General Biology: Macromolecules, Cell Structure, and Function Study Guide

Organic Compounds and Macromolecules

Introduction to Organic Compounds

Organic compounds are molecules that contain carbon and are fundamental to all living organisms. They form the basis of macromolecules essential for life.

• Hydrocarbons: Compounds containing only hydrogen and carbon (e.g., methane).

• Functional Groups: Specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Examples include hydroxyl (–OH), carboxyl (–COOH), amino (–NH2), and phosphate (–PO4).

Key Functional Groups

• Hydroxyl Group: –OH

• Carboxyl Group: –COOH

• Amino Group: –NH2

• Phosphate Group: –OPO3 (PO4)

Properties of Molecules

• Hydrophobic: Molecules that do not mix with water and avoid water (e.g., lipids).

• Hydrophilic: Molecules that mix with water and are attracted to water (e.g., carbohydrates, some proteins).

Monomers and Polymers

Macromolecules are large molecules formed by joining smaller units called monomers. The process of joining monomers is called polymerization.

• Monomer: The individual building block of a polymer.

• Polymer: A chain of monomers joined together.

Polymerization Reactions

• Dehydration Synthesis: Reaction that removes a water molecule to form a covalent bond between monomers, building polymers.

• Hydrolysis: Reaction that adds water to break polymers down into their monomers.

Table: Biological Macromolecules and Their Monomers

Monomer	Polymer
Monosaccharide	Carbohydrate
Fatty Acid	Lipid
Nucleotide	Nucleic Acid
Amino Acid	Protein

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as a primary energy source and structural component in cells.

• Monosaccharides: Simple sugars; monomers of carbohydrates (e.g., glucose).

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

• Polysaccharides: Polymers consisting of many monosaccharides (e.g., starch, glycogen, cellulose, chitin).

• Starch: Storage polysaccharide in plants; digestible by humans.

• Glycogen: Storage polysaccharide in animals.

• Cellulose: Structural polysaccharide in plant cell walls; indigestible by humans.

• Chitin: Structural polysaccharide in fungal cell walls and exoskeletons of arthropods.

Lipids

Structure and Function

Lipids are hydrophobic molecules that include fats, oils, phospholipids, and steroids. They are important for energy storage, membrane structure, and signaling.

• Triglycerides: Composed of glycerol and three fatty acids; main form of stored energy in animals.

• Saturated Fats: No double bonds; solid at room temperature (e.g., butter).

• Unsaturated Fats: One or more double bonds; liquid at room temperature (e.g., oils).

• Phospholipids: Two fatty acid chains and a phosphate group; form the phospholipid bilayer of cell membranes.

• Steroids: Lipids with four fused rings; include cholesterol and hormones.

• Cholesterol: A steroid that helps maintain membrane fluidity and is a precursor for hormones.

Proteins

Structure and Function

Proteins are polymers of amino acids and perform a vast array of functions, including catalyzing reactions, providing structure, and regulating processes.

• Amino Acids: Monomers of proteins; each contains an amino group, carboxyl group, hydrogen atom, and an R group (side chain).

• Peptide Bond: Covalent bond between amino acids formed by dehydration synthesis.

• Polypeptide: A chain of amino acids.

• Enzymes: Specialized proteins that speed up chemical reactions.

• Denaturation: Loss of protein structure and function due to environmental changes (e.g., heat, pH).

• Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Local folding (α-helix, β-sheet).

  • Tertiary: 3D folding of a single polypeptide.

  • Quaternary: Association of multiple polypeptides.

Nucleic Acids

Structure and Function

Nucleic acids store and transmit genetic information. They are polymers of nucleotides, each consisting of a phosphate group, a sugar, and a nitrogenous base.

• DNA (Deoxyribonucleic Acid): Double helix; stores genetic information.

• RNA (Ribonucleic Acid): Single-stranded; involved in protein synthesis.

Cell Structure and Function

Cell Theory

• All organisms are made of cells.

• The cell is the basic unit of life.

• All cells arise from pre-existing cells.

• Modern additions: Energy flows within cells; cells have similar composition; cells pass genetic information to new cells.

Microscopy

• Light Microscope: Can display living cells.

• Scanning Electron Microscope (SEM): Shows surface of cells at high magnification.

• Transmission Electron Microscope (TEM): Shows internal structures of cells.

Cell Membranes and Organelles

• Plasma Membrane: Outer boundary of the cell; composed of a phospholipid bilayer with proteins.

• Surface Area: Total area of the cell's surface; important for exchange of materials.

• Cytosol: Fluid component of cytoplasm.

• Cytoplasm: Everything inside the cell except the nucleus.

• Nucleoid: Region in prokaryotes where DNA is located (no membrane).

• Nucleus: Membrane-bound organelle in eukaryotes containing DNA.

• Nucleolus: Region within the nucleus where ribosomal RNA is synthesized.

• Ribosomes: Sites of protein synthesis; composed of rRNA and proteins.

• Rough Endoplasmic Reticulum (RER): Studded with ribosomes; synthesizes proteins for export or membrane insertion.

• Smooth Endoplasmic Reticulum (SER): Synthesizes lipids and detoxifies toxins.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for storage or transport out of the cell.

• Vesicles: Small membrane-bound sacs that transport substances within the cell.

• Lysosomes: Contain digestive enzymes to break down waste.

• Vacuoles: Storage organelles; large central vacuole in plant cells.

• Mitochondria: Site of cellular respiration; produces ATP.

• Chloroplasts: Site of photosynthesis in plants and algae.

• Cytoskeleton: Network of protein filaments (microtubules, microfilaments, centrioles) that provide structure and facilitate movement.

Table: Major Cell Organelles and Their Functions

Organelle	Function
Nucleus	Stores genetic material (DNA); controls cell activities
Ribosome	Protein synthesis
Rough ER	Protein synthesis and processing
Smooth ER	Lipid synthesis and detoxification
Golgi Apparatus	Modifies, sorts, and ships proteins and lipids
Lysosome	Digests macromolecules and old organelles
Mitochondria	ATP production via cellular respiration
Chloroplast	Photosynthesis (plants and algae)
Vacuole	Storage of water, nutrients, and waste
Cytoskeleton	Structural support and movement

Key Study Questions and Concepts

• Be able to identify the monomer and polymer for each macromolecule (carbohydrates, lipids, proteins, nucleic acids).

• Know the structure and function of each organelle.

• Understand the differences between types of microscopes and what they are used to observe.

• Be able to describe the process of dehydration synthesis and hydrolysis.

• Recognize the importance of functional groups in organic molecules.

• Understand the classic and modern cell theory.

Additional info: Some explanations and context have been expanded for clarity and completeness based on standard General Biology curriculum.