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Cell Theory
- 1. Every living organism is comprised of cells.
- 2. The cell is the smallest living unit.
- 3. Cells come from preexisting cells
- 4. Cells contain DNA
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Prokaryotic cells
- Archaeans and bacteria
- Have few if any internal membrane & enclosed compartments
- Are the smallest and structurally simplest cells
- Protein filaments under the plasma membrane impart shape to the cell
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Eukaryotic cells
- Protists plants fungi and animal
- Have a (true) nucleus and other membrane enclosed compartments
- They differ in internal parts and surface specializations.
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Cytoskeleton key concepts
Diverse protein filaments reinforce a cell’s shape and keep its parts organized. As some filaments lengthen and shorten, they move cell structures or the whole cell.
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First Microscope
Invented by Hans and Zacharias Janssen 1590
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Robert Hooke
Examined a thinly sliced cork from a mature tree and named the tiny compartments cellulae coining the term cell.
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Robert Brown
First to identify a plant nucleus
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Matthias Schleiden
Hypothesized a plant cell is an independent living unit
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Rudolf Virchow
Discovered that cells divide into descendant cells
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Antoni van Leeuwenhoek
The first to observe living microscopic “animalcules” and “beasties”
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Plasma Membrane
- The cell's outer membrane
- Selectively controls the movement of materials in and out of the cytoplasm
- It separates metabolic activities from events outside of the cell, but does not isolate the cell's interior
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Nucleus
Double-membraned sac holding a eukaryotic cell's DNA
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Nucleoid
Region of cytoplasm where the DNA is concentrated
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Cytoplasm
- Semifluid mixture of water, sugars, ions, and proteins between the plasma membrane and the region of DNA
- Cell compartments are suspended in cytoplasm
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Ribosomes
Structures on which proteins (polypeptides) are built
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Lipid Bilayer
- Double layer of lipids organized so that their hydrophobic tails are sandwiched between their hydrophilic heads
- Forms the structural framework of all cell membranes
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Surface-to-volume ration
A physical relationship that constrains increases in cell size and shape
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What are the most abundant type of lipid in cell membranes.
Phospholipids
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What are some protein cell functions? (Not all inclusive)
- They...
- -form channels through a bilayer
- -pump substances across the bilayer
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Cell wall
- Surrounds the plasma membrane of nearly all prokaryotes
- Permeable to dissolved substances: composed of protein or peptidoglycan
- Cell walls of most bacteria consist of peptidoglycan
- Consists of proteins
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Peptidoglycan
Polymer of cross linked peptides and polysaccharides
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Capsule
- Formed of sticky polysaccharides
- Slime layer
- Helps cells adhere to many types of surfaces
- Protect cell from predators and toxins
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Flagellum
- Slender cellular structures used for motion.
- (Organized array of microtubules - eukaryotic)
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Pilus
- Help cells cling to or move across surfaces
- (Sex) pilus attaches to another cell to transfer genetic material from one cell to the other
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Plasmids
Small circles of DNA that carry a few genes that confer advantages, such as resistance to antibiotics
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Biofilm
- Shared mass of slime composed of secreted polysaccharides and glycoproteins upon which communities of bacteria live
- May include bacteria, algae, fungi, protest, and archaeans
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Benefits of the biofilm
- Serves as permanent scaffolding
- Species break down toxic chemicals allowing other, more sensitive, species to thrive
- Waste products of some species serve as building materials for others
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Organelle
Structure that carries out a specialized function inside a cell
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Organelles of Eukaryotic Cells
- Nucleus
- ER
- Golgi body
- Vesicles
- Mitochondrion
- Chloroplast
- Lysosome
- Peroxisome
- Vacuole
- Ribosomes
- Centriole
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Nucleus function
Protect and control access to DNA
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ER function
Routing, modifying new polypeptide chains; synthesizing lipid; other tasks
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Golgi body function
Modifying new polypeptide chains; sorting, shipping proteins and lipids
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Vesicles function
Transporting, storing or digesting substances in a cell; other functions
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Mitochondrion function
- Making ATP by sugar breakdown called aerobic respiration
- Two membrane
- Have their own DNA
- Are all Maternal
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Chloroplast function
- Making sugars in plants, some protists
- Photosynthetic organelle
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Lysosome function
Intercellular digestion
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Peroxisome function
Inactivating toxins
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Ribosomes function
Assembling polypeptide chains
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Centriole function
Anchor for cytoskeleton
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Components of the Nucleus
- Nuclear envelope
- Nucleoplasm
- Nucleolus
- Chromatin
- Chromosome
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Chromosome
Circular DNA molecule and many proteins associated with it
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Nuclear envelope
Pore-riddled double membrane that controls which substances enter and leave the nucleus
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Nucleoplasm
Semifluid interior portion of the nucleus
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Nucleolus
Rounded mass of proteins and copies of genes for ribosomal RNA used to construct ribosomal subunits
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Chromatin
Total collection of all DNA molecules and associated proteins in the nucleus; all of the cell's chromosomes
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Chromosome appearance
- When a cell is not dividing - grainy
- Preparing for division - DNA in each is copied or duplicated
- During division – Condense
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Endomembrane System
- A series of interacting organelles between the nucleus and the plasma membrane
- Its main function is to make lipids, enzymes, and proteins for secretion or insertion into cell membranes.
- It also destroys toxins, recycles wastes, and has other specialized functions.
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Endomembrane System (Make up)
- Nucleus
- Rough ER
- Vesicles
- Smooth ER
- Golgi Body
- Plasma Membrane
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Rough ER
- Contains ribosomes which synthesize polypeptide chains, which extrude into the interior of the ER.
- The proteins fold and take on their tertiary structure.
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Smooth ER
- Has no ribosomes
- Uses enzymes to make the cell membrane lipids.
- Breaks down carbohydrates, fatty acids and some drugs and poisons
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Vesicles
- Small membrane enclosed saclike organelle.
- Transport substances from one organelle to another or to and from plasma membrane
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Golgi Body
- Sort modify and transport proteins
- Attach phosphate groups
- Cleave polypeptide chains
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Lysosomes
Vesicles that contain powerful digestive enzymes to digest the content of vacuoles carrying particles or molecules for disposal
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Central Vacuole
Keeps plant cells and structures firm
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Cytoskeleton
- Basis of eukaryotic cell shape, internal structure and movement
- Interconnected system of many protein filaments
- Reinforce, organize and move cell structures and the whole cell
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Microtubules
- Long hollow cylinders that consist of subunits of the protein tubulin
- For dynamic scaffolding for many cellular process, rapidly assembling when they are needed, disassembling when they are not.
- Example:
- Form in the growing end of a young nerve cell support and guide its lengthening in a particular direction
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Microfilaments
- Fibers that consist primarily of subunits of the globular protein actin
- Strengthen or change the shape of eukaryotic cells
- Make up the cell cortex
- Example:
- Microfilaments of myosin and actin interact in muscle cells to bring about contraction
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Intermediate filaments
- Strengthen and maintain cell and tissue structures
- Example:
- Lamins form a layer that structurally supports the inner surface of the nuclear envelope.
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Kinesin
A motor protein used to move chloroplasts toward or away from a light source
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Dynein
A motor protein used to bend a flagellum
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Primary wall
The main constituent of a plant’s primary cell wall
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Secondary wall
Layers of firm material secreted onto the primary cell wall’s inner surface that strengthen the wall and maintain its shape
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Tight junctions
Seal abutting cells that line the outer surfaces and internal cavities of animals so no fluids can pass between them
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Adhering junctions
Anchor cells to each other and to the extracellular matrix
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Gap junctions
Open channels that connect the cytoplasm of neighboring animal cells
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Plasmodesmata
Cytoplamic channels that cross the cell walls and join neighboring plant cells
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Middle lamella
A sticky layer in between the primary walls of adjoining cells
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Pectin
Substance a young plant cell first secretes onto the outer surface of its plasma membrane
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Cellulose
The main constituent of a plant’s primary cell wall
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lignin
A strong waterproof component of the secondary cell walls of older stems and roots
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Cuticle
A protective body covering made of cell secretions
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Extracellular matrix (ECM)
Nonliving mixture of fibrous proteins and polysaccharides surrounding the cells that secrete it
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