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Structure and Function of Cells
Learning Outcomes
Explain the cell theory
Explain why cell size is usually very small
Describe the Fluid Mosaic Model of membranes Describe similarities and differences between prokaryotic and eukaryotic cells
Explain the structure and function of the eukaryotic organelles (nucleus, rough & smooth ER, Golgi apparatus, lysosomes, mitochondria, chloroplasts)
Describe the three types of cytoskeletal filaments and associated motor proteins
Antoni van Leeuwenhoek (1632-1723)
improved microscope used it to look at everything
Red Blood Cells
Image from a replica of a Van Leeuwenhoek Microscope
The Cell Theory
All organisms are composed of cells.
Cells are the fundamental units of life.
All cells come from preexisting cells.
Corollary 1 – All cells contain genetic information.
Corollary 2 -- All cells are capable of an independent existence.
1. All living things are made of cells (1824).
Dutrochet stated that growth results from both an increase in the volume of cells and from the addition of new cells.
Rene Dutrochet (1776-1847)
Schleiden (1804-1881)
Schwann (1810-1882)
2. The cell is the basic unit of life (1839).
"Omnis cellula e cellula"
3. All cells arise from other cells (1858).
Rudolf Virchow (1821-1902)
Cells are Very Small
Cells are Very Small
1 – 10 nm 100 nm 1 – 2 µm 10 – 100 µm
Cells are Very Small
Cells depend on diffusion for obtaining nutrients and getting rid of waste products
The driving force for diffusion is the random movement of molecules as a result of thermal energy.
Diffusion is the NET movement of atoms or molecules from areas of high concentration to areas of low concentration.
Cells are Very Small
Light Microscopes
Scientists use Microscopes to Study Cells
Transmission Electron Microscope
What are the basic components of a cell?
DNA
1) Plasma Membrane
2) Genetic Material
3) Protein Machinery
boundary
blueprint
translates info in DNA into physical parts of the cell (proteins)
The Cell – A Minimalist View
Biological Membranes are Lipid Bilayers
Biological Membranes are Lipid Bilayers
Fluid Mosaic Model of Membrane Structure
Fluid – lipid and protein components are free to diffuse in the plane of the membrane
Mosaic – membrane contains two different types of macromolecules – lipids and proteins
Prokaryotic and Eukaryotic Cells
Prokaryotic and eukaryotic cells differ in their organization at the subcellular level.
cytoplasm, with ribosomes
DNA in nucleoid
plasma membrane cell wall
capsule pilus
bacterial flagellum
Prokaryotic Cells
Ribosomes: Protein Synthesis Machinery
Eukaryotic Cells Contain Many Organelles
central vacuole
rough ER
smooth ER
Golgi body vesicle
Nucleus
Nuclear envelope
nuclear pore
nucleolus
nucleoplasm DNA
Synthesis Sorting Delivery
The Endomembrane System
Proteins needed in the ER, Golgi, lysosomes, or PM, and secreted proteins are synthesized on the RER and then transported through the endomembrane system to their final destination.
Nucleus
Smooth ER Rough ER
Transport vesicle
Lysosome
Nuclear envelope
Golgi apparatus
Plasma membrane
Transport vesicle
Endoplasmic Reticulum
Rough and Smooth ER are both networks of membranes – but they have VERY DIFFERENT FUNCTIONS
RER SER
Rough ER
Synthesis of proteins destined for the plasma membrane, secretion, or lysosomes.
Smooth ER
Synthesis of lipids, phospholipids, steroids Detoxification of many drugs
Golgi Apparatus
Proteins enter from the RER
Proteins are sorted to their final destination
Golgi Apparatus
modifies proteins adds sugars sorts proteins to final destination – lysosomes plasma membrane secretory vesicles
Digestion of macromolecules
Lysosomes
Nucleus
Smooth ER
Rough ER
Transport vesicle
Lysosome
Nuclear envelope
Golgi apparatus
Plasma membrane
Transport vesicle
The Endomembrane System
Vacuoles – plant central vacuole
central vacuole
Energy Transducers – Mitochondria and Chloroplasts
Transduction - transforming energy from one form to another Examples -- One chemical form to another (e.g., glucose ATP) Electrical to chemical Light to chemical
Mitochondria
inner compartment outer compartment inner membrane outer membrane
Site of cellular respiration
Chloroplasts
Site of photosynthesis
The Cytoskeleton
Microfilaments Intermediate Filaments Microtubules
Increasing diameter
actin various IF proteins tubulin
Three filament systems
Intermediate Filaments
Structural components of cells
Hair is made of keratin, an intermediate filament protein
Microfilaments & Microtubules
In addition to having roles in maintaining cell structure, these cytoskeletal components also play roles in generating motility.
cytoskel motor motile process (examples)
actin myosin muscle contraction phagocytosis
tubulin dynein kinesin mitosis
cilia and flagella
Microfilaments
Involved in support and movement
https://youtu.be/0WCWgMqouaI
Microtubules
Involved in support and movement of components within cells
Most cells have arrays of actin (blue), microtubules (green), and IFs (red).
