Page 1: Overview of Cells

• Cell Definition: The basic structure and organization of a living organism.

• Bacteria Discovery:

  • First termed 'animalcules' by Leeuwenhoek.

  • Robert Hooke named the first 'cell'.

• Size Comparisons:

  • Plant and animal cells: 10 micrometers to 100 micrometers.

  • Bacteria: 1 micrometer to 10 micrometers.

  • Viruses: about 100 nanometers (smaller than micrometers).

• Cell Theory:

  • Original principles:

    1. All organisms are composed of one or more cells.

    2. The cell is the smallest unit having the properties of life.

    3. All cells come from preexisting cells.

  • Contributors: Schleiden, Schwann, and Virchow.

• Modern Cell Theory:

  • Cells contain DNA (in chromosomes) and RNA (in nucleus and cytoplasm).

  • Cells of similar species share chemical compositions.

  • Energy flow occurs within cells (metabolism and biochemistry).

  • Organism activity relies on the total activity of its cells.

Page 2: Organelles / Eukaryotic vs. Prokaryotic

• Organelles and Their Functions:

  • Nucleus: Storage of DNA.

  • Mitochondria: Energy production, converting food energy to ATP, the cell's currency.

  • Ribosome: Protein synthesis; links amino acids together.

  • Rough ER: Protein production and modification, supports ribosomes in real-time.

  • Smooth ER: Lipid production and detoxification.

  • Golgi Apparatus: Protein transportation, sorting, and modification.

  • Peroxisome: Lipid breakdown; converts peroxide into water.

  • Lysosome: Dismantles unwanted proteins and organelles with enzymes.

  • Cytoskeleton: Provides cell movement and internal organization.

    • Functions of the Cytoskeleton:

      • Structural Support: Provides a framework that helps maintain cell shape and organizes the internal structure.

      • Cell Movement: Involved in amoeboid movement, muscle contraction (in animal cells), and the beating of cilia and flagella.

      • Intracellular Transport: Acts as tracks for the transport of materials within the cell, critical for distribution and recycling of cellular components.

      • Cell Division: Essential in forming the mitotic spindle during mitosis and cytokinesis, ensuring proper chromosome separation.

      • Signal Transduction: The cytoskeleton interacts with signaling molecules, contributing to cellular responses to external stimuli.

      • Cytoskeleton

        The cytoskeleton is a complex network of protein filaments and tubules that provide structural support, shape, and organization to cells. It plays crucial roles in various cellular functions, enabling movement, intracellular transport, and maintaining cell integrity.

        Components of the Cytoskeleton:

        1. Microfilaments (Actin Filaments):

           • Composed of the protein actin.

           • Involved in cell shape and movement, including muscle contraction in animal cells.

           • Facilitate cytokinesis during cell division.

        2. Intermediate Filaments:

           • Made of various proteins, providing tensile strength and mechanical stability to cells.

           • Help anchor organelles in place.

           • Examples include keratin in skin cells and neurofilaments in neurons.

        3. Microtubules:

           • Hollow tubes made of tubulin proteins.

           • Key role in maintaining cell shape, enabling intracellular transport, and facilitating cell division (spindle fibers).

           • Serve as tracks for the movement of organelles and vesicles, powered by motor proteins like kinesin and dynein.

      Differences in Cytoskeleton Function Between Plant and Animal Cells:

      • Structural Differences:

        • In animal cells, the cytoskeleton is more dynamic, adapting quickly to shape changes due to its role in movement and motility.

        • Plant cells have a more rigid structure due to the presence of a cell wall, leading to less dependence on the cytoskeleton for maintaining shape.

      • Mechanism of Movement:

        • Animal cells utilize actin filaments and microtubules for muscle contraction and cell motility.

        • In contrast, plant cells primarily rely on the cytoskeleton for stability and transport within the rigid cell wall structure rather than movement.

      • Cell Division:

        • While both cell types have microtubules for spindle formation, animal cells undergo cleavage furrow formation driven by the contractile ring formed by actin filaments, whereas plant cells form a cell plate due to their rigid cell wall.

      • Types of Cytoskeletal Polymers:

        • Animal and plant cells have similar cytoskeletal components, but the composition and arrangement can vary. For instance, some specific proteins that contribute to microtubule stability differ, influencing growth patterns and structural dynamics in plants compared to animals.

  • Cell Membrane: Selectively permeable barrier; manages cell communication.

  • Cell Wall: Provides structural support (found in plants, fungi, bacteria).

  • Cytosol: Cellular fluid, supports organelles.

  • Chloroplasts: Photosynthesis in plants.

  • Vacuole: Storage in plant cells (central vacuole regulates water).

  • Vesicle: Membrane bubbles for transport between organelles.

Page 3: Prokaryotic vs. Eukaryotic Cells

• Differences:

  • Eukaryotic cells are larger and more complex than prokaryotic cells.

  • Eukaryotic cells can synthesize proteins, while prokaryotic cells generally cannot.

  • Eukaryotic cells are compartmentalized for specialization; prokaryotic cells lack organized compartments.

• Bacterial Cells:

  • Prokaryotic and lack many organelles found in eukaryotes.

  • Characteristics include: no ribosomes, no membrane-bound organelles, and no nuclei.

Page 4: Common Features in Cell Types

• Common Features:

  • Prokaryotes and eukaryotes share:

    • Ribosomes, cytoplasm, and plasma membranes.

  • DNA Location:

    • Eukaryotic cells: located within the nucleus (double membrane).

    • Prokaryotic cells: found in a nucleoid region, not membrane-bound.

Page 5: Endoplasmic Reticulum and Cell Functions

• Endoplasmic Reticulum (ER):

  • Two types: Rough ER (with ribosomes) and Smooth ER (without ribosomes).

  • Rough ER involved in protein synthesis; Smooth ER in lipid synthesis and detoxification.

• Lysosomes: Digestive organelles for hydrolysis of macromolecules.

• Mitochondria: Powerhouse of the cell; processes cellular respiration.

• Cytoskeleton: Provides structure and mediates movement.

Page 6: Pathway of Protein Synthesis

• Protein Pathway:

  • Newly synthesized proteins follow this route: ER → Golgi apparatus → vesicles → plasma membrane.

• Endomembrane System:

  • Comprises the nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, and plasma membrane.

  • Functions include protein synthesis, transport, metabolism of lipids, detoxification.

Page 7: Nucleotide and Organelles

• Nucleotides: Basic building blocks of nucleic acids (RNA and DNA).

• Mitochondria: Exclusive to eukaryotic cells, not found in prokaryotes.

• Endomembrane System: Known for interconnectivity among its components.

Page 8: Genetic Material in Cells

• Nucleoid: Irregularly shaped region containing genetic material of prokaryotic cells.

• Animal vs. Plant Cells: Centrioles are present in animal cells but absent in plant cells.

Page 9: Nucleus and Endosymbiotic Theory

• Nucleus: Spherical structure tasked with ribosome production.

• Endosymbiotic Theory: Suggests some organelles in eukaryotic cells originated from prokaryotic organisms.

• Golgi Apparatus: Composed of a cis side (receives) and trans side (ships).

Page 10: Mitochondria and Chloroplast Function

• Mitochondria: Engage in cellular respiration, converting nutrients into usable energy (ATP).

• Chloroplasts: Conduct photosynthesis to convert light energy into chemical energy (glucose).

• Centrioles: Aid in organizing microtubules during cell division, found in animal cells only.

Page 11: Cell Size and Efficiency

• Cell Size: Remains small to enhance nutrient absorption and exchange efficiency.

• Surface Area: Smaller cells have a greater surface-area-to-volume ratio, enhancing exchange processes.

Page 12: Cell Membrane Structure and Function

• Cell Membrane Goals:

  • Communicate with other cells, protect cell contents, and regulate material exchange.

• Membrane Composition: Made of phospholipid bilayer; hydrophilic heads and hydrophobic tails.

Page 13: Membrane Dynamics

• Fluid Mosaic Model of Membrane: Diverse components work together for transport and cellular communication.

• Endocytosis: The process cells use for taking in large particles.

• Lipids and Proteins: Structural components and functional agents for communication and transport.

Page 14: Endosymbiotic Theory

• Endosymbiotic Theory Recap: Mitochondria and chloroplasts originated from independent prokaryotic microbes.

• Cell Transport: Endocytosis and exocytosis for large particles.

Page 15: Molecular Movement

• Molecular Speed: Gas molecules have the fastest movement; solids vibrate the least.

• Diffusion: Movement of molecules from high concentration to low concentration without energy input.

Page 16: Equilibrium and Diffusion

• Equilibrium: Establishes when incoming molecules match outgoing, maintaining a net change of 0.

• Diffusion Types:

  • Simple diffusion: For small nonpolar molecules.

  • Facilitated diffusion: For polar molecules using transport proteins.

Page 17: Osmosis

• Osmosis: Diffusion specifically for water molecules, occurring from areas of low solute concentration to high.

• Concentration Gradient: Independent water and sugar concentrations.

Page 18: Tonicity and Cell Volume

• Tonicity: Measurement of how solutions affect cell volume by altering water content.

  • Hypotonic: Water entry causes cell swelling.

  • Hypertonic: Water exit leads to cell shrinking.

  • Isotonic: No volume change occurs.

• Osmoregulation: Process of maintaining water balance.

Page 19: Active Transport Mechanism

• Active Transport: Involves moving molecules against their concentration gradient.

  • Requires energy input.

  • Example: Proton pumps create H+ gradients across membranes.

Page 20: Electrogenic Pumps

• Electrogenic Pumps: Create voltage differences across cell membranes, managing ion distribution and acidity.

Page 21: Endocytosis and Exocytosis Processes

• Endocytosis: Cells obtain large materials that cannot cross the membrane directly, forming vesicles.

• Exocytosis: Expulsion of large materials from the cell via vesicle fusion with the plasma membrane.

Page 22: Microscopy Techniques

• Light Microscopy Advantages:

  • Allows viewing of live specimens (dynamic processes).

  • Produces less preparation artifacts than electron microscopy.

• Electron Microscopy Limitations:

  • Preparation methods often kill cells, making them unsuitable for observing live processes.

• Super-resolution Microscopy: Modern advancements enabling resolution of tiny cell structures down to 10-20 nm.

Page 23: Key Differences in Microscopy

• Electron Microscopes:

  • Utilize electron beams to magnify cell structures.

  • Achieve higher magnification than light microscopes but kill specimens.

• Light Microscopes:

  • Use visible light, suitable for live organism observation without lethal effects.

Overview of Cells

Cell Definition

Cells are the fundamental units of structure and organization in all living organisms, serving as the building blocks of life. They encase all necessary components for metabolic functions, growth, and reproduction.

Bacteria Discovery

• First Observations: The discovery of bacteria dates back to the late 17th century when Antonie van Leeuwenhoek first observed them through his handcrafted microscopes, coining the term 'animalcules.'

• Naming of Cells: In 1665, Robert Hooke introduced the term 'cell' after observing cork under a microscope, where he noted tiny, box-like structures that mirrored the layout of monastic cells.

Size Comparisons

• Plant and Animal Cells: Typically range from 10 micrometers to 100 micrometers in diameter, demonstrating diversity in size and shape depending on the organism and specific function.

• Bacteria: These cells are much smaller, ranging from 1 micrometer to 10 micrometers, which allows them to reside in various environments.

• Viruses: Among the smallest biological entities, viruses measure about 100 nanometers, highlighting the distinction between cellular life and viral particles.

Cell Theory

• Original Principles:

  • All organisms are composed of one or more cells, signifying the diversity of life forms based on cellular organization.

  • The cell is the smallest unit capable of exhibiting the properties of life, emphasizing its role as a self-contained system.

  • All cells arise from preexisting cells, outlining the continuity and reproduction processes vital for life.

• Key Contributors: The formulation of cell theory was significantly advanced by scientists like Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.

Modern Cell Theory

• Encompasses advancements in our understanding that include:

  • Cells carry genetic material (DNA within chromosomes), dictating the biological functions and traits of the organism.

  • Biochemical compositions of cells within a particular species are remarkably similar, aiding in research and understanding of life forms.

  • Energy flow within cells underscores metabolic processes, necessitating a constant supply of energy for cellular activities.

  • The overall activity of organisms is a direct consequence of the cumulative behavior of their cells, showcasing the interconnectedness of cell functionality and organismal health.

Cell Specialization

Cell specialization refers to the process by which generic cells in a multicellular organism develop into distinct cell types with specific structures and functions that are tailored to carry out unique roles within an organism. This is critical for the efficiency and effectiveness of biological processes in both plant and animal cells.

Examples of Specialized Cells

• Animal Cells:

  • Neuron: Neurons are specialized for the transmission of electrical signals throughout the nervous system. Their long, branched structures facilitate communication between distant body parts, indicating a significant relationship between their form and function.

  • Erythrocytes (Red Blood Cells): These cells lack a nucleus and are biconcave in shape, maximizing their surface area for oxygen transport. Their design allows optimal movement through blood vessels and efficient gas exchange in the lungs.

• Plant Cells:

  • Guard Cells: Guard cells surround stomata on leaf surfaces and regulate gas exchange. Their specialized shapes and ability to change size control water loss and intake of carbon dioxide, illustrating how their structure serves the function of regulating photosynthesis and respiration.

  • Xylem Cells: These cells are specialized for the conduction of water and minerals from the roots to the leaves. They have thicker cell walls and hollow structures that promote efficient transport, demonstrating how the form of xylem cells meets their essential function in plant survival.

Form Meets Function

The principle that "form follows function" is evident in these specialized cells. Each cell's structure is intricately designed to optimize its role within the organism. For instance, the elongated shape of muscle cells allows for contraction and movement, while the leaf's broad surface area maximizes sunlight absorption for photosynthesis. This specialization not only enhances efficiency but also allows organisms to adapt to their environments and perform complex biological processes effectively.

Microscopy Techniques

Light Microscopes

• Description: Light microscopes use visible light and lenses to magnify specimens, enabling observation of cellular structures and live organisms.

• Advantages:

  • Allows viewing of live specimens, making it suitable for observing dynamic processes and interactions within cells.

  • Produces less preparation artifacts compared to electron microscopy, yielding clearer images of structural details.

• Applications:

  • Commonly used in educational settings, laboratories for biological research, and clinical pathology to examine tissue samples.

  • Ideal for viewing cells, tissues, and some cellular organelles in living specimens.

Electron Microscopes

• Description: Electron microscopes utilize electron beams to magnify cell structures far beyond the capabilities of light microscopes, allowing for much higher resolution images.

• Limitations:

  • Preparation methods required often kill cells, making them unsuitable for observing live processes.

  • Generally more expensive and complex to operate compared to light microscopes.

• Applications:

  • Used extensively in research to study cellular ultrastructure, viral infections, and material sciences, providing detailed insights into cellular components at the nanometer scale.

  • Essential for fields like nanotechnology, materials science, and virology due to their ability to resolve structures not visible with light microscopy.