Microscope: History and Types

What is a Microscope?

• A microscope is used to observe objects not clearly visible with the naked eye
• It uses lenses to produce a magnified image
• Microscopy is the science of investigating small objects via a microscope
• The word "microscope" comes from the Greek words "micro" (tiny) and "scope" (to view)
• A microscope magnifies the size of an object for closer study

Microscope Invention

• Zaccharias Janssen and Hans Lipperhey (1595) created the compound microscope
• They did this by placing different lenses at opposite ends of tubes
• Robert Hooke (1665) built compound microscopes, but the lenses were low quality
• Anton van Leeuwenhoek (1674) made his own simple microscope with only one lens
• He was skilled at grinding lenses and achieved 300x magnification
• Leeuwenhoek saw living, moving unicellular organisms (Protista) and bacteria, calling them 'animalcules'
• He is considered the founder of microscopy and contributed to cell theory

Types of Microscopes

• Microscopes are grouped by radiation type: light and electron microscopes
• Light microscopes use a beam of light to form an image
• Electron microscopes utilize a beam of electrons
• Microscopes are categorized by number of lenses: simple and compound microscopes

Simple Light Microscope

• Made of a single convex lens to magnify an object
• Examples include hand lenses (magnifying glasses) and reading lenses
• They can magnify objects ten to twenty times (10X-20X)

Compound Light Microscope

• Employs multiple lens systems for magnification and resolution
• It has eyepiece (ocular) and objective lenses
  • Objective lenses include:
    • Lower power (4x)
    • Middle power (10x)
    • High power (40x)
    • Oil immersion (100x)
• A lens is a glass piece that converges or diverges light to form optical images
• Resolution enables the microscope to show the detailed parts of an object
• Microscopes have two major abilities: magnification and resolution
  • Magnification increases the apparent size of an object
  • Resolution shows the detailed parts of an object and distinguishes separate points

Microscope Use

• Eyepiece lenses usually magnify objects ten times (10X)
• Objective lenses magnify objects four to one hundred times
• Total magnification is calculated by multiplying the magnification
• Mounting is preparing a specimen for observation
• Focusing is adjusting the focus to see the specimen clearly
• A specimen is a sample for examination or study

Cell Theory

• Robert Hooke (1665) used a microscope to observe a thin slice of cork
• He saw porous, tiny square boxes resembling monastery rooms, naming them "cells" after the Latin "cellula" (small room)
• By the late 1830s, Matthias Schleiden and Theodor Schwann proposed the unified cell theory
  • all living things are composed of one or more cells
  • the cell is the basic unit of life
  • all new cells arise from pre-existing cells

What is a Cell?

• Basic units of living organisms that carry out structural, functional, and biological processes

Structure of a Cell

• Cells are the tiny units of life made of different parts
• These parts are known as sub-cellular structures or organelles
• All cells share four common components:
  • cell membranes
  • cytoplasm
  • ribosomes
  • DNA
• Red blood cells lack a nucleus

Plasma Membrane

• Outer covering that separates the cell's interior
• Functions:
  • Acts as a barrier
  • Regulates the movement of substances
  • Provides structural support

Nucleus

• Controls all activities of the cell
• Spherical or oval-shaped structure
• Surrounded by a double membrane called the nuclear envelope, which contains pores
• Contains the nucleolus and chromatin (DNA and associated proteins)
• Functions:
  • Houses genetic material (DNA)
  • Controls growth, reproduction, and metabolism
  • Produces ribosomal RNA (rRNA) in the nucleolus for protein synthesis

Cytoplasm

• Contains sub-cellular structures where chemical processes take place
• Cytosol is the part of the cytoplasm without organelles
• It is a medium where organelles are suspended and biochemical reactions occur

Mitochondrion

• Known as the "powerhouse of the cell"
• Double-membrane organelle where cellular respiration occurs
• Structure:
  • Double-membraned with outer and folded inner membranes (cristae)
  • Inner membrane encloses the matrix
• Functions:
  • Generates ATP through cellular respiration
  • Involved in fatty acid oxidation and the citric acid cycle
  • Converts glucose into ATP

Chloroplast

• Unique to plant cells
• Site of photosynthesis
• Structure:
  • Double-membraned organelle
  • Contains thylakoids (stacked into grana)
  • Contains stroma (fluid-filled space)
• Function:
  • Conducts photosynthesis, converting light energy into glucose
  • Contains chlorophyll to absorb sunlight

Ribosome

• Site of protein synthesis
• Found in almost every cell

Endoplasmic Reticulum

• Interconnected membranous tubules modifying proteins and synthesizing lipids
• Two types:
  • Rough (RER): ribosomes attached, studded appearance, modifies proteins
  • Smooth (SER): few or no ribosomes, continuous with RER
• SER’s functions:
  • Synthesis of carbohydrates, lipids, and steroid hormones
  • Detoxification
  • Contains calcium ions

Golgi Apparatus

• Series of flattened membranous sacs
• Sorts, tags, packages, and distributes lipids and proteins
• Packages what goes out

Lysosomes

• In animal cells, lysosomes area cell's “garbage disposal.”
• They contain digestive enzymes that break down proteins, polysaccharides, lipids, nucleic acids, and worn-out organelles
• Important for digestion and recycling

Vesicles and Vacuoles

• Membrane-bound sacs for storage and transport
• The central vacuole in plant cells regulates water concentration

Peroxisomes

• Maintain turgor pressure and provide structural support
• Small, round organelles enclosed by single membranes
• They carry out oxidation reactions of fatty acids and amino acids
• Detoxify poisons

Cell Shape and Size

• Cell shapes and sizes are related to their functions
• Plant cells have rectangular, rigid walls
• Animal cells have irregular shapes due to the lack of a cell wall
• Bacteria cell shape:
  • oval (cocci)
  • rod-shaped (bacilli)
  • spiral
  • star-shaped
  • rectangular
• Egg cells are the largest cells, about 0.12 mm in diameter in humans
• Mycoplasma gallicepticum is the smallest cell at 0.0001 mm in diameter

Multicellular Organisms

• Composed of many cells
• Plants and animals are multicellular organism
• Cells specialize in different functions
• Humans consist of of different types of cells like blood cells, skin cells, brain cells, heart cells etc
• Plants have stem cells and root cells

Tissues

• Multicellular organisms have of cells that combine to make tissues
• Tissues are groups of similar cells carrying out the same function
• Examples include muscle, connective, and nervous tissue

Organs

• Collections of tissues grouped together based on function
• Present in animals and plants:
  • Plants: flowers, roots, stems, and leaves
  • Animals: brain, heart, stomach, eyes

Respiration

• Process of breaking down simple sugars into carbon dioxide and water to release energy (ATP)

Cellular Respiration

• Occurs in the mitochondria
• Also known as the “powerhouses” or “energy factories"
• Uses ATP, the main energy-carrying molecule
• Mitochondria are oval-shaped, double membrane organelles
• Membranes are phospholipid bilayers embedded with proteins
• The inner layer has folds called cristae to increase surface area
• The area surrounded by the folds is the mitochondrial matrix
• Cristae and matrix have different roles in respiration

Types of respiration

• The formation of ATP from the breakdown of glucose occurs through aerobic and anaerobic respiration
• Aerobic respiration is a series of chemical reactions that uses oxygen to produce energy, carbon dioxide, and water

Cellular Respiration Stages

• Glycolysis
• Oxidation of pyruvates or Link reaction
• Tricarboxylic Acid (TCA) or Citric Acid cycle
• Electron transport chain (ETC) and chemiosmosis

Aerobic Respiration

• 36-38 ATP molecules are produced from a single glucose molecule
• Formula: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 38ATP (Glucose + 6 Oxygen → 6 Carbon Dioxide + 6 Water + 38ATP)
• Oxygen is essential and is the "final electron acceptor"/oxidizing agents

Anaerobic respiration

• Can take place anaerobically (without oxygen), to transfer energy
• Uses the incomplete breakdown of glucose into lactic acid
• This occurs when the body can't supply enough oxygen for aerobic respiration, such as during vigorous exercise.
• This process is called lactic acid fermentation
• Simplified equation:
  • C6H12 O6 → 2 CH3CH (OH) COOH + 2 CO2 + 2 ATP Glucose → lactic acid + carbon dioxides+ 2ATP
• Microorganisms, such as yeast, respires to produce carbon dioxide and ethanol:
  • C6H12 O6 → 2 C2H5OH + 2 CO2 + 2 ATP

Aerobic vs Anaerobic

Photosynthesis

• Plants use energy from sunlight to change carbon dioxide (CO2) and water (H20) into glucose (C6H12 O6) and oxygen (O2)
• Occurs in the chloroplast of the plant cell
• Chloroplasts have outer and inner membranes
• They also contain thylakoids, interconnected and stacked, fluid-filled membrane sacs
• Each stack of thylakoids is called a granum (plural grana)
• Fluid enclosed by the inner membrane is called the stroma
• Chloroplasts contain pigment chlorophyll, which captures the sunlight

Photosynthesis Conversion

• Photosynthesis is a series of chemical reactions that convert carbon dioxide and water into glucose (sugar) and oxygen
• Formula: Carbon dioxide + Water Glucose (sugar) + Oxygen+ Water
  • 6CO2 + 12H2O C6H12 O6+6O2+6H2O

Photosynthesis and Respiration Importance

• Photosynthesis converts radiant/solar energy into chemical energy
• It provides oxygen in atmosphere for all living organism to perform cellular respiration
• It maintains the balanced level of oxygen and carbon dioxide ecosystem