Organic Molecules Review - Lipids, Proteins, Carbohydrates (Lecture Notes)

A comprehensive set of Q&A flashcards covering lipids, proteins, carbohydrates, functional groups, and basic biochemical reactions based on the provided notes.

What characteristic binds lipids together as a group of organic molecules?

Hydrophobic, nonpolar.

What is the fat-energy storage molecule composed of glycerol and three fatty acids?

Triglyceride (triacylglycerol).

Which polysaccharide is used for energy storage in plants?

Starch (amylose/amylopectin); composed of alpha-glucose units.

Which polysaccharide is used for energy storage in animals?

Glycogen; highly branched storage polymer of glucose.

Which polysaccharide provides structural support in plants and is made of beta glucose?

Cellulose; beta-1,4 linkages; forms plant cell walls and is indigestible to most animals.

Which polysaccharide forms exoskeletons in arthropods and fungal cell walls?

Chitin; made from N-acetylglucosamine; structural polymer.

Which organism has a symbiotic relationship with bacteria to digest cellulose?

Termites; gut bacteria help break down beta-glucose cellulose.

What feature of phospholipids makes the tails hydrophobic and the head hydrophilic?

Two fatty acid tails (nonpolar) and a phosphate-containing head group (polar).

How does the structure of a steroid differ from other lipids?

Steroids have four fused carbon rings instead of long hydrocarbon chains.

Name major steroids mentioned.

Cholesterol, testosterone, estrogen (and other steroid hormones).

What makes cellulose difficult to digest for many animals?

Beta glucose linkages (beta-1,4) and lack of the enzyme to digest them.

What are the three basic parts of an amino acid molecule? Which part differs among amino acids?

Amino group, carboxyl group, and side chain (R group); the side chain differs.

What are the four structural levels of organization of polypeptide chains?

Primary, secondary, tertiary, and quaternary structure.

Primary structure describes what?

The sequence of amino acids linked by peptide bonds.

Secondary structure refers to what features?

Alpha helices and beta pleated sheets stabilized by hydrogen bonds between backbone atoms.

Tertiary structure refers to what?

The overall 3D shape of a single polypeptide, formed by interactions among side chains.

Quaternary structure refers to what?

The arrangement of multiple polypeptide chains into a functional protein.

Name a functional category of proteins and an example.

Enzymatic — e.g., amylase; other examples: structural, transport, hormonal, defensive, contractile.

What is an enzymatic protein and give an example?

A protein that catalyzes chemical reactions; example: amylase.

What is a structural protein and give an example?

A protein that provides support and shape; example: collagen.

What is a transport protein and give an example?

A protein that carries molecules; example: hemoglobin.

What is a hormonal regulatory protein and give an example?

A protein involved in chemical signaling; example: insulin.

What is a defensive protein and give an example?

A protein that protects the body; example: antibodies.

What is a contractile/movement protein and give an example?

A protein that enables movement; example: actin (with myosin).

What are the three R-group categories for amino acids?

Hydrophobic (nonpolar), Hydrophilic (polar), Ionic (charged).

What is the significance of hydrophobic R groups in proteins?

They avoid water and cluster inside the protein core, helping stabilize folding.

What is the significance of hydrophilic R groups in proteins?

They interact with water and other polar molecules, often on the protein surface to promote solubility.

What is the significance of ionic R groups in proteins?

They can form ionic (salt) bridges with opposite charges, contributing to folding, stability, and active sites.

What is the function of quaternary structure?

Assembly of multiple polypeptide chains into a functional protein; enables protein complexes and cooperative activity.

What is a condensation (dehydration) reaction?

Removal of water to form covalent bonds (e.g., peptide bonds during protein formation).

What is a hydrolysis reaction?

Addition of water to break covalent bonds (e.g., breaking peptide bonds in proteins).

What is the basic building block of carbohydrates?

Monosaccharide.

What is maltose and how is it formed?

A disaccharide formed by dehydration between two glucose units; glucose–glucose linked by an alpha-1,4 glycosidic bond.

How do glucose, galactose, and fructose differ structurally?

Glucose and galactose are aldoses; fructose is a ketose; carbonyl placement differs (C1 vs C2).

Name three disaccharides formed by dehydration synthesis.

Maltose (glucose-glucose), sucrose (glucose-fructose), lactose (galactose-glucose).

Are methyl groups polar or nonpolar?

Nonpolar.

What macromolecule contains methyl groups and what is their effect?

Lipids; methyl groups contribute to nonpolarity and energy storage, making molecules less soluble.

Are carbonyl groups polar or nonpolar?

Polar.

Name a macromolecule that contains carbonyl groups.

Nucleic acids and amino acids (carbonyl groups in peptide bonds and backbone).

How does the carbonyl group contribute to a molecule's shape/function?

Part of the backbone; contributes to polarity and hydrogen bonding, aiding folding and structure.