Eukaryotic cells have a nucleus; prokaryotic cells do not.

The plasma membrane is made of a bilayer of phospolipids (see Large Biological Molecule cards). It acts as a barrier and gateway between the cell and the outside. Cells strive to maximize surface area while minimizing volume. 

The cytoplasm is everything within the plasma membrane. The cytosol is the aqueous area in the cytoplasm. 

The nucleus contains:

• The nucleur envelope, a double membrane connected by nucleus pores
• The nucleus lamina, a net of proteins around the inside wall of the nucleus which helps to hold structure.
• Chromatin (sing. chromosome)
• The nucleolus, which creates the large and small subunits of ribosomes.

The nucleus is the HQ of the cell and participates in transcription of mRNA molcules from DNA, which are used in protein synthesis.

Ribosomes are made from a large and small subunit of proteins created it the nucleolus of the nucleus. 

Ribosomes are the protein factory. mRNA from the nucleus is translated here by the rRNA. tRNA brings amino acid to the ribosome in the order with which the rRNA specifies.

Ribosomes are found floating freely in the cytosol and on the rough ER. Free ribosomes generally create proteins which will stay in the cytosol. Bound ribosomes often create secrotory proteins, membrane proteins, or proteins to function in other organelles.

The smooth ER is attached to the nucleur envelope and rough ER. It is found around the nucleus.

The smooth ER:

• synthesizes lipids
• metabolizes carbohydrates
• detoxifies drugs and poisons
• stores calcium ions 

The rough ER is deemed "rough," because of the ribosomes attached to it. It is con-fluent with the nucleur envelope and smooth ER.

The rough ER's ribosomes create secrotory proteins, membrane proteins and proteins to be used in other organelles. Many produced are "glycoproteins" - proteins with carbohydrate groups attached covalently.

The Golgi apparatus is a warehouse for transport vesicles, often containg protein. The apparatus can modify or direct the vesicles to other domains. Many proteins require to be sent to the Golgi apparatus to be modified before they are ready to work.

The "cis" face of the apparatus is the face facing the nucleus. The "trans" face is the opposite face.

Lysosome are vesicles containing digestive enzymes which hydrolyze polymers to break them down. The pH inside the organelle is low, thus it can be involved in cell self-destruction if too many break. They are found only in animal cells.

Lysosomes can also envelope damaged organelles or vesicles, break them down and recycle them in a process known as phagocytosis.

In many ways, it is like the central vacuole in plant cells.

The endosymbiont theory applies to mitochondria and certain other organelles. It hypothesizes that long ago eukaryotic cells enveloped certain prokaryotic cells (like the mitochondria and chloroplast) and eventually they become one.

This theory has support because certain organelles like the mitochondria contain their own DNA, double membrane, and floating ribosomes.

Mitochondria are the site of cellular respiration (O2 + sugars, etc. 

-> ATP).

Mitochondrion have a smooth outer membrane and a curved intermembrane with infoldings called cristae. Located inside the inner membrane is the mitochondrial matrix (similar to cytosol for cells). The matrix contains enzymes, DNA and ribosomes. 

Chloroplasts are the site of photosynthesis in plant cells.

They contain a double membrane. Inside the inner membrane is a third membrane shaped like stacks of poker chips, referred to as thylakoids. Each stack is called a granum. The fluid outside of the thylakoids is called the stroma.

Peroxisomes transfer H2 from various substrates and attach them to O2 to obtain H2O2. It then turns the H2O2 into H2O.

This reaction can take place for many reasons, including to break down fatty acids to send to the mitochondria or to detoxify alcohol.