Cell Organelles and Features

Plasma/Cell Membrane• Found in both prokaryotes and eukaryotes• Structure:• Composed of: phospholipids, cholesterol, and proteins• Organization:

• Phospholipids form a bilayer• Proteins and cholesterol are embedded in the bilayer

Cell-Membrane = Fluid Mosaic Model• Membrane’s lipids and proteins move laterally within the

bilayer• The “pattern” of the mosaic is always changing

Function of the Membrane Components1. Phospholipids

a. Control what enter and exit the cellb. Give structure to the cell

2. Proteinsa. Control what enter and exit the cellb. Interact with external environmentc. Facilitate chemical reactionsd. Receive signals

3. Cholesterola. Maintain fluidity of cell

Nucleus• Structure:

1. Nucleoplasm2. Nuclear envelope with nuclear pores

• Double membrane3. Nucleolus

• Contains DNA

Functions of Nucleus

1. Nucleoplasm• Surrounds and protects DNA

2. Nuclear envelope and nuclear pores• Controls what enters and exits the nucleus

3. Nucleolus• Production of ribosomes (structures that synthesize proteins)

Ribosomes• NOT technically organelles• Made of proteins and RNA, but have NO membrane• Some ribosomes are free-floating in cytoplasm others are

bound to the endoplasmic reticulum

Endoplasmic Reticulum (ER)• Structure: system of membranous tubes and sacs (cristernae)

• Two types of ER: Rough and Smooth• Rough ER is covered with ribosomes• Smooth ER lacks ribosomes

Function of the ER• Both types of ER serve as intracellular highway along which

molecules move from one part of the cell to the other

• RER • Produces phospholipids and proteins

• SER• Build lipids, such as cholesterol and steroid hormones• Detoxifies blood and poisons

Golgi Apparatus• Structure: system of flattened, membranous sacs• Function:

1. Modifies proteins that it receives from the RER 2. Exports protein to the appropriate location

Vesicles• Structure: • small, spherically shaped sacs• Surrounded by single membrane

• Vesicles are classified by their contents• Often migrate and merge with plasma membrane to release

contents

• Types of Vesicles: lysosomes, peroxisomes, glyoxysomes, endosomes

Lysosomes• Contain digestive enzymes

• Created by the Golgi apparatus

• Responsible for breaking down cells when it is time for the cell to die = autolysis

Food Vacuoles are referred to as endosomes

Peroxisomes• Contain enzymes that breakdown alcohol and drugs into

peroxide (H2O2)• Neutralize free radicals

• Not created by the Golgi apparatus

• Special type of peroxisome = glycoxysomes• Found in seeds of some plants

Ribosomes, ER, Golgi, and Vesicles all play a role in protein synthesis1. Proteins are assembled by ribosomes on the RER2. Vesicles transport proteins to the Golgi apparatus3. Golgi modify proteins and package them into new vesicles4. Vesicles fuse with the plasma membrane to release proteins

outside the cell5. Vesicles containing enzymes that remain inside the cell form

lysosomes, peroxisomes, endosomes, etc.

Mitochondria• Structure: • Outer and inner membrane

• Inner membrane has many folds = cristae• Contain DNA

• Function: transfer energy from organic molecules to ATP (cellular respiration)

Cytoskeleton• Structure: Network of thin tubes and filaments that crisscross

in the cytosol

• Three major components:1. Microtubules2. Microfilaments3. Intermediate filaments

• Function:1. Give shape and support to the cell2. Acts as a system of internal tracks for intracellular movement

Cytoskeleton

Cilia and Flagella• Structure: Hairlike structures that extend from the surface of

the cell• Part of the cytoskeleton• Function: Assist in movement

Centrioles• Structure: two short cylinders of microtubules at right angles• In the cytoplasm near the nuclear envelope

• Part of the cytoskeleton of animal cells

• Function: organize microtubules during cell division

Do all cells contain all of these organelles in the same concentration?

What organelle(s) would you find a lot of in muscle cells?

What organelle(s) would you find a lot of white blood cells?

What organelle(s) would you find in a skin cell?