Carbohydrates and States of Matter: Study Guide for CHEM 102 (Chapters 6 & 7)

Chapter 6: Carbohydrates – Life's Sweet Molecules

Classification of Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically with the formula Cn(H2O)n. They are classified based on the number of sugar units:

• Monosaccharides: Single sugar units (e.g., glucose, fructose).

• Disaccharides: Two monosaccharides linked together (e.g., sucrose, lactose).

• Oligosaccharides: 3–10 monosaccharide units.

• Polysaccharides: Long chains of monosaccharide units (e.g., starch, cellulose, glycogen).

Soluble fibers dissolve in water (e.g., pectin), while insoluble fibers do not (e.g., cellulose).

Organic Functional Groups in Monosaccharides

• Alcohols: Contain -OH groups. Classified as primary (attached to one carbon), secondary (two carbons), or tertiary (three carbons).

• Aldehyde: Contains a terminal carbonyl group (–CHO).

• Ketone: Contains an internal carbonyl group (C=O) not at the end of the chain.

Monosaccharides are either aldoses (with an aldehyde group) or ketoses (with a ketone group).

Structural Properties of Monosaccharides

• D- and L-stereoisomers: Refers to the configuration around the chiral carbon farthest from the carbonyl group. D-isomers are most common in nature.

• Enantiomers: Non-superimposable mirror images (e.g., D-glucose and L-glucose).

• Epimers: Differ at only one chiral center (e.g., glucose and galactose).

• Diastereomers: Stereoisomers that are not mirror images.

Common monosaccharides: Glucose, galactose, fructose, ribose.

Reactions at the Anomeric Carbon

• Cyclic α and β anomers: When monosaccharides cyclize, the anomeric carbon can form two isomers: α (OH down) and β (OH up).

• Oxidation: Aldoses can be oxidized to form acids.

• Reduction: Carbonyl groups can be reduced to alcohols (e.g., glucose to sorbitol).

Glycosidic Bonds in Disaccharides

• Condensation: Formation of a glycosidic bond with the loss of water.

• Hydrolysis: Breaking a glycosidic bond by adding water.

• Glycosidic bond naming: Based on the carbons involved and the α or β configuration (e.g., α(1→4)).

• Common disaccharides: Sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose).

• Sweetness scale: Sucrose is the standard (value = 1); fructose is sweeter, lactose is less sweet.

Polysaccharides

• Starch: α(1→4) and α(1→6) glycosidic bonds; energy storage in plants.

• Glycogen: Similar to starch but more highly branched; energy storage in animals.

• Cellulose: β(1→4) glycosidic bonds; structural component in plants, insoluble fiber.

Blood Group Compatibility and Heparin

• ABO blood groups: Determined by specific oligosaccharide patterns on red blood cells.

• Heparin: A highly sulfated polysaccharide; acts as an anticoagulant.

Chapter 7: States of Matter and Their Attractive Forces

Gas Laws

• Pressure unit conversions: 1 atm = 760 mmHg = 101.3 kPa.

• Kinetic Molecular Theory: Gases consist of particles in constant, random motion; collisions are elastic.

• Boyle’s Law: $P_1V_1 = P_2V_2$ (at constant T and n)

• Charles’s Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (at constant P and n)

• Gay-Lussac’s Law: $\frac{P_1}{T_1} = \frac{P_2}{T_2}$ (at constant V and n)

• Combined Gas Law: $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$

• Ideal Gas Law: $PV = nRT$

Attractive Forces and Physical Properties

• Types of attractive forces:

  • London dispersion forces (all molecules)

  • Dipole-dipole interactions (polar molecules)

  • Hydrogen bonding (H with N, O, or F)

  • Ion-dipole forces (ions and polar molecules)

  • Ionic bonds (between ions)

• Boiling point: Increases with stronger attractive forces.

• Vapor pressure: Decreases with stronger attractive forces.

• Hydrogen bonds: Drawn as dashed lines between H and N/O/F atoms.

• States of matter: Solid, liquid, gas; changes involve energy and attractive forces.

Solubility in Water

• Golden rule of solubility: "Like dissolves like" (polar dissolves polar, nonpolar dissolves nonpolar).

• Predicting solubility: Polar molecules and ions are generally soluble in water.

• Amphipathic molecules: Contain both polar and nonpolar regions (e.g., soap, phospholipids).

• Emulsifier: A substance that stabilizes mixtures of oil and water by reducing surface tension (e.g., lecithin).

• Micelle: Spherical structure formed by amphipathic molecules in water, with hydrophobic tails inward and hydrophilic heads outward.

Fats, Oils, and Triglycerides

• Fat vs. oil: Fats are solid at room temperature (more saturated), oils are liquid (more unsaturated).

• Melting point: Increases with saturation and chain length; decreases with unsaturation.

• Triglyceride: Formed from glycerol and three fatty acids via esterification.

Cell Membrane Structure

• Phospholipid bilayer: Double layer of phospholipids with hydrophilic heads facing outward and hydrophobic tails inward.

• Polar and nonpolar regions: Phospholipid heads are polar; tails are nonpolar. Cholesterol is embedded within the bilayer, modulating fluidity.

• Cell membrane: Semi-permeable barrier that controls movement of substances in and out of the cell.

Table: Comparison of Types of Carbohydrates

Type	Number of Units	Example	Function
Monosaccharide	1	Glucose	Energy source
Disaccharide	2	Sucrose	Transported sugar in plants
Oligosaccharide	3–10	Raffinose	Cell recognition
Polysaccharide	Many	Starch, Cellulose	Energy storage, structure

Table: Types of Attractive Forces

Force	Occurs Between	Relative Strength	Example
London Dispersion	All molecules	Weakest	O2, N2
Dipole-Dipole	Polar molecules	Moderate	HCl
Hydrogen Bonding	H with N, O, or F	Strong	H2O
Ion-Dipole	Ions and polar molecules	Very strong	Na+ in water
Ionic	Cations and anions	Strongest	NaCl

Example: Predicting boiling points: Water (H2O) has a higher boiling point than methane (CH4) due to hydrogen bonding.

Additional info: Some explanations and examples have been expanded for clarity and completeness.