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Unit 1 Topics 1-6

Review of Biological Molecules

Student Learning Objectives

  • Define and use key terms: macromolecule, monomer, organic or biological molecule, saturated, unsaturated, function.

  • Recognize key features visually of biological molecules.

  • Describe four major types of macromolecules (carbohydrates, lipids, proteins, nucleic acids) and their common structures and functions.

Introduction to Biological Molecules

Biological macromolecules are large, complex organic molecules that are essential for life, primarily composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. These macromolecules are crucial for maintaining the structure and function of cells.

  • They are composed of smaller subunits known as monomers, which retain the chemical properties of their respective classes when combined to form polymers.

  • Each macromolecule class serves fundamental functions within the cell, significantly contributing to the cell's overall dry mass, which is vital for cellular processes and structural integrity.

Types of Biological Macromolecules

  1. Carbohydrates

    • Function: Provide energy and structural support.

    • Common Structures: Includes simple sugars (monosaccharides like glucose) and complex carbohydrates (polysaccharides like starch and cellulose).

  2. Lipids

    • Function: Serve as long-term energy storage, structural components of cell membranes, and signaling molecules.

    • Common Structures: Composed of fatty acids and glycerol; examples include triglycerides, phospholipids, and steroids.

  3. Proteins

    • Function: Catalyze biochemical reactions (enzymes), provide structural support, transport, and play roles in immune response.

    • Common Structures: Made up of amino acid chains which fold into specific three-dimensional shapes; categorized based on structure into primary, secondary, tertiary, and quaternary levels.

  4. Nucleic Acids

    • Function: Store and transmit genetic information.

    • Common Structures: Composed of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base; includes DNA and RNA.

Cellular Metabolism and Enzymes

Student Learning Objectives

  • Understand terms: biochemical, enzyme, activation energy, Gibbs free energy, metabolic pathways.

  • Differentiate between catabolic and anabolic reactions.

  • Describe enzyme structure and function; explain how enzymes affect activation energy.

Energy and Metabolism

Cells utilize biochemical pathways to maintain homeostasis, employing both catabolic and anabolic reactions:

  • Catabolic Reactions: These reactions release energy by breaking down larger molecules into smaller ones, which is critical for the production of ATP (adenosine triphosphate) that powers cellular activities.

  • Anabolic Reactions: These reactions consume energy to synthesize complex molecules from simpler subunits, which is necessary for cellular growth and repair.

  • Overall metabolic processes (catabolism + anabolism) are essential for converting food to energy, biosynthesis, and maintaining cellular functions.

Enzymes

  • Enzymes are specialized proteins that act as catalysts, lowering the activation energy required for biochemical reactions to occur. Their structure contains an active site that specifically binds to substrates, enabling the conversion into products.

Structure of Cell Membranes

Student Learning Objectives

  • Understand the composition and functions of plasma membranes.

  • Identify molecules in biological membranes: phospholipids, proteins, cholesterol.

Biological Membranes

  • Plasma membranes are primarily composed of a bilayer of phospholipids, creating a selectively permeable barrier that regulates the flow of substances in and out of the cell.

  • Embedded proteins perform essential functions, including transport of molecules, acting as channels or carriers, and facilitating cell-cell communication and signaling.

  • Cholesterol molecules interspersed within the bilayer enhance membrane fluidity and stability, allowing membranes to maintain their structure under varying temperatures.

Movement Across Cell Membranes

Passive Transport

  • The movement of substances across membranes without energy input, driven by concentration gradients.

    • Diffusion: The net movement of molecules from an area of higher concentration to an area of lower concentration.

    • Osmosis: The diffusion of water across membranes in response to solute concentrations, classifying solutions as hypertonic (higher solute concentration), hypotonic (lower solute concentration), or isotonic (equal solute concentration).

Active Transport

  • Active transport requires energy (from ATP) to move substances against their concentration gradients, essential for maintaining the cells' internal environment.

    • This process involves specific transport proteins or pumps (e.g., sodium-potassium pump), as well as endocytosis and exocytosis for the uptake and export of larger molecules and particles.

Eukaryotic Cells

Unique Features

Eukaryotic cells are characterized by the presence of membrane-bound organelles, facilitating compartmentalization of cellular functions, distinguishing them from prokaryotic cells.

Organelles and Their Functions

  • Nucleus: Contains genetic material and is the control center for cell metabolism and reproduction.

  • Mitochondria: Powerhouses of the cell, responsible for ATP production via cellular respiration.

  • Endoplasmic Reticulum: Smooth ER is involved in lipid synthesis, while Rough ER is studded with ribosomes for protein synthesis.

  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport.

  • Cytoskeleton: Provides structural support and plays roles in intracellular transport, cell division, and cell shape maintenance.

  • Lysosomes: Contain enzymes for digesting macromolecules and recycling cellular components.

Evolution of Multicellular Eukaryotes

Key Adaptations for Multicellularity

  • Cell Adhesion: Cells are capable of adhering to each other, forming tissues and contributing to cooperative behaviors that enhance survival and functionality of multicellular organisms.

  • Cell Communication: Essential for coordination and management of cellular activities among different cell types in a multicellular organism, utilizing chemical signals and receptor interactions.

  • Differentiation: Cells undergo specialization to perform distinct functions, facilitating the complexity of organismal systems and allowing for a division of labor that enhances efficiency.

The evolutionary advantages of multicellularity include improved resource acquisition, enhanced survival strategies due to specialized functions, and the ability to respond to environmental changes more effectively.