structure and function of the cell. cells make up all living things
TRANSCRIPT
CELL THEORY
1674 – Anton Van Leeuwenhoek - first to look at living cells
- saw “animalcules” or little animals
CELL THEORY
1838 – Schleiden - All plants are made of these Cells
1839 – Schwann - All animals are made of these cells
1855 – Virchow –Noticed that Cells make more of
themselves.
FINAL CELL THEORY
• All living things are made up of one or more cells
• Cells are the basic unit of structure and function in living things
• Cells come from previously existing cells – NO spontaneous generation!
Prokaryotes Vs. Eukaryotes
Prokaryotes:
- literally means “before nucleus”
- primitive single celled life, the first!
- example: bacteria
- still has DNA just not enclosed in a nucleus
Prokaryotes Vs. EukaryotesEukaryotes:
- literally means “true nucleus”
- DNA enclosed by the nuclear membrane
- Can be single celled like protists (amoebas, paramecium)
- Or can be part of a multicellular organism like: plants, animals or fungi
Prokaryotes Vs. EukaryotesEukaryotes:
- significantly larger than prokaryotic cells
- have many more organelles than prokaryotic cells
How do we study cells?
• Microscopy – using a device that magnifies an image of a very small specimen
– Magnification:
– Resolution:
Light microscopy
• Pros: more affordable– Easier prep– Can observe living cells
• Cons: – More limited in terms of
Mag/Res
Electron microscopy
• Pros: – Significantly greater
mag/res
• Cons: – Specimen Prep is much
more involved– Specimen prep will kill
specimen, no live observations
All cells must perform the same few functions to stay alive
BUT, since they have different organelles, they might go about it differently
I. All cells must control what enters and exits a cell
II. All cells must convert the energy in nutrients to into energy it can use
III. All cells must make, modify and ship proteins to where they need to go
IV. All cells must be able to store nutrients, digest large molecules and recycle damaged organelles
V. All cells must grow and divide
VI. All cells have a particular shape and can move IF THEY NEED TO
Plasma Membrane
Phospholipid bilayer that surrounds all cells and certain organelles within the cell
Double layer allows:
• All hydrophobic parts to be away from water
• All hydrophilic parts to be near water
Plasma membrane contains:
Proteins embedded in phospholipid bilayer;
Cholesterol tucked between fatty acids
Carbohydrate chains
Why proteins?
• Proteins increase contact with water and act as channels through which certain molecules can pass
Why cholesterol?
• Cholesterol keeps the membrane fluid and flexible; prevents solidification
Why Carbs?
Carbohydrate chains act as cell “ID” tags.
Fluid Mosaic Model: theory that describes the composition of the membrane
- Fluid because it is flexible; p-lipids and proteins can shift position
- Mosaic because it is made of many small molecules that work together as a whole
Membrane acts as a semi-permeable barrier (think bouncer!)
some stuff passes right through the phospholipids:
- small, hydrophobic, uncharged
some stuff can’t:
- ions (Na+, Cl-, K+, Ca++) - polar molecules (Sugars, Amino Acids)
- large nonpolar
But don’t we need these?!?! We’re getting there….
There are two general categories of transport:
Passive transport: The easy way; no energy required; molecules just flow
naturally across
Active Transport: the hard way; energy required; molecules need to
be pushed or carried across
Passive Processes: No energy needed
• Diffusion: Movement of solutes from areas of high concentration to areas of low concentration until concentrations are equal.
• Concentration Gradient = differences in Concentration
Facilitated Diffusion – movement of solute from high concentration to low concentration BUT requires
transport protein to move molecule that are too big or polar to get
through the bilayer on their own
Glucose is too big to fit through phospholipids and will be diffused through a transport protein to get
into the cell
Osmosis – A Passive Process where water moves across a cell membrane from an area that is hypotonic (lots of water, little solute) to an area that is hypertonic (little water, lots of solute)
think of the water as trying to dilute the concentrated side to make the concentration even
Weak Iced Tea Strong Iced Tea
Move water until you get
Two perfect Iced teas
Tonicity – term used to compare the concentration of one solution to another
- will determine where water goes
3 ConditionsHypotonic
Isotonic
Hypertonic
The solution with the higher concentration is called Hypertonic.
The solution with the lower concentration is called Hypotonic
If the concentrations are equal, they are called isotonic
PlasmolysisVs.
Turgidity in Plant cells
- Turgor pressure: Pressure that the water INSIDE the cell puts on
the cell wall. Supports plant
Active TransportCell must use energy to force molecules to move across the
membrane from a low concentration to a high
concentration. Usually used to move ion and since ions can not go through the phospholipids requires a transport protein
Active Transport:
Vesicle Transport
Vesicle transport is different from Diffusion, Osmosis, facilitate diffusion and active transport in that we are moving large quantities (many molecules) rather than individual molecules. The cell must package the material in a vesicle and bring it in or out of the cell depending on the goal.
• Making a vesicle requires the cell to exert energy in the form of ATP, but we don’t have to concern ourselves with concentration differences. The two types of vesicle transport depend on direction -
• Moving materials into a cell in a vesicle is called endocytosis. Moving materials out of a cell is called exocytosis.
Phagocytosis: “cell eating” large proteins, dead cells, bacteria substances WAY too big for even a protein;
Making/moving a vesicle requires energy ATP
Pinocytosis: Cell drinking; bulk ingestion of liquids
Particularly important in kidney and intestinal cells
Exocytosis – Bulk Transport out of cell
Way of releasing large quantities of stuff from the cell including : Hormones, mucus and cell wastes
NEEDS ATP