OVERVIEW OF THE CELL Biology 20 Paramecium Human Cheek CellsOnion Cells 1

Before we could see cells..  There had to be the microscope!  Early lens makers (often physicists) allowed for the study of microbiology 2

The first people to see cells...  Robert Hooke - He was looking at cork and noted that he saw a “great many boxes” (1665).  Anton van Leeuwenhock – observed living cells in pond water. He called these “animalcules”. (1673) 3

The first people to see cells...  Theodore Schwann- observed that the tissues of animals had cells (1839)  Mattais Schleiden– observed that plants contained cells (1845)  Rudolf Virchow – every living thing is made up of cells (1850) 4

The Cell Theory 1. Every living organism is made of one or more cells. 2. The cell is the basic unit of structure and function. It is the smallest unit that can perform life functions. 3. All cells arise from pre-existing cells. 5

Question for you...  Why is the Cell Theory called a Theory and not a Fact? 6

Main Points  All organisms are made up of cells. They can be: Unicellular (1 cell) OR multicellular (many cells)  In unicellular organisms all life functions are carried out by a single cell.  In multicellular organisms, cells specialise to perform specific functions – division of labour. 7

Cells as seen with a microscope  Living protoplasm surrounded by surface membrane (& non-living cell wall in plants).  The living material between the nucleus and the cell surface membrane is known as cytoplasm.  Cytoplasm contains variety of cell organelles. 8

Two main types of cells 9

Prokaryotic Cells  Very simple cells, probably first to inhabit the earth.  Do not contain a membrane bound nucleus. Their nucleus material (DNA) lies free in a region known as nucleoid.  Example: Bacteria. DNA of bacteria is circular.  The word "prokaryote" means "before the nucleus" 10

Eukaryotic Cells  More advanced cells.  Possess true nucleus and nucleus material are found inside the nucleus surrounded by the two membranes, i.e nucleus envelope.  Example: plant cell, animal cell. 11

Eukaryotic Cells 4 main parts: cell membrane - outer boundary cytoplasm - jelly-like fluid interior nucleus - the "control center”, contains the cell's DNA (chromosomes) organelles - "little organs" that carry out cell functions 12

Organelles in Animal & Plant Cells Animal CellPlant Cell 13

DiagramCell PartFunction MitochondriaEnergy center or "powerhouse" of the cell. Turns food into useable energy RibosomesMake protein Golgi ApparatusProcesses, packages and secretes proteins. Like a factory. LysosomeContains digestive enzymes, breaks things down Endoplasmic Reticulum Smooth ER - no ribosomes Rough ER - ribosomes Transport, "intracellular highway". Ribosomes are positioned along the rough ER, protein made by the ribosomes enter the ER for transport. 14

DiagramCell PartFunction NucleolusLocated inside the nucleus, makes ribosomes VacuoleStores water or other substances, plant cells contain a large central vacuole. ChloroplastUses sunlight to create food, photosynthesis (only found in plant cells) Cell WallProvides additional support (plant and bacteria cells) MicrotubulesPart of the cytoskeleton, function in support Also make up cilia and flagella (cell movement) 15

Differences in Animal & Plant Cells  Lysosomes  Cell Wall  Chloroplasts  Chromoplasts/Amyloplasts Found only in Animal CellsFound Only in Plant Cells 16

Prokaryotic versus Eukaryotic Cells Prokaryotic cellEukaryotic cell Nucleus material are not enclosed by nuclear membrane Nucleus material are enclosed by nuclear membrane Contains few organellesContains many organelles No membrane bounded organelles such as; chloroplast and mitochondria Has membrane bounded organelles DNA is circular and lies free in cytoplasmDNA is linear and enclosed in nucleus No mitosis or meiosis, divide by binary fissionMitosis and meiosis occur It contains 70s ribosome (smaller)It contains 80s ribosome (larger) Mainly unicellularMainly multi-cellular 17