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Questions and Answers
What are the two layers that compose the basal lamina?
Which component is primarily responsible for forming the reticular lamina?
Which function is NOT associated with the basement membrane?
What type of tissue is characterized by being avascular but innervated?
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Which of the following is a defining characteristic of extracellular matrix (ECM)?
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In which scenario does the basement membrane indicate early stages of cancer?
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Which type of ECM consistency is associated with cartilage?
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What is the correct order of organization in the human body?
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Which type of tissue covers the exterior surfaces of the body and lines internal cavities?
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What is the primary function of connective tissue?
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Which type of tissue is responsible for contraction and movement when excited?
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What is the primary function of a cell in a living organism?
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What does the extracellular matrix (ECM) primarily consist of?
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Which of the following accurately describes a prokaryotic cell?
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How many different cell types are estimated to exist in the human body?
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What is the role of the basement membrane?
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Which statement about eukaryotic cells is true?
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What defines the interstitial fluid in the context of the extracellular matrix?
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Which layer of the basement membrane is typically visible under a light microscope?
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In which area of a prokaryotic cell is the genetic material located?
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What process do prokaryotic cells primarily use for reproduction?
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How thick is the basal lamina typically when viewed under an electron microscope?
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Which component is shared by both prokaryotic and eukaryotic cells?
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What is the approximate size range of human cells?
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What is the highest total magnification power achievable with a 40x objective lens?
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What does resolution power refer to in microscopy?
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Which of the following is a key difference between light microscopes and electron microscopes?
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What is the typical resolving power of a light microscope?
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Which component is responsible for generating a circular magnetic field in an electron microscope?
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How many types of electromagnetic lenses does the imaging system of an electron microscope utilize?
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When calculated, how many nanometers are there in one micrometer?
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What is the function of the projector lens in an electron microscope?
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What type of electron microscopy provides detailed images of internal cell structures?
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What is the resolution power of Transmission Electron Microscopy (TEM)?
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Which microscope uses two separate beams of light to create three-dimensional images of unstained samples?
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What staining agents are commonly used in the preparation of specimens for electron microscopy?
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Which statement about Scanning Electron Microscopy (SEM) is correct?
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Which of the following best describes the function of phase contrast microscopy?
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What is the primary benefit of using heavy metal salts in electron microscopy preparation?
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What is the typical thickness of ultra-thin sections prepared for electron microscopy?
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Study Notes
Introduction to Cell Biology
- Cell Biology is the study of the structure and function of cells, at the cellular and molecular levels.
- The cell is the smallest and fundamental unit of a living organism.
- The human body is made up of various types of cells.
- Cell size ranges from 4 to 200 microns.
- Living organisms can be unicellular or multicellular.
- Cells cannot be seen with the naked eye, but only with a microscope.
Histology
- Histology is the branch of science focused on the microscopic study of tissues and their organization into organs.
- Cells form tissues, and tissues create organs.
Body & Cells
- The body is comprised of cells and extracellular matrix (ECM).
Cell Classification
- Cells are broadly classified into prokaryotes and eukaryotes.
- Prokaryotic cells lack a nucleus, their genetic material is located in the cytoplasm within an area called the nucleoid. They do not possess membrane-bound organelles.
- Eukaryotic cells have a nucleus and membrane-bound organelles.
- Both prokaryotes and eukaryotes share four key elements: a cell membrane, cytoplasm, genetic material, and ribosomes.
Prokaryote Cells
- Their DNA is circular, known as a genophore, found within the nucleoid region.
- Prokaryotes reproduce through a process known as binary fission.
Eukaryote Cells
-
Equivalent lengths:
- 1 millimeter (mm) = 1000 micrometers (micron)
- 1 micrometer (um) = 1000 nanometers
- 1 nanometer (nm) = 10 angstroms
Prokaryote vs. Eukaryote
- Prokaryotes are simpler cells lacking a nucleus and membrane-bound organelles, while eukaryotes have a nucleus and other organelles.
- Prokaryotes reproduce by binary fission while eukaryotes reproduce through processes like mitosis and meiosis.
Human Cell Types
- There are approximately 200 cell types in the human body.
- Different cell types have unique appearances and perform different functions.
Tissues
- The four main types of tissues in the human body are:
- Epithelial tissue: covers exterior surfaces, lines internal cavities and passageways, and forms glands.
- Connective tissue: binds cells and organs together.
- Muscular tissue: contracts forcefully when stimulated, enabling movement.
- Nervous tissue: is excitable, generating and transmitting electrochemical signals in the form of nerve impulses.
Extracellular Matrix (ECM)
- ECM is the non-cellular substance that fills the spaces between cells.
- It is secreted by cells.
- Composed of proteins and other molecules, it provides support, structure, and communication pathways for cells and tissues within the body.
Types of Extracellular Matrix (ECM)
- There are two main forms of ECM:
- Basement membrane: sheet-like depositions of ECM at the base of epithelial cells and surrounding muscle cells. Contains collagen, laminin, and proteoglycans.
- Interstitial fluid: a thin layer of fluid surrounding cells, containing water, proteins, electrolytes, acids, hormones, and waste materials.
Basement membrane
- It is found underneath epithelial cells and surrounds muscular cells.
- It is visible with light microscopy.
- Composed of two layers: basal lamina and reticular lamina.
Basal lamina
- It is visible with electron microscopy (EM).
- It measures about 20-100 nm in thickness.
- Secreted by epithelial cells.
- Contains two layers: lamina lucida and lamina densa.
- In diabetes mellitus, basement membranes of small blood vessels, particularly in the retina and kidney, become thickened.
Components of the Basal Lamina
- Type IV (4) collagen is a main component of the basal lamina.
Reticular Lamina
- It is formed by reticular fibers.
- Usually thicker than the basal lamina.
- Secreted by connective tissue cells (fibroblasts).
Epithelial Tissue
- Epithelial cells are densely packed together in sheets and tightly connected.
- Avascular but innervated, receiving nutrition from the underlying connective tissue.
- Functions of the basement membrane:
- Anchoring epithelial cells to underlying tissue.
- Pathway for cell migration.
- Promoting wound healing.
- Barrier between epithelial cells and connective tissue.
- Participating in blood filtration in the kidneys.
- Involved in the early stages of cancer (carcinoma in situ)
Cellular Structures
- Plasma membrane: also known as the cell membrane, surrounds the cell, separates the interior from the exterior, and protects the cell.
- Basal lamina: thin layer of ECM found beneath epithelial cells.
- Basement membrane: sheet-like ECM underlying epithelial cells and surrounding muscle cells.
- Intracellular matrix: the substance filling the inside of the cell, also known as cytoplasm.
Extracellular Matrix Variations
- Amount of ECM varies according to tissue type (minimal in epithelium, abundant in connective tissue).
- Consistency of ECM varies:
- Jelly-like: connective tissue
- Rubbery: cartilage
- Hard: bone
- Fluid: blood
ECM Functions
- Supports cells.
- Provides nutrition and oxygen.
- Facilitates communication between cells.
- Removes waste products.
Human Body Organization
- The human body is organized hierarchically:
- Cells
- Tissues
- Organs
- Systems
Microscopes
-
Light microscopy: uses visible light to illuminate and magnify specimens.
- Objective lenses: 5x, 10x, 40x.
- Total magnification power: Product of ocular lens magnification and objective lens magnification (e.g., 10x * 40x = 400x).
Microscope Capacity
- Magnification power: the ability to enlarge objects.
-
Resolution power: the ability to distinguish between two closely spaced objects as separate entities.
- Healthy naked eye: 0.2 millimeters
- Light microscopy: 0.2 micrometers (um)
- Electron microscopy: 0.2 nanometers (nm)
Electron Microscope (EM)
- Provides high resolution images.
- Uses a beam of electrons as the light source.
- Image formation based on the interaction of electron beams with the specimen.
- The beam travels through a vacuum tube.
- Electromagnetic coils act as lenses.
EM Components
- Illuminating system: electron gun and condenser lens.
- Imaging system: electromagnetic lenses (2-3) and a screen.
Electron Microscope Images
- Appear on a screen that emits light when struck by electrons.
- Images consist of light areas (electron lucent) and dark areas (electron dense).
- This is due to the passage of electrons through certain areas.
Sample Preparation
- Tissues and cells require special preparation:
- Embedding in resin
- Cutting into very thin sections (ultra-thin sections: 0.01 microns)
- Mounting on copper grids
Staining
- Sections are stained with salts of heavy metals, such as lead nitrate and uranyl acetate, to create contrast.
EM Magnification
- EM can magnify images thousands of times (up to 200,000x).
- Resolution power: 0.2 nanometers (nm).
Types of Electron Microscopes
- Transmission EM (TEM): electron beams pass through the specimen, revealing internal structures.
- Scanning EM (SEM): electron beams are reflected from the specimen's surface, providing a three-dimensional image.
Phase Contrast Microscope
- Creates visible images from transparent objects (unstained).
- Light speed changes when passing through cellular and extracellular structures, resulting in variations in refractive index.
- Objects appear lighter or darker depending on their refractive index.
- Useful for examining living cells and tissue cultures (e.g., blood cells and sperm).
Differential Interference Contrast Microscope (DIC)
- An advanced version of phase contrast microscopy for transparent or unstained samples.
- Creates a three-dimensional appearance.
- Uses two separate beams of light.
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Description
This quiz covers the fundamental concepts of cell biology, including the structure, function, and classification of cells. It also explores the relationship between cells, tissues, and organs, and distinguishes between prokaryotic and eukaryotic cells. Test your knowledge on the essential units of life!
