Questions and Answers
What do prokaryotic cells lack?
A membrane-bound nucleus.
Which of the following domains do prokaryotic cells belong to?
What are the three basic shapes of bacteria?
Spherical (coccus), rod-shaped (bacillus), and spiral (spirillum or spirochete).
What is the function of the cell wall in bacteria?
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Eukaryotic cells are smaller than prokaryotic cells.
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Which of the following are included in the domain Eukarya?
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What is the role of the plasma membrane?
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What is the primary function of the nucleus?
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What process allows the separation of cell parts?
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Which statement accurately describes the structure of chloroplasts?
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What role do mitochondria play in cellular respiration?
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Which component is not part of the cytoskeleton?
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During photosynthesis, what is the main function of thylakoids?
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What is the matrix within the mitochondria primarily composed of?
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What is the main function of the rough endoplasmic reticulum?
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Which of the following statements accurately describes the Golgi apparatus?
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Lysosomes are involved in which of the following processes?
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What characterizes the smooth endoplasmic reticulum?
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Which component of the endomembrane system is responsible for receiving vesicles from the rough endoplasmic reticulum?
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What is a primary function of lysosomes within a cell?
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What type of cellular reaction does the endomembrane system help compartmentalize?
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What is one of the main roles of vesicles within the endomembrane system?
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Which of the following best describes the structure of the Golgi apparatus?
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What is produced by lysosomes during cellular digestion?
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What distinguishes peroxisomes from lysosomes?
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How do chloroplasts capture solar energy?
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What is the primary function of the Golgi apparatus in the endomembrane system?
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What is the role of chlorophyll in chloroplasts?
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Which organelle is primarily responsible for energy production through cellular respiration?
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Which of the following statements is true regarding vacuoles in plant cells?
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What is the overall chemical reaction that describes photosynthesis?
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Which cellular structure is crucial for the transport of proteins within the endomembrane system?
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Which organelles are membrane-bounded vesicles that contain digestive enzymes?
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What is the primary role of the rough endoplasmic reticulum?
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Which pigment is specifically associated with capturing light in photosynthetic organisms?
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What process occurs when vesicles fuse with the plasma membrane?
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Study Notes
Cell Types
- Prokaryotic cells lack a membrane-bound nucleus, are smaller and simpler than eukaryotic cells.
- Prokaryotic cells are categorized into two domains: Bacteria and Archaea, the latter inhabiting extreme environments.
- Eukaryotic cells, part of Domain Eukarya, include protists, fungi, plants, and animals.
Structure of Bacteria
- Bacteria are typically 1–1.5 μm wide and 2–6 μm long, with three common shapes:
- Spherical (coccus)
- Rod-shaped (bacillus)
- Spiral (spirillum and spirochete).
- The cell envelope includes:
- Plasma membrane: lipid bilayer with embedded proteins, forming internal pouches called mesosomes.
- Cell wall: provides structure and is fortified with peptidoglycan.
- Glycocalyx: a polysaccharide layer, often structured as a capsule, resistant to removal.
Cytoplasm and Genetic Material
- Cytoplasm is a semifluid solution bounded by the plasma membrane, containing water, organic/inorganic molecules, and enzymes.
- The nucleoid region houses a single, circular DNA molecule.
- Plasmids are small, accessory DNA rings independent of chromosomal DNA.
Appendages in Bacteria
- Flagella: structures aiding in motility.
- Fimbriae: small, bristle-like structures that help adhere to surfaces.
- Sex pili: tubular structures that facilitate DNA transfer between cells.
Eukaryotic Cell Characteristics
- Eukaryotic cells possess a membrane-bound nucleus that contains DNA and specialized organelles.
- Generally larger than prokaryotic cells, some have a cell wall (e.g., plant cells).
- Organelles perform specific functions and compartmentalize cellular processes.
Organelles in Eukaryotic Cells
- Eukaryotic organelles can be divided into:
- Endomembrane system: organelles that communicate through membrane channels and vesicles.
- Energy-related organelles: mitochondria and chloroplasts, known for their independence and self-sufficiency.
Cell Fractionation
- Cell fractionation involves breaking apart cellular components for analysis.
- Differential centrifugation separates cell parts based on size and density, akin to a washing machine's spin cycle; faster spins isolate smaller components.
Animal Cell Anatomy
- Plasma membrane: regulates the flow of molecules into and out of the cell.
- Nucleus: serves as the cell's command center, encompassed by a double membrane called the nuclear envelope.
- Cytoskeleton: maintains cell shape and aids in cellular movement and organization.
Energy-Related Organelles: Chloroplasts
- Chloroplasts are double-membrane organelles involved in photosynthesis.
- Inner membrane contains disc-like thylakoids, stacked into structures called grana.
- Stroma is the semi-fluid matrix where thylakoids are suspended, containing chlorophyll.
- Photosynthesis equation: Solar energy + CO2 + H2O → Carbohydrates + O2.
- Only plants, algae, and specific bacteria can perform photosynthesis.
Energy-Related Organelles: Mitochondria
- Mitochondria are smaller than chloroplasts and contain ribosomes and their own DNA.
- Surrounded by a double membrane; the inner membrane is convoluted, forming cristae.
- The matrix, a semifluid interior, houses respiratory enzymes for carbohydrate breakdown.
- Mitochondria are crucial for cellular respiration, producing most ATP utilized by the cell.
Endomembrane System
- Comprises a network of intracellular membranes, compartmentalizing cellular functions.
- Includes: Nuclear envelope, endoplasmic reticulum (ER) membranes, Golgi apparatus, and vesicles.
- Proteins synthesized in rough ER and lipids from smooth ER are transported to Golgi apparatus in vesicles.
- Golgi apparatus modifies, sorts, and packages proteins and lipids for cellular destinations.
Golgi Apparatus
- Consists of 3-20 flattened saccules resembling a stack of pancakes.
- Modifies incoming proteins and lipids from ER, organizing them for transport.
- Packages products in vesicles for delivery within or outside the cell.
Endoplasmic Reticulum (ER)
- Rough ER is studded with ribosomes; involved in protein synthesis and modification (e.g., glycoproteins).
- Smooth ER lacks ribosomes; involved in lipid synthesis, detoxification, and storage processes.
- Both types contribute to the formation of transport vesicles for cellular distribution.
Lysosomes
- Membrane-bound vesicles produced by the Golgi apparatus, absent in plant cells.
- Contain powerful digestive enzymes, crucial for the breakdown of large molecules and cellular recycling.
- Involved in apoptosis, or programmed cell death, for proper development.
- Genetic defects in lysosomal enzymes can lead to storage diseases, such as Tay-Sachs.
Peroxisomes
- Membrane-bounded vesicles containing enzymes synthesized by free ribosomes in the cytoplasm.
- Active in lipid metabolism and catalyze reactions that yield hydrogen peroxide (H2O2), a toxic byproduct.
- H2O2 is broken down into water and oxygen by the enzyme catalase.
Vacuoles
- Larger than vesicles, serving as storage sacs for excess materials.
- Plant cells have a central vacuole that can comprise up to 90% of cell volume.
- Functions: Storage of nutrients, water, pigments, and waste; contributes to turgor pressure.
- Some vacuoles perform functions akin to lysosomes in non-plant eukaryotic cells.
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Description
This quiz explores the differences between prokaryotic and eukaryotic cells, focusing on cell types, particularly bacteria. It covers the structural features of bacteria, including their cell envelope and cytoplasm. Test your knowledge on the fundamental characteristics of these essential biological units.