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Cells & Cell TransportCell and Cell Transport
The Cell Theory
Is the result of work done by many scientists:
Hooke (named cells)
Leeuwenhoek (microscope)
Schwann (animal cells)
Schleiden (plant cells)
Virchow (cell division)
All living things are made up of cells
The basic unit of structure and function for living things is the cell
All cells come from other cells
Microscopes
Three major types of microscopes:
light microscope (LM)
scanning electron microscope (SEM)
transmission electron microscope (TEM)
The type of microscope used depends on what you want to see
A photo taken by a microscope is called a micrograph
MicroscopesMagnification Pros Cons
Light(LM)
Uses lightMagnification depends upon type of LM
Color micrographsLiving specimensRange of usesAffordable ($, time)
Magnification not always enough
Transmission(TEM)
Uses e- traveling through specimen
Very high mag
Can see extremely small things
Prep timeExpenseSpecimens usually not alive
Scanning(SEM)
Uses e- bouncing off surface of specimenVery high mag
Can see extremely small things
Prep timeExpenseSpecimens usually not alive
Electron Microscopes
Micrographs
Prokaryotes vs. EukaryotesNo nucleus (nuclear membrane)
Smaller in size
Circular DNA (plasmid)
Simple in structure, small organelles, few organelles
Usually have a cell wall and/or a capsid
Often have flagella for motility
Include both eubacteria & archaebacteria
Has a nucleus (nuclear membrane)
Larger in size
Larger thread like DNA (chromatin/chromosomes)
Larger, more specialized organelles, more organelles
Mitochondria and Chloroplasts (plastids) can exist inside these cells
Include all other organisms (plants, animals, fungus and protists)
Cell Membrane
Cell membrane (plasma membrane): a phospholipid bilayer surrounding the cell
Each phospholipid has a polar phosphate head and lipid tails
Cytoplasm
AKA protoplasm
The watery environment of the cell where all cell activity takes place
Made up of mostly water, with ions, proteins, and other compounds
Cytoskeleton
A network of fibers throughout the cytoplasm called microfilaments and microtubulesThey provide structure to the cell, points of attachment for organelles (MT), and are used in cell movement (MF)
Cytoplasmic Streaming Animation
http://www.youtube.com/watch?v=7pR7TNzJ_pA
Nucleus
Surrounded by a nuclear membrane AKA nuclear envelope which is a bilayer like the cell membrane
Contains nuclear pores for transport in and out of the nucleus
Chromatin
Made up of sections of DNA called genes
Uncurled: chromatin
Curled up for transport: chromosomes (these are stained & visible under a microscope)
They do not leave the nucleus
Nucleolus
Found inside the nucleusA mass of RNA, not an official membrane bound organelle like the rest described here‘Disappears’ during cell divisionRNA can leave the nucleus for protein synthesis
Centrioles
(AKA centrosomes)Lay just outside the nucleus, made up of microtubules Involved in cell division (although they are not present in plant cells)Replicate into two centrioles before cell division and migrate to opposite ends of nucleus
Endoplasmic Reticulum
Can be rough (with ribosomes attached) or smooth (no ribosomes)
Functions include: transportation (rough ER), toxin breakdown and phospholipid production (smooth ER)
Ribosome
Can be free (in the cytoplasm) or bound (found on the rough ER)Made up of two subunits (large & small), equal parts protein & RNAThe location of protein production (the site of protein synthesis)
Golgi Body
AKA golgi apparatusResponsible for protein processing which includes:*marking proteins with their destination location
*preparing proteins to become active and able to do their job (ex: enzyme folding)
MitochondriaOften called the ‘powerhouse’ of the cell, has a 2nd inside membrane AKA the cristaeIt generates ATP from glucose moleculesContains its own DNA unlike every other organelle in the cellIs thought to have once lived on its own
Vacuole
Used for storage for a variety of things including food, waste, and proteins to be transported out/around the cellA moving vacuole is called a vesiclePlants have a large central vacuole for water storage to keep the shape of the plant cell
Lysosome
A vacuole containing digestive enzymesThey fuse with vacuoles containing substances to be broken down (food, waste, invading bacteria) AKA suicide sacs because if they leak their enzymes, the cell can be damaged
Cell Wall
Found in bacteria, fungus, plant, and some protistsMade up of cellulose in plant cellsAdds extra security/protection and/or provides structure (shape) for cells
Flagella and CiliaUsed for movement in some protist and animal cells, made of microtubulesFlagella are whip like tails (one or more) for movement much like a tail is used for swimming by fishCilia are hair like extensions (circular movement is like that of a bullet)
Video comparing flagella and cilia movement:
http://www.youtube.com/watch?v=QGAm6hMysTA
Chloroplasts
Contain chlorophyll (green, yellow, red color)Only found in cells that do photosynthesis (plants, some protists, some bacteria)Like mitochondria, they contain their own DNA and are thought to have lived as single celled organisms at one time
Plant vs. Animal Cells
No centrioles for cell divisionA large central vacuoleCell wall of cellulose to help maintain square shapeChloroplasts containing chlorophyll for photosynthesis
Use centrioles for cell divisionNo central vacuole
No cell wall
No chloroplasts, no chlorophyll, no photosynthesis
The Cell Membrane in Detail
Fluid Mosaic Model
The cell membrane used to be thought of as a solid layer
Now it is known as the fluid mosaic model: it can move (fluid) and it has many parts (a mosaic) including proteins, carbohydrates, & lipids
The cell membrane is semi-permeable (aka selectively permeable)
http://www.youtube.com/watch?v=LKN5sq5dtW4
Components of the Cell Membrane
Structure Function
Phospholipids Make up bulk of membraneMainly hydrophobic (nonpolar)
Protein channels Faciliated diffusion of hydrophilic (polar) substances
Protein carriers (pumps)
Active transport of substances against their concentration gradient
Cholesterol (lipid) Cell membrane fluidity/rigidity
Oligosaccharides (carbohydrates)
Attached to proteins for cell signaling (cell communication)
Two Types of Transport
Passive Transport
Does not require energy to be used by the cell
Typically involves small particles moving down the concentration gradient (high to low concentration)
Active Transport
Requires energy to be used by the cell to move the substance
This is due to either the very large size of the item
OR that the cell is moving it against (up) its concentration gradient (low to high)
Solutions
Solution: a well mixed mixture
Solute: what is mixed into the solution
Solvent: what the solute is mixed into
Passive Transport
Diffusion
The movement of a substance from HIGH concentration to LOW concentration
Facilitated diffusion: diffusion through a protein channel
Passive Transport
Osmosis: the diffusion of water across a semi-permeable membrane
Tonicity
Hypertonic: when one solution has more solute than the other
Hypotonic: when one solution has less solute than the other
Isotonic: when both solutions have the same amount of solute
Dynamic Equilibrium: all solution pairs attempt to reach an isotonic state of equilibrium, particles are constantly moving
Tonicity
Tonicity
80% water
20% NaCl
90% water
10% NaCl
Which way will the salt move…in or out of the cell?
Which way will the water move…in or out of the cell?
Tonicity
92% water
8% NaCl
90% water
10% NaCl
Which way will the salt move…in or out of the cell?
Which way will the water move…in or out of the cell?
Tonicity
82% water
18% NaCl
82% water
18% NaCl
Which way will the salt move…in or out of the cell?
Which way will the water move…in or out of the cell?
What do we call these two solutions?
Tonicity
A cell in a hypotonic solution could take in so much water that it bursts
This is known as lysis (cell dies)
A cell in a hypertonic solution could lose so much water that it significantly shrinks
This is called plasmolysis and can lead to cell death
Tonicity
Tonicity
Active Transport
Protein carriersAka protein pumpsCarries substances up (against) their concentration gradient (from LOW concentration to HIGH concentration)
Endo/exocytosis p.122Aka phago (solids) & pinocytosis (liquids)The movement of very large substances with the use of microfilaments under the cell membrane and vacuoles/vesicles
EndocytosisA form of active transportSubstance is too large to go through normal cell membrane channelsMicrofilaments help cell to move around the substance and engulf itPhagocytosis vs. Pinocytosis
Amoeba eating using endocytosis:
http://www.youtube.com/watch?v=W6rnhiMxtKU
Active Transport: Endo/Exocytosis
http://www.youtube.com/watch?v=XV8jawQwRaghttp://www.youtube.com/watch?v=1w10R9lv7eQ
Active Transport: Protein Carriers/pumps
Protein carriers/pumps:
Passive vs. Active Transport
http://www.youtube.com/watch?v=1ZFqOvxXg9M