Biology Module Quiz: Eukaryotic vs Prokaryotic Cells
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Questions and Answers

What is a key characteristic of eukaryotic cells that distinguishes them from prokaryotic cells?

  • Presence of introns in all their genes
  • Larger ribosomes compared to prokaryotes (correct)
  • Absence of membrane-bound organelles
  • Presence of a single circular chromosome
  • Which of the following microscopy techniques allows for higher resolution than standard light microscopy due to the use of fluorescent dyes?

  • Fluorescence microscopy (correct)
  • Brightfield microscopy
  • Phase contrast microscopy
  • Electron microscopy
  • What is the typical size range for eukaryotic cells?

  • 10 - 100 microns
  • 0.5 - 50 microns
  • 1 - 10 microns
  • 2 - 1000 microns (correct)
  • What biomedical tool is limited to a magnification of approximately 2000X due to the wavelength of visible light?

    <p>Light microscope (A)</p> Signup and view all the answers

    Which statement correctly describes the DNA structure in eukaryotic cells compared to prokaryotic cells?

    <p>Eukaryotic cells have multiple linear chromosomes (B)</p> Signup and view all the answers

    What is one of the primary aims of the module?

    <p>To introduce basic concepts of cell biology (C)</p> Signup and view all the answers

    What is emphasized as a vital skill during lectures?

    <p>Actively making notes to enhance understanding (A)</p> Signup and view all the answers

    What percentage of the final assessment is attributed to the lab report?

    <p>70% (B)</p> Signup and view all the answers

    Which aspect is NOT mentioned as a learning outcome of the module?

    <p>Designing and analyzing complex experiments (C)</p> Signup and view all the answers

    What is one ethical consideration mentioned in the aims of the module?

    <p>Acquiring and presenting experimental data ethically (A)</p> Signup and view all the answers

    What is likely to enhance your ability to learn from lectures?

    <p>Processing the material actively during the lecture (A)</p> Signup and view all the answers

    Which of these is a key goal for students at the end of this module?

    <p>Acquiring an understanding of cell and molecular biology (C)</p> Signup and view all the answers

    Who is best known as the 'Father of Microbiology'?

    <p>Anton van Leeuwenhoek (C)</p> Signup and view all the answers

    What did the early 19th-century biologists propose about living things?

    <p>All living things are composed of cells. (B)</p> Signup and view all the answers

    Which statement accurately reflects a key tenet of the Cell Theory?

    <p>Cells are the smallest living unit of structure and function. (B)</p> Signup and view all the answers

    What did Rudolf Virchow contribute to the Cell Theory in 1855?

    <p>Cells arise only from pre-existing cells. (B)</p> Signup and view all the answers

    What principle did the Cell Theory discard?

    <p>Spontaneous generation of cells occurs. (C)</p> Signup and view all the answers

    Which of the following structures were observed by Anton van Leeuwenhoek?

    <p>Muscle fibers and bacteria (B)</p> Signup and view all the answers

    Who were the scientists that formed the foundational statements of the Cell Theory in 1839?

    <p>Theodor Schwann and Matthias Schleiden (C)</p> Signup and view all the answers

    What does the phrase 'Omnis cellula e cellula' mean?

    <p>All cells arise from pre-existing cells. (A)</p> Signup and view all the answers

    What is the smallest living unit of structure and function in all organisms?

    <p>Cell (A)</p> Signup and view all the answers

    Which of the following is NOT a principle of the Cell Theory?

    <p>All cells have a nucleus. (A)</p> Signup and view all the answers

    What distinguishes prokaryotic cells from eukaryotic cells?

    <p>Eukaryotic cells have a defined nucleus, while prokaryotic cells do not. (D)</p> Signup and view all the answers

    Which outlined concept refers to the variety of ways in which cells can communicate?

    <p>Signal transduction (C)</p> Signup and view all the answers

    In the context of cell biology, what is the primary function of ribosomes?

    <p>To synthesize proteins. (D)</p> Signup and view all the answers

    What type of cell structure allows for the selective transport of materials into and out of the cell?

    <p>Cell membrane (D)</p> Signup and view all the answers

    Which of the following is a characteristic of multicellular organisms?

    <p>They show cellular specialization. (D)</p> Signup and view all the answers

    What term describes the theory that explains the origin of eukaryotic cells through symbiotic relationships?

    <p>Endosymbiotic theory (A)</p> Signup and view all the answers

    Which shape corresponds to rod-shaped bacteria?

    <p>Bacilli (D)</p> Signup and view all the answers

    Which scientist is credited with the first discovery of cells?

    <p>Robert Hooke (B)</p> Signup and view all the answers

    What is one main role of programmed cell death in multicellular organisms?

    <p>To eliminate damaged or unnecessary cells (C)</p> Signup and view all the answers

    What is the primary function of proteins in cells?

    <p>Performing various functions in the cell (C)</p> Signup and view all the answers

    Which of the following is a key characteristic of all cells?

    <p>A cell membrane surrounding the cell (A)</p> Signup and view all the answers

    Which process is NOT a fundamental activity of cells?

    <p>Photosynthesis in all cell types (A)</p> Signup and view all the answers

    What is the term for the region of DNA concentration in prokaryotic cells?

    <p>Nucleoid (A)</p> Signup and view all the answers

    Which of the following best describes eukaryotic DNA?

    <p>Linear and membrane-bound (D)</p> Signup and view all the answers

    Which type of cell is represented by bacteria?

    <p>Prokaryotic cells without a nucleus (A)</p> Signup and view all the answers

    What role does a cell membrane play in a cell?

    <p>Controls the movement of substances in and out of the cell (C)</p> Signup and view all the answers

    Which of the following activities does NOT involve cellular signaling?

    <p>Transport of nutrients (A)</p> Signup and view all the answers

    What is the function of cytoplasm in a cell?

    <p>It is the interior space of the cell excluding the nucleus. (C)</p> Signup and view all the answers

    What occurs as bleached molecules diffuse out of a bleached area in cellular membranes?

    <p>Intact fluorescent molecules diffuse into the area. (B)</p> Signup and view all the answers

    In the fluid mosaic model, where do the apolar regions of lipids and proteins interact?

    <p>In the core of the membrane. (D)</p> Signup and view all the answers

    Which characteristic is NOT associated with the abundance of eukaryotic cells?

    <p>High genetic diversity. (C)</p> Signup and view all the answers

    What distinguishes the nuclear envelope of eukaryotic cells?

    <p>It is formed from lipid bilayers. (A)</p> Signup and view all the answers

    What is a primary function of intracellular organelles in eukaryotic cells?

    <p>To perform specific functions. (D)</p> Signup and view all the answers

    Which of the following statements accurately summarizes the mobility of membrane proteins in the fluid mosaic model?

    <p>They can freely move within the lipid bilayer. (C)</p> Signup and view all the answers

    Which of the following is NOT a feature of prokaryotic cells?

    <p>They have a nuclear envelope. (A)</p> Signup and view all the answers

    What role does cholesterol play in a lipid bilayer?

    <p>Acts as a fluidity buffer (A)</p> Signup and view all the answers

    Which type of membrane protein spans across the lipid bilayer?

    <p>Integral proteins (D)</p> Signup and view all the answers

    What structure is primarily responsible for the selective transport of substances in eukaryotic cells?

    <p>Cell membrane. (B)</p> Signup and view all the answers

    What is a characteristic feature of the membranes in eukaryotic cells?

    <p>They are dynamic and fluid. (B)</p> Signup and view all the answers

    How do anchored proteins differ from integral and peripheral proteins?

    <p>They are linked to lipids or carbohydrates. (B)</p> Signup and view all the answers

    What describes the movement of phospholipids within the lipid bilayer?

    <p>They can laterally diffuse within the membrane plane. (C)</p> Signup and view all the answers

    What type of cell organelles are characterized as resembling bacteria?

    <p>Chloroplasts. (B)</p> Signup and view all the answers

    Which property of cholesterol contributes to making the lipid bilayer less permeable?

    <p>Its rigid structure (D)</p> Signup and view all the answers

    What mechanism is used to study protein mobility in membranes?

    <p>Fluorescence recovery after photobleaching (FRAP) (C)</p> Signup and view all the answers

    What characterizes the shape of integral proteins?

    <p>They are amphipathic. (B)</p> Signup and view all the answers

    Which of the following best describes the lipid fluid mosaic model?

    <p>Membranes consist of a mosaic of various components that can move laterally. (A)</p> Signup and view all the answers

    What is a common role of peripheral proteins in cell membranes?

    <p>They provide structural support by forming filaments. (C)</p> Signup and view all the answers

    What is the primary purpose of cholesterol in cellular membranes?

    <p>To stabilize membrane structure (D)</p> Signup and view all the answers

    What is the role of the nuclear envelope's pore structures?

    <p>To allow movement of molecules between nucleus and cytoplasm (B)</p> Signup and view all the answers

    Which of the following statements is true regarding the endoplasmic reticulum?

    <p>Secretory cells typically have more rough endoplasmic reticulum than nonsecretory cells. (B)</p> Signup and view all the answers

    What is the primary function of the Golgi apparatus?

    <p>Post-translational modification and packaging of proteins (C)</p> Signup and view all the answers

    What is a key characteristic of lysosomes?

    <p>They contain hydrolytic enzymes for digestion. (B)</p> Signup and view all the answers

    Which organelles are known to support the endosymbiotic theory?

    <p>Mitochondria and chloroplasts (C)</p> Signup and view all the answers

    Which function do mitochondria perform?

    <p>Energy generation through respiration (C)</p> Signup and view all the answers

    What distinguishes smooth endoplasmic reticulum from rough endoplasmic reticulum?

    <p>Functions in lipid synthesis and storage (D)</p> Signup and view all the answers

    What is the function of secretory vesicles?

    <p>To transport proteins to the cell membrane for secretion (D)</p> Signup and view all the answers

    What role do lysosomes play in cellular waste management?

    <p>They contain enzymes to digest old organelles and invaders. (C)</p> Signup and view all the answers

    Which of the following is a shared characteristic of mitochondria and chloroplasts?

    <p>They replicate DNA independently. (B)</p> Signup and view all the answers

    Flashcards

    Cell Theory

    The fundamental idea that all living organisms are composed of cells, and that cells arise from pre-existing cells.

    Unicellular Organisms

    Living organisms consisting of a single cell, such as bacteria, yeasts, and protozoa.

    Multicellular Organisms

    Living organisms composed of many cells organized into tissues, organs, and organ systems, such as animals, plants, and fungi.

    Cell Size

    Cells vary greatly in size, from a few micrometers (like bacteria) to a millimeter or more (like a frog egg).

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    Cocci

    Spherical-shaped bacteria.

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    Bacilli

    Rod-shaped bacteria.

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    Spirilli

    Spiral-shaped bacteria.

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    Robert Hooke

    An English scientist who, in 1665, discovered and named cells while observing thin slices of cork.

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    Anton van Leeuwenhoek

    A Dutch draper who, in the 17th century, independently discovered cells and made significant contributions to microbiology.

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    Cellular and Molecular Biology

    A field of study focusing on the structure, function, and interactions of cells, the basic units of life. It encompasses a wide range of topics including cell structure, biological macromolecules, molecular biology, cell communication, and genetics.

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    Learning Outcomes

    The specific knowledge, understanding, and skills that students are expected to acquire by the end of a course or module. It outlines the key concepts and abilities they should possess after successful completion.

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    Active Note Taking

    A learning strategy that involves engaging with lecture content by summarizing key points, drawing diagrams, asking questions, and making connections to previous knowledge. It helps to actively process information and enhance understanding.

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    In-Class Test

    An assessment method that evaluates a student's understanding of course material through a written test conducted within the classroom setting.

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    Lab Report

    A written document that details the methods, results, and analysis of a scientific experiment. It showcases the student's experimental skills and scientific thinking.

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    Weighting

    The relative importance assigned to different assessment components in a course. Higher weighting indicates a greater contribution to the overall grade.

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    The Iceberg Illusion: Success

    A concept highlighting the potential for underestimating the effort and preparation required for academic success. Like an iceberg, most of the work supporting success lies hidden beneath the surface, requiring dedication and diligent effort.

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    Cell Chemistry

    All cells share a similar chemical makeup and function through the same basic principles. This includes using similar molecules in similar reactions.

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    Genetic Instructions

    All living things store their genetic information, or genes, in DNA molecules. They use the same genetic code and molecular machinery to translate these instructions.

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    Proteins: The Activators

    Proteins are the main output of the genetic instructions. They perform a wide variety of functions within the cell, acting as the 'activators' of cellular processes.

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    Cell Integrity

    A fundamental cell activity is maintaining its own integrity, keeping the inside contents separate from the outside environment.

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    Information Storage

    Cells need to store information to build themselves and reproduce. This information is encoded in their DNA.

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    Energy Conversion

    Cells capture and transform energy to fuel their activities. This is essential for growth, movement, and other functions.

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    Intracellular Transport

    Cells transport substances both within themselves and across their membranes. This allows for communication and exchange of materials.

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    Cell Division

    Cells divide to create new cells, allowing for growth, repair, and reproduction.

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    Environmental Response

    Cells can receive and respond to signals from their environment, allowing them to adapt and survive.

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    Cell Membrane

    All cells have a surrounding membrane, called the cell membrane, that acts as a barrier and regulates what enters and exits the cell.

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    Eukaryotic Cell

    A type of cell characterized by a membrane-bound nucleus, multiple linear chromosomes, and various membrane-bound organelles.

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    Prokaryotic Cell

    A type of cell lacking a membrane-bound nucleus and other internal membrane-bound organelles. Its genetic material is organized in a single circular chromosome.

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    What are the differences in ribosomes between prokaryotes and eukaryotes?

    Eukaryotic ribosomes are larger (80S/18S) and found mainly outside the nucleus. Prokaryotic ribosomes are smaller (70S/16S).

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    Brightfield Microscopy

    A basic form of light microscopy where a sample is illuminated from below, and white light is transmitted through it. It offers low contrast and is simple to use.

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    Fluorescence Microscopy

    A type of microscopy that uses fluorescent dyes to illuminate specific structures within a cell. The illuminating light passes through filters to excite and observe fluorescence.

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    Who discovered animalcules?

    Anton van Leeuwenhoek, a Dutch draper, was the first to observe and describe single-celled organisms, which he called 'animalcules.'

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    What is the Cell Theory?

    The Cell Theory is a fundamental principle in biology stating that all living organisms are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

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    What did Schwann & Schleiden contribute?

    Theodor Schwann and Matthias Schleiden proposed that all living organisms are composed of one or more cells, and that the cell is the most basic unit of life.

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    What did Virchow contribute?

    Rudolf Virchow extended the Cell Theory in 1855 by stating that all cells arise only from pre-existing cells.

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    What are the principles of the Cell Theory?

    1. All living things are made of cells. 2. The cell is the smallest living unit of structure and function. 3. All cells arise from pre-existing cells.
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    What does 'Omnis cellula e cellula' mean?

    This Latin phrase, meaning 'All cells from cells,' is the third principle of the Cell Theory, stating that new cells can only be produced from existing cells.

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    What was the impact of the Cell Theory?

    The Cell Theory revolutionized our understanding of life, disproving the idea of spontaneous generation and establishing the importance of cells as the fundamental units of all living organisms.

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    What is spontaneous generation?

    Spontaneous generation is a discredited theory that believed living organisms could arise from non-living matter, such as flies emerging from rotting meat.

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    How are cells organized?

    Cells are organized into tissues, which are groups of similar cells working together. Tissues form organs, which perform specific functions, and organs collaborate to form organ systems.

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    What is the universal structure of all cells?

    All cells share a common structural organization, including a cell membrane, cytoplasm, and genetic material (DNA).

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    Lateral Diffusion

    The movement of molecules within the plane of a membrane, like a boat drifting on a lake.

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    Fluid Mosaic Model

    A model describing the structure of cell membranes as a flexible and dynamic mosaic of lipids and proteins.

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    Aqueous Environments

    Water-based environments inside and outside the cell where membrane components interact.

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    Organelles

    Specialized structures within cells that perform specific functions, like tiny factories within a cell.

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    Membrane-Derived Organelles

    Organelles formed from membranes, like the nucleus and endoplasmic reticulum.

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    Bacteria-Like Organelles

    Organelles that resemble bacteria, like mitochondria and chloroplasts.

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    Nucleus

    The control center of the cell, containing DNA and responsible for regulating cellular activities.

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    Nuclear Envelope

    Two membranes surrounding the nucleus, controlling the exchange of molecules between the nucleus and cytoplasm.

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    DNA

    The genetic material that contains the instructions for building and maintaining an organism.

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    Prokaryotes

    Organisms that lack a membrane-bound nucleus and other internal membrane-bound organelles.

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    Histones

    Proteins that eukaryotic DNA is associated with, helping to package and organize it within the nucleus.

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    Nuclear Pores

    Openings in the nuclear envelope that allow the passage of molecules like proteins, RNA, and ions.

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    Endoplasmic Reticulum (ER)

    A network of interconnected membranes within the cytoplasm, involved in protein synthesis and lipid production.

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    Rough Endoplasmic Reticulum (RER)

    Type of ER with ribosomes attached, responsible for protein synthesis.

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    Smooth Endoplasmic Reticulum (SER)

    Type of ER without ribosomes, involved in lipid and carbohydrate metabolism.

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    Golgi Apparatus

    A stack of flattened membrane-bound sacs that modifies, sorts, and packages proteins.

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    Vesicles

    Small membrane-bound sacs involved in storage and transport within the cell.

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    Lysosomes

    Specialized vesicles containing enzymes that break down waste materials and old organelles.

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    Endosymbiotic Theory

    The theory that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by early eukaryotic cells.

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    Cholesterol's Role

    Cholesterol is a lipid found in cell membranes. It helps regulate membrane fluidity by filling spaces between phospholipids, making the membrane more rigid and less permeable.

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    Amphipathic Cholesterol

    Cholesterol, like phospholipids, is amphipathic, meaning it has both a hydrophilic (water-loving) and hydrophobic (water-fearing) part.

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    Integral Proteins

    One type of membrane protein that spans the entire cell membrane, embedded within the lipid bilayer.

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    Peripheral Proteins

    Membrane proteins that do not fully penetrate the membrane but attach to its surface, interacting with the lipid bilayer.

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    Anchored Proteins

    Membrane proteins that are not embedded in the membrane but are attached to lipids or carbohydrates within the bilayer.

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    Flip-Flop

    Phospholipid movement from one side of the membrane to the other, which is a slow process.

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    Protein Mobility

    Proteins within the membrane can move laterally and even rotate.

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    FRAP Technique

    A method used to study protein mobility in cell membranes. It involves bleaching a small area of the membrane, then watching how the bleached area recovers fluorescence as proteins move back into it.

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    Study Notes

    Module 006283: Cellular and Molecular Biology

    • Aims to introduce basic cell biology concepts, including cell structure, biological macromolecules, molecular biology, cell communication, and genetics.
    • Aims to provide laboratory experience to develop skills in acquiring and presenting experimental data, with ethical considerations and health and safety concerns.
    • Aims to provide a sufficient background to complement other current modules and enable subsequent specialized courses.

    Learning Outcomes

    • Students should acquire an understanding of key concepts in cell and molecular biology.
    • Students should be able to design, perform, and analyze simple experiments.

    Working with Lectures

    • Lectures introduce topics and provide new information.
    • Lectures aim to present material to help students learn facts and understand the subject matter.
    • Actively taking notes is crucial for capturing understanding.
    • Passive listening is an ineffective learning method.
    • Lectures aim to be informative and accessible, recognizing diverse learning styles.
    • Feedback on lectures is appreciated.

    Assessment Information

    • Two assessment elements are included:
      • In-class test (December 10th, 2024, Groups A, B, C, D): 30% weighting.
      • Lab report (Canvas submission by 2 PM on November 29th, 2024): 70% weighting

    The Iceberg Illusion: Success

    • Success is like an iceberg; what people see (e.g., persistence, sacrifice, good habits) is only a small part of the whole picture.
    • Other unseen aspects (e.g., dedication, disappointments) are equally – or even more – important.

    Textbooks

    • Recommended textbooks, available as Kortext e-books, include:
      • Essential Cell Biology, Fifth Edition: designed to provide fundamentals of cell biology for biomedical and broader biological issues.
      • Another textbook: delivers comprehensive content, clearly written, and illustrated for today's students, in a user-friendly format.
      • A third text is aimed at the advanced reader, going more in-depth than the previous textbook.

    Brief Overview of Module Topics

    • Cells (cell theory), and cell membranes
    • Subcellular organelles and endosymbiotic theory
    • Membrane transport
    • Biological macromolecules
    • DNA structure and replication
    • Transcription & Translation
    • Cell cycle & cell division
    • Cell death (programmed cell death)
    • Signal transduction – how cells communicate

    Question: Defining 'Life'

    • This question is posed for consideration.

    What is a Cell?

    • Cells are the fundamental units of life.
    • Cells exist as unicellular organisms or in communities in multicellular organisms (animals, plants, and fungi).
    • Cells vary greatly in appearance and function in size, ranging from small micrometers to a larger frog egg, measured by millimeters.

    An Idea of Cell Size

    • The sizes of various biological structures are measured on a logarithmic scale, comparing the size of atoms, lipids, viruses, bacteria, mitochondria, and cells from various species to humans on the order of millimeters.

    Cells Come in a Variety of Shapes and Sizes

    • Cells exhibit diverse shapes and sizes, including spherical (cocci), spiral-shaped (spirilla), rod-shaped (bacilli), neurons, amoeba (Paramecium), petal surfaces, white blood cells (macrophages), and fission yeast.

    Brief History of Cell Biology

    • Robert Hooke, in the 17th century, observed and described cells in cork slices, coining the term "cell."

    Anton van Leeuwenhoek

    • Anton van Leeuwenhoek, a contemporary of Robert Hooke, improved microscopes.
    • He observed and described single-celled organisms (microorganisms) – animalcules.
    • His observations included muscle fibers, bacteria, spermatozoa, and blood flow in capillaries.

    Cell Theory

    • Cells are the basic units of life and form all organisms.
    • All living organisms are made up of one or more cells.
    • All cells arise from pre-existing cells (Cell Theory Principle #3 introduced in 1855 by Virchow, extending the theory by Schleiden and Schwann introduced in 1839).

    Principles of Cell Theory

    • All living things are made of cells.
    • The cell is the smallest living unit of structure and function in all organisms.
    • All cells arise from preexisting cells (disproving spontaneous generation).

    All Living Things are Constructed from Cells

    • Living things, from bacteria to butterflies to roses to dolphins, are built from cells.

    All Cells Have Similar Chemistry and Work by the Same Basic Principles

    • All cells use similar molecules and reactions.
    • DNA stores genetic information (genes).
    • Protein molecules are the readouts (activators) of genetic instructions, performing various functions within the cell.

    Fundamental Cell Activities

    • Maintaining cell integrity (inside and outside).
    • Storing information for cell building and reproduction.
    • Converting information into activators (primarily proteins).
    • Capturing energy for cell activities.
    • Transporting substances within and outside the cell.
    • Dividing to create new cells.
    • Responding to environmental signals.

    Characteristics of All Cells

    • All cells have a surrounding membrane (cell membrane).
    • All cells have cytoplasm (interior of the cell, excluding the nucleus).
    • Internal structures (organelles) dedicated to specific tasks such as mitochondria.
    • Intracellular DNA (either inside a nucleus or elsewhere).

    Membrane-Bound DNA or Not...

    • Defines two fundamental cell types (prokaryotic and eukaryotic) in the classification of living things.
    • Prokaryotic cells do not have a membrane-bound nucleus.
    • Eukaryotic cells have DNA enclosed within a membrane-bound nucleus.

    Prokaryotic Cells

    • Possibly the first cell type on Earth.
    • Includes Bacteria and Archaea (two domains of prokaryotes).
    • Unicellular.
    • Lack a membrane-bound nucleus.
    • Nucleoid region where DNA concentrates.
    • Lack of membrane-bound organelles.

    Eukaryotic Cells

    • Have a nuclear membrane encasing DNA, organized within linear chromosomes.
    • Possess a nucleus and many membrane-bound organelles.
    • Are generally larger than prokaryotic cells.
    • Form the complex cells of plants, animals, and fungi.

    Differences Between Eukaryotic and Prokaryotic Cells

    • Eukaryotes have a membrane-bound nucleus and multiple linear chromosomes with associated proteins (histones).
    • Eukaryotic cells contain introns, repetitive DNA sequences that aren't transcribed.
    • Eukaryotic cells possess larger ribosomes (80S/18S) located outside the nucleus.
    • Prokaryotes have a single circular chromosome. Introns are found in archaebacteria. Prokaryotic cells utilize smaller ribosomes (70s/16s)
    • Prokaryotes lack the extensive cytoskeleton and internal membrane systems found in eukaryotes.
    • Eukaryotes have a typical size range of 10-100 micrometers, while prokaryotes are typically 0.5-50 micrometers.

    Representative Eukaryotic Cell

    Microscopy

    • Brightfield microscopy: simplest light microscopy method, with low contrast. The specimen is illuminated from below and white light is transmitted through the specimen.
    • Fluorescence microscopy: uses fluorescent dyes to stain cells and illuminate them with light passed through two filter systems. This enables the visualization of specific structures or molecules by exciting specific wavelengths to illuminate the fluorescent dye, revealing the location/distribution of the specific molecules in the cell.
    • Electron microscopy: uses high-energy electrons and has higher resolution than light microscopy, allowing for visualization of detailed structures within cells. These are two types – TEM (transmission) and SEM (scanning).

    Limits of Light Microscopy

    • Light microscopes have a fundamental limitation due to the wavelength of visible light and can not resolve details smaller than the wavelength of the illuminating light.
    • Resolving power is the shortest distance between two points on a specimen that can be distinguished as separate points.

    Electron Microscopy (TEM & SEM)

    • Transmission electron microscopy (TEM): analogous to light microscopy, where electrons pass through the specimen for imaging. Contrast is created by staining, allowing specific parts of the specimen to either absorb/scatter/reflect illuminating electrons.
    • Scanning electron microscopy (SEM): scans the surface of a specimen with a focused beam of electrons, detecting secondary electrons.

    The Cell Membrane

    • A cell membrane is a critical boundary.
    • The plasma membrane separates a cell's cytoplasm from its external environment.
    • Membrane presence is essential for defining cells and facilitating cellular activities.
    • Biological membranes are composed primarily of lipids and proteins, with varying ratios depending on cell type.

    Membrane Lipids

    • Membrane lipids are amphipathic, having both polar and nonpolar parts.
    • The hydrophobic tails of all membrane lipids are nonpolar but the head groups are polar.
    • The basic structural model of membrane lipids is a bilayer structure where tails point inwards and head groups outwards, creating a barrier between two aqueous environments.

    Membrane Lipids: Glycerophospholipids

    • Glycerophospholipids are the most abundant lipids, with glycerol as part of their structure.
    • They are based on the glycerol-3-phosphate structure.
    • Long-chain fatty acids are attached to the glycerol backbone.
    • Polar groups, like choline, serine, ethanolamine or inositol, are attached to a phosphate, creating polar head groups.

    Structure of Membrane Phospholipids

    • Long fatty acid chains attach to the glycerol backbone of phospholipids.
    • A polar group attaches to a phosphate group, giving a polar head to the phospholipid.

    Fatty Acid Components of Membrane Lipids

    • Fatty acid chains vary in length (C14-C24).
    • Often they are the same length, but can differ.
    • Fatty acids can be saturated, containing only single bonds, or unsaturated, containing at least one double bond. The presence of cis double bonds create kinks within the structure of the hydrophobic fatty acyl tails, resulting in more fluidity.

    Fatty Acid Configurations

    • Saturated fatty acids have no double bonds.
    • Unsaturated fatty acids have one or more double bonds.
    • Cis unsaturated fatty acids have bent configurations.
    • Trans unsaturated fatty acids have straight configurations.

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    Test your understanding of eukaryotic and prokaryotic cells with this quiz, which covers key characteristics, microscopy techniques, and important concepts in cellular biology. You will also explore the aims and objectives of the module, emphasizing skills and ethical considerations in biomedical studies.

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