Questions and Answers
What is the primary function of chloroplasts in plant cells?
Which organelle is described as the 'powerhouse' of the cell?
What is the primary role of lysosomes in animal cells?
Which structure is essential for protein synthesis and is often associated with the rough endoplasmic reticulum (ER)?
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What role do microtubules play in animal cells?
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What is the main function of the Golgi apparatus in cells?
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What is the main function of peroxisomes in cells?
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Which statement about vacuoles is true?
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What is a major difference between plant cells and animal cells?
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Which of the following is NOT a component that all cells share?
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In what stage of the cell cycle does the DNA synthesis occur?
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Which statement accurately describes prokaryotic cells?
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What occurs during the stage of cytokinesis?
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Which phase takes up most of the cell's life?
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What is the correct sequence of stages during mitosis?
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What role do microtubules play during the cell cycle?
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Who was the first individual to record the observation of cells?
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What are the three postulates of cell theory?
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Which scientist concluded that plants are made of cells?
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What is the primary function of the nucleus in a cell?
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Which of the following organelles acts as a security guard for the cell?
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What does the term 'omnis cellula e cellula' imply?
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Which of the following best describes the cytoplasm?
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Which structure in plant cells provides protection and helps keep everything inside the cell?
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What is the primary role of the G1 checkpoint in the cell cycle?
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What occurs during the G2 checkpoint of the cell cycle?
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Which phase of meiosis involves the exchange of genetic material?
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What is the main consequence of failed checkpoints in the cell cycle?
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What happens during Metaphase 1 of meiosis?
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What is the purpose of the Mitosis checkpoint?
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Which statement correctly describes the result of Telophase 1 in meiosis?
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What stage occurs after Prophase 2 in meiosis?
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Study Notes
Cell Theory
- Cells are the fundamental building blocks of all living organisms, varying in shape and size.
- Robert Hooke first observed cells in 1665 by examining cork through a microscope, coining the term “cellulae.”
- Key contributors to cell theory: Theodor Schwann, Matthias Schleiden, Rudolph Virchow.
- Three main postulates of cell theory:
- All living things are made of one or more cells.
- Cells are the basic unit of life.
- All cells arise from preexisting cells.
Discovery Timeline
- Robert Hooke (1665): First recorded cells in cork.
- Antoine van Leeuwenhoek (1660s): Observed protists and bacteria, describing them as "animacules."
- Matthias Schleiden (1838): Established that all plants are composed of cells.
- Theodor Schwann (1839): Stated that animals consist of cells and their products.
- Robert Remak (1842): Identified three embryonic layers: ectoderm, mesoderm, endoderm.
- Rudolph Virchow (1855): Concluded "omnis cellula e cellula" - all cells originate from existing cells.
Organelles in Plant & Animal Cells
- Organelles perform specific functions within cells and include:
- Cell Membrane: Protective barrier assisting in transport.
- Cell Wall (Plant): Provides structural protection.
- Cytoplasm: Gel-like fluid containing dissolved substances.
- Nucleus: Control center for growth and reproduction.
- Nucleolus: Produces ribosomal RNA within the nucleus.
- Chloroplast (Plant): Site of photosynthesis, converting sunlight to sugar.
- Mitochondria: Energy production through cellular respiration.
- Golgi Apparatus: Processes and packages proteins for export.
- Smooth ER: Synthesizes and stores lipids.
- Rough ER: Involved in protein synthesis with ribosomes.
- Vacuole: Storage for nutrients and waste, larger in plants.
- Ribosomes: Assemble proteins from amino acids.
- Peroxisome: Breaks down fatty acids and detoxifies.
- Lysosome (Animal): Digests macromolecules and recycles cellular waste.
- Microtubules (Animal): Support structure and assist in cell division.
- Centrioles (Animal): Aid in cell division; found in pairs.
Cell Types
- Organisms can be unicellular or multicellular, with humans composed of trillions of cells.
- Two major cell types:
- Prokaryotes: Simple, no membrane-bound organelles, no nucleus, oldest cell type (3.5 billion years).
- Eukaryotes: Complex, membrane-bound organelles, contain a nucleus, appeared 1.5 billion years ago.
- Similarities: Both have DNA and a cell membrane, containing essential biomolecules.
- Differences: Eukaryotes are significantly larger than prokaryotes.
Cell Cycle
- Comprises three main stages: Interphase, Mitosis, Cytokinesis.
-
Interphase:
- G1 Phase: Rapid growth and routine functions, longest duration.
- S Phase: DNA replication occurs.
- G2 Phase: Prepares for mitosis, assembles microtubules.
- Mitosis: Division of the nucleus into two identical nuclei, includes prophase, metaphase, anaphase, and telophase.
- Cytokinesis: Division of the cytoplasm resulting in two daughter cells.
Control of the Cell Cycle
- Three checkpoints monitor cell conditions:
- G1 Checkpoint: Assesses size, health, and environmental factors before S phase.
- G2 Checkpoint: Checks for DNA errors prior to mitosis.
- Mitosis Checkpoint: Verifies successful completion of mitosis before returning to G1.
- Checkpoint failures can lead to cancer or uncontrollable cell growth.
Meiosis
- A specialized type of cell division producing four haploid daughter cells (sex cells).
- Ensures organisms from sexual reproduction have proper chromosome numbers.
- Stages:
- Prophase 1: Chromosome condensation and crossing over occur.
- Metaphase 1: Chromosome pairs align randomly.
- Anaphase 1: Chromosome pairs separate to opposite sides.
- Telophase 1: New nuclei form, resulting in two haploid cells.
- Prophase 2: Prepares for formation of four haploid cells.
- Metaphase 2: Chromosomes align individually for separation in the next step.
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Description
Explore the fundamental insights of cell theory, including the contributions of key scientists such as Robert Hooke, Theodor Schwann, Matthias Schleiden, and Rudolf Virchow. This quiz covers the postulates that define cells as the basic unit of life, emphasizing their role as the building blocks of all living organisms.
