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What structure develops between daughter cell nuclei during cell plate formation?
What structure develops between daughter cell nuclei during cell plate formation?
Which of the following is NOT a characteristic feature of plant cells?
Which of the following is NOT a characteristic feature of plant cells?
How do animal cells typically divide compared to plant cells?
How do animal cells typically divide compared to plant cells?
What is the primary function of microtubules during cell plate formation?
What is the primary function of microtubules during cell plate formation?
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Which component is absent in animal cells but present in plant cells?
Which component is absent in animal cells but present in plant cells?
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What significant conclusion is associated with Rudolf Virchow?
What significant conclusion is associated with Rudolf Virchow?
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Which scientist discovered the nucleus in plant and animal cells?
Which scientist discovered the nucleus in plant and animal cells?
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What is the maximum magnification capability of compound microscopes?
What is the maximum magnification capability of compound microscopes?
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What distinguishes dissecting microscopes from compound microscopes?
What distinguishes dissecting microscopes from compound microscopes?
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Which of the following best describes the Cell Theory?
Which of the following best describes the Cell Theory?
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What was Eduard Buchner's significant discovery in 1897?
What was Eduard Buchner's significant discovery in 1897?
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What type of microscope uses a beam of electrons to produce an image?
What type of microscope uses a beam of electrons to produce an image?
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What is the role of light in light microscopes?
What is the role of light in light microscopes?
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What is the basic unit of life that all living things are composed of?
What is the basic unit of life that all living things are composed of?
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Which of the following statements accurately reflects a feature shared by all cells?
Which of the following statements accurately reflects a feature shared by all cells?
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What significant discovery did Robert Hooke make in 1665?
What significant discovery did Robert Hooke make in 1665?
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What term refers to the lifecycle stage where a cell prepares for division?
What term refers to the lifecycle stage where a cell prepares for division?
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Which of the following cell types has a more complex structure, eukaryotic or prokaryotic?
Which of the following cell types has a more complex structure, eukaryotic or prokaryotic?
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Which organelle is primarily responsible for energy production in eukaryotic cells?
Which organelle is primarily responsible for energy production in eukaryotic cells?
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Which of these historical figures contributed to the understanding of single-celled organisms?
Which of these historical figures contributed to the understanding of single-celled organisms?
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What concept did Jean Baptiste de Lamarck advance regarding living organisms?
What concept did Jean Baptiste de Lamarck advance regarding living organisms?
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What is the primary function of the nucleus in a cell?
What is the primary function of the nucleus in a cell?
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What describes the structure of the cell membrane?
What describes the structure of the cell membrane?
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Which component of the nucleus is primarily composed of RNA?
Which component of the nucleus is primarily composed of RNA?
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What is the difference between Rough ER and Smooth ER?
What is the difference between Rough ER and Smooth ER?
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What is the primary role of ribosomes in the cell?
What is the primary role of ribosomes in the cell?
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What type of cellular structure is the endoplasmic reticulum?
What type of cellular structure is the endoplasmic reticulum?
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What happens to chromatin strands during cell division?
What happens to chromatin strands during cell division?
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Which of the following best describes the fluid mosaic model?
Which of the following best describes the fluid mosaic model?
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What is the primary outcome of mitosis?
What is the primary outcome of mitosis?
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What occurs to chromosomes during prophase?
What occurs to chromosomes during prophase?
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What is the role of the spindle fibers during metaphase?
What is the role of the spindle fibers during metaphase?
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How do sister chromatids behave during anaphase?
How do sister chromatids behave during anaphase?
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Which structures disappear during prophase?
Which structures disappear during prophase?
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What marks the completion of telophase?
What marks the completion of telophase?
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What is the function of kinetochore during mitosis?
What is the function of kinetochore during mitosis?
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What occurs to the spindle fibers at the end of telophase?
What occurs to the spindle fibers at the end of telophase?
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What is the primary function of dictyosomes in a cell?
What is the primary function of dictyosomes in a cell?
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Which of the following components is NOT found within chloroplasts?
Which of the following components is NOT found within chloroplasts?
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How do vesicles form from dictyosomes?
How do vesicles form from dictyosomes?
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What distinguishes chromoplasts from other plastids?
What distinguishes chromoplasts from other plastids?
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Which process occurs within the thylakoid membranes of chloroplasts?
Which process occurs within the thylakoid membranes of chloroplasts?
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What is a characteristic feature of mitochondria?
What is a characteristic feature of mitochondria?
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Which type of plastid is known for synthesizing starches?
Which type of plastid is known for synthesizing starches?
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Which of the following is a product released from the vesicles pinched off from dictyosomes?
Which of the following is a product released from the vesicles pinched off from dictyosomes?
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Study Notes
Introduction to Cells
- All living things are made of cells.
- All living things begin as a single cell.
- Early cells resulting from a single cell are similar.
- Differentiation changes cell structure and function.
- Specializations allow transport of nutrients (like food and water).
- Other specializations allow cells to secrete fluids.
- Cells have varying life spans.
- Cells share common features.
Cells: History
- 1665: Robert Hooke discovered cells.
- 1670s: Marcello Malpighi and Nehemiah Grew observed and described single-celled organisms, calling them "animacules".
- 1809: Jean-Baptiste de Lamarck proposed that organisms needed cellular components to live.
- 1824: René Dutrochet stated that all plant and animal tissues are made of cells.
- 1831: Robert Brown discovered the nucleus.
- 1838: Schleiden and Schwann formulated the Cell Theory, stating all living things are composed of cells and cells form the structural base of organization.
- 1858: Rudolf Virchow proposed cells only arise from pre-existing cells.
- 1862: Louis Pasteur experimentally disproved spontaneous generation and showed fermentation involved yeast activity.
- 1897: Eduard Buchner discovered that extracts from cells contain the enzymes necessary for fermentation.
Modern Microscopes: Light Microscopes
- Increase magnification using glass or calcium fluoride crystals.
- Include compound and dissecting (stereomicroscopes).
Compound Microscopes
- Light passes through thinly sliced material.
- Can distinguish organelles 2 micrometers or larger in diameter.
- Magnification up to 1500x.
Dissecting Microscopes
- Also known as stereomicroscopes allowing 3D views of opaque objects.
- Magnification up to 30x.
Electron Microscopes
- Use beams of electrons to visualize.
- Includes transmission and scanning electron microscopes.
Transmission Electron Microscopes
- 200,000x magnification but material needs to be extremely thin.
Scanning Electron Microscope
- 10,000x magnification, allowing observation of surface details on thick objects.
Scanning Tunneling Microscopes
- Uses a probe that tunnels electrons to scan samples.
- Creates surface maps.
- Achieves atomic level resolution. (first picture of DNA segment showing its helical structure)
Eukaryotic versus Prokaryotic Cells
- Prokaryotic cells lack a nucleus (e.g., bacteria).
- Eukaryotic cells contain a nucleus (e.g., unicellular eukaryotes, fungi, plants, animals).
- Eukaryotic cells have membrane-bound organelles.
Cell Structure and Communication
- Cell wall surrounds the protoplasm (all living parts of a cell).
- Protoplasm is bound by the plasma membrane.
- Cytoplasm is the space between the plasma membrane and nucleus containing cytosol.
- Organelles are persistent structures within the cytoplasm.
- Organelles are usually, but not always, membrane-bound with specialized functions.
Anatomy of a Young Plant Cell
- Diagrams showing labeled components.
Cell Size
- Cells of higher plants range from 10 to 100 micrometers in length.
- Smaller cells have a higher surface-to-volume ratio, enabling efficient cell communication.
Cell Wall
- Main component is cellulose (long glucose chains).
- Other components include hemicellulose, pectin, and glycoproteins.
- Middle lamella is the first formed in new cell walls between adjacent cells.
Primary Cell Wall
- Flexible, laid down on either side of the middle lamella.
- Consists of a network of cellulose, hemicellulose, pectin, and glycoproteins.
Secondary Walls
- Produced inside the primary walls, by lignin inclusion.
- Cellulose microfibrils embedded in lignin for strength.
Communication Between Cells
- Fluids and dissolved substances pass through the primary walls via tiny openings called plasmodesmata.
- Plasmodesmata are cytoplasmic strands extending between cells.
Plasma Membrane
- Semipermeable outer boundary.
- Regulates substance movement in and out of the cell.
- Composed of phospholipid bilayer and proteins.
- Fluid mosaic structure.
Nucleus
- Control center of the cell.
- Contains DNA.
- Sends coded messages.
- Bound by a double membrane (nuclear envelope) with complex pores.
- Pores regulate molecules passing between nucleus and cytoplasm.
Components of the Nucleus
- Nucleoplasm: fluid medium for nuclear processes.
- Nucleolus: composed mainly of RNA.
- Chromatin strands: composed of DNA and proteins, coiling to form chromosomes.
Endoplasmic Reticulum
- Network of flattened sacs and tubes within cytoplasm.
- Facilitates cell communication and materials channeling.
- Synthesizes membranes for other organelles and modifies proteins (rough ER has ribosomes, smooth ER does not).
Ribosomes
- Consist of two subunits (RNA and proteins).
- Link amino acids to form complex proteins.
- Assembled in the nucleolus.
- Can be on the rough ER, in the cytoplasm or chloroplasts, or in other organelles.
Dictyosomes
- Stacks of flattened disks or vesicles (Golgi bodies in animal cells).
- Modify proteins with attached carbs, assemble polysaccharides, and package them into vesicles.
Function of Dictyosomes
- Modify carbohydrates attached to ER-synthesized proteins.
- Assemble and collect polysaccharides in small vesicles.
- Vesicles pinch off from dictyosome margins, migrate to membrane, and release their contents outside the cell.
Plastids
- Chloroplasts are the most conspicuous.
- Bound by two membranes, containing grana, thylakoids (site of chlorophyll and photosynthesis).
- Stroma (matrix of enzymes for photosynthesis)
- Contains circular DNA encoding photosynthesis proteins.
- Other plastids: chromoplasts (synthesize and store carotenoids), leucoplasts (colorless, store starches or oils).
Mitochondria
- Release energy from cellular respiration.
- Bound by two membranes (inner membrane forms cristae, increasing surface area for enzymes in the matrix).
- Matrix contains DNA and RNA.
Microbodies
- Small, spherical bodies containing specialized enzymes (e.g. peroxisomes in photorespiration, and glyoxysomes for fat to carbohydrate conversion).
- Bound by a single membrane.
Vacuoles
- Large fluid-filled spaces in mature cells.
- Bound by vacuolar membranes (tonoplast).
- Filled with cell sap (watery fluid containing salts, sugars, organic acids, proteins, and pigments like anthocyanins).
- Function in maintaining cell pressure and pH, storing metabolites and waste products.
The Cytoskeleton
- Network of microtubules and microfilaments.
- Involved in cell movement, architecture.
- Microtubules control cellulose addition to the cell wall, and are in flagella/cilia, spindle fibers/phragmoplast.
- Microfilaments are involved in cytoplasmic streaming.
Cellular Reproduction
- Cell cycle: a series of events when cells divide (interphase and mitosis).
- Interphase (up to 90% of cycle):
- G1: cell increases in size.
- S: DNA replication occurs.
- G2: organelles (including mitochondria) divide, and microtubules are created.
Mitosis
- Process of cellular division, producing two identical daughter cells.
- Occurs in meristems.
- Stages: prophase, metaphase, anaphase, telophase.
Chromosomes in Prophase
- Condensation of chromosomes: coiling makes them shorter and thicker.
- Structure: chromosomes made of two identical sister chromatids held together by a centromere.
- Kinetochore (protein complex) on the outer surface of each centromere.
Prophase
- Spindle fibers attach to kinetochores and anchor to opposite cell poles.
- Nuclear envelope and nucleolus disintegrate.
Metaphase
- Chromosomes line up at the cell's equator.
- Spindle fibers (collectively called the spindle) align chromosomes.
- Centromeres hold sister chromatids together.
Anaphase
- Spindle fibers shorten, pulling chromatids to opposite poles.
- Separation makes daughter chromosomes.
Telophase
- Chromosomes reach opposite poles.
- Nuclear envelope reforms around each group of chromosomes.
- Nucleoli reappear.
- Spindle fibers disappear.
Cell Plate Formation
- Phragmoplast (a complex of microtubules and ER) forms between new nuclei.
- Vesicles from dictyosomes move along microtubules and fuse to form the cell plate.
- Cell plate extends outward towards mother cell walls.
Higher Plant Cells Versus Animal Cells
- Plant cells have cell walls, a cell plate that forms during division and plasmodesmata, and chloroplasts/vacuoles.
- Animal cells lack cell walls, have plasma membranes, divide by pinching in two, do not have cell plates or plasmodesmata and have centrioles and no chloroplasts/vacuoles.
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Description
Test your knowledge on cell biology with this quiz covering topics such as cell division, the differences between plant and animal cells, and the history of cell discovery. Explore concepts related to microscopes and foundational principles in cell theory.
