Looking Inside the Cell Cells are the basic units of structure and function in living things. All plants and animals from the smallest plankton to the largest trees, and from the smallest amoebas to the largest whales are made up of groups of cells or single cells. Amoeba Blue Whale

Protozoa Bacteria

Levels of Organization in Nature Cell – smallest unit that can live and reproduce on its own or as part of a multicelled organism. It has an outer membrane, DNA, and other components called organelles. Tissue – cells form tissues. It is an organized group of similar cells that perform the same task. For example, muscle is a tissue that is made up of muscle cells. Cardiac muscle

Organ – which is composed of one or more types of tissues. For example, the heart is composed of muscle, nerve, fat, and other types of tissues. Human Heart

System – which is composed of different organs. For example, the circulatory system is composed of the heart and blood vessels.

Individual Organism – which is composed of different systems of organs. The human is composed of the circulatory system, the digestive system, the respiratory system, the nervous system, the reproductive system, the endocrine system, the skeletal system, the muscular system, the lymphatic system, and the urinary system.

Think of a cell as a factory. Most factories are set up in essentially the same way. All factories have exterior walls that create separate work areas. They usually have some kind of production line where a product is assembled and an executive department that decides what product is made. A finishing department processes and prepares the product for shipping, and a packing department wraps the product.

In addition, a factory has a receiving department that brings in the components it needs to make its product, a communications department that allows it to contact suppliers, and a power plant that provides the energy it needs to run. Finally a custodial staff keeps everything clean and in good working order. Cells are very similar to factories. To stay alive and function properly, cells have a division of labor similar to that found in factories.

All cells are composed of a cell (plasma) membrane, a nucleus, and cytoplasm. These structures can be compared with a factory’s departments. Cell (Plasma) Membrane – the membrane of the cell provides a very thin, but effective, protective surrounding for the cell. It also gives the cell shape and strength. The membrane keeps the material substance of the cell from leaking out into its surroundings. Nourishment and waste do pass through the membrane.

Cytoplasm – is the cellular material between the nucleus and the cell membrane. It is a clear, thick liquid containing the vacuoles, the mitochondria, and the ribosomes. Think of the cell membrane as the skin of the cell, and the cytoplasm as the body of the cell. Many functions for life occur in the cytoplasm.

Nucleus – runs the cell factory and controls all cell activity. It determines what proteins are to made and stores all the plans for any proteins that the cell currently makes or has made in the past. The nucleus is the “brain” of the cell.

A nuclear envelope surrounds the nucleus. It protects the nucleus. Materials pass in and out of the nucleus through pores in the nuclear envelope. Chromatin are the strands of genetic material found in the nucleus. These contain the instructions for directing the cell’s functions. Nucleous is where ribosomes are made. Ribosomes are the organelles where proteins are produced.

Organelles in the Cytoplasm Mitochondria – are rod-shaped structures. These are known as the “powerhouses” of the cell. They convert energy in food molecules to energy the cell can use to carry out its functions.

Endoplasmic Reticulum – looks like a maze of passageways (or halls). These passageways carry proteins and other materials from one part of the cell to another.

Ribosomes – attached to some surfaces of the endoplasmic reticulum are small, grainlike bodies called ribosomes. Ribosomes function as factories to produce proteins.

Lysosome = organelles that contain protein digesting enzymes that break down large food particles into smaller ones.

Cell Wall – are found in plants cells. It is a tough, rigid structure made of cellulose which is the outside of the cell membrane. It provides physical support and shape.

Vacuole -- a large organelle in cells that stores various products. In plant cells, water is stored here. In animal cells, water, food material, and wastes are among the materials that can be stored here.

Chloroplasts – organelles present in plant cells that contains chlorophyll and absorbs light energy from sun that used in photosynthesis.