Introduction to Biochemistry – Lecture Review

A comprehensive set of flashcards covering matter, chemical bonding, enzymes, pH, macromolecules (carbohydrates, lipids, proteins, nucleic acids), and associated key terms and concepts from the lecture.

What is the scientific definition of matter?

Anything that occupies space and has mass.

What is an element?

A substance that cannot be broken down into other substances by chemical means.

What tiny particles make up an element?

Atoms.

What is a chemical bond?

An attraction between atoms that enables them to stay close together.

Name the two main types of chemical bonds covered in this lecture.

Ionic bonds and covalent bonds.

What is an ion?

An atom that has gained or lost an electron and therefore carries an electrical charge.

How are electrons involved in an ionic bond?

They are transferred from one atom to another, resulting in oppositely charged ions that attract.

How are electrons involved in a covalent bond?

Atoms share one or more pairs of outer-shell electrons.

What does a Lewis (electron-dot) structure show?

The valence electrons of atoms and the bonding between them.

When a neutral atom loses one electron, what charge does it acquire?

It becomes a positively charged ion (cation).

When a neutral atom gains one electron, what charge does it acquire?

It becomes a negatively charged ion (anion).

In reaction classifications, what does ‘reduction’ refer to?

Gain of electrons.

In reaction classifications, what does ‘oxidation’ refer to?

Loss of electrons.

What type of metabolic reaction builds larger molecules from smaller ones?

Anabolic (endergonic) reaction.

What type of metabolic reaction breaks larger molecules into smaller ones?

Catabolic (exergonic) reaction.

Enzymes are composed of what type of biomolecule?

Proteins.

What is the primary function of an enzyme?

To speed up (catalyze) chemical reactions by lowering the activation energy.

Define activation energy.

The amount of energy reactants must absorb to start a reaction.

What name is given to the specific reactant that an enzyme acts upon?

Substrate.

What is the active site of an enzyme?

The region on the enzyme where the substrate binds and the reaction occurs.

How does an acid affect the hydrogen-ion concentration of a solution?

It donates H⁺ ions, increasing [H⁺] and lowering pH.

How does a base affect a solution?

It donates OH⁻ ions (or accepts H⁺), decreasing [H⁺] and raising pH.

Which has the higher hydrogen-ion concentration: pH 5 or pH 6?

pH 5 (every unit decrease in pH is a ten-fold increase in [H⁺]).

Name the four major classes of biological macromolecules.

Carbohydrates, lipids, proteins, and nucleic acids.

What reaction links monomers into polymers?

Dehydration synthesis (condensation).

What reaction breaks polymers into monomers?

Hydrolysis.

What is the primary function of carbohydrates?

Serve as an energy source.

Give three common monosaccharides.

Glucose, fructose, galactose.

What is a disaccharide and how is it formed?

Two covalently bonded monosaccharides, formed by dehydration synthesis.

Name three biologically important disaccharides.

Maltose, lactose, and sucrose.

What are polysaccharides?

Long chains of monosaccharides (complex carbohydrates).

Give one storage polysaccharide in plants and one in animals.

Starch (plants) and glycogen (animals).

What structural polysaccharide forms plant cell walls?

Cellulose.

List two primary functions of lipids.

Long-term energy storage and formation of cell membranes.

What molecules make up a triglyceride?

One glycerol and three fatty acids.

What distinguishes saturated from unsaturated fats?

Saturated fats have no double bonds in fatty acids; unsaturated fats have one or more double bonds.

What are the main components of a phospholipid?

A glycerol backbone, two fatty acids, and a phosphate group.

Why are phospholipids described as amphipathic?

They have a hydrophilic (polar) head and hydrophobic (non-polar) tails.

Describe the basic skeleton of a steroid molecule.

Four fused carbon rings.

What is the biological role of cholesterol?

It stabilizes cell membranes and serves as a precursor for steroid hormones.

Differentiate LDL and HDL in cholesterol transport.

LDL delivers cholesterol to tissues (excess can clog arteries); HDL removes excess cholesterol to the liver.

List at least four functions of proteins.

Transport, structural support, enzymatic catalysis, defense (antibodies), signaling (hormones), storage, contractile movement.

What monomers build proteins?

Amino acids.

What covalent bond joins amino acids?

A peptide bond.

How many different amino acid R groups are found in proteins?

Twenty.

What level of protein structure is a sequence of amino acids?

Primary structure.

What stabilizes secondary protein structure (α-helices and β-sheets)?

Hydrogen bonds between backbone atoms.

What interactions determine tertiary protein structure?

Interactions among amino acid side-chains (hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges).

What is quaternary protein structure?

Association of two or more polypeptide subunits into a functional protein.

Give an example of a protein with quaternary structure.

Hemoglobin (four subunits—2α and 2β).

Name the two main types of nucleic acids.

DNA and RNA.

What is the monomer of nucleic acids and its three components?

Nucleotide: a five-carbon sugar, a phosphate group, and a nitrogenous base.

Which nitrogenous bases are found in DNA?

Adenine, guanine, cytosine, and thymine.

Which base replaces thymine in RNA?

Uracil.

How are nucleotides linked along a single DNA strand?

By covalent bonds between the sugar of one nucleotide and the phosphate of the next (sugar-phosphate backbone).

What type of bond holds the two DNA strands together?

Hydrogen bonds between complementary nitrogenous bases.

List two structural differences between DNA and RNA.

DNA is double-stranded with deoxyribose sugar; RNA is single-stranded with ribose sugar.