The Cell Wall

1. The Cell Wall Cell wall: a rigid structure that gives support to the cell. Cell walls are made of different materials: some plant cell walls are made of a complex sugar called cellulose. Animal cells do not have cell walls

2. Cell Membrane All cells have a cell membrane made up of proteins and lipids. Cell membrane: is a protective barrier that encloses a cell. It separates the cell’s contents from the cell's environment, and is the outer most structure in cells that lack a cell wall. Cell membrane: has two layers of phospholipids.

3. Cell Membrane Each phospholipid has a hydrophobic, or water fearing end and a hydrophilic, or water loving end. Hydrophobic tails Hydrophilic heads

4. Cell Membrane Some materials, such as nutrients and wastes, must pass through the cell membrane. These materials are able to pass through passageways made of proteins. Nutrients move into the cell—and wastes move out of the cell—through these protein passageways.

5. The Cytoskeleton Cytoskeleton: a web of proteins in the cytoplasm of some cells. Both plant cells and animal cells have a cytoskeleton. The cytoskeleton is a network of protein fibers that anchors the cell’s organelles and other components of its cytoplasm. Microfilaments are also used to move objects around within the cell.

6. The Nucleus All eukaryotic cells have a membrane-bound nucleus. Nucleus: is a large organelle that contains the cell’s DNA. DNA is the genetic material that contains the instructions on how to make a cell’s proteins, and its the Proteins that control the chemical reactions within the cell. They also provide structural support for cells and tissues. However, proteins are not made in the nucleus. Instructions on how to make proteins are given by the DNA and sent out of the nucleus through the membranes that surround it. The nucleus is covered by two membranes. Materials cross this double membrane by passing through pores.

7. The dark area of the nucleus is called the nucleolus (nooKLEEuhluhs). Ribosomes are made partly in the nucleolus. What is the purpose of the nucleus?

8. Ribosomes Ribosome: organelles that make proteins. Ribosomes are the smallest of all the organelles, and there are more ribosomes than there are any other organelles in a cell. Ribosomes make proteins by assembling chains of amino acids. Amino acids are organic molecules that are used to make proteins. All cells need proteins, thus all cells have ribosomes.

9. Endoplasmic Reticulum Endoplasmic Reticulum (ER): is a system of folded membranes in which proteins, lipids, and other materials are made. The folded part of the ER contains many tubes and passageways. Substances move through the ER to different places in the cell. The ER is either smooth or rough. The part of the ER covered by ribosomes is rough ER, and is usually found near the nucleus. Ribosomes on the rough ER make many of the proteins the cell needs. The ER then delivers these proteins throughout the cell. The smooth ER make lipids and break down toxic materials that could damage the cell.

10. Endoplasmic Reticulum

11. Mitochondria Mitochondria: the main power source of a cell. It is the organelle in which sugar is broken down to release energy Mitochondria are covered by two membranes. Energy released from this organelle is stored in a substance called ATP (adenosine Triphosphate). The cell then uses ATP to do work. ATP can be made at several places in a cell, but most of a cell’s ATP is made on the inner membrane of the cell’s mitochondria. Mitochondria is common to most eukaryotic cells, and they have their own DNA. Additionally, mitochondria can divide within a cell.

13. Chloroplasts Chloroplasts: organelles in which photosynthesis takes place. They are found in plant, algae, and some prokaryotic cells. Like mitochondria, chloroplasts have two membranes and contain their own DNA. Chloroplasts are green because they contain chlorophyll, a green pigment. Chlorophyll traps the energy of sunlight, which is used to make sugar. The sugar is then used by mitochondria to make ATP.

15. The Golgi Complex Golgi Complex: organelle that packages and distributes proteins. The Golgi complex looks like a smooth ER. Lipids and proteins from the ER are delivered to the Golgi complex, which then modifies the lipids and proteins to do different jobs. The final products are enclosed in a piece of the Golgi complex’s membrane. The membrane then pinches off to form a small bubble. The bubble transports its contents to other parts of he cell or out of the cell.

16. The Golgi Complex

17. The Golgi Complex

18. Vesicles Vesicle: is a small sac that surrounds material to be moved into or out of a cell. All eukaryotic cells have vesicles, and they also move some materials within the cell itself. Vesicles carry new proteins from the ER to the Golgi complex. Other vesicles carry material from the Golgi complex to other parts of the cell. Some vesicles form when apart of he cell membrane surrounds an object that is outside the cell. The electron tomogram of a complete yeast cell reveals the cellular architecture. It shows plasma membrane, microtubules and light vacuoles [green], nucleus, dark vacuoles and dark vesicles [gold], mitochondria and large dark vesicles [blue] and light vesicles [pink].

19. Lysosomes Lysosomes: are vesicles found mainly in animal cells; they contain digestive enzymes and are responsible for digestion in side a cell. Lysosomes destroy worn-out or damaged organelles, get rid of waste materials, and engulf foreign invaders. The foreign invaders are digested, and most of them are no longer harmful to the cell.

20. Vacuoles Vacuole: a type of vesicle found in cells. In plant and fungal cells, some vacuoles ac like lysosomes by storing digestive enzymes, thus aiding in digestion within the cell. The large central vacuole in plant cells stores water and other liquids. Some plants wilt when their large central vacuoles lose water