Cells Life Science

Cell Theory Cells are the basic units of structure and function for living things. Organelles are the structures that make up the inside of a cell. The work of Schleiden, Schwann, Virchow and others led to the development of cell theory. Cell theory states: All living things are made of cells. Cells are the basic units of structure and function in living things. Living cells come only from other living cells.

Cell Structure All living things are made up of one or more cells. Most cells are much to small to be seen without the aid of a microscope. Within a cell are even smaller structures called organelles.

Cell Structure Structures within a cell provide the following functions: protection and support (wall) a barrier between the cell & its environment (membrane) Building, storing & repairing cell parts (nucleus, ribosomes, Golgi apparatus, vacuoles transporting materials (endoplasmic reticulum, vesicles) storing and releasing energy (mitochondria & chloroplast) getting rid of waste materials (lysosome) increasing in number (centrioles, nucleus)

Cell Structure

Cell Wall Cell walls are structures that provide support and protection to plant cells. A cell wall is made up of cellulose, a long chain of sugar molecules manufactured by the cell. The cell wall helps to protect and support the plant so that it can grow tall.

Cell Wall The cell wall also allows water, oxygen, carbon dioxide, and certain dissolved materials to enter and exit the cell. Cell walls are only found in bacteria, plants and some fungus. Animal cells do not have a cell wall, they have a structure called a cell membrane.

Cell Membrane In plant cells, the cell membrane is just inside the cell wall. In animal cells, the cell membrane is the outer covering of the cell. The cell membrane has several important jobs including controlling what enters and leaves the cell.

Cell Membrane A cell membrane is made of phospholipid, protein & cholesterol molecules. Some materials pass right thru the membrane while others have to be helped thru by proteins.

The Nucleus The nucleus is a large, oval structure that is the control center of the cell. The nucleus acts as the “brain” for the cell by regulating or controlling all activities in the cell.

The Nuclear Membrane The nuclear membrane or envelope is a membrane that surrounds the nucleus of the cell and allows material to pass in and out of the nucleus through pores. The pores are spaced regularly around the nucleus and act as the passageways.

Chromosomes Chromosomes are thick, rod like objects floating in the nucleus. The chromosomes direct all the activities of the cell including growth and reproduction. Chromosomes are also responsible for passing on the traits of the cell to new cells.

Chromosomes The large complex molecules that make up chromosomes are called nucleic acids. Two of the nucleic acids found in the chromosomes are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) DNA and RNA are the carriers of the blueprints of life. While DNA remains in the nucleus and stores the information, RNA travels outside into the cell with it’s protein building instructions.

Chromosomes

Nucleolus The nucleolus is a round structure found inside that nucleus that is the site of ribosome production.

Cytoplasm The cytoplasm is a thick, jelly like substance that fills the interior of the cell. The cell organelles are located in the cytoplasm. The cytoplasm is constantly moving by a process called cytoplasmic streaming that moves around substances in the cell like water and sugars.

Endoplasmic Reticulum The endoplasmic reticulum looks like a series of tubular passageways (flattened sacs) that lead from the nucleus towards the cell membrane. The endoplasmic reticulum acts as the transport system of the cell carrying proteins from one area to another.

Ribosomes Ribosomes are small grain-like bodies attached to the endoplasmic reticulum. Ribosomes make proteins for the cell. Ribosomes are produced by the nucleolus and are made of RNA.

Mitochondria Mitochondria are large, rod-shaped structures that supply the energy for the cell. Mitochondria break down the food in the cell and produce water, CO2 and large amounts of energy (when oxygen is available). The more active a cell is, the more mitochondria it has.

Vacuoles Vacuoles are large, round, water-filled sacs floating in the cytoplasm. Most plant cells and some animal cells have vacuoles. Vacuoles act like storage tanks for the cell and may contain food, enzymes, waste or excess water.

Lysosome Lysosomes are small, round structures with digestive enzymes. Lysosomes are common in animal cells but rare in plant cells. Lysosomes digest old cell parts and use enzymes to break down large food molecules into smaller ones which are then passed on to the mitochondria. .

Chloroplasts are large, irregular shaped green structures floating in the cytoplasm of plant and some bacteria cells. Chloroplasts are green because they contain chlorophyll, a green pigment. Chlorophyll captures energy from the sun and converts it into food for the plant cell by a process called photosynthesis. Chloroplasts