Biology Notes- pt. 2

Endoplasmic Reticulum (ER)

A network of membranous channels

• located near the nucleus

• 2 types:

1. Rough ER

• has ribosomes

• PRODUCES PROTEINS

2. Smooth ER

• has a smooth surface

• PRODUCES LIPIDS

Golgi Complex

Looks like the smooth ER

• highly specialized

• 3 functions:

1. Separate proteins and lipids from the ER according to their destination

2. Modifies some molecules

3. Packages material into vesicles

Mitochondria

Found in both plants and animals

• captures energy from food molecules as high energy bonds of ATP

• a double membrane bound organelle

Chloroplast

Found ONLY in plants and some bacteria

• convert the suns energy into high energy bonds of glucose

• a double membrane bound organelle

Lysosomes

Intercellular digestion

• contain digestive enzymes

• Used to break down food particles

Plastids and Vacuoles

Both used for storage

Plastids:

• double membrane (chloroplast)

• Used to store

1. Pigments

2. Poisons

3. Sugars (starch)

Vacuoles:

• contain water

• Single membrane

• Have both temporary and permanent functions

Cytoskeleton

Protein fiber network

• most organelles attach to it

Includes:

1. microtubules (thick)

2. Intermediate filaments

3. Microfilaments (thin)

Functions:

1. Provides shape to cells with no cell wall

2. Aid in cell movement

3. Move organelles from one place to another

4. Essential in cell division

Cilia and Flagella

Both are whiplike extension of the PM

Cilia:

• short and numerous

• Stiff rowing motion

• Humans = smoking pretty much kills it

Flagella:

• long and few

• Whiplike motion

• Humans = sperm

Plasma Membrane

Functions:

1. Isolates the cytoplasm from the external environment

2. Regulates the flow of material between the cytoplasm and the external environment

3. Allows interaction with other cells

4. Identifies the cells as belonging to the same species as

Fluid Mosaic Model

The phospholipid

• hydrophilic head

• hydrophobic tails

Cholesterol is bound to phospholipids

• Provides stability and integrity

Protein Mosaic Model

Many membrane proteins are bound in the membrane

• membrane proteins are held in place by interactions between amino acids

3 categories:

1. Transport proteins

• regulate the movement of most water soluble molecules through the plasma membrane

2. Receptor proteins

• acts as molecular triggers that set off

• cellular responses when specific molecules bind to them

3. Recognition proteins

• act as cellular ID tags

Transport across membranes

Fluids:

Any substance that can change shape in response to environmental forces without breaking apart

Concentration:

The number of molecules per unit volume

Gradient:

Any physical difference between two regions of space so that molecules tend to move from one to the other

Concentration Gradient:

A physical difference in the number of molecules per unit volume between two regions of space so that molecules tend to move from one to the other other

Movement of Molecules

Molecules in a fluid are in constant motion