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Questions and Answers
Which statement accurately describes the division process of mitochondria?
Which statement accurately describes the division process of mitochondria?
What is the primary function of the enzymes found within the mitochondrial matrix?
What is the primary function of the enzymes found within the mitochondrial matrix?
What role do matrix granules have in mitochondria?
What role do matrix granules have in mitochondria?
The inner mitochondrial membrane is primarily responsible for which of the following functions?
The inner mitochondrial membrane is primarily responsible for which of the following functions?
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How does ATP yield its energy to another molecule?
How does ATP yield its energy to another molecule?
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Which type of tissue is NOT classified under body tissues?
Which type of tissue is NOT classified under body tissues?
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What is the primary function of the cytoplasm?
What is the primary function of the cytoplasm?
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Which of the following organelles is classified as a non-membranous organelle?
Which of the following organelles is classified as a non-membranous organelle?
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Which of the following statements about membranous organelles is true?
Which of the following statements about membranous organelles is true?
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What does the cytoplasmic matrix consist of?
What does the cytoplasmic matrix consist of?
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Which structure acts as a barrier between the internal and external environment of the cell?
Which structure acts as a barrier between the internal and external environment of the cell?
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Which component is NOT found within the cytoplasm?
Which component is NOT found within the cytoplasm?
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What defines the cells as the smallest structural and functional units of living organisms?
What defines the cells as the smallest structural and functional units of living organisms?
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What is the primary function of phagocytosis?
What is the primary function of phagocytosis?
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What happens to the vesicle after phagocytosis is completed?
What happens to the vesicle after phagocytosis is completed?
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Which of the following functions does exocytosis serve?
Which of the following functions does exocytosis serve?
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What is one of the primary roles of mitochondria in the cell?
What is one of the primary roles of mitochondria in the cell?
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How do the number of mitochondria vary among different cell types?
How do the number of mitochondria vary among different cell types?
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Which structure within mitochondria is responsible for energy production?
Which structure within mitochondria is responsible for energy production?
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Which of the following best describes pinocytosis?
Which of the following best describes pinocytosis?
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What role do mitochondria play in ion-transporting cells?
What role do mitochondria play in ion-transporting cells?
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What is the main structure of the cell membrane as seen under an electron microscope?
What is the main structure of the cell membrane as seen under an electron microscope?
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Which types of proteins are recognized as constituents of the cell membrane?
Which types of proteins are recognized as constituents of the cell membrane?
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How do phospholipid molecules arrange themselves in the cell membrane?
How do phospholipid molecules arrange themselves in the cell membrane?
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Which process requires energy in the transport of substances across the cell membrane?
Which process requires energy in the transport of substances across the cell membrane?
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What do carbohydrates in the cell membrane primarily become part of?
What do carbohydrates in the cell membrane primarily become part of?
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What characterizes facilitated diffusion across the cell membrane?
What characterizes facilitated diffusion across the cell membrane?
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What is most likely NOT a function of the cell membrane?
What is most likely NOT a function of the cell membrane?
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What is a key characteristic of the unit membrane as depicted in diagrams?
What is a key characteristic of the unit membrane as depicted in diagrams?
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Study Notes
Histology
- The study of tissues
- Microscopic observations reveal that the body is composed of different tissues
- Tissues are made of cells
General Histology
- Covers the study of cells (cytology) and body tissues
Body Tissues
- Epithelial
- Connective
- Muscular
- Nervous
Cytology
- The study of cells
The Cell
- The basic structural and functional unit of living organisms
- Contains:
- Protoplasm
- Nucleus
- Cytoplasm
Cytoplasm
- Part of the protoplasm located around the nucleus
- Responsible for synthetic and metabolic activities
- Consists of:
- Cytosol (structure's matrix)
- Cytoplasmic organelles
- Inclusions
- Cytoskeleton
Cytoplasmic Matrix
- Non-organelle component of the cytoplasm
- Occupies the intracellular spaces between organelles and inclusions
- Contains soluble proteins, lipids, carbohydrates, and small ions
Cytoplasmic Organelles
- Permanent and living structures within the cytoplasm
- Perform specific functions
- Two types:
- Membranous organelles
- Non-membranous organelles
Membranous Organelles
- Possess a bounding membrane
- Include:
- Cell membrane
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
- Peroxisomes
Non-Membranous Organelles
- Lack a bounding membrane
- Include:
- Ribosomes
- Centrioles
Organelles
- Definition
- Observation methods:
- Light Microscope (LM)
- Electron Microscope (EM)
- Functions
Cell Membrane
- Also known as plasmalemma or plasma membrane
- Outer membrane of the cell
- Acts as a barrier between the internal and external environment
- Too thin to be seen with light microscope (LM)
- Appears as a trilaminar structure with electron microscope (EM)
- Consisting of outer and inner electron-dense layers separated by an intermediate electron-lucent layer
The Cell Boundary
- Cell membrane condensation on the inner aspect of the cell
- Stain condensation on the carbohydrate-rich coat
- Obliquity of sections
Unit Membrane
- Is a trilaminar structure
- The image shows a diagram of a cell membrane. The unit membrane is labelled with an arrow.
Molecular Structure of the Cell Membrane
- Fluid mosaic model
- Composed of:
- Phospholipids
- Proteins
- Carbohydrates
Phospholipids
- Form a central bimolecular layer
- Each molecule has two ends:
- Polar or hydrophilic (water-loving) end
- Non-polar or hydrophobic (water-fearing) tail
- Hydrophilic ends are directed outward
- Hydrophobic tails are directed inward toward the center of the membrane
Proteins
- Second major constituent of the cell membrane
- Arranged as globules moving freely within the lipid layer
- Two types:
- Intrinsic or integral proteins:
- Firmly attached to the lipid bilayer
- Some extend throughout the entire thickness of the membrane and constitute transmembrane channels
- Extrinsic or peripheral proteins:
- Only partially embedded to either aspect of the membrane
- Intrinsic or integral proteins:
Carbohydrates
- Conjugated with protein (glycoprotein) and lipid (glycolipid) molecules of the cell membrane
- Project from the outer surface of the cell membrane as cell coat or glycocalyx
Functions of the Cell Membrane
- Passive Diffusion
- Facilitated Diffusion
- Active Transport
- Selective transport
- Endocytosis and exocytosis
Passive Diffusion
- Entrance of small molecules
- Depends on a concentration gradient across the plasma membrane
- Diffusion of lipid-soluble substances, oxygen, CO2, water, and small ions
Facilitated Diffusion
- Depends on a concentration gradient across the plasma membrane
- Transport of large water-soluble molecules such as glucose and amino acids
- Requires carriers
Active Transport
- Requires the utilization of energy (ATP)
- Sodium-potassium pump (sodium out and potassium in)
Selective Transport
- Depends on the presence receptors to pick up specific molecules
- Example: hormones
Endocytosis
-
Engulfment of substances by the cell membrane
-
Two types:
- Phagocytosis: engulfment of solid particles
- Pinocytosis: engulfment of minute droplets of fluid
-
The engulfed material is surrounded by pseudopodia
-
After complete surrounding, the plasma membrane fuses forming a vesicle (phagosome or endocytotic vesicle)
-
The phagosome detaches and floats freely
-
The image shows a diagram of an endocytosis process. The left side of the diagram shows phagocytosis where a cell consumes a solid particle. The right side of the diagram shows pinocytosis where a cell consumes drops of fluid.
Exocytosis
-
Release of substances from the cell
-
Some membranous vesicles fuse with the cell membrane
-
Release their contents outside the cells
-
Occurs in many secretory processes
-
The image shows a diagram of exocytosis. A vesicle containing proteins fuses with the cell membrane, releasing the proteins into the extracellular environment.
Other Functions of the Cell Membrane:
- Transmission of nerve impulses in muscle and nerve cells
- Myelin sheath formation (Schwan cell around peripheral nerves)
- Share in the formation of microvilli, cilia, flagella, and cell junctions
Functions of the Cell Coat:
- Mechanical and chemical protection
- Induction of immunological (antigen-antibody) response
- Site for binding of hormones
- Formation of intercellular adhesions
- Formation of the basement membrane
- Cell recognition
Mitochondria:
- Membranous organelles
- Involved in cell respiration and energy production
- With LM:
- Granules
- Rod-like
- Thread-like
Mitochondria Number
- Highly variable based on the energy requirements of the cells
- Liver cells (active cells) contain as many as 1000 mitochondria
- Small lymphocytes (inactive cells) contain very few
Mitochondria Location
- Motile organelles
- Localize at intracellular sites of high-energy requirements such as basal regions of ion-transporting cells
Mitochondria with EM
-
Ovoid or elongated structures bounded by two membranes
-
The inner membrane is covered with tiny spherical projections about 9 µm in diameter supported at narrow stalks, called inner membrane spheres or elementary particles
-
The image shows a diagram of a mitochondrion viewed with an electron microscope. It clearly shows an outer membrane and an inner membrane. The inner membrane has several invaginations called cristae. In the center, a matrix is shown which is bounded by the inner membrane.
Mitochondria Matrix
- Contains many electron-dense granules called matrix granules that are the sites for Ca++ ions storage
- Contains DNA and RNA
- The matrix is the site for mitochondrial growth, division, and protein synthesis.
Mitochondria are Semiautonomous:
- Motile
- Divide by binary fission
- Contain DNA and RNA
- Synthesize proteins
Binary Fission
- The image shows a series of diagrams of binary fission. The first diagram shows a mitochondrion with two copies of its DNA molecule. The second diagram shows the mitochondrion getting elongated. The third diagram shows a complete separation of the mitochondrion.
Mitochondria Functions:
- House the chains of enzymes that catalyze reactions that provide the cells with most of its ATP (adenosine triphosphate)
- On demand, the ATP yields its high-energy phosphate bond to another molecule and becomes transformed into ADP
- Within the mitochondrial matrix, ADP is transformed again into ATP
Mitochondria Functions:
- These processes take place within:
- Mitochondrial matrix
- Inner mitochondrial membranes
- The matrix contains enzymes of the Krebs cycle and fatty acid oxidation
- The inner membrane contains the cytochromes and the enzymes involved in ATP production
- Participate in the regulation of calcium level within the cytosol
References
- Netter's Essential Histology, Ovalle, 2013
- Functional Histology, Kerr, 2009
- Wheater's Review of Histology & Basic Pathology, Baldwin, 2009
- Color Textbook of Histology 3rd Ed, Hiaat, 2014
- Internet source
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Description
This quiz explores the fundamental concepts of histology and cytology, including the study of tissues and cells. It covers different types of tissues such as epithelial, connective, muscular, and nervous, along with the structural components of a cell. Test your knowledge on the intricacies of body tissues and cellular structures.
