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Questions and Answers
What characteristic of oxygen molecules allows them to pass through the phospholipid bilayer of the cell membrane?
Why are sodium ions unable to cross the artificial membrane as described?
Which factor is NOT mentioned as affecting the permeability of the cell membrane?
What role do channel or carrier proteins play for sodium ions in the cell membrane?
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How do organic solvents affect the cell membrane's permeability?
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What is a primary advantage of using an electron microscope compared to a light microscope?
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Which of the following is NOT visible under a light microscope with a maximum magnification of 1600x?
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What is the purpose of adding iodine solution when preparing a slide for a light microscope?
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What is the highest magnification achievable by a transmission electron microscope?
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When focusing a slide with a light microscope, which step comes first?
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What type of structure does a scanning electron microscope provide?
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To observe more cells within the field of view using a light microscope, which adjustment should be made?
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Which of the following components is primarily facilitated by the use of a microscope?
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What is the main function of phagocytosis in unicellular organisms like Amoeba?
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Which statement accurately describes the uptake of nutrients in plants?
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What is primarily responsible for the decrease in the rate of product formation during an enzymatic reaction, as illustrated in the experiments?
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How does cyanide affect cellular respiration?
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From the described experiment, when does the volume of gas collected plateau?
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What role do white blood cells (WBC) play in the immune system?
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In an experiment measuring the effect of enzyme concentration on the rate of reaction, which variable was controlled?
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Which statement is incorrect regarding the effects of concentration and volume on enzyme reactions?
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What best describes the term 'fluid' in the fluid mosaic model?
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What is the primary reason for water molecules to move during osmosis?
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How does the water level behave inside the dialysis tubing when 20% sucrose solution is present?
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What would primarily stop the movement of water molecules into the dialysis tubing?
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Which factor does NOT influence the rate of rise of water level in a capillary tube?
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What is the ultimate effect of increasing the solute concentration in a solution regarding water potential?
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What would best describe the arrangement of proteins in the fluid mosaic model?
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What process allows for the exchange of materials across a differentially permeable membrane?
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Which vitamin is primarily responsible for promoting the absorption of calcium and phosphate?
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Which of the following sources is rich in Vitamin A?
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What is the major consequence of Vitamin D deficiency in children?
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What is the role of hydrogen bonds in the structure of proteins?
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Which amino acids must be obtained from the diet?
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What is a symptom of Vitamin A deficiency?
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Which type of foods are sources of Vitamin C?
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What is the primary role of proteins in the body?
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Study Notes
Light Microscopes
- Produces coloured images
- Can only see nucleus, chloroplasts, vacuoles, and cell walls
- Maximum magnification: 1600x
Electron Microscopes
- Produce images with higher magnification and resolution
- Allows scientists to discover the structure of cell organelles
- Scanning Electron Microscope: provides 3D images of the external structure of the cell, max magnification: 200,000x
- Transmission Electron Microscope: provides 2D images of the internal structure of the cell, max magnification: 1,500,000x
Operating a Light Microscope
- To stain a specimen: Add iodine solution to make cell structures more distinct and visible.
- To observe more cells within the field of view: Reduce the distance between the slide and the objective lens.
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Focusing on a specimen:
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From low power to high power:
- Focus with the low power objective first.
- Center the field of view with the low power objective.
- Adjust the position of the slide to the center of the field of view.
- Focus with the high-power objective.
- Use the course adjustment knob for initial focusing and fine adjustment knob for precise adjustments.
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From low power to high power:
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Cell membrane:
- Differentially permeable, meaning it allows some substances to pass through while others it restricts.
- The core of the membrane is hydrophobic, which makes it difficult for polar molecules to pass through.
Transport Across the Cell Membrane
- Oxygen molecules: Nonpolar and small, allowing them to easily pass through the phospholipid bilayer.
- Sodium ions: Charged and repelled by the hydrophobic bilayer, requiring channel or carrier proteins to move across the membrane. Artificial membranes lack these proteins, preventing sodium ions from passing through.
Movement of Substances Across the Membrane
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Factors affecting membrane permeability:
- Temperature: Higher temperature increases membrane permeability.
- Organic solvents (e.g., ethanol, alcohol): Dissolve phospholipids in the membrane, damaging the cell membrane and vacuole, leading to pigment release and colour intensity changes.
Fluid Mosaic Model
- Fluid: The phospholipid bilayer is fluid, allowing the phospholipids to move laterally.
- Mosaic: Proteins are embedded within the membrane in a mosaic pattern, distributed asymmetrically.
Diffusion
- Definition: Net movement of particles down a concentration gradient, from an area of higher concentration to an area of lower concentration.
- Equilibrium: When particles are evenly distributed, resulting in no net movement but random movement continues.
- Importance: Facilitates exchange of materials for obtaining useful substances and removing waste, including gas exchange and absorption of nutrients.
Osmosis
- Definition: Movement of water molecules across a differentially permeable membrane from a region of higher water potential to a region of lower water potential.
- Water potential: Determined by the solute concentration and hydrostatic pressure.
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Factors affecting osmosis:
- Solute concentration: Higher solute concentration, lower water potential, stronger attraction between solute and water molecules.
- Hydrostatic pressure: Increased pressure inside a cell will reduce the movement of water into the cell.
- Importance: Facilitates the transport of water molecules across membranes where other molecules are too large to pass through.
Active Transport
- Definition: Movement of molecules across a membrane against their concentration gradient, requiring energy.
- Importance: Allows cells to obtain additional useful materials that are already present in high concentrations within the cell, such as nutrients like glucose and amino acids.
- Examples: Absorption of nutrients in the digestive system, absorption of minerals from soil into plant roots.
Phagocytosis
- Definition: The uptake of large particles into the cell by packaging them into vacuoles formed from the cell membrane.
- Energy requirement: Energy is required to change the shape of the cell membrane for engulfment.
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Importance:
- Unicellular organisms' nutrition: Used by Amoeba for obtaining food.
- Body defence: White blood cells use phagocytosis to engulf harmful substances, protecting the body against diseases.
Anabolic and Catabolic Reactions
- Anabolic reactions: Reactions involving the building of complex molecules from simpler ones, requiring energy.
- Catabolic reactions: Reactions involving the breakdown of complex molecules into simpler ones, releasing energy.
Experiment Graphs
- Volume of gas collected with time: The total amount of product formed depends on the concentration and volume of the substrate and enzyme.
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Graph interpretation:
- Initial increase: The volume of the product increases as the enzyme breaks down the substrate.
- Decreasing slope: The rate of product formation decreases as the amount of product formed per second diminishes.
- Plateau: The volume stops increasing once all the substrate is broken down.
Lipids
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Functions:
- Storage of energy: Stored as triglycerides in adipose tissue.
- Insulation: Provide insulation against cold temperatures.
- Protection: Protect vital organs.
- Cell membrane structure: Phospholipids are a key component of cell membranes.
- Hormone production: Some lipids serve as precursors for hormone production.
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Types:
- Triglycerides: Made up of glycerol and three fatty acids.
- Phospholipids: Contain glycerol, two fatty acids, and a phosphate group.
- Steroids: Include cholesterol, sex hormones, and vitamin D.
- Waxes: Have a long-chain fatty acid attached to a long-chain alcohol.
Proteins
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Functions:
- Enzymes: Catalyze biochemical reactions.
- Structural components: Form structural components like hair, skin, and nails.
- Hormones: Act as chemical messengers.
- Antibodies: Protect the body against disease.
- Transport: Carry substances across membranes.
- Composition: Made up of amino acids linked together by peptide bonds.
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Structure: The sequence of amino acids determines the protein's structure and function.
- Primary structure: Linear sequence of amino acids.
- Secondary structure: Folding of the polypeptide chain into alpha-helices or beta-sheets.
- Tertiary structure: Three-dimensional shape of the protein.
- Quaternary structure: Interaction of multiple polypeptide chains.
Vitamins
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Vitamin A (retinol)
- Sources: Fish liver oils, liver, eggs, milk, dairy products, carrots, pumpkin, sweet potatoes, mangoes (contain carotene which our liver converts to vitamin A).
- Functions: Needed for the formation of a pigment in the retina of the eye, essential for vision in dim light. Also important for maintaining healthy cornea, skin, lining of the alimentary canal, and breathing system.
- Deficiency: Night blindness, drying of the cornea and skin, increased risk of infection in the lungs and trachea.
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Vitamin D (calciferol)
- Sources: Sunlight, fatty fish (salmon, tuna), fish liver oils, liver, egg yolk.
- Functions: Promotes absorption of calcium and phosphate, which are essential for strong bones and teeth development.
- Deficiency: Rickets in children causes soft bones and bone deformities.
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Vitamin C (ascorbic acid)
- Sources: Fresh vegetables and fruits (bell peppers, oranges, lemons, broccoli, strawberries).
- Functions: Aids in the growth and repair of connective tissues, important for keeping body structures in place. Acts as an antioxidant, protecting cells from damage caused by free radicals.
- Deficiency: Scurvy, characterized by weakness, fatigue, bleeding gums, and delayed wound healing.
DCPIP Decolorization
- Use: DCPIP is a blue dye used to measure the rate of photosynthesis.
- Explanation: DCPIP accepts electrons from chlorophyll during photosynthesis, causing it to decolorize. The rate of decolorization is proportional to the rate of photosynthesis, allowing you to assess the factors affecting the process.
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Description
Explore the world of microscopes through this quiz focusing on light and electron microscopes. Understand their functionalities, magnifications, and techniques for specimen observation. Perfect for biology students aiming to deepen their knowledge of cellular structures.
