Chapter 7; Section 1 Introduction to Cells Key Ideas: How were cells discovered? Why does cell shape vary? What enables eukaryotes to perform more specialized functions than prokaryotes?

Discovery of Cells Robert Hooke (1665) Coins term “cell” after looking at cork and seeking the cell walls

Robert Brown (1831) Pointed out nucleus

Matthias Schleiden (1838) Plants are made of cells

Theodore Schwann (1839) Declared that animals are composed of cells First to create term “cell theory” German scientist Declared that animals are composed of cells First to create term “cell theory”

Rudolf Virchow (1858) “every cell comes from a cell” German pathologist Altered the ideas of cellular biology “every cell comes from a cell”

Cell Theory states that: all living things are composed of cells cells are the basic units of structure and function in living things new cells come from existing cells. The observations & ideas were put together to form the cell theory in the 1800s It states that: all living things are composed of cells cells are the basic units of structure and function in living things new cells come from existing cells

Cell Theory

Cells vary greatly in size and shape shape reflects its function. branched, flat, round, or rectangular. size is limited by a cell’s surface area-to-volume ratio. Cheek cells vary greatly in size and shape shape reflects its function. size is limited by a cell’s surface area-to-volume ratio. can be branched, flat, round, or rectangula Nerve cell

Looking at Cells To enter or leave a cell a substance must cross the surface of the cell. ability to move substances across its surface can be estimated by finding its surface area-to-volume ratio. greater surface area-to-volume ratios allows substances to be exchanged more efficiently. All substances that enter or leave a cell must cross the surface of the cell. ability to move substances across its surface can be estimated by finding its surface area-to-volume ratio. Cells with greater surface area-to-volume ratios can exchange substances more efficiently.

Relationship between Surface Area and Volume small cells have greater surface area-to-volume ratios than large cells. small cells function more efficiently than large cells.

Features of ALL Cells cell membrane outer layer; covers a cell’s surface acts as a barrier between the outside environment and the inside of the cell. Cytoplasm: region of the cell within the cell membrane. “shock absorber” protects the organelles ribosome makes proteins. DNA provides instructions for making proteins regulates cellular activities enables cells to reproduce.

Features of Prokaryotic and Eukaryotic Cells

Characteristics of Prokaryotic Organisms Single cell NO nucleus or other internal compartments. Genetic material is a single loop of DNA. Single cell NO nucleus or other internal compartments. Genetic material is a single loop of DNA. For millions of years – they were the only organisms on Earth.

Characteristics of Eukaryotic Organisms Can be unicellular or multicellular ALL multicellular organisms are made of eukaryotic cells DNA is found in the nucleus. have membrane-bound organelles. An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell. complex organization enables them to carry out more specialized functions than prokaryotic cells organism made up of one or more eukaryotic cells. All multicellular organisms are made of eukaryotic cells. DNA is found in the nucleus. have membrane-bound organelles. An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell. The complex organization of eukaryotic cells enables them to carry out more specialized functions than prokaryotic cells

Comparing Prokaryotes and Eukaryotes

Comparing Prokaryotes and Eukaryotes Two cell Types Prokaryotes Eukaryote No nucleus Nucleus No membrane bound organelles Many organelles Most 1 – 10µ in size Many 2 – 1,000 µm in size Evolved 3.5 billion years ago Evolved 1.5 billion years ago Only bacteria All other cells

Summary Microscope observations of organisms led to the discovery of the basic characteristics common to all living things. A cell’s shape reflects its function. Cell size is limited by a cell’s surface area-to-volume ratio. The complex organization of eukaryotic cells enable them to carry out more specialized functions than prokaryotic cells.