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