The Cell Biology 314 Mr. Doron

The Cell The cell is the structural and functional unit of all living organism and is sometimes called the "building block of life. Some organisms, such as bacteria are unicellular consisting of a single cell. Another example is the ameba. Other organisms, such as humans are multi-cellular (humans have an estimated 100 trillion cells).

The Animal Cell - Picture

Plant Cell Picture

The Cell It is the smallest structural unit of an organism that is capable of independent functioning All living things are composed of cells. These cells come from preexisting cells Consists of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semi-permeable cell membrane.

Properties of a cell Each cell is at least somewhat self- contained and self-maintaining: a cell can take in nutrients convert these nutrients into energy carry out specialized functions and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities.

Components of a cell A cell has three basic components –1) The cell or cytoplasmic membrane –2) the cytoplasm –3) the nucleus –The cell membrane: –this is the outside part of the cell –separates its interior from its environment –regulates what moves in and out (selectively permeable) –maintains the electric potential of the cell.

How do Cells Stay Alive? –Cells needs nutrients, oxygen and water. –Taken from the environment –Excretes waste products into environment

Exchanges Between Cell and its Environment Occurs in three ways –1) diffusion –2) osmosis –3) endocytosis

Diffusion Movement of particles from an area with high concentration to an area of low concentration Click the play button to see the video

Osmosis Passage of a solvent (i.e. water) across a semi-permeable membrane Click the image for a video

Endocytosis Whereby the cell ingests whole solid or liquid particles 2 examples of endocytosis are phagocytosis and pinocytosis Phagocytosis - capacity of the cell membrane to invaginate or form a pocket which engulfs solid substances and draws them into the cytoplasm to be digested

Pinocytosis Capacity of the cell membrane to invaginate and engulf liquid substances and draws them into the cytoplasm to be digested. Active transport: the cell uses energy to move molecules against their concentration gradient (low  high)

Nucleus The nucleus is a membrane-enclosed organelle The main function of the cell nucleus is to control gene expression and mediate the replication of DNA during the cell cycle. Chromosomes are responsible for passing hereditary characteristics such as eye colour, hair texture, blood type etc.

Cytoplasm Cytoplasm is a jelly-like material that fills cells. The cytoplasm is inside the cell. It ensures the transport of the different substances that enter or leave the cell. Carries particles that are suspended called organelles. Each organelle has at least one definite job or function and has a definite form.

Organelles An organelle is a discrete structure of a cell having a specialized functions. An organelle is to the cell what an organ is to the body.

Golgi Apparatus integral in modifying, sorting, and packaging proteins. In this respect it can be thought of as similar to a post office; it packages and labels "items" and then sends them to different parts of the cell.

Lysosome They are organelles that contain digestive enzymes They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. The membrane surrounding a lysosome prevents the digestive enzymes inside from destroying the cell.

Mitochondrion Responsible for energy production

Vacuole storage & homeostasis

Endoplasmic Reticulum modification and folding of new proteins and lipids