Chapter 5: The Structure and Function of Large Biological Molecules

Macromolecules: Types and Importance

Macromolecules are large, complex molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids. Each class has unique monomers and functions.

• Monomers and Polymers: Monomers are small, repeating units that join to form polymers through chemical reactions.

• Dehydration Synthesis and Hydrolysis: Dehydration synthesis removes water to form bonds between monomers, while hydrolysis adds water to break these bonds.

• Carbohydrates: Serve as energy sources and structural materials. Monosaccharides are simple sugars; disaccharides and polysaccharides are larger carbohydrates.

• Lipids: Include fats, phospholipids, and steroids. Lipids are hydrophobic and serve as energy storage, membrane structure, and signaling molecules.

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

• Phospholipids: Contain hydrophilic heads and hydrophobic tails, forming the basis of cell membranes.

• Proteins: Polymers of amino acids with diverse functions, including catalysis (enzymes), structure, transport, and signaling.

• Amino Acids: The sequence and chemical properties of amino acids determine protein structure and function.

• Protein Structure: Four levels: primary (sequence), secondary (alpha helices, beta sheets), tertiary (3D folding), and quaternary (multiple polypeptides).

• Nucleic Acids: DNA and RNA store and transmit genetic information. Both are polymers of nucleotides.

• DNA vs. RNA: DNA is double-stranded and stores genetic information; RNA is single-stranded and involved in protein synthesis.

Chapter 6: Tour of the Cell

Cell Theory and Types

The cell is the basic unit of life. All living organisms are composed of cells, which arise from pre-existing cells.

• Plasma Membrane: A selectively permeable barrier that encloses the cell contents.

• Prokaryotic vs. Eukaryotic Cells: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have both.

• Plant vs. Animal Cells: Plant cells have cell walls, chloroplasts, and large central vacuoles; animal cells do not.

Cell Structure and Function

• Nucleus: Contains genetic material and controls cellular activities.

• Endomembrane System: Includes the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and vesicles. Functions in synthesis, transport, and processing of biomolecules.

• Mitochondria and Chloroplasts: Sites of cellular respiration and photosynthesis, respectively. Both contain their own DNA.

• Cytoskeleton: Network of microfilaments, intermediate filaments, and microtubules that provide structural support and facilitate movement.

• Extracellular Matrix (ECM): Provides structural and biochemical support to surrounding cells (mainly in animal tissues).

• Cell Junctions: Include tight junctions, desmosomes, and gap junctions in animal cells; plasmodesmata in plant cells.

Chapter 7: Membrane Structure and Function

Cell Membrane Structure

Cell membranes are composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates, providing fluidity and selective permeability.

• Phospholipid Bilayer: Hydrophilic heads face outward; hydrophobic tails face inward.

• Membrane Proteins: Integral and peripheral proteins serve in transport, signaling, and structural roles.

• Fluid Mosaic Model: Describes the dynamic and heterogeneous nature of the membrane.

Membrane Transport

• Passive Transport: Movement of substances down their concentration gradient without energy input (e.g., diffusion, osmosis, facilitated diffusion).

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Hypertonic, Hypotonic, Isotonic Solutions: Describe relative solute concentrations and their effects on cell volume.

• Active Transport: Movement of substances against their concentration gradient, requiring energy (usually ATP).

• Bulk Transport: Includes endocytosis (phagocytosis, pinocytosis, receptor-mediated) and exocytosis.

Chapter 8: Introduction to Metabolism

Energy and Thermodynamics

Metabolism encompasses all chemical reactions in a cell, governed by the laws of thermodynamics.

• Kinetic and Potential Energy: Kinetic energy is energy of motion; potential energy is stored energy.

• Thermodynamics: The first law states that energy cannot be created or destroyed; the second law states that entropy (disorder) increases in spontaneous processes.

• Exergonic vs. Endergonic Reactions: Exergonic reactions release energy; endergonic reactions require energy input.

• ATP: The cell's main energy currency, coupling exergonic and endergonic reactions.

• Enzymes: Biological catalysts that speed up reactions by lowering activation energy.

Chapter 9: Cellular Respiration and Fermentation

Overview of Cellular Respiration

Cellular respiration is the process by which cells extract energy from glucose to produce ATP, involving glycolysis, the citric acid cycle, and oxidative phosphorylation.

• Equation for Cellular Respiration:

• Stages: Glycolysis (cytoplasm), citric acid cycle (mitochondrial matrix), oxidative phosphorylation (mitochondrial inner membrane).

• ATP Production: Most ATP is produced during oxidative phosphorylation via the electron transport chain and chemiosmosis.

• Fermentation: Anaerobic process that allows ATP production without oxygen, producing lactic acid or ethanol.

• Substrate-level vs. Oxidative Phosphorylation: Substrate-level phosphorylation directly transfers a phosphate to ADP; oxidative phosphorylation uses a proton gradient and ATP synthase.

• Facultative vs. Obligate Anaerobes: Facultative anaerobes can survive with or without oxygen; obligate anaerobes cannot tolerate oxygen.

Comparison Table: Cellular Respiration vs. Fermentation