Cell Structure
A2.2 - Cell Structures and Functions
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Cell Structures
Organelles
Membranes and Membrane Transport
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Cells as Basic Units
Cells are the smallest structural units capable of energy use for sustaining life.
Cell Theory:
All living organisms are composed of one or more cells.
Cells are the basic unit of life.
Cells arise from pre-existing cells.
Exceptions include viruses and atypical cells.
Microscopy Skills:
Prepare a thin layer of cells/tissues.
Lay specimen on slide.
Use water or stain for visibility.
Lower cover slip carefully.
Use coarse and fine focus for clarity.
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Calculating Magnification:
Magnification = Image Size / Actual Size
Examples of calculations for clarity between image and actual sizes in nanometers.
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Developments in Microscopy:
Electron Microscopy uses electron beams for higher resolution compared to light microscopes.
Differences between Light and Electron Microscopes:
Advantages: High resolution, living cells in color, easy to use.
Disadvantages: High cost, requires cell killing.
Types of Electron Microscopy:
Transmission Electron Microscopy (TEM): Internal structures.
Scanning Electron Microscopy (SEM): Surface structures.
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Cryo-EM and Fluorescent Staining:
Cryogenic Microscopy shows proteins in functional states by freezing samples and reducing damage from the electron beam.
Immunofluorescence uses fluorescence to highlight specific cell structures for easier visual identification.
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Cell Diagrams:
Key parts of Animal and Prokaryotic Cells:
Mitochondria, Ribosomes, Plasma Membrane, Nucleus, etc.
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Common Cell Structures:
Plasma Membrane, Cytoplasm, DNA, Ribosomes are essential to all living cells.
Differences between Prokaryotic and Eukaryotic cells are discussed.
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Eukaryotic Cell Structures:
Distinct structures found in plant, animal, and fungal cells with focus on organelle functions like the nucleus, ER, and Golgi Apparatus.
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Differences between Prokaryotic and Eukaryotic Cells:
Prokaryotes: Simpler structure, smaller size, binary fission division.
Eukaryotes: Complex structure, larger size, mitosis and meiosis division.
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Differences Among Eukaryotic Cells:
Variations in structures and functions across animals, fungi, and plants.
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Atypical Cell Structures:
Red Blood Cells (anucleate), Aseptate Fungal Hyphae (no separations), Skeletal Muscle (multiple nuclei) are discussed as examples of discrepancies.
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Origin of Eukaryotic Cells - Endosymbiosis:
Evidence of evolution from a common ancestor; subjects such as mitochondria and chloroplasts.
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Evidence of Endosymbiosis:
Structural and genetic similarity of mitochondria and chloroplasts to prokaryotes.
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Cell Differentiation:
Multicellularity allows specialization and larger body size, determined by gene expression patterns.
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Organelles as Subunits:
Organelles perform specific functions and may contain various numbers of membranes.
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Compartmentalization Advantages:
Controlled conditions allow specific functions, enhancing metabolic efficiency.
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Nuclear Membrane Functions:
Protects DNA, regulates transport of materials, and has large pores for macromolecule movement.
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Nuclear Pore Complexes:
Enable selective transport between the nucleus and cytoplasm.
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Ribosomes:
Role in protein synthesis, differences between free and membrane-bound ribosomes outlined.
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Endoplasmic Reticulum Functions:
Structure and function of the Rough and Smooth ER within the endomembrane system.
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Vesicle Formation:
Mechanisms of vesicle transport and clathrin's role in vesicle formation.
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Vesicle Fusion:
Importance of vesicle membrane merging with cell membranes for transporting substances.
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Role of Gated Ion Channels:
Function in nerve cells to control ion flow and maintain membrane potential.
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Plasma Membrane Structure:
Bilayer of phospholipids forming selectively permeable barriers for substance regulation.
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Simple Diffusion Mechanism:
Describes passive movement across membranes influenced by concentration gradient, temperature, and surface area.
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Membrane Bound Proteins Functions:
Various receptor proteins aiding in signal transduction and transport mechanisms.
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Transport Mechanisms:
Differences among facilitated diffusion, active transport, and simple diffusion.
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Active Transport Overview:
Importance of pump proteins in moving substances against concentration gradients using ATP.
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Membrane Selectivity:
Explanation of selective permeability in facilitated diffusion and active transport.
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Fluid Mosaic Model:
Describes phospholipid bilayer structure and the hydrophobic/hydrophilic nature of membranes.
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Impact of Fatty Acid Composition:
Relationship between fatty acid types and membrane fluidity.
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Cholesterol's Role:
Modulates membrane fluidity, essential for maintaining structural integrity at varying temperatures.
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Vesicle Formation and Function:
Overview of processes involved in vesicle endocytosis and exocytosis.
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Neuron Function and Gated Channels:
Mechanisms behind neuron action potentials, involving Na+/K+ pumps and channel gating.