Biological Macromolecules and Atom Structure

Electron Shells and Niels Bohr Model

• In the Bohr model, atoms consist of a positively charged nucleus containing protons and neutrons, surrounded by negatively charged electrons.
• Electrons occupy specific energy levels called electron shells, defined by their principal quantum number.
• Electrons fill lower energy orbitals first, followed by higher energy orbitals until all electrons are placed.
• Atoms tend to be most stable with a full outer shell (containing 8 electrons), leading to the "octet rule."

Biological Macromolecules

• Large, complex molecules essential for life.
• Built from smaller organic molecules.
• Play crucial roles in structure, function, and regulation of living organisms.
• Four major classes: carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Formula: (CH2O)n, where n is the number of carbons.
• Provide energy and structural support.
• Examples: Glucose, starch, and cellulose.

Microscopy

• Microscopes magnify objects, making them appear larger.
• Light microscopes use visible light.
• Electron microscopes use a beam of electrons.
• Magnification refers to the enlargement of an object's appearance.
• Resolution refers to the ability to distinguish between two closely spaced objects.
• Light microscopes typically magnify up to 400x with a resolution of 200 nanometers.
• Electron microscopes provide much higher magnification (100,000x) and a resolution of 50 picometers.

Compound Microscope

• Invented by Zacharias Janssen and Hans Janssen.
• Uses multiple lenses for magnification.

Electron Microscopes

• Use a beam of electrons to image specimens.
• Higher magnification and detail compared to light microscopes.
• Preparation kills specimens due to the vacuum requirement.

Microscope Components

• Base: Provides stability and support.
• Arm: Connects the base to the head, used for carrying.
• Stage: Platform for holding microscope slides.
• Stage Clips: Secure the slide in place.
• Coarse Adjustment Knob: Moves the stage up and down for initial focusing.
• Fine Adjustment Knob: Used for precision focusing after using the coarse knob.
• High-Power Eyepiece: Magnifies the image from the objective lens, typically 15x or 20x.
• Objective Lens: Magnifies the specimen initially.
• Condenser Lens: Focuses light onto the specimen.
• Illuminator: Provides the light source for viewing.
• Field Diaphragm: Controls the light beam diameter, improving image quality.

Microscope Slide Presentation

• Thought-out methodology for clear sample explanation.
• Slide Mount: The way a specimen is placed on a slide.
• Dry Mount: Simple mount for specimens.
• Wet Mount: Used for observing motile specimens.
• Smear Mount: Used for examining blood samples.

Staining Media

• Enhances contrast of specimens for easier visualization.
• Iodine: Stains starch black-blue.
• Methylene Blue: Stains nuclei blue.
• Crystal Violet: Used in Gram staining, results in deep violet or purple.
• Eosin Y: Stains cytoplasm bright pink-red.
• Toluidine Blue: Stains acidic tissues like nucleic acids blue.

Tissue Preparation for Study

• Fixation: Prevents putrefaction and degradation.
• Dehydration: Removes water from the tissue.
• Clearing: Alcohol is removed.
• Infiltration and Embedding: Tissue is placed in paraffin wax to provide support for sectioning.
• Sectioning or Trimming: Thin slices of tissue are obtained for observation.
• Cryostat: Used for long-term tissue storage.

Intracellular and Extracellular Matrix

• Intracellular Matrix: Supports internal cellular processes.
• Extracellular Matrix: Provides external support and facilitates cell-to-cell communication.

Cell Theory

• Proposed by Matthias Schleiden and Theodor Schwann.
• States that all living things are made of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells.

Eukaryotic Cells

• Have a true nucleus and specialized organelles.
• Nucleus: Contains the cell's DNA and controls protein and ribosome production.
• Mitochondria: Powerhouses of the cell, generate ATP through cellular respiration.
• Endoplasmic Reticulum (ER): Rough ER synthesizes proteins, smooth ER synthesizes lipids.
• Golgi Apparatus: Sorts, tags, packages, and distributes lipids and proteins.
• Peroxisomes: Break down fatty acids and amino acids, detoxify poisons.
• Vesicles and Vacuoles: Membrane-bound sacs for storage and transport, vacuoles are larger than vesicles.

Plant Cells

• Have cell walls, large central vacuoles, and chloroplasts.
• Cell Wall: Provides protection, structural support, and shape.
• Large Central Vacuole: Regulates water content, especially in different environments.
• Chloroplasts: Carry out photosynthesis, converting sunlight into energy.

Animal vs. Plant Cells

• Both have common organelles such as the nucleus, mitochondria, ER, Golgi apparatus.
• Animal cells have centrosomes and lysosomes.
• Centrosomes: Organize microtubules near the nucleus.
• Lysosomes: Break down waste materials and cellular debris.