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 structures 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 (e.g., glucose) are the monomers; polysaccharides (e.g., starch, cellulose) are polymers.

• Lipids: Include fats, phospholipids, and steroids. Triglycerides are formed from glycerol and three fatty acids. Phospholipids are key components of cell membranes due to their hydrophilic heads and hydrophobic tails.

• Proteins: Polymers of amino acids. Their function depends on their three-dimensional shape, which is determined by the sequence of amino acids and interactions among them.

• Nucleic Acids: DNA and RNA store and transmit genetic information. Both are polymers of nucleotides, but differ in structure and function.

Example: The structure of a protein determines whether it acts as an enzyme, structural component, or signaling molecule.

Chapter 6: Tour of the Cell

Cell Theory and Types of Cells

The cell theory states that all living things are composed of cells, which are the basic units of life. Cells can be prokaryotic or eukaryotic.

• Plasma Membrane: A selective barrier that encloses the cell, controlling the movement of substances in and out.

• Prokaryotic vs. Eukaryotic Cells: Prokaryotic cells (e.g., bacteria) lack a nucleus and membrane-bound organelles, while eukaryotic cells (e.g., plants, animals) have both.

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

Example: Chloroplasts in plant cells enable photosynthesis, a function not found in animal cells.

Cell Structure and Function

• Nucleus: Contains genetic material and controls cellular activities.

• Endomembrane System: Includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vesicles. Responsible for synthesis, modification, and transport of cellular products.

• Energy Organelles: Mitochondria (site of cellular respiration) and chloroplasts (site of photosynthesis in plants).

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

• Cell Surface Structures: Cilia and flagella aid in movement; cell walls provide support in plants.

• Cell Junctions: Include tight junctions, anchoring junctions, and gap junctions, which connect and communicate between cells.

Example: Gap junctions in animal cells allow for direct communication between neighboring cells.

Chapter 7: Membrane Structure and Function

Cell Membrane Structure

The cell membrane is a fluid mosaic of phospholipids, proteins, and carbohydrates, providing a selective barrier for the cell.

• Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails, forming a semi-permeable membrane.

• Membrane Proteins: Serve as channels, receptors, enzymes, and anchors.

• Carbohydrates: Attached to proteins and lipids, important for cell recognition.

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 the relative solute concentrations inside and outside the cell, affecting water movement.

• Active Transport: Movement of substances against their concentration gradient, requiring energy (e.g., sodium-potassium pump).

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

Example: Red blood cells placed in a hypotonic solution will swell due to water influx.

Chapter 8: Introduction to Metabolism

Energy and Thermodynamics

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

• Energy Types: Kinetic, potential, chemical, and heat energy.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Second Law of Thermodynamics: Every energy transfer increases the entropy (disorder) of the universe.

• ATP: The cell's energy currency, used to drive endergonic (energy-requiring) reactions.

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

Example: The enzyme amylase accelerates the breakdown of starch into sugars.

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.

• General Equation:

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

• Electron Transport Chain: Transfers electrons to produce a proton gradient, driving ATP synthesis.

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

• Comparison: Aerobic respiration yields more ATP than fermentation.

• Substrate Utilization: Both fats and proteins can be used for cellular respiration when glucose is scarce.

Example: Muscle cells perform lactic acid fermentation during intense exercise when oxygen is limited.

Summary Table: Prokaryotic vs. Eukaryotic Cells