The Cell, The Whole Cell and Nothing But The Cell The Basic Structural and Functional Unit of Life

Discovery of the Cell  1665 English scientist Robert Hooke used a simple microscope to observe thin slices of cork he called the little boxes he saw “Cells”  1673 Leeuwenhook was the first person to observe living cells “animacules” with his microscope.

Cell Theory-150 years later  All living things are composed of 1 or more cells All plants are composed of cells-Schleiden (1838) All animals are composed of cells-Schwann (1839)  Cells are the basic structural and functional component of life  Cells come only from the reproduction of existing cells-Virchow (1855)

Cell Diversity-Differences Size, Shape and Organization  Size-Cells are limited in size by the ratio between their outer surface area and their volume.  The surface of a cell, its membrane, is the site of exchange between its interior and its external environment. This surface must allow sufficient exchange to support the contents of the cell. As an object increases in size its volume increases as the cube of its linear dimensions while surface area increases as the square. As these cubes illustrate the surface area to volume ratio of a small object is larger than that of a large object of similar shape. This ratio limits how large cells can be.

Cell Diversity-Differences Size, Shape and Organization  Cells come in a variety of shapes  How a cell is shaped tells something about its function Skin Cells-Flat and wide for covering and protecting surfaces Nerve Cells-Long extensions for communication with a central process center Bone Cells-Stiff and Rigid for support of Body during Motion, attachment site for muscles, assists terrestrial animals in resisting downward pull of gravity.

Life of the Cell Internal Organization  The cell contains special components called organelles “little organs”, that perform special functions for the cell.  Organelles maintain the life functions for the cell.  All cells have Cell Membrane-Controls what enters and leaves the cell Cytoplasm-Aqueous solution that contains biomolecules Genetic Material-DNA and RNA

2 Basic Cell Types Prokaryote vs Eukaryote  Prokaryote Cells or Bacteria  Do Not Have Membrane- Bound Organelles Cell Wall Cell Membrane Cytoplasm Ribosomes Nucleoid-location for genetic material (no membrane)  Eukaryote Cells-Animal and Plant Cells  Do Have Membrane-Bound Organelles Cell Membrane Cytoplasm Nucleus

Cell Organelles-Eukaryotes Plants and Animals Mitochondrion-Convert energy from food into ATP Ribosomes-Protein Synthesis Golgi Apparatus-Processes and Packages Cell Products Nucleus-Stores Hereditary Information Cilia and Flagella-Cell Movement Cell Wall-Supports and Protects the Cell Membrane in Plants Microfilaments and Microtubules- Support, Movement and Division in cells Plastids-Store food (Starch) and Pigments (chlorophyll) in Plants Vacuole-Stores Water, Enzymes and Waste Products

Multicellular Organization(pg 86)  Cells are organized into Tissues- groups of cells that carry out a special function  Tissues are organized into Organs- several types of tissues that work together to perform a special function  Organ System-group of organs that work together to perform a set of related tasks for the organism.

Plant Cellular Organization  In plants dermal tissue make up the outer plant, ground tissue make up the roots and stems and the vascular tissue system transports water throughout the plant  The 4 plant organs are Roots Stems Leaves Flowers

Evolution of Multicellular Organization  Fossil Evidence suggests that the earliest cells resembled present day bacteria  Increasing populations of single cells gave rise to cells living in groups or colonial organisms-a group of genetically identical cells that live together in a closely connected group.  Some members of this Volvox colony specialize in reproduction, others specialize in propelling the colony through the water.  As colonial organisms evolved their cells became more specialized and lost the ability to live independently.

Cellular Summary  The cell is the basic structural and functional unit of all life on the planet  The cell theory states that: All living things are composed of one or more cells Cells are the basic structural and functional unit of all life Cells come only from the reproduction of preexisting cells  All cells possess A Cell Membrane Cytoplasm Genetic Material  Cells possess structures that carryout life functions for the cell called Organelles  There are 2 Types of Cells Prokaryotes or Bacterium-No Membrane bound Organelles Eukaryotes-Plant and Animal Cells-Membrane bound Organelles  Multicellular animals and plants have tissues, organs and organ systems  Colonial organisms gave rise to multicellular organisms.