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Questions and Answers
What is the primary function of ribosomes as mentioned in the content?
What is the primary function of ribosomes as mentioned in the content?
- Sorting of cellular materials
- Synthesis of lipids
- Modification of carbohydrates
- Synthesis of proteins (correct)
Which sequence correctly describes the transport process of proteins from the endoplasmic reticulum?
Which sequence correctly describes the transport process of proteins from the endoplasmic reticulum?
- Endoplasmic Reticulum → Cis-Golgi Network → Trans-Golgi Network (correct)
- Trans-Golgi Network → Ribosomes → Lysosomes
- Plasma Membrane → Endoplasmic Reticulum → Golgi Apparatus
- Ribosomes → Golgi Apparatus → Plasma Membrane
What are vesicles primarily used for in the Golgi apparatus?
What are vesicles primarily used for in the Golgi apparatus?
- Transporting waste products out of the cell
- Transporting proteins and lipids between cisternae (correct)
- Synthesis of cellular enzymes
- Modifying carbohydrates and steroids
Which face of the Golgi apparatus is located near the nucleus?
Which face of the Golgi apparatus is located near the nucleus?
What happens to proteins that are incorrectly exported from the Golgi apparatus?
What happens to proteins that are incorrectly exported from the Golgi apparatus?
What structures do chromatins condense to form during cell division?
What structures do chromatins condense to form during cell division?
Which function does the nucleus NOT serve?
Which function does the nucleus NOT serve?
What is the shape of mitochondria commonly described as?
What is the shape of mitochondria commonly described as?
What is the main function of the inner membrane of the mitochondria?
What is the main function of the inner membrane of the mitochondria?
How does mitochondria replicate?
How does mitochondria replicate?
Where are chloroplasts predominantly found in plants?
Where are chloroplasts predominantly found in plants?
Which component is found in the stroma of chloroplasts?
Which component is found in the stroma of chloroplasts?
What is the primary role of plastids in high-level plants?
What is the primary role of plastids in high-level plants?
What is the main purpose of an eye-piece graticule in microscopy?
What is the main purpose of an eye-piece graticule in microscopy?
What is the actual size of one eyepiece graticule division given that 100 divisions equal 0.25 mm?
What is the actual size of one eyepiece graticule division given that 100 divisions equal 0.25 mm?
Which type of electron microscope provides the best resolution?
Which type of electron microscope provides the best resolution?
Which of the following is NOT a limitation of using an electron microscope?
Which of the following is NOT a limitation of using an electron microscope?
How is the diameter of a cell calculated using eyepiece graticule measurements?
How is the diameter of a cell calculated using eyepiece graticule measurements?
Which characteristic differentiates a scanning electron microscope (SEM) from a transmission electron microscope (TEM)?
Which characteristic differentiates a scanning electron microscope (SEM) from a transmission electron microscope (TEM)?
Why is the cost of operation relatively low for light microscopes compared to electron microscopes?
Why is the cost of operation relatively low for light microscopes compared to electron microscopes?
What physical form do specimens require when viewed under an electron microscope?
What physical form do specimens require when viewed under an electron microscope?
What is the primary function of centrioles within the centrosome?
What is the primary function of centrioles within the centrosome?
What distinguishes cilia from flagella in terms of movement?
What distinguishes cilia from flagella in terms of movement?
Which of the following correctly describes the arrangement of microtubules in cilia and flagella?
Which of the following correctly describes the arrangement of microtubules in cilia and flagella?
What role does the cytoskeleton play within a cell?
What role does the cytoskeleton play within a cell?
Which characteristic is shared between basal bodies and centrioles?
Which characteristic is shared between basal bodies and centrioles?
In terms of cellular locomotion, which statement is true regarding flagella?
In terms of cellular locomotion, which statement is true regarding flagella?
Which component is NOT a part of the cytoskeleton?
Which component is NOT a part of the cytoskeleton?
During cell division, centrioles help organize which structures?
During cell division, centrioles help organize which structures?
What is the primary composition of the cell wall?
What is the primary composition of the cell wall?
Which component of the plasma membrane is involved in maintaining fluidity?
Which component of the plasma membrane is involved in maintaining fluidity?
What structure allows for the lateral movement of proteins in the plasma membrane?
What structure allows for the lateral movement of proteins in the plasma membrane?
What characterizes peripheral proteins in the plasma membrane?
What characterizes peripheral proteins in the plasma membrane?
Which statement about the structure of membranes is true?
Which statement about the structure of membranes is true?
What are the hydrophilic parts of phospholipids called?
What are the hydrophilic parts of phospholipids called?
What term describes the model that explains the arrangement of proteins in the plasma membrane?
What term describes the model that explains the arrangement of proteins in the plasma membrane?
Which type of protein extends through the entire membrane?
Which type of protein extends through the entire membrane?
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Study Notes
Measuring Cells
- Accurate measurement of cells and organelles is essential for scientific research.
- Two essential tools:
- Eye-piece graticule: Transparent scale with 100 divisions in the microscope eyepiece.
- Stage micrometer: Miniature ruler placed on the microscope stage.
- Magnification formula: Magnification = Size of image / Actual size of specimen.
- 100 eyepiece graticule divisions = 0.25 mm, resulting in 1 division = 2.5 µm.
- Example: A cell with a diameter of 20 divisions measures 50 µm.
Electron Microscopy Principles
- Electron Microscope: Uses electrons to illuminate specimens, capable of resolving sub-cellular structures due to effective wavelength < 1 nm.
- Limitations:
- Specimens must be dead and fixed in plastic for viewing in a vacuum.
- Susceptible to damage from electron beams.
- Requires staining with heavy metals (e.g., osmium, lead, gold).
- Types:
- Transmission Electron Microscope (TEM): Transmits electrons through thin specimens; provides the best resolution.
- Scanning Electron Microscope (SEM): Scans specimens with a fine electron beam, providing 3D images but poorer resolution.
Comparison of Microscopes
- Light microscopes:
- Cost-effective (RM400 – 2000).
- Easy to operate and portable.
- Simple sample preparation.
- Electron microscopes:
- High cost (over RM500,000).
- Expensive operation and complex sample preparation.
Cell Division and Chromosomes
- During division, chromatin condenses into chromosomes, composed of DNA and histone proteins.
- Non-dividing nucleus appears grainy due to chromatin presence.
- Functions of the nucleus include housing genetic material, controlling cellular activities, and producing ribosomes and RNA.
Mitochondria
- Present in all cells except red blood cells; shapes can vary (oval, rod, sphere).
- Average dimensions: ~2.5 µm (length), ~1 µm (diameter).
- Primarily generates ATP through aerobic respiration; features two membranes (outer smooth, inner folded into cristae).
- Contains own DNA and ribosomes; replicates independently via division but cannot replicate outside the cell.
Chloroplast
- Found primarily in the mesophyll of high-level plants, especially palisade mesophyll.
- Conducts photosynthesis and stores starch; typical diameter: 8-10 µm.
- Contains stroma, DNA, ribosomes, and photosynthetic enzymes.
Ribosomes
- Key functions include synthesizing proteins and enzymes.
- Ribosomes on the endoplasmic reticulum (ER) transfer proteins to the Golgi apparatus for processing.
Golgi Apparatus
- Composed of stacked membrane sacs; functions like a cell's post office.
- Processes proteins from the ER, modifies them, sorts them, and directs them to their destinations.
- Contains two faces: cis (near ER) and trans (further from nucleus).
- Vesicles transport proteins and other materials between sacs.
Centrosome and Centrioles
- Contains centrioles made of microtubules in a "9+0" pattern.
- Organizes microtubules that attach to chromosomes during cell division.
Cilia and Flagella
- Cilia: Short projections used for cellular movement; found in paramecium and oviducts.
- Flagella: Longer, whiplike structures seen in algae, protozoa, and some bacteria, generating thrust with undulating motion.
- Both organelles feature a "9+2" tubule arrangement.
Cytoskeleton
- Network of fibers providing mechanical support, maintaining cell shape, and enabling cellular movement.
- Composed of microtubules, actin filaments, and intermediate filaments.
Cell Wall
- Thick structure outside the plasma membrane, providing strength and rigidity.
- Primarily made of cellulose, freely permeable to solutes.
Plasma Membrane
- Separates the cell's internal environment from its surroundings, composed of a phospholipid bilayer.
- Fluid mosaic model describes dynamic structure where proteins and phospholipids move laterally.
Fluid Structure of Membranes
- Layers of membrane components move over one another; lateral diffusion is common, while flip-flop is rare.
- Integral and peripheral proteins embedded in the phospholipid framework.
Extracellular Matrix
- Contains glycoproteins, glycolipids, and proteins, contributing to cellular communication and structure.
- Hydrophilic heads of phospholipids face outward, while hydrophobic tails are oriented inward, forming a bilayer for cell homeostasis.
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