1. Cell Types

2. Cell Theory Every living organism is made of one or more cells The smallest organisms are made of single cells while multicellular organisms are made of many cells All cells arise from pre-existing cells

3. Cell Function Limits Cell Size most cells are small, ranging from 1 to 100 micrometers in diameter cells need to exchange nutrients and wastes with the environment no part of the cell can be far away from the external environment surface area to volume ratios must be kept rather large

4. All Cells Share Common Features a plasma membrane encloses all cells and regulates material flow in and out of the cell cytoplasm is the fluid interior where a cell’s metabolic reactions occur (cytosol) DNA (deoxyribonucleic acid) is the hereditary blueprint and RNA (ribonucleic acid) copies DNA for protein production (universal genetic code)

5. Two Basic Cell Types Prokaryotic Cells (bacteria) DNA is in the form of circular loops and is free in the cytoplasm cells contain no internal membranes and no organelles except for ribosomes Eukaryotic Cells (protists, fungi, animals, plants) DNA is linear, bound with histone proteins in structures called chromosomes and housed in a central structure called a nucleus cells contain complex internal membrane systems and specialized organelles

6. ‘Naked ring of DNA’ X

7. Spherical (cocci) 1 µm Rod-shaped (bacilli) 2 µm Spiral 5 µm

11. Making Scientific Illustrations Draw only on white, unlined paper. One drawing per page. Draw large – but not off the edge of the page. Draw only in pencil. Do not shade or color your drawings. Stay focused on FORM. Use clean, unbroken lines. No artsy sketching. Have a title, magnification, and appropriate labeling on each drawing. Draw only biological structures! Do not draw air bubbles, dust, debris, and other irrelevant objects just because you see them. Pay attention to detail. Draw less, draw big (fill the space), draw carefully.