Microscopes and Their Operations

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Questions and Answers

What characteristic of oxygen molecules allows them to pass through the phospholipid bilayer of the cell membrane?

Oxygen molecules have a high solubility in water.

Oxygen molecules are charged ions.

Oxygen molecules are large and nonpolar.

Oxygen molecules are hydrophobic and small. (correct)

Why are sodium ions unable to cross the artificial membrane as described?

Sodium ions can diffuse freely through any membrane.

Sodium ions can only be transported through passive diffusion.

Sodium ions require enzymes to transport across membranes.

Sodium ions are repelled by the lipid bilayer. (correct)

Which factor is NOT mentioned as affecting the permeability of the cell membrane?

Temperature

Organic solvents like alcohol

Type of solute

pH levels (correct)

What role do channel or carrier proteins play for sodium ions in the cell membrane?

They help in the transport of sodium ions across the membrane. Signup and view all the answers

How do organic solvents affect the cell membrane's permeability?

They dissolve the phospholipids of the membrane. Signup and view all the answers

What is a primary advantage of using an electron microscope compared to a light microscope?

It allows for the observation of the internal structures of cells. Signup and view all the answers

Which of the following is NOT visible under a light microscope with a maximum magnification of 1600x?

Mitochondria Signup and view all the answers

What is the purpose of adding iodine solution when preparing a slide for a light microscope?

To stain the specimen for better visibility. Signup and view all the answers

What is the highest magnification achievable by a transmission electron microscope?

1500000x Signup and view all the answers

When focusing a slide with a light microscope, which step comes first?

Turn the coarse adjustment knob. Signup and view all the answers

What type of structure does a scanning electron microscope provide?

3D representations of external structures. Signup and view all the answers

To observe more cells within the field of view using a light microscope, which adjustment should be made?

Reduce the distance between the slide and the objective. Signup and view all the answers

Which of the following components is primarily facilitated by the use of a microscope?

Analyzing the structure of cellular organelles. Signup and view all the answers

What is the main function of phagocytosis in unicellular organisms like Amoeba?

To uptake large particles for nutrition Signup and view all the answers

Which statement accurately describes the uptake of nutrients in plants?

Plants uptake minerals through their roots. Signup and view all the answers

What is primarily responsible for the decrease in the rate of product formation during an enzymatic reaction, as illustrated in the experiments?

A decrease in substrate concentration Signup and view all the answers

How does cyanide affect cellular respiration?

Inhibits electron transport chain Signup and view all the answers

From the described experiment, when does the volume of gas collected plateau?

At time X seconds Signup and view all the answers

What role do white blood cells (WBC) play in the immune system?

They engulf and eliminate harmful substances. Signup and view all the answers

In an experiment measuring the effect of enzyme concentration on the rate of reaction, which variable was controlled?

Volume of enzyme added Signup and view all the answers

Which statement is incorrect regarding the effects of concentration and volume on enzyme reactions?

The amount of product formed is independent of substrate concentration. Signup and view all the answers

What best describes the term 'fluid' in the fluid mosaic model?

Phospholipids can move laterally, allowing for flexibility. Signup and view all the answers

What is the primary reason for water molecules to move during osmosis?

To equalize the concentration gradient on both sides of a membrane. Signup and view all the answers

How does the water level behave inside the dialysis tubing when 20% sucrose solution is present?

The water level rises because water moves from an area of lower concentration to higher concentration. Signup and view all the answers

What would primarily stop the movement of water molecules into the dialysis tubing?

The hydrostatic pressure inside the tubing reaches equilibrium. Signup and view all the answers

Which factor does NOT influence the rate of rise of water level in a capillary tube?

The concentration of solute in the water. Signup and view all the answers

What is the ultimate effect of increasing the solute concentration in a solution regarding water potential?

It creates a stronger attraction between solute and water molecules, decreasing water potential. Signup and view all the answers

What would best describe the arrangement of proteins in the fluid mosaic model?

Proteins are interspersed in a mosaic pattern and asymmetrically placed. Signup and view all the answers

What process allows for the exchange of materials across a differentially permeable membrane?

Diffusion and osmosis based on concentration gradients. Signup and view all the answers

Which vitamin is primarily responsible for promoting the absorption of calcium and phosphate?

Vitamin D Signup and view all the answers

Which of the following sources is rich in Vitamin A?

Carrots and sweet potatoes Signup and view all the answers

What is the major consequence of Vitamin D deficiency in children?

Rickets Signup and view all the answers

What is the role of hydrogen bonds in the structure of proteins?

They hold amino acids together in a specific way. Signup and view all the answers

Which amino acids must be obtained from the diet?

Essential amino acids Signup and view all the answers

What is a symptom of Vitamin A deficiency?

Night blindness Signup and view all the answers

Which type of foods are sources of Vitamin C?

Fresh vegetables and fruits Signup and view all the answers

What is the primary role of proteins in the body?

Growth and repair of tissues Signup and view all the answers

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.
Focusing on a specimen:
- From low power to high power:
  1. Focus with the low power objective first.
  2. Center the field of view with the low power objective.
  3. Adjust the position of the slide to the center of the field of view.
  4. Focus with the high-power objective.
  5. Use the course adjustment knob for initial focusing and fine adjustment knob for precise adjustments.
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

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.
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.
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.
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

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.
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

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.
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

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.
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.
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.