General Biology Study Guide: Chemistry of Life and Macromolecules

Biology and Scientific Research

What is Biology?

Biology is the scientific study of life and living organisms. It encompasses the structure, function, growth, origin, evolution, and distribution of living things.

• Characteristics of Life: Organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation.

• Cells: The basic unit of life.

• Replication: Organisms pass hereditary or genetic information encoded in nucleic acids (genes).

• Energy: All living things acquire and use energy.

• Evolution: Populations of organisms evolve over generations.

• Levels of Biological Organization: This course focuses on multiple levels, from molecules to ecosystems.

Scientific Research

• Process of the Scientific Method:

  1. Ask a question

  2. Make a hypothesis or testable explanation

  3. Test the hypothesis based on the hypothesis

  4. Analyze data and draw conclusions

  5. Report results; use results to make new hypotheses or predictions

• Scientific Literature: Peer-reviewed literature is more reliable in scientific reporting.

Chemistry of Life

Chemical Bonds

• Covalent Bonds: Atoms share electrons. Can be non-polar (equal sharing) or polar (unequal sharing).

• Ionic Bonds: Complete transfer of electrons from one atom to another, resulting in attraction between oppositely charged ions.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Strength of Bonds

• Nonpolar covalent bonds: Strong

• Polar covalent bonds: Strong

• Ionic bonds: Strong in dry environments, weaker in aqueous solutions

• Hydrogen bonds and van der Waals interactions: Weak

Important elements in biology: C, N, O, H, S, P

Hydrophobic, Hydrophilic, and Amphipathic Molecules

• Hydrophilic: "Water-loving"; molecules that dissolve in water.

• Hydrophobic: "Water-fearing"; molecules that do not dissolve in water.

• Amphipathic: Molecules with both hydrophilic and hydrophobic regions (e.g., phospholipids).

Acids and Bases

• Acids: Substances that release H+ ions in solution.

• Bases: Substances that accept H+ ions or release OH- ions.

• pH: A measure of hydrogen ion concentration; calculated as $pH = -\log[H^+]$

• Buffers: Substances that resist changes in pH by absorbing or releasing H+ ions.

Macromolecules

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and chemical reactivity. Examples include hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups.

Monomers and Polymers

• Polymers: Large molecules made of repeating monomer units.

• Monomers: Building blocks of polymers.

• Condensation (Dehydration) Reactions: Form polymers by removing water.

• Hydrolysis Reactions: Break polymers into monomers by adding water.

Types of Macromolecules

Macromolecule	Monomer	Bond Type	Function
Carbohydrates	Monosaccharides	Glycosidic bond	Energy storage, cell structure, cell recognition
Lipids	Fatty acids & glycerol		Energy storage, membrane structure, signaling
Proteins	Amino acids	Peptide bond	Catalysis, structure, transport, signaling
Nucleic Acids	Nucleotides		Information storage and transfer

Proteins

• Amino Acids: Contain amino, carboxyl, hydrogen, and R group (side chain).

• Peptide Bond: Formed between the carboxyl group of one amino acid and the amino group of another.

Levels of Protein Structure:

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets stabilized by hydrogen bonds.

• Tertiary: 3D folding due to R group interactions (hydrophobic, ionic, hydrogen bonds, disulfide bridges).

• Quaternary: Multiple polypeptide chains interact.

Protein Functions: Enzymes, structure, transport, signaling, defense.

Nucleic Acids

• DNA: Double-stranded helix, stores genetic information.

• RNA: Single-stranded, involved in protein synthesis and gene regulation.

• Transcription: Synthesis of RNA from DNA template.

• Translation: Synthesis of proteins from mRNA template.

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose).

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

• Polysaccharides: Many monosaccharides (e.g., glycogen, starch, cellulose, peptidoglycan).

• Functions: Energy storage, cell structure, cell recognition.

• Glycoproteins: Proteins covalently bonded to carbohydrates; important for cell recognition and signaling.

Lipids

• Fatty Acids: Saturated (no double bonds) or unsaturated (one or more double bonds).

• Phospholipids: Amphipathic molecules forming cell membranes.

• Steroids: Lipids with four fused rings (e.g., cholesterol).

• Trans Fats: Unsaturated fats with trans double bonds; associated with health risks.

Functions of Lipids: Energy storage, membrane structure, signaling molecules.

Additional info:

• Penicillin and cephalosporin inhibit bacterial cell wall synthesis by interfering with peptidoglycan cross-linking.

• Buffers are crucial for maintaining pH homeostasis in biological systems.