becomes Na+ and chloride becomes Cl-; ions become stabilized by full electron shells

What is hydration’s role in ionic bonds?

Water molecules hydrate ions and prevent reassociation

What is an acid?

A proton (H+) donor

What is a base?

A proton (H+) acceptor

What is pH?

The negative log of the hydrogen ion concentration [H+]

What is the pH of pure water at 25°C?

pH 7 (neutral)

What is buffering?

Regulation of pH by a weak acid and its conjugate base

What is the major buffering system in blood?

The carbonic acid/bicarbonate system (H2CO3/HCO3-)

Why is buffering important in biology?

Small pH changes can alter protein shape and function; buffers resist pH changes

What is the approximate pH of human blood?

Around 7.4

What is the relationship between a 1-unit pH change and [H+]?

A 1 pH unit change corresponds to a tenfold change in [H+]