Bio Study Guide Cell Theory and Membranes Essay

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CELL THEORY AND MEMBRANES
Cell Theory
Hooke: First to look at cells (dead cork)
Leevwenhoek: first to look at living cells (pond water) Determined organisms live in peoples’ mouths.
Dutrochet: “All things are made of cells”  had no/little support
Brown: Discovered the nucleus of cells
Dujardin: Discovered the cytoplasm
Schleiden: all plants are made up of cells
Schwann: all animals are made of cells
Virchow: all cells come from previous living cells
Cell Theory:
1. A cell is the smallest unit capable of performing the functions of life
2. All organisms are composed of cells
3. All cells come from pre-existing cells
Membranes
-Made up of phospholipids, cholesterol, proteins, glycolipids, glycoproteins
-Controls what goes/comes into and out of the cell
-Selectively permeable (semi permeable)
Fluid Mosaic Model:

Mosaic- membrane is made up of several components
Fluid- constantly moving
**Phospholipids move very fast, proteins move slowly**
How a membrane maintains fluidity
-A membrane needs to be fluid in order to allow substances to cross it
-If the membrane is TOO fluid  all substances can pass through
-If the membrane is TOO solid  nothing can pass through
Phospholipids- cell can change the fatty acid tails
-More saturated  more solid
-More unsaturated  more liquid/fluid

Cholesterol-
-Acts as a temperature buffer
-Cold temperatures helps prevent tight packing of phospholipids
-Hot/warm temperatures restricts the uncontrolled movement of phospholipids
Glycolipids and Glycoproteins function-
-Cell recognition
- Immune system needs to be able to identify body cells from foreign invaders Molecule Characteristics 1. Nonpolar passes more easily than polar 2. Liquid soluble passes easily 3. Smaller molecules pass more easily than larger molecules 4. Substances that are uncharged pass through more easily than charged substances
Passive Transport
-Movement of a substance without the use of energy
-Movement from a region of a high concentration to low concentration
-Moving towards equilibrium
**Water always uses passive transport**
Concentration Gradient- difference in concentration of a substance between the 2 sides of the membrane (outside and inside of cell)

Diffusion- tendency of molecules to spread out

Facilitated Diffusion- special type of diffusion that moves molecules from highlow concentration with the help of proteins
-Channel Protein: Hollow core that creates a passage from one side of the membrane to another

-Carrier Protein: When the substance comes into contact with the protein, there is a change in the shape that allows the protein to literally carry the substance across the membrane
Osmosis- diffusion of water
-movement of water from high concentration of waterlow concentration of water

Dynamic Equilibrium- molecules are still moving but no net change in concentration
Osmoregulation- balance of water within organisms
Types of Solutions
-Hypotonic: Solution with a lower solute concentration
-Hypertonic: Solution with a higher solute concentration
-Isotonic: Solutions that have equal solute concentrations

Hypotonic
Hypertonic
Isotonic
Animal Cell
-H2O moves into the cell
-Possibility or cell bursting (lysis)

-Loses H2O
-Cell shrinks/ crispy/ hard (crenation)
-Dynamic Equilibrium
-Molecules still move but no net change in concentration
-Ideal environment

Plant Cell…