Cell Structure

Cell Theory All living organisms are made of one or more cells. The cell is the basic organizational unit of life. All cells come from pre-existing cells.

Visualizing Cells

Organelles Nucleus The nucleus is contained in the centre of the cell, and is the control centre. Information relating to the cell and processes are kept on genes, which make up chromatin. During cellular reproduction chromatin strands shorten and thicken to make chromosomes. The nucleus is enclosed by a nuclear envelope. This membrane allows molecules to travel in and out via nuclear pores.

Nucleus

Organelles Cell Membrane The cell membrane is made by a two layers of phospholipids (fats with a phosphate head), also known as a phospholipid bilayer. The membrane is semi permeable letting smaller objects move freely into and out of the cell. Also within this bilayer are large protein molecules which allow for large molecules to enter and exit the cell. The membrane is said to be a ‘fluid mosaic’ always changing and flowing.

Organelles Cytoplasm/Cytostol The cytoplasm is a fluid jelly with in the cell which supports other organelles. The cytoplasm is the workplace of the cell. Many chemical reactions take place within the cytoplasm.

Organelles Mitochondria The mitochondria is often called the powerhouse of the cell. Within the mitochondria sugars are broken down into usable energy called adenosine triphosphate (ATP). This is called cellular respiration.

Organelles Ribosomes Ribosomes are responsible for creating or synthesizing proteins. Proteins are used for many cellular functions, including growth. A protein is created by long chains of amino acids. The ribosome uses RNA from the nucleus to link the proper amino acids. Ribosomes may be found free floating in the cytoplasm or attached to rough ER.

Organelles Endoplasmic Reticulum (ER) Two types smooth and rough. The difference is that rough ER has ribosomes attached to its outside wall giving it a rough look. Although usually only pictured around the nucleus it is a network of canals throughout the cell. The ER is responsible for the creation of many hormones, fats, lipids, proteins, etc. and their transfer.

Organelles Golgi Apparatus The golgi apparatus is responsible for storage, modification and the packaging of proteins made in the rough ER. The golgi apparatus is made up of sacs which pinch off vesicles that will transport proteins outside the cell.

Organelles Lysosomes Lysosomes are a special vesicle formed by the golgi apparatus. They contain enzymes used in the breakdown of macromolecules. Lysosomes are also an important part of our defense system because they release enzymes that can destroy the bacteria and white blood cells containing the bacteria.

Organelles Microfilaments and Microtubules Microfilaments and microtubules are pipelike structures found throughout the cell. They give the cell its shape and support. But are also an important transport system for materials throughout the cell. They also aid in cell division Microfilaments and microtubules are formed from proteins, and can also be found in cillia and flagella.