Cell

Cell

A cell is the basic structural unit of all life, with every living organism being either a single cell or a collection of many interdependent cells. The human body is made up of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. Cells also contain hereditary material which allows them to make copies of themselves.

The Cell Theory

• All living things are made up of cells
• All living things are composed of one or more cells
• New cells arise from existing cells
• There is no life apart from the life of a cell
• Cells arise from other cells through cellular division

The Expanded Version of the Cell Theory

• Cells carry genetic material passed to daughter cells during cellular division
• All cells are essentially the same in chemical composition
• Energy flow (metabolism and biochemistry) occurs within cells

Scientists Who Contributed to the Development of Cell Theory

• Matthias Schleiden
• Theodor Schwann
• Rudolf Virchow
• Robert Hooke
• Anton van Leeuwenhoek

Types of Cells

• Prokaryotic: All Prokaryotic cells are unicellular organisms, although some occur in colonies. True bacteria and blue-green bacteria are the most recognizable prokaryotes
• Eukaryotic: Eukaryotic cells are much larger than prokaryotic cells and far more complex. Single-celled algae and fungi and all protozoa are eukaryotic unicellular organisms. All animals, and all multi-celled fungi and algae, are composed of eukaryotic cells

Types of Cells in the Human Body

• Red blood cells
• White blood cells
• Neuroglial cells
• Muscle cells
• Stem cells
• Cartilage cells
• Bone cells
• Skin cells
• Endothelial cells
• Epithelial cells
• Fat cells
• Sex cells
• Platelets
• Nerve cells

Cell Size and Diversity

Eukaryotic cells are rarely smaller than 10 microns in diameter. Prokaryotic cells are considerably smaller, with the largest measuring no more than about 3 microns across. The smallest prokaryotes, the mycoplasmas, are generally well under a micron in size. Among eukaryotic cells, those of plants tend to be larger than those of animals.

Forms in Which Living Cells Exist

• Cells live as a colony
• They live as filaments
• As independent or single living organisms

Characteristics of Cells

• Plasma membrane
• Cytoplasm
• DNA
• Ribosomes

Cell Structures

• Cell membrane and cell wall
• Cytoplasm
• Nucleus and nucleolus
• Endoplasmic reticulum
• Ribosomes
• Golgi apparatus
• Lysosomes
• Vacuoles and vesicles