Chapter 7: Inside the Cell

Introduction

This chapter explores the structure and function of cells, the basic units of life. It reviews the four classes of biological molecules and distinguishes between the two major types of cells: prokaryotes and eukaryotes.

• Prokaryotes include bacteria and archaea. They lack a nucleus and most membrane-bound organelles.

• Eukaryotes include plants, animals, fungi, and protists. They have a nucleus and various organelles.

• Understanding cell structure is essential for studying how cells function and interact in multicellular organisms.

7.1: Bacterial and Archaeal Cell Structures and Their Functions

• Prokaryotes organize their chromosome in a nucleoid region (not membrane-bound).

• Chromosomes contain DNA, which encodes genes.

• Some prokaryotes have extra-chromosomal DNA found in plasmids.

• Photosynthetic prokaryotes have internal membrane complexes for photosynthesis.

• Ribosomes manufacture proteins and are found in prokaryotes and eukaryotes.

• Other structures: cell wall, plasma membrane, flagella, and fimbriae.

7.2: Eukaryotic Cell Structures and Their Functions

• Eukaryotic cells have membrane-bound organelles, including:

  • Nucleus: Contains genetic material (DNA).

  • Ribosomes: Protein synthesis.

  • Endoplasmic Reticulum (ER): Protein and lipid synthesis.

  • Golgi apparatus: Modifies, sorts, and ships proteins and lipids.

  • Lysosomes: Digestion and waste processing.

  • Vacuoles: Storage (especially in plants and fungi).

  • Peroxisomes: Breakdown of fatty acids and detoxification.

  • Mitochondria: ATP production via cellular respiration.

  • Chloroplasts (plants and algae): Photosynthesis.

  • Cytoskeleton: Structural support, movement, and transport.

• Each organelle has a specific function that contributes to the cell's overall operation.

7.3: Putting the Parts into a Whole

• Multicellular organisms have specialized cells with distinct structures and functions.

• Cell specialization allows for division of labor and complex body organization.

7.4: Cell Systems & Nucleocytoplasmic Transport

• Transport of molecules into and out of the nucleus is regulated by nuclear pores.

• Nuclear pores are protein complexes that control the passage of RNA, proteins, and other molecules.

7.5: Cell Systems II: The Endomembrane System Manufactures, Ships, and Recycles Cargo

• The endomembrane system includes the nuclear envelope, ER, Golgi apparatus, lysosomes, and vesicles.

• It is responsible for the synthesis, modification, packaging, and transport of proteins and lipids.

• Vesicles transport materials between organelles and to/from the cell membrane.

7.6: Cell Systems III: The Dynamic Cytoskeleton

• The cytoskeleton is a network of protein filaments that provides structural support and enables cell movement.

• Main components:

  • Microfilaments (actin filaments): Cell shape and movement.

  • Intermediate filaments: Mechanical strength.

  • Microtubules: Organelle movement, cell division, and cilia/flagella structure.

Energy and Enzymes (Chapter 8)

Introduction

This chapter examines how cells obtain and use energy, focusing on chemical reactions and the role of enzymes.

8.1: What Happens to Energy in Chemical Reactions?

• Potential energy: Stored energy due to position or structure.

• Kinetic energy: Energy of motion.

• Energy can be transformed from one type to another (e.g., chemical to kinetic).

• In cells, chemical energy stored in bonds is converted to usable forms (e.g., ATP).

• Enthalpy (H): Total energy in a system.

• Gibbs free energy (G): Energy available to do work. Change in free energy () determines if a reaction is spontaneous.

• Exergonic reactions: (spontaneous, release energy).

• Endergonic reactions: (require energy input).

8.2: Nonspontaneous Reactions May Be Driven Using Chemical Energy

• Cells use energy coupling to drive endergonic reactions by pairing them with exergonic reactions (often via ATP hydrolysis).

• Phosphorylation (adding a phosphate group) can activate molecules and make reactions more favorable.

8.3: How Enzymes Work

• Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• They are highly specific for their substrates.

• Enzyme activity can be affected by temperature, pH, and inhibitors.

• Enzymes work by binding substrates at their active site, forming an enzyme-substrate complex.

8.4: What Factors Affect Enzyme Function?

• Enzyme function is optimized for specific conditions (e.g., temperature, pH).

• Enzyme inhibitors can decrease activity; activators can increase it.

8.5: Enzymes Can Work Together in Metabolic Pathways

• Metabolic pathways are series of enzyme-catalyzed reactions.

• Pathways can be catabolic (break down molecules) or anabolic (build molecules).

• Feedback inhibition regulates pathways by inhibiting an early enzyme when the end product accumulates.

Chapter 9: Cellular Respiration & Fermentation

Introduction

This chapter describes how cells harvest energy from organic molecules, primarily glucose, to produce ATP.

• ATP is the main energy currency of the cell.

• Cellular respiration includes glycolysis, pyruvate processing, the citric acid cycle, and electron transport/chemiosmosis.

9.1: An Overview of Cellular Respiration

• Cellular respiration is the process by which cells convert biochemical energy from nutrients into ATP.

• It involves oxidation of glucose and reduction of electron carriers (NAD+, FAD).

• Overall equation:

• Main stages: Glycolysis, Pyruvate Processing, Citric Acid Cycle, Electron Transport Chain (ETC) & Chemiosmosis.

9.2: Glycolysis: Oxidizing Glucose to Pyruvate

• Occurs in the cytosol.

• Glucose (6C) is split into two pyruvate (3C) molecules.

• Net products per glucose: 2 ATP, 2 NADH, 2 pyruvate.

• ATP is produced by substrate-level phosphorylation.

9.3: Processing Pyruvate to Acetyl CoA

• Pyruvate is transported into the mitochondria (eukaryotes).

• Each pyruvate is converted to acetyl CoA, producing 1 NADH and releasing 1 CO2 per pyruvate.

• Acetyl CoA enters the citric acid cycle.

9.4: The Citric Acid Cycle: Oxidizing Acetyl CoA to CO2

• Also called the Krebs cycle or TCA cycle.

• Occurs in the mitochondrial matrix.

• Each acetyl CoA is oxidized, producing:

  • 3 NADH

  • 1 FADH2

  • 1 ATP (or GTP)

  • 2 CO2

• Cycle turns twice per glucose molecule.

9.5: Electron Transport and Chemiosmosis: Building a Proton Gradient to Produce ATP

• Electron transport chain (ETC) is located in the inner mitochondrial membrane (eukaryotes).

• Electrons from NADH and FADH2 are transferred through protein complexes, releasing energy to pump protons (H+) into the intermembrane space.

• This creates a proton gradient (electrochemical gradient).

• ATP synthase uses the flow of protons back into the matrix to synthesize ATP from ADP and Pi (chemiosmosis).

• Oxygen is the final electron acceptor, forming water.

Table: Summary of ATP Yield from Cellular Respiration

9.6: Fermentation

• Fermentation is an anaerobic process that allows glycolysis to continue when oxygen is absent.

• It regenerates NAD+ by transferring electrons from NADH to pyruvate or its derivatives.

• Types:

  • Lactic acid fermentation: Pyruvate is reduced to lactate (e.g., in muscle cells).

  • Alcohol fermentation: Pyruvate is converted to ethanol and CO2 (e.g., in yeast).

• Fermentation produces much less ATP than cellular respiration.

Additional info: This study guide covers the main concepts and processes in cell biology, energy transformation, and metabolism, as outlined in the provided notes. For more detailed mechanisms and regulation, refer to your textbook or lecture materials.