Cell Organelle Notes Green Workbook P. 37

Nucleolus

A dark area in a nucleus which makes the ribosomes.

Mitochondria

A mitochondrion is the main power source of a cell. A mitochondrion is the organelle in which sugar is broken down to release energy. Mitochondria are covered by two membranes. Energy released by mitochondria 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. Most eukaryotic cells have mitochondria. Mitochondria are the size of some bacteria. Like bacteria, mitochondria have their own DNA, and mitochondria can divide within a cell.

Vacuole/Vesicle

A vacuole is another type of vesicle found in cells. In plant and fungal cells, some vacuoles act like lysosomes. They store digestive enzymes and aid in digestion within the cell. The large central vacuole in a plant cell stores water and other liquids. Large central vacuoles that are full of water help support the cell. Some plants wilt when their large central vacuoles lose water.

Cell Membrane

All cells have a cell membrane made up of proteins and lipids. The cell membrane is a protective barrier that encloses a cell. It separates the cell's contents from the cell's environment. The cell membrane is the outermost structure in cells that lack a cell wall. In cells that have a cell wall, the cell membrane lies just inside the cell wall. A phospholipid is a type of lipid. Each phospholipid has a hydrophobic, or "water fearing," end and a hydrophilic, or "water loving," end. The "water fearing" ends are on the inside of the cell membrane. This structure makes it difficult for materials to pass through the membrane. Not allowing materials to pass trough is one way the cell membrane protects the cell. 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.

Nucleus

All eukaryotic cells have a membrane-bound nucleus. The nucleus is a large organelle in a eurkaryotic cell. It contains the cell's DNA. DNA is the genetic material that contains the information on how to make a cell's proteins. Proteins control the chemical reactions in a cell. They also provide structural support for cells and tissues. But proteins are not made in the nucleus. Messages for how to make proteins are given by the DNA. These messages are then 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. In many cells, the nucleus has a dark area celled the nucleolus. A cell begins to make its ribosomes in the nucleolus.

Chloroplast

Animal cells cannot make their own food. Plant cells are different. Some of them have chloroplasts. Chloroplasts are organelles in which photosynthesis takes place. They are found in plant, algae, and some prokaryotic cells. Like mitochondria, chloroplasts have two membranes and their own DNA. Photosynthesis is the process by which cells, such as plant cells, use sunlight, carbon dioxide, and water to make sugar and oxygen. Chloroplasts are green because they contain chlorophyll, a green pigment. Chlorophyll is found in an internal membrane system within a chloroplast. Chlorophyll traps the energy of sunlight. This energy is used to make sugar. The sugar produced by photosynthesis is then used by mitochondria to make ATP.

Cytoplasm

Cytoplasm is the stuff inside a cell that makes up for the empty space that is not occupied by an organelle. It holds the cell's organelles. The cytoplasm is also jelly-like.

Lysosomes

Lysosomes are vesicles found mainly in animal cells. Lysosomes contain digestive enzymes. They are responsible for digestion inside 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. When eukaryotic cells engulf particles, they enclose the particles in vesicles. Lysosomes bump into the vesicles, shown in purple, and pour enzymes into them. These enzymes digest the particles in the vesicles.

Endoplasmic Reticulum (ER)

Many chemical reactions take place in a cell. Many of these reactions happen on or in the edoplasmic reticulum. The endoplasmic retiulum, or ER, is a system of folded membranes in which proteins, lipids, and other materials are made. The ER is part of the internal delivery system of the cell. Its folded membrane contains many tubes and passageways. Substances move through the ER to different places in the cell. The endoplasmic reticulum is either rough or smooth. The part of the ER covered in ribosomes is rough ER. Rough ER is usually found near the nucleus. Ribosomes on rough ER make many of the cell's proteins. The ER then delivers these proteins throughout the cell. Thee ER that lacks ribosomes is the smooth ER. The functions of smooth ER include making lipids and breaking down toxic materials that could damage the cell.

Nuclear Membrane

Nuclear membrane is the membrane that surrounds a cell's nucleus. The membrane allows things in and out by pores in its membrane.

Ribosomes

Organelles that make proteins are celled ribosomes. Ribosomes are the smallest organelles. And there are more ribosomes than there are any other organelles in a cell. Some ribosomes float freely in the cytoplasm. Others are attached to membranes or the cytoskeleton. Unlike most organelles, ribosomes are not covered b a membrane. Ribosomes make proteins by assembling chains of amino acids. An amino acid is any of about 20 different organic molecules that are used to make proteins. All cells need proteins to live. Thus, all cells have ribosomes.

Cell Wall

Plant cells have an outermost structure called a cell wall. A cell wall is a rigid structure that gives support to a cell. The cell walls of plants, fungi, archaea, and bacteria can be made of different materials. For example, plants and algae have cell walls made of complex sugar called cellulose. Animal cells do not have cell walls.

Chromosomes

The chromosomes is one of the structures in the nucleus or a ring around the nucleus.

Golgi Complex

The organelle that packages and distributes proteins is called the Golgi complex. It is named after Camillo Golgi, the Italian scientist who first identified the organelle. The Golgi complex looks like smooth ER. Lipids and proteins from the ER are delivered to the Golgi complex. There, the lipids and proteins may be modified to do different jobs, The final products are enclosed in a piece of the Golgi complex's membrane. This membrane pinches off to form a small bubble. The bubble transports its contents to other parts of the cell or out of the cell.