CELLS

What is a cell? simplest unit of life structural and functional component of living things all organisms are made of cells single celled: unicellular many cells: multicellular>>specialization all cells are related by their descent from other cells

Studying Cells cells are tiny light microscope—passes visible light through specimen –LM up to 1000X –resolving limit 200 nm (bacterium) –live cell observation electron microscope—focuses beam of e - through or on –SEM –TEM –prep kills cell

c green alga

Cell Fractionation study of cell structure and function isolate components of cells based on size and density biochemistry & cytology –presence of cellular respiration enzymes –large numbers of mitochondria

cell fractionation campbell fig6.5 pg 97

Major Cell Types prokaryotic –bacteria –plasma membrane, cytosol, chromosomes, ribosomes –DNA in cytoplasm, region called nucleoid (no nuclear membrane) eukaryotic –protists, fungi, plants, animals –plasma membrane, cytosol, chromosomes, ribosomes –DNA in nucleus (surrounded by nuclear membrane) –membrane bound organelles

Size of Cells prokaryotic: typically 1-5 μm eukaryotic: typically μm surface to volume ratio: generally keeps cells small –as cell grows, volume grows more than s.a. –larger organisms--more not larger cells selective barrier of plasma membrane –limited amount of substance crosses/sec.

campbell fig 6.8 pg 99 surface to vol ratio

A Closer Look at Cells The cell is the lowest level of organization that can perform all activities of life The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms

LE µm

The Cell’s Heritable Information Cells contain DNA, the heritable information that directs the cell’s activities DNA is the substance of genes Genes are the units of inheritance that transmit information from parents to offspring

LE 1-6 Sperm cell Nuclei containing DNA Egg cell Fertilized egg with DNA from both parents Embryo’s cells With copies of inherited DNA Offspring with traits inherited from both parents

Each DNA molecule is made up of two long chains arranged in a double helix Each link of a chain is one of four kinds of chemical building blocks called nucleotides

LE 1-7 DNA double helixSingle strand of DNA Nucleotide Cell Nucleus DNA

A Hierarchy of Biological Organization 1.Biosphere: all environments on Earth 2.Ecosystem: all living and nonliving things in a particular area 3.Community: all organisms in an ecosystem 4.Population: all individuals of a species in a particular area 5.Organism: an individual living thing

A Hierarchy of Biological Organization (continued) 6.Organ and organ systems: specialized body parts made up of tissues 7.Tissue: a group of similar cells 8.Cell: life’s fundamental unit of structure and function 9.Organelle: a structural component of a cell 10. Molecule: a chemical structure consisting of atoms

Ecosystems The biosphere Organisms Populations Communities Cells Organelles Molecules Tissues Organs and organ systems Cell 1 µm Atoms 10 µm 50 µm