 Cells are basic units of living organisms.

 The cell theory has three parts:  1. All organisms are made of one or more cells.  2. The cell is the basic unit of structure and organization of organisms.  3. All cells come from preexisting cells. (cells divide and make more cells)

 All cells contain small specialized structures called organelles. Many organelles are surrounded by membranes. Each organelle has a specific function in the cell.

 A cell with membrane-bound organelles is a eukaryote cell. A eukaryote has a nucleus.  A Prokaryote cell has no membrane-bound organelles. A prokaryote has no nucleus.

Which one is the prokaryote? Which one is the eukaryote?

 The nucleus is the central organelle that controls all cell functions.  The nucleus is “the brain” of the cell.  The nucleus has a special membrane called a nuclear envelope.

 The plasma membrane is the flexible boundary between cells and their environments (like your skin is the boundary between you and the world).  The plasma membrane controls what nutrients come in and out.

The Plasma Membrane It looks complicated…but it has too be able to let certain things in and keep certain things out.

 Plant cells have a rigid protective structure around the cell called the cell wall. The plant cell wall is made of cellulose.  This cell wall gives plant cells more of a square appearance.

 Chloroplasts are found only in plant cells.  Chloroplasts are organelles that do photosynthesis in plants.

 Cytoplasm is the clear, gelatinous fluid inside a cell.  All the organelles float around in the cytoplasm.

 The cytoskeleton is the framework for the cell (similar to your skeleton).  The cytoskeleton is made of microtubules (thin, hollow cylinders made of protein) and microfilaments (small solid protein fibers).

 The endoplasmic reticulum (or ER) is the organelle where chemical reactions occur (making proteins, lipids, and storing nutrients).  The ER is the folded organelle outside the nucleus.

 There are two types of ER (rough and smooth). The difference is ribosomes are on the rough ER.  Ribosomes make protein in the cell.

Rough or Smooth ER?

 The Golgi apparatus is a flattened sack of tubular membranes that package proteins into little bags called vesicles.

Vesicle Golgi Apparatus

 Lysosomes digest worn out organelles, food particles, viruses, and bacteria.  Lysosomes fuse with vacuoles and dispense their waste into the vacuole.

 A vacuole is a temporary storage sack.  The vacuole stores food, enzymes, and waste products given to it by the Lysosomes.  Animal cells usually do not have vacuoles, but plant cells have very large vacuoles.

 The mitochondria are membrane- bound organelles that make energy for the cell.  Some cells (like muscle cells) have more mitochondria because they need more energy.

 The nucleolus is an organelle inside the nucleus which makes ribosomes.