Chapter 4 Biology Ikenna Opara

4.1 Cell Theory

1. Discuss cell theory.

• All organisms are composed of one or more cells.

• The life processes of metabolism and heredity occur within these cells.

• Cells are the smallest living units and the basic units of organization in life.

• Cells arise only by the division of pre-existing cells.

2. Describe the factors that limit cell size.

• Surface area available for diffusion.

• Temperature.

• Concentration gradient of diffusing substances.

3. Categorize the structural and functional similarities in cells.

• Cell membrane (plasma membrane) – regulates entry and exit of substances.

• Cytoplasm – contains organelles and the cytosol.

• Genetic material (DNA/RNA) and ribosomes – responsible for genetic information and protein synthesis.

4.2 Prokaryotic Cells

1. Describe the organization of prokaryotic cells.

• Unicellular organisms lacking a nucleus.

• Components: Cell wall, plasma membrane, capsule, flagella, pili, fimbriae, cytoplasm, and nucleoid region.

• Reproduce by binary fission.

4.3 Eukaryotic Cells

1. Compare the organization of eukaryotic and prokaryotic cells.

• Prokaryotic cells: No nucleus, smaller, simpler, lack membrane-bound organelles.

• Eukaryotic cells: Have a nucleus, larger, more complex, contain membrane-bound organelles.

2. Discuss the role of the nucleus in eukaryotic cells.

• Stores genetic information.

• Regulates gene expression.

• Coordinates cellular activities.

3. Describe the role of ribosomes in protein synthesis.

• Composed of ribosomal RNA and proteins.

• Catalyze the assembly of amino acids into proteins.

4.4 The Endomembrane System

1. Identify the different parts of the endomembrane system.

• Nuclear envelope, Endoplasmic Reticulum (ER), Golgi apparatus, lysosomes, and vacuoles.

2. Contrast the different functions of internal membranes and compartments.

• Rough ER: Synthesizes proteins.

• Smooth ER: Stores lipids, transports substances within the cell, stores Ca²⁺, and detoxifies foreign substances.

3. Evaluate the importance of each step in the protein-processing pathway.

1. Transcription: DNA is transcribed into mRNA in the nucleus.

2. Translation: mRNA interacts with ribosomes and tRNA to synthesize proteins in the cytoplasm.

4.5 Mitochondria and Chloroplasts: Cellular Generators

1. Describe the structure of mitochondria and chloroplasts.

• Both have double membranes.

• Contain their own DNA and protein synthesis machinery.

2. Compare the function of mitochondria and chloroplasts.

• Mitochondria: Metabolize sugar to generate ATP.

• Chloroplasts: Use light energy to generate ATP and synthesize sugar.

3. Explain the probable origin of mitochondria and chloroplasts.

• Endosymbiotic theory: They originated when a free-living prokaryotic cell was engulfed but not digested.

4.6 The Cytoskeleton

1. Contrast the structure and function of different fibers in the cytoskeleton.

• Actin filaments (microfilaments): Aid in cell crawling and contraction.

• Microtubules: Move vesicles within the cell; composed of α- and β-tubulin dimers.

• Intermediate filaments: Strongest cytoskeletal elements; prevent excessive stretching of cells.

2. Illustrate the role of microtubules in intracellular transport.

• Organize the cytoplasm.

• Transport materials within the cell.

4.7 Extracellular Structures and Cell Movement

1. Describe how cells move.

• Actin filaments allow cells to crawl.

• Flagella and cilia assist in movement.

2. Identify the different cytoskeletal elements involved in cell movement.

• Actin filaments, flagella, cilia.

3. Classify the elements of the extracellular matrix (ECM) in animal cells.

• ECM: Collection of extracellular molecules secreted by cells for structural and biochemical support.

• Composed of various glycoproteins.

4.8 Cell-to-Cell Interactions

1. Describe the roles of surface proteins.

• Help identify cells.

2. Differentiate between types of cell junctions.

• Tight junctions: Connect plasma membranes of adjacent cells, forming a barrier.

• Adhesive junctions: Attach the cytoskeleton of one cell to another.

• Communicating junctions: Allow ions and small molecules to pass between cells.

Mitochondria: Contains Cristate and is the site of cellular respiration

Nucleus: Most conspicuous organelle that houses our genetic material

Rough ER’ Studded with ribosomes and acts as membrane factoring for cells

Smooth ER: Carries out many functions including synthesis of lipids

Vacuole: Largest organelle found in plants cells which help maintain water balance

Peroxisome: Breaks fatty acids using enzymes that transfer hydrogen

Plasma membrane: Made up by a phospholipid bilayer and protect cell

Chloroplast: Found in plant cell and function in photosynthesis

Microtubules: Made from tubulin subunit and function during cell division

Adhesive Junction: To anchor cells together into sheets

Tight Junction: Prevents leakage of extracellular fluid pressing cells together

Gap Junction: Provide cytoplasmic channels between adjacent animal cells

Plasmodesmata: Transport structures between adjacent plant cells

• Tight Junctions: Seal adjacent epithelial cells together, preventing the passage of molecules between them.