cellparts

Within a cell there are small structures called organelles.  Just like your organs, they work together to provide the cell with basic functions.  They form a barrier between the cell and its environment, provide structure and support, build and repair parts, transport materials, store and release energy, get rid of waste materials and reproduce. Plant cells and animal cells differ in many ways.  The first is in a structure called the cell wall.  The cell wall is found in plant cells.  This is a firm outer wall that allows plants to stand tall and firm.  Animal cells do not have cell walls.  Instead the cell membrane of an animal cell is reinforced by cholesterol.  People who eat too many animal cells often suffer from high cholesterol.  High levels of cholesterol block the healthy functions of a cell. Both plant and animal cells have a cell membrane. The cell membrane rests just inside of the cell wall in a plant cell, and is the outer most barrier in an animal cell.  The cell membrane acts as a porous barrier that allows materials to selectively pass through, to the cell.  We will discuss later the methods of allowing material to pass through the cell. Inside the cell there is a control center.  A brain if you will.  This brain is called the nucleus.  The nucleus controls all the activities of a cell.  The nucleus is surrounded by a nuclear membrane, which acts in much the same way as the cell membrane, only allowing certain things in and out. Inside the nucleus are chromosomes.  Chromosomes are large rod like structures made up of nucleic acids.  DNA and RNA.  For now, they are the blueprints for cell making.  We will discuss in length the job of a nucleic acid.  Both DNA and RNA have specific functions. The last part of the nucleus we will discuss is the nucleolus.  The “little nucleus”, as it is referred to, produces ribosomes. Ribosomes reside outside of the nucleus and are where the cell manufactures protein.  Protein is the most important aspect of producing healthy cells.  Ribosomes are made of RNA.  The ribosomes are found in the endoplasmic reticulum. The endoplasmic reticulum is the transpiration site of the cell.  It is a canal system that runs through the cell.  Think of tunnels designed to carry protein through the cell.  Much like the subway system of a major city, the endoplasmic reticulum is in constant motion and without it the cell cannot function. The endoplasmic reticulum rests on the cytoplasm of the cell. The cell is filled with a thick Jell-O like substance called cytoplasm.  It is in constant motion, and houses the organelles in the cell. The mitochondria are the powerhouses of cells.  Inside the mitochondria simple food substances such as sugar are broken down into water and carbon dioxide.  When the sugars are broken down large amounts of energy are released. Vacuoles are storage tanks for cells.  Few animal cells have vacuoles, but most plant cells have one very large vacuole.  The vacuole is where waste can be stored as well as food and water.  How a cell “feeds” determines how many and what type of vacuole is needed. Lysosomes are found in animal cells, but rarely in plant cells.  Lysosomes break down larger food particles and supplies the simpler food substances to the mitochondria.  The lysosomes also “eat” all the dead cell parts. Plant cells have a structure unique to them called chloroplasts.   The chloroplast is a green structure; which captures sunlight.  The chloroplast contain chlorophyll and are essential in photosynthesis; which we will discuss later.