Unit 1-6: The Chemical Basis of Life and Biomolecules (Lecture Notes)

A comprehensive set of practice questions (Q&A) based on the lecture notes, covering atoms, bonds, water, biomolecules, lipids, carbohydrates, nucleotides, and origin-of-life concepts.

What are the three forms of matter found in living organisms?

Solid, liquid, and gas.

What is an atom?

The smallest functional unit of matter that forms all chemical substances and organisms.

What particles form the nucleus of an atom?

Protons and neutrons.

Where are electrons located in an atom?

Outside the nucleus in orbitals around the nucleus.

What is the simplest atom in the world?

Hydrogen.

What is a chemical element?

A specific type of atom, such as hydrogen, nitrogen, or oxygen.

What is an orbital?

A cloud-like region where an electron is most likely found.

What is the maximum number of electrons in a single orbital?

2 electrons.

What does an atom’s atomic number represent?

The number of protons in the nucleus.

What is atomic mass primarily the mass of?

The nucleus (protons and neutrons).

Which atom is described as the simplest and most fundamental element?

Hydrogen (H).

What are the three basic subatomic particles and their charges?

Electrons (negative), protons (positive), neutrons (neutral).

In a neutral atom, how do electrons relate to protons?

Electrons balance the positive charge of protons; overall charge is neutral.

What is a molecule?

Two or more atoms bonded together.

What is a compound?

A molecule composed of two or more different elements.

What is a single covalent bond?

Two atoms share a pair of electrons.

What is a double covalent bond?

Two atoms share two pairs of electrons.

What is a triple covalent bond?

Two atoms share three pairs of electrons.

What is electronegativity?

The ability of an atom to attract electrons in a bond.

What is a polar covalent bond?

A covalent bond in which shared electrons are pulled toward the more electronegative atom, creating partial charges.

Why is water considered polar?

Oxygen is more electronegative than hydrogen, pulling electrons toward itself.

What determines whether a molecule is polar or nonpolar?

Differences in electronegativity and the distribution of electrons within the molecule.

What is meant by hydrophilic?

Molecules that are water-loving and dissolve in water.

What is meant by hydrophobic?

Molecules that are water-fearing and are not soluble in water.

What factors influence boiling and melting points in molecules?

Polarity and intermolecular forces; polar molecules generally have higher boiling/melting points.

What is a hydrogen bond and how does it form in water?

A weak attraction between a partially positive hydrogen and a partially negative atom (like oxygen) in water.

What is an ionic bond?

An attraction between positively and negatively charged ions due to electron transfer.

What happens when an atom or molecule gains or loses electrons?

It becomes an ion with a net electric charge.

Between which types of elements do ionic bonds typically form?

Between a metal (low electronegativity) and a nonmetal (high electronegativity).

What is a covalent bond?

Electrons are shared between two nonmetals.

What happens in a chemical reaction at the molecular level?

Bonds are broken and formed to produce new substances.

What are solutes and solvents in solutions?

Solutes dissolve in solvents to form solutions; aqueous solutions are water-based.

What does it mean for a molecule to be hydrophilic?

It dissolves in water.

What does it mean for a molecule to be hydrophobic?

It is insoluble in water or water-repelling.

What roles does water play in living organisms?

Participates in chemical reactions, lubrication (saliva), waste elimination, support, and cooling via evaporation.

What are the four major biomolecule groups?

Carbohydrates, proteins (amino acids), lipids, nucleic acids (DNA and RNA).

What elements are most common in biological systems, and which minor elements may be present?

Common: C, H, O, N; trace/minor elements include S and others as needed.

What are biomolecules?

Essential organic molecules involved in maintenance and metabolism of living organisms.

What is a hydroxyl group and where is it found?

-OH; found in alcohols and carbohydrates; adds solubility and hydrogen-bonding ability.

What is a carbonyl group and its importance?

C=O; essential in reactions like condensation and hydrolysis.

What is a carboxyl group and its acid behavior?

-COOH; acts as an acid by donating protons.

What is an amino group and its basic behavior?

-NH2; found in amino acids; can act as a base by accepting protons.

What is a phosphate group and where is it crucial?

-PO4; crucial in nucleic acids (DNA/RNA) and energy transfer (ATP).

What is a sulfhydryl group and its role?

-SH; helps stabilize protein structures via disulfide bonds.

What is a methyl group and its regulatory role?

-CH3; found in biomolecules and can influence gene expression.

What is an ester group and where is it found?

-COO-; common in lipids; involved in energy storage and membrane structure.

What is an amide group and where is it found?

-CONH2; found in proteins and nucleic acids (peptide bonds link amino acids).

What is carbon’s bonding capacity and example of a simple carbon compound?

Carbon forms four covalent bonds; example is methane (CH4).

What is the general formula for carbohydrates and their carbon-to-oxygen-to-hydrogen ratio?

(CH2O)n with a 1:2:1 ratio.

What is the simplest sugar and what suffix do many monosaccharides have?

Glucose; suffix -ose.

What is a monosaccharide, disaccharide, and give examples of disaccharides?

Monosaccharide: single sugar (e.g., glucose); Disaccharides: two monosaccharides (e.g., lactose, maltose, sucrose).

What is a glycosidic linkage?

The bond connecting monosaccharides in a polysaccharide.

What is a polysaccharide and how is it structured?

A long chain of monosaccharides linked by covalent bonds; can be branched or unbranched.

What are some storage polysaccharides and where are they found?

Starch in plants; glycogen in animals (primarily liver and muscles).

What are structural polysaccharides?

Polysaccharides like cellulose and chitin that contribute to structure.

What is an amino acid and what is its basic structure?

The building block of proteins; central carbon with a hydrogen, amino group, carboxyl group, and a variable R group.

What makes some amino acids essential and others non-essential?

Essential amino acids must be obtained in the diet; non-essential can be synthesized by the body.

Name some essential amino acids.

Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine.

Name some non-essential amino acids.

Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Proline, Serine, Tyrosine (plus others like Selenocysteine).

What is the role of hemoglobin?

The main protein responsible for transporting oxygen from the lungs to tissues and CO2 back for elimination.

What is a nucleotide made of?

A phosphate group, a nitrogenous base, and a five‑carbon sugar.

What are Purines and Pyrimidines?

Purines: adenine and guanine; Pyrimidines: cytosine, thymine (DNA), uracil (RNA).

What is ATP and its role?

Adenosine triphosphate; energy-carrying molecule with three phosphates used to power cellular processes.

What are nucleic acids and what are the two main types?

Polymers of nucleotides; DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

What are lipids and what are their general roles?

Hydrophobic biomolecules (fats, oils, phospholipids) involved in energy storage, membranes, and signaling.

What is a fatty acid?

Long hydrocarbon chain with a terminal carboxyl group (-COOH).

How do saturated and unsaturated fatty acids differ?

Saturated: no double bonds, straight, solid at room temp; Unsaturated: one or more double bonds, kinked, liquid at room temp.

What is cholesterol in lipids and what is HDL?

A lipid that is part of membranes; HDL refers to “high-density lipids” often called the “good fat.”

What is a phospholipid and its membrane relevance?

Glycerol with a phosphate head (hydrophilic) and two fatty acid tails (hydrophobic); amphipathic and essential for membranes.

What is the phospholipid bilayer and its orientation?

A double layer with hydrophilic heads facing water and hydrophobic tails inward; forms the membrane foundation.

What two membrane properties do phospholipids influence?

Fluidity (movement) and selectivity (controls entry/exit) of the membrane.

What is the origin-of-life four-stage hypothesis about?

Four overlapping stages: synthesis of nucleotides/amino acids, polymerization into RNA/DNA and proteins, enclosure in membranes, and membranes acquiring cellular properties.

What are the three systems thought to start life first?

Proteins, RNA, and DNA.

What is abiotic synthesis in the origin-of-life context?

Non-biological formation of organic monomers from inorganic compounds.

What is a pre-cell as described in origin-of-life models?

A membrane-enclosed compartment containing self-replicating molecules.

What is meant by polymers enclosed in membranes acquiring cellular properties?

Stage 4: enclosed polymers (nucleic acids, proteins, etc.) within a membrane exhibit basic cellular functions.