A&p

Front 1

Cell

Back 1

• The basic unit of all living things
  
• Two primary classifications found in nature
  
• Prokaryotic Cells
  
• Eukaryotic Cells

Front 2

Prokaryotic Cells

Back 2

• Simplest form of cells
  
• Pro ("before") karyon ("nucleus") - have no true nucleus.
  
• Most are unicellular bacteria
  

Front 3

Eukaryotic Cells

Back 3

• Eu ("true") karyon ("nucleus")
  
• complex cells with a true membrane bound nucleus and organelles
  
• All fungi, plants, and animals are eukaryotes.
  

Front 4

A generalized cell

Back 4

• All cells have some common structures and functions
  
• All eukaryotic cells are composed of 3 main parts:
  

1. Plasma membrane
   
2. Cytoplasm
   
3. Nucleus - contains the DNA
   

Front 5

The Plasma Membrane

Back 5

• Forms the cell's outer boundary
  
• Separates the cell's internal environment (intracellular) from the outside environment (extracellular)
  
• Selectively permeable barrier
  
• Allows the passage of some substances but not others.
  
• Also involved in many other functions.
  

Front 6

The Cytoplasm

Back 6

• A gelatin-like substance plus structural fibers and organelles.
  
• Contains all the cellular contents between the plasma membrane and the nucleus.
  
• Nucleus not considered part of the cytoplasm
  
• Cytosol
  
• the fluid portion (mostly water)
  
• Organelles are structures embedded in the cytosol. They have characteristic shapes and specific functions.
  

Front 7

The nucleus

Back 7

• Large organelle that contains the DNA of a eukaryotic cell
  
• DNA forms large molecules called chromosomes
  
• Each chromosome consists of DNA and associated packaging proteins
  
• Chromosomes can contain thousands of hereditary units called genes
  

--- genes contain the structure for making proteins.

Front 8

Plasma Membrane (2)

Back 8

The plasma membrane is much more than just a "fence" separating the outside and inside of the cell, it also:

• Covers and protects the cell
  
• Controls what goes in and comes out
  
• forms psychical links to other cells
  
• Files certain "flags" to tell other cells "who" it is
  

Front 9

Fluid Mosaic Model

Back 9

• This model describes the arrangement of molecules within the membrane
  

They remember a sea of phospholipids with proteins and other molecules floating in it.

• The phospholipids and the thick, nonpolar region that they form in the middle of the bilayer act as a barrier to most polar substances.
  
• Proteins act as "gatekeepers", allowing passage of specific molecules and ions in and out of the cell that cannot cross through the bilayer directly.
  
• Other molecules found have various roles in membrane function
  

Front 10

The Structure of the Membrane

Back 10

Phospholipids

• Form the majority of the lipid bilayer
  
• called bilayer because they are arranged in double layer form.
  
• Cholesterol and glycolipids (carbohydrates bound to lipids) also contribute to membrane fluidity and structure.
  

Front 11

Selective Permeability

Back 11

• Due to the arrangement and type of lipids that compromise the membrane, the lipid component of the bilayer allows some substances across but not others.
  
• Rule of thumb:
  
• Small, neutrally charged and lipid soluble substances can freely pass.
  
• Water is a special case - it is highly polar, yet still permeable
  
• However, only permeable to a certain rate as only so much water can pass per unit time.
  

Front 12

Pass Easily

Back 12

1. Water (unique)
   
2. gases
   
3. small, fat-soluble molecules
   

Front 13

Mild Pass

Back 13

1. charged ions (K+, Na+, Ca++, HPO4-, etc)
   

Front 14

Don't Pass

Back 14

1. Large, water-soluble molecules (e.g. proteins)