Structure and Function of Eukaryotic Organelles

• Nucleus: Contains genetic material and controls cellular activities.

• Endomembrane system: Includes nuclear envelope, endoplasmic reticulum (smooth and rough), Golgi apparatus, lysosomes, peroxisomes, and vacuoles (in plants).

• Plasma membrane: Regulates entry and exit of substances.

• Energy organelles: Mitochondria (cellular respiration) and chloroplasts (photosynthesis in plants).

Endosymbiotic Theory

• Proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

• Evidence: Double membranes, their own DNA, and ribosomes similar to prokaryotes.

Structures Unique to Plant and Animal Cells

• Plant cells: Have cell walls, chloroplasts, and large central vacuoles.

• Animal cells: Have centrioles and lysosomes.

Chapter 7: Membrane Structure and Function

Phospholipids, Proteins, and Cholesterol

The plasma membrane is a selectively permeable barrier composed of a phospholipid bilayer with embedded proteins and cholesterol.

• Phospholipids: Form the basic structure; hydrophilic heads face outward, hydrophobic tails inward.

• Proteins: Serve as channels, carriers, receptors, and enzymes.

• Cholesterol: Modulates membrane fluidity and stability.

Fluid Mosaic Model

• Describes the membrane as a dynamic structure with proteins floating in or on the fluid lipid bilayer.

Types of Membrane Proteins

• Integral (transmembrane) proteins: Span the membrane and are involved in transport and signaling.

• Peripheral proteins: Attached to the membrane surface, often involved in signaling or maintaining cell shape.

Membrane Transport Mechanisms

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

• Active transport: Movement against the concentration gradient, requiring energy (usually ATP).

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

• Tonicity: The ability of a solution to cause a cell to gain or lose water (isotonic, hypertonic, hypotonic).

• Membrane potential: Voltage difference across the membrane, maintained by ion pumps (e.g., sodium-potassium pump).

Bulk Transport

• Endocytosis: Uptake of materials via vesicles (phagocytosis, pinocytosis, receptor-mediated endocytosis).

• Exocytosis: Release of materials from the cell via vesicles.

Chapter 8: Metabolism

Bioenergetics and Metabolic Pathways

Metabolism encompasses all chemical reactions in a cell, divided into catabolism (breakdown) and anabolism (synthesis).

• Bioenergetics: Study of how energy flows through living organisms.

• Catabolism: Breakdown of molecules to release energy.

• Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.

• Potential energy: Stored energy; kinetic energy: energy of motion.

First Law of Thermodynamics

• Energy cannot be created or destroyed, only transformed from one form to another.

ATP and Enzymes

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

• ATP Cycle: ATP is hydrolyzed to ADP + Pi, releasing energy; ADP is regenerated to ATP.

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

• Active site: Region on the enzyme where substrate binds.

• Enzyme inhibition: Can be competitive (inhibitor binds active site) or noncompetitive (inhibitor binds elsewhere).

• Allosteric regulation: Enzyme activity is regulated by molecules binding at sites other than the active site.

Feedback Inhibition

• End product of a metabolic pathway inhibits an earlier step, preventing overproduction.

Chapter 9: Cellular Respiration

Overview and Equations

Cellular respiration is the process by which cells extract energy from glucose to produce ATP.

• Overall equation:

Fermentation vs. Aerobic Respiration

• Fermentation: Anaerobic process; produces less ATP and end products like lactic acid or ethanol.

• Aerobic respiration: Requires oxygen; produces more ATP.

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

• Cellular respiration involves a series of redox reactions transferring electrons from glucose to oxygen.

Stages of Cellular Respiration

• Glycolysis: Occurs in cytoplasm; breaks glucose into two pyruvate molecules; produces ATP and NADH.

• Pyruvate oxidation: Converts pyruvate to acetyl-CoA, producing NADH and CO2.

• Citric acid cycle (Krebs cycle): Completes breakdown of acetyl-CoA; produces ATP, NADH, FADH2, and CO2.

• Oxidative phosphorylation: Includes electron transport chain and chemiosmosis; produces most ATP.

Key Equations and Intermediates

• Glycolysis:

• Citric Acid Cycle: Main steps involve oxidation of acetyl-CoA, generation of NADH, FADH2, and ATP.

• Electron Transport Chain: Electrons from NADH and FADH2 are transferred through protein complexes, driving ATP synthesis.

Fermentation

• Occurs when oxygen is not available; regenerates NAD+ for glycolysis.

• Types: Lactic acid fermentation (in muscles), alcoholic fermentation (in yeast).

Energy Use in Cells

• Cells use carbohydrates, lipids, and proteins for energy, entering cellular respiration at different points.

Evolutionary Significance

• Glycolysis is a universal pathway, suggesting it evolved early in the history of life.