Cell Biology Mock Exam

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.