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Chapter 6- A Tour of the Cell - Coggle Diagram
Chapter 6- A Tour of the Cell
The Discovery and Study of Cells
Cell Theory
All living things are made of cells
The cell is the basic unit of life
All cells come from preexisting cells
Microsopy Techniques
Light Microscopy (LM)
Uses visible light
Can observe living cells, limited resolution
Electron Microscopy (EM)
Transmission EM (TEM): internal structure
Scanning EM (SEM): surface structure
Cell Fractionation
Breaks cells apart and separates organelles by size/density (centrifugation)
Types of Cells
Prokaryotic Cells
Domains: Bacteria and Archaea
No nucleus — DNA in nucleoid region
Lack membrane-bound organelles
Smaller and simpler
Eukaryotic Cells
Protists, fungi, animals, plants
True nucleus with nuclear envelope
Membrane-bound organelles
Typically larger than prokaryotes
Shared Features (All Cells)
Plasma membrane
Cytosol (semifluid interior)
Chromosomes (DNA)
Ribosomes (protein synthesis)
Surface Area-to-Volume Ratio
Efficiency of Transport
Surface area limits rate of exchange with environment
Larger cells have relatively less surface area → inefficient
Cells remain small or develop surface extensions (e.g., microvilli)
Eukaryotic Cell Structures
The Nucleus and Ribosomes
Nucleus
Surrounded by nuclear envelope (double membrane with pores)
Contains chromatin (DNA + proteins)
Nucleolus synthesizes ribosomal RNA (rRNA)
Ribosomes
Made of rRNA and protein
Carry out protein synthesis
Free ribosomes: float in cytosol
Bound ribosomes: attached to rough ER
Endomembrane System
Endoplasmic Reticulum (ER)
Smooth ER
Lipid synthesis
Detoxification
Calcium ion storage
Rough ER
Has ribosomes
Modifies proteins (folding, glycosylation)
Golgi Apparatus
Modifies, sorts, and packages proteins and lipids
Cis face = receiving side
Trans face = shipping side
Lysosomes
Contain hydrolytic enzymes
Digest macromolecules, damaged organelles
Autophagy: recycling of the cell’s own components
Vacuoles
Food vacuoles: formed by phagocytosis
Contractile vacuoles: pump excess water (protists)
Central vacuole: in plant cells, stores ions, water, pigments, toxins
Energy-Transforming Organelles
Mitochondria
Site of cellular respiration (ATP production)
Double membrane; inner membrane = cristae
Contains own DNA and ribosomes
Chloroplasts (plants & algae)
Site of photosynthesis
Contain green pigment chlorophyll
Double membrane + internal membranes (thylakoids, grana)
Contains own DNA and ribosomes
Endosymbiont Theory
Mitochondria and chloroplasts were once prokaryotes
Evidence: double membranes, circular DNA, ribosomes
Cytoskeleton
Micortubules
Hollow tubes of tubulin
Shape, organelle movement, cilia/flagella movement
Centrosomes and centrioles (animal cells): microtubule organizing center
Microfilaments (Actin Filaments)
Thinnest fibers
Cell shape, muscle contraction, cytoplasmic streaming
Intermediate Filaments
Middle-sized
Reinforce cell shape and anchor organelles
More permanent structures
Cell Surfaces and Junctions
Cell Wall (Plants)
Made of cellulose
Provides structure and protection
Plasmodesmata: channels between plant cells
Extracellular Matrix (Animals)
Made of glycoproteins (e.g., collagen)
Binds to integrins in membrane, provides support and signaling
Intercellular Junctions
Tight junctions: seal cells together
Desmosomes: anchor cells using intermediate filaments
Gap junctions: channels for ions and molecules (animal cell equivalent of plasmodesmata)