3.2-3.5 - Chemical Basis of Life

What are the four major classes of macromolecules/biomolecules?

Carbohydrates, Lipids, Proteins (Polypeptides), and Nucleic Acids.

What reaction links monomers together to form polymers by removing a water molecule?

Dehydration synthesis.

What chemical bond links monomers together during dehydration synthesis?

Covalent bond.

What process breaks polymers down into individual monomers using water?

Hydrolysis.

What is the general chemical formula for carbohydrates, and what is the C:H:O ratio?

(CH2O)n, with a ratio of 1 Carbon : 2 Hydrogens : 1 Oxygen.

Why are carbohydrates hydrophilic and soluble in water?

They contain polar carbonyl (C=O) and hydroxyl (-OH) groups.

What are the three categories of monosaccharides based on carbon count?

Triose (3 carbons), Pentose (5 carbons), and Hexose (6 carbons).

What is the difference between an aldose and a ketose monosaccharide?

Aldoses have the carbonyl group at the end of the carbon chain; ketoses have it in the middle.

What ring structure do monosaccharides typically form in an aqueous solution?

Steroisomer rings (e.g., α-D-Glucose).

What type of bond links two monosaccharides together to form a disaccharide?

Glycosidic bond (a type of covalent bond).

Name three common examples of disaccharides.

Sucrose, maltose, and lactose.

What is starch and what are its two structural forms?

A plant storage polysaccharide made of glucose; forms are unbranched Amylose (α-1,4 linkages) and branched Amylopectin (α-1,6 linkages).

What is glycogen and where is it stored in animal bodies?

A highly branched storage polysaccharide in animals, stored mainly in liver and muscle cells.

Why is glycogen's highly branched structure functionally important?

Its high degree of branching creates a dense network of glucose monomers that can be rapidly broken down for energy.

What is cellulose and what type of bond links its glucose monomers?

A linear structural polysaccharide forming plant cell walls, linked by β-1,4-glycosidic bonds with H-bonds between parallel strands.

What structural polymer is found in fungal cell walls and insect/crustacean exoskeletons?

Chitin (monomer: N-acetylglucosamine / NAG).

What are the primary biological functions of carbohydrates?

Store chemical energy, provide fibrous structural support, act as precursors for amino acids/nucleotides, and serve as cell identity tags.

What defining chemical feature separates lipids from other macromolecules?

They are nonpolar hydrocarbons and insoluble in water (hydrophobic).

What components make up a triglyceride (triacylglycerol) molecule?

One glycerol backbone linked to three fatty acids.

What specific bond joins fatty acids to glycerol in a fat molecule?

Ester linkage (formed via dehydration synthesis).

How do saturated fatty acids differ structurally and physically from unsaturated fatty acids?

Saturated fatty acids have only single C-C bonds and are solid at room temp; unsaturated fatty acids have one or more double C=C bonds (kinks) and are liquid at room temp.

Why do fats hold more energy per gram than carbohydrates?

Fats contain significantly more nonpolar C-C and C-H bonds, which have high potential energy.

What is the structure of a phospholipid?

A glycerol backbone linked to a phosphate group (polar/hydrophilic head) and two fatty acid chains (nonpolar/hydrophobic tails).

What term describes a molecule like a phospholipid that has both hydrophilic and hydrophobic regions?

Amphipathic.

How do phospholipids arrange themselves in a cell membrane?

Into a bilayer with hydrophilic heads facing the aqueous environment and hydrophobic tails facing inward away from water.

Which types of molecules cross a lipid bilayer easily via selective permeability?

Small or nonpolar molecules (e.g., O2, CO2, steroid hormones).

Which types of molecules pass through a lipid bilayer slowly or not at all without transport proteins?

Large polar molecules and charged ions (e.g., glucose, Na+, Cl-, H2O).

What is the structural characteristic common to all steroid molecules?

A core structure of four interconnected carbon rings.

What is the primary steroid precursor from which other steroids (like estrogen and testosterone) are derived?

Cholesterol.