General Biology: Biological Macromolecules, Chemical Bonds, and Functional Groups

Study Guide - Smart Notes

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Week 3 Overview and Study Planning

Course Schedule and Exam Preparation

This week covers foundational topics in General Biology, focusing on the chemistry of life and biological macromolecules. Students are expected to review lecture content, complete assignments, and prepare for the upcoming exam.

Exam 1: Scheduled for Wednesday, September 17. The exam includes multiple choice, matching, fill-in-the-blank, and short answer questions. Students should bring writing utensils and a calculator (not a phone).
Study Tips: Review lecture slides, reorganize notes, use online study tools, complete quizzes and worksheets, and seek help for difficult concepts.

Chemical Foundations of Biology

Subatomic Particles and Atomic Structure

Understanding the structure of atoms is essential for studying biological molecules. Atoms are composed of subatomic particles: protons, neutrons, and electrons.

Protons: Positively charged particles found in the nucleus.
Neutrons: Neutral particles also located in the nucleus.
Electrons: Negatively charged particles orbiting the nucleus.
Atomic Number: The number of protons in an atom, defining the element.

Types of Chemical Bonds

Chemical bonds are forces that hold atoms together in molecules. The type of bond affects the properties of the resulting molecule.

Nonpolar Covalent Bonds: Electrons are shared equally between atoms (e.g., O2).
Polar Covalent Bonds: Electrons are shared unequally, creating partial charges (e.g., H2O).
Ionic Bonds: Electrons are transferred from one atom to another, resulting in oppositely charged ions (e.g., NaCl).
Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).
Van der Waals Interactions: Weak, transient interactions due to temporary dipoles.

Hydrophobic and Hydrophilic Molecules

Molecules interact with water differently based on their polarity.

Hydrophobic: Nonpolar molecules that do not interact well with water (e.g., oils, lipids).
Hydrophilic: Polar or charged molecules that readily dissolve in water (e.g., salts, sugars).

Molarity and Molecular Mass

Molarity is a measure of solute concentration in a solution, important for preparing solutions in biological experiments.

Molarity (M):
Molecular Mass: The sum of the atomic masses of all atoms in a molecule.

Functional Groups and Isomerism

Functional Groups

Functional groups are specific groups of atoms within molecules that confer characteristic chemical properties and reactivity.

Carbonyl Group (–C=O): Carbon atom double bonded to oxygen. Found in aldehydes and ketones.
Carboxyl Group (–COOH): Carbon atom double bonded to oxygen and bonded to a hydroxyl group. Acts as an acid.
Hydroxyl Group (–OH): Increases solubility in water; found in alcohols.
Amino Group (–NH2): Acts as a base; found in amino acids.
Phosphate Group (–PO4): Important in energy transfer (e.g., ATP).
Methyl Group (–CH3): Affects gene expression and molecular shape.

Isomers

Isomers are compounds with the same molecular formula but different structures and properties.

Structural Isomers: Differ in the covalent arrangement of atoms.
Cis-Trans Isomers: Differ in spatial arrangement around a double bond.
Enantiomers: Mirror-image isomers important in biology (e.g., L- and D-amino acids).

pH and Acids/Bases

pH Scale

The pH scale measures the concentration of hydrogen ions (H+) in a solution, indicating its acidity or basicity.

Acid: Substance that increases H+ concentration (pH < 7).
Base: Substance that decreases H+ concentration (pH > 7).
Neutral: Pure water has a pH of 7.

Equation:

Biological Macromolecules

Overview of Macromolecules

Macromolecules are large, complex molecules essential for life. They are typically polymers built from monomers.

Carbohydrates: Sugars and polymers of sugars.
Lipids: Diverse group of hydrophobic molecules.
Proteins: Polymers of amino acids with diverse functions.
Nucleic Acids: Polymers of nucleotides (DNA and RNA).

Polymerization and Hydrolysis

Polymers are formed and broken down by specific chemical reactions.

Dehydration Synthesis (Condensation): Monomers are joined by covalent bonds, releasing a water molecule.
Hydrolysis: Polymers are broken down into monomers by the addition of water.

Carbohydrates

Monosaccharides

Monosaccharides are the simplest carbohydrates, serving as monomers for more complex sugars.

General Formula:
Examples: Glucose, galactose, fructose.
Aldoses: Contain an aldehyde group (e.g., glucose).
Ketoses: Contain a ketone group (e.g., fructose).
Pentoses: 5-carbon sugars (e.g., ribose).
Hexoses: 6-carbon sugars (e.g., glucose, galactose, fructose).

Disaccharides

Disaccharides are formed by joining two monosaccharides via a glycosidic linkage (covalent bond).

Examples: Sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose).
Formation: Dehydration reaction joins two monosaccharides, releasing water.

Polysaccharides

Polysaccharides are long chains of monosaccharides linked by glycosidic bonds. They serve storage and structural roles.

Storage Polysaccharides: Starch (plants), glycogen (animals).
Structural Polysaccharides: Cellulose (plants), chitin (fungi and arthropods).
Starch: Polymer of α-glucose; energy storage in plants.
Glycogen: Highly branched polymer of glucose; energy storage in animals.
Cellulose: Polymer of β-glucose; major component of plant cell walls; indigestible by humans (dietary fiber).

Polysaccharide	Monomer	Function	Organism
Starch	α-glucose	Energy storage	Plants
Glycogen	α-glucose	Energy storage	Animals
Cellulose	β-glucose	Structural (cell wall)	Plants

Lipids

Types and Structure

Lipids are hydrophobic molecules, not true polymers, and include fats, phospholipids, and steroids.

Fats (Triglycerides): Composed of glycerol and three fatty acids joined by ester linkages.
Saturated Fatty Acids: No double bonds; solid at room temperature (e.g., butter).
Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature (e.g., oils). Includes cis and trans isomers.
Essential Fatty Acids: Not synthesized by the body; must be obtained from diet.

Phospholipids

Phospholipids are major components of cell membranes, consisting of a glycerol backbone, two fatty acids, and a phosphate group.

Amphipathic: Contain both hydrophilic (phosphate head) and hydrophobic (fatty acid tails) regions.
Form bilayers: Basis of biological membranes.

Steroids

Steroids are lipids with a carbon skeleton consisting of four fused rings.

Cholesterol: Component of animal cell membranes; precursor to steroid hormones.
Hormones: Include testosterone and estradiol, important in metabolism and signaling.

Summary Table: Macromolecules

Macromolecule	Monomer	Polymer	Function
Carbohydrates	Monosaccharide	Polysaccharide	Energy storage, structure
Lipids	Fatty acids, glycerol	Triglyceride, phospholipid, steroid	Energy storage, membranes, signaling
Proteins	Amino acid	Polypeptide	Catalysis, structure, transport, signaling
Nucleic Acids	Nucleotide	DNA, RNA	Genetic information, protein synthesis

Additional info:

Students are encouraged to use the Biology Student Lounge for group or individual study.
Reviewing the relationship between structure and function is critical for understanding macromolecules.