Questions and Answers
Which of the following statements accurately reflects a characteristic of eukaryotic cells compared to prokaryotic cells?
During which phase of the cell cycle does DNA synthesis primarily occur?
Which organelle is primarily responsible for energy production in eukaryotic cells?
What is a key function of desmosomes in epithelial tissue?
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Which of the following accurately describes a characteristic of cancerous cells?
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Study Notes
Cell Theory
- Fundamental principle stating that all living organisms are composed of cells.
- Establishes that the cell is the basic unit of life.
- Highlights that all cells arise from pre-existing cells.
Important Events in Cell Theory
- 1665: Robert Hooke first observes cells in cork.
- 1838: Matthias Schleiden proposes that all plants are made of cells.
- 1839: Theodor Schwann extends the theory to animals.
- 1855: Rudolf Virchow concludes that all cells come from existing cells.
Postulates of Cell Theory
- All living things are made of one or more cells.
- The cell is the basic unit of structure and function.
- All cells arise from existing cells.
Types of Organisms
- Unicellular organisms: Single-celled, e.g., bacteria, protozoa.
- Multicellular organisms: Made up of multiple cells, e.g., plants, animals.
Types of Cells: Similarities and Differences
- Prokaryotic cells: Lack a nucleus, typically smaller, simpler structure, e.g., bacteria.
- Eukaryotic cells: Contain a nucleus, larger and more complex, e.g., animals, plants, fungi.
- Both types share essential components: cell membrane, cytoplasm, and ribosomes.
Organelles in Prokaryotic and Eukaryotic Cells
- Prokaryotic cells: Ribosomes, plasma membrane, cell wall, cytoplasm, genetic material (nucleoid).
- Eukaryotic cells: Nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, chloroplasts (in plants).
Cell Modification and Specialization
- Apical: Surface cells exposed to an internal or external environment; often involved in absorption or secretion.
- Basal: Cells anchored to the basement membrane; involved in adhesion and communication with connective tissue.
- Lateral: Cells that interact with neighboring cells; important for cell signaling and maintaining tissue structure.
Structures and Their Uses
- Cilia: Hair-like projections that enable movement or transportation of materials across cell surfaces.
- Flagella: Tail-like structures that aid in cell movement.
- Pseudopodia: “False feet” used by some cells (like amoeba) for movement and feeding.
- Villi: Small, finger-like projections that increase surface area for absorption in the intestines.
- Microvilli: Even smaller projections that further enhance surface area for absorption.
- Desmosomes: Junctions that provide strong adhesion between cells.
- Gap junctions: Allow for direct communication between adjacent cells.
- Tight junctions: Seal gaps between cells to prevent leakage of substances.
Specialized Cells
- Root cells: Absorb water and nutrients from soil; specialized for water uptake.
- Guard cells: Control the opening and closing of stomata in leaves; regulate gas exchange.
Cell Cycle
- Two main types: Mitosis and meiosis.
- Interphase: The phase where the cell prepares for division; consists of G1, S, and G2 phases.
Phases of Interphase
- G1 Phase: Cell growth and normal functions occur; cell prepares for DNA synthesis.
- S Phase: DNA replication takes place, leading to two complete sets of chromosomes.
- G2 Phase: Further growth and preparation for mitosis; checks for DNA errors.
Metaphase and G0 Phase
- Metaphase: Chromosomes align at the cell equator; spindle fibers attach.
- G0 Phase: A resting stage where cells exit the cell cycle and do not actively divide.
Cell Checkpoints
- Critical control points that ensure proper cell division; detect errors and prevent the progression of the cycle if issues are found.
Cancer Overview
- Cancer can be benign (non-cancerous, localized) or malignant (invasive, capable of spreading).
- Oncogenes are mutated genes that promote cell division and can lead to cancer.
- Proto-oncogenes are normal genes that may become oncogenes due to mutations.
- Tumor suppressor genes regulate cell division; mutations can lead to unregulated growth and cancer.
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Description
Test your knowledge with this comprehensive 500-item mock exam covering various aspects of cell theory, including its postulates, important events, and comparisons between prokaryotic and eukaryotic cells. You will explore organelles, cell modifications, and specializations in detail to solidify your understanding of cellular biology.
