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Questions and Answers
Which statement best describes eukaryotic cells?
Which statement best describes eukaryotic cells?
What is the primary role of the plasma membrane in cells?
What is the primary role of the plasma membrane in cells?
What distinguishes transmission electron microscopes (TEMs) from scanning electron microscopes (SEMs)?
What distinguishes transmission electron microscopes (TEMs) from scanning electron microscopes (SEMs)?
Which component of the cell membrane is primarily responsible for its structural integrity?
Which component of the cell membrane is primarily responsible for its structural integrity?
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What is the main function of ribosomes in eukaryotic cells?
What is the main function of ribosomes in eukaryotic cells?
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What type of junction prevents fluid from moving across a layer of cells?
What type of junction prevents fluid from moving across a layer of cells?
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Which of the following components are included in the cytoplasm?
Which of the following components are included in the cytoplasm?
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Which type of cell junction facilitates communication between adjacent cells?
Which type of cell junction facilitates communication between adjacent cells?
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What structure is formed by the fusion of two layers of glycocalyx in certain epithelia?
What structure is formed by the fusion of two layers of glycocalyx in certain epithelia?
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Which of the following functions is NOT typical for desmosomes?
Which of the following functions is NOT typical for desmosomes?
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What is the primary role of the extracellular matrix?
What is the primary role of the extracellular matrix?
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Which type of cytoplasmic component is specifically referred to as the gel-like matrix?
Which type of cytoplasmic component is specifically referred to as the gel-like matrix?
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How do tight junctions primarily function in epithelial tissues?
How do tight junctions primarily function in epithelial tissues?
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What is the primary role of the phospholipid bilayer in the plasma membrane?
What is the primary role of the phospholipid bilayer in the plasma membrane?
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Which component is involved in cell signaling and helps extracellular matrix adhesion?
Which component is involved in cell signaling and helps extracellular matrix adhesion?
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What is the primary benefit of a high surface-to-volume ratio in cells?
What is the primary benefit of a high surface-to-volume ratio in cells?
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Which statement about carbohydrates in the context of the cell membrane is true?
Which statement about carbohydrates in the context of the cell membrane is true?
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What is one function of cholesterol within the plasma membrane?
What is one function of cholesterol within the plasma membrane?
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Which of the following structures is involved in the extracellular matrix?
Which of the following structures is involved in the extracellular matrix?
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What characterizes a hydrophobic tail in phospholipids?
What characterizes a hydrophobic tail in phospholipids?
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Fibronectin is primarily associated with which structural role?
Fibronectin is primarily associated with which structural role?
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Which of the following best describes the microfilaments in the cytoplasm?
Which of the following best describes the microfilaments in the cytoplasm?
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Which of the following elements is not a component of the plasma membrane structure?
Which of the following elements is not a component of the plasma membrane structure?
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Study Notes
Introduction to Cytology
- Cytology is the study of cell structure and function.
- Histology is the study of the microscopic structure of tissues and organs of the human organism.
- Embryology is the study of embryonic development (formation) of the human body.
The Cell
- The cell is the smallest structural and functional unit of multicellular organisms.
- Cells are self-regulating, self-regenerating, and self-governing biological systems.
- A cell possesses all the characteristics of the organism, including metabolism, growth, irritability, and movement.
Microscopy
- Scientists use microscopes to visualize cells that are too small to see with the naked eye.
- Light microscopes (LM) use visible light passing through a specimen and lenses to magnify the image.
- Lenses refract (bend) light to magnify the image.
- Important parameters of microscopy include magnification, resolution, and contrast.
Cell Sizes and Microscopy
- Sizes of various biological structures are shown in a diagram.
- Unaided eye can view larger structures, such as a human.
- Light microscopes can zoom in to see smaller structures, such as cells.
- Electron microscopes (EM) provide better resolution to view smaller structures like viruses, proteins, and molecules.
Types of Cells in the Human Body
- A diagram illustrates various cell types in the human body.
- Smooth muscle, bone, connective tissue, blood, neurons in the brain, fat cells, ovum, and sperm are examples of cell types.
Cells and Matrix
- Cells produce a matrix which is an extracellular component.
Cell Structures
- The cell membrane is the selective barrier that allows passage of nutrients, oxygen, and wastes.
- The biological membrane is a double layer of phospholipids.
- Membrane contents include lipids, proteins, and carbohydrates.
- Lipids may include phospholipids and cholesterol.
Membrane Proteins
- Proteins make up about 50% of membrane content and have many functions.
- Functions of membrane proteins include channels, pumps, receptors, enzymes, integrative, and structural functions.
Extracellular Matrix
- The extracellular matrix is a structure that supports and organizes cells.
- The extracellular matrix is composed of components like collagen, fibronectin, and proteoglycans.
Membranes
- Membranes are present in various cell structures including the outer membrane, organelles, vesicles, and nuclear envelope.
Cell Structure
- Cells consist of a cell membrane, nucleus, cytoplasm (cytosol, organelles, inclusions).
Cell Junctions
- Cell junctions are multiprotein complexes that connect neighboring cells or connect a cell to the extracellular matrix.
- Types of cell junctions include gap junctions, tight junctions, and desmosomes.
Tight Junction
- Tight junctions occur in various types of epithelial cells.
- Two layers of glycocalyx are fused as a barrier.
- Tight junctions prevent the movement of molecules into intercellular spaces.
Gap Junctions
- Gap junctions allow direct chemical communication between adjacent cells.
- Gap junctions allow diffusion of materials through the cytoplasm without contact of extracellular fluid.
- Gap junctions are common in muscle tissue.
Desmosomes
- Desmosomes are the most common type of cell junctions.
- Desmosomes provide cell attachment.
Cytoplasm and Nucleus
- Cytoplasm consists of a matrix, or cytosol, organelles, and inclusions.
- Inclusions are non-living components within the cell that may contain secretions or pigments.
Organelles
- Organelles are categorized by structure (membranous/non-membranous) and by function (general functions/specialized functions).
Rough Endoplasmic Reticulum (RER)
- RER is composed of a membranous network of cisternae, the internal space is continuous with the perinuclear space but separate from cytosol.
- RER is studded with ribosomes giving it a 'rough' appearance.
- RER functions in protein synthesis.
Smooth Endoplasmic Reticulum (SER)
- Consists of tubules located near the cell periphery.
- SER functions in lipid synthesis, carbohydrate metabolism, drug detoxification, and steroid metabolism.
- SER also stores calcium ions in muscle cells.
Golgi Apparatus
- The Golgi apparatus, also known as the Golgi complex or Golgi body, is an organelle common in eukaryotic cells.
- It was first identified in 1897 by Camillo Golgi and named after him in 1898.
- The Golgi apparatus looks like a pack of sacs.
Golgi Apparatus - Functions
- Synthesizes various substances that were initiated in the endoplasmic reticulum.
- Forms complex molecules, including glycoproteins and lipoproteins.
- Produces lysosomes and secretory vesicles.
Mitochondria
- Mitochondria are membrane-enclosed organelles found in most eukaryotic cells.
- Mitochondria contain outer and inner membranes composed of phospholipid bilayers and proteins.
- The inner mitochondrial membrane has folds called cristae.
- The inside of the mitochondria (matrix) contains respiratory enzymes.
Mitochondria - Function
- Mitochondria provide energy for various cellular functions.
- Mitochondria produce ATP molecules by processes like the Krebs cycle.
Lysosomes
- Lysosomes are round vesicles containing acid hydrolase enzymes.
- They break down waste materials and cellular debris.
- Lysosomal enzymes help digest materials in phagosomes.
- They are analogous to the cell’s stomach.
Lysosome Cycle
- Lysosomes are formed by the Golgi complex.
- Primary lysosomes fuse with phagosomes to form secondary lysosomes.
- Undigested material can remain in the cell as residual bodies.
Non-membranous Organelles
- Non-membranous organelles include microfilaments, microtubules, centrioles, and ribosomes.
Cytoskeleton
- The cytoskeleton consists of three types of protein filaments including actin filaments (also called microfilaments), intermediate filaments, and microtubules.
- These provide the cell's structure and function.
Cell Center
- The cell center consists of centrioles which are 9 x 3 microtubules.
- Two centrioles form a cell center.
- The cell center functions in forming the mitotic spindle.
Nucleus
- Eukaryotic cells have a nucleus.
- The nucleus is a membrane-limited structure.
- Parts of the nucleus include nucleolemma, nucleoplasm, nucleolus, chromatin, and chromosomes.
Nuclear Envelope
- The nuclear envelope consists of two membranes.
- The outer layer is continuous with the endoplasmic reticulum.
- The inner layer adheres to the ends of chromosomes.
Nuclear Pores
- The nuclear envelope has gaps called nuclear pores.
- Nuclear pores transport materials to and from the cytoplasm.
Nucleolus
- The nucleolus is the site for amplified DNA molecules.
- The nucleolus is the site for ribosome RNA (rRNA) synthesis.
- rRNA binds with proteins to form ribosomes.
Chromosome
- Chromosomes are DNA molecules that are coiled around a histone core.
- Eight histone molecules form the histone core.
- Histone core and DNA form nucleosomes.
Chromatin
- Chromatin consists of DNA and proteins.
- The functions of chromatin are packaging DNA, strengthening DNA for mitosis, DNA protection, and control of gene expression.
- Euchromatin is active chromatin while heterochromatin is inactive.
Chromosome
- Chromosomes are organized structures of DNA and protein.
Cell Cycle
- The cell cycle is a cyclic process that describes the life of a somatic cell.
- The cell cycle consists of interphase and mitosis.
Interphase
- Interphase is the period between cell divisions.
- Interphase consists of 3 phases: G1, S, and G2.
- G₀ phase is when a cell leaves the cycle and stops dividing.
G1 Phase
- In the G1 phase, the cell grows and performs its routine functions.
- Non-dividing cells remain in G1 phase until the end of their life.
- Dividing cells prepare for the next phase in G1 phase.
S Phase (Synthesis Phase)
- During the S phase, DNA molecules are duplicated in each chromosome.
- Each chromosome consists of two DNA molecules or two chromatids.
- At the end of the S phase, the chromosome number increases to 4N.
G2 Phase
- Synthesis of proteins required for cell division occurs during the G2 phase.
- Mitosis usually begins after the G2 phase.
Mitosis
- Mitosis is the process of somatic cell division.
- Mitosis has 4 phases: prophase, metaphase, anaphase, and telophase.
Prophase
- Chromosomes become more coiled and recognizable in the prophase.
- The nuclear membrane disintegrates, and nucleoli disappear during prophase.
- Two centrioles move to opposite sides of the cell.
- Centrioles produce microtubules that form a spindle during prophase.
Metaphase
- Chromosomes align along the middle of the cell, called the equatorial plate.
- Chromosomes align at the cell's middle point between the two centrioles during metaphase.
Anaphase
- Chromatids separate and move to opposite poles of the cell during anaphase.
Telophase
- Two daughter nuclei are formed as nuclear membranes appear around the chromosomes.
- The chromosomes elongate and become indistinct in the telophase.
- Nucleoli reappear during telophase.
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