3. A single ~200 micrometer (m) cell, the human egg, with sperm, which are also single cells. From the union of an egg and sperm will arise the 10 trillion cells of a human body.
4. Eubacteria; note dividing cells. These are Lactococcus lactis, which are used to produce cheese such as Roquefort, Brie, and Camembert.
5. A mass of archaebacteria ( Methanosarcina ) that produce their energy by converting carbon dioxide and hydrogen gas to methane. Some species that live in the rumen of cattle give rise to >150 liters of methane gas/day.
6. Blood cells, shown in false color. The red blood cells are oxygen-bearing erythrocytes, the white blood cells (leukocytes) are part of the immune system and fight infection, and the green cells are platelets that provide substances to make blood clot at a wound.
7. A colonial single-celled green alga, Volvox aureus . The large spheres are made up of many individual cells, visible as blue or green dots. The yellow masses inside are daughter colonies, each made up of many cells.
8. A single Purkinje neuron of the cerebellum, which can form more than a hundred thousand connections with other cells through the branched network of dendrites. The cell was made visible by introduction of a fluorescent protein; the cell body is the bulb at the bottom.
11. Electron micrograph of a thin section of Escherichia coli, a common intestinal bacterium. The nucleoid, consisting of the bacterial DNA, is not enclosed within a membrane. E. coli and some other bacteria are surrounded by two membranes separated by the periplasmic space. The thin cell wall is adjacent to the inner membrane.
12. Electron micrograph of a plasma cell, a type of white blood cell that secretes antibodies. Only a single membrane (the plasma membrane) surrounds the cell, but the interior contains many membrane-limited compartments, or organelles.
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15. Scanning electron micrograph of mature oocysts and emerging sporozoites. Oocysts abut the external surface of stomach wall cells and are encased within a membrane that protects them from the host immune system. [
16. The yeast Saccharomyces cerevisiae reproduces sexually and asexually.
26. The watery interior of cells is surrounded by the plasma membrane, a two-layered shell of phospholipids.
27. ATP is the most common molecule used by cells to capture and transfer energy.
28. External signals commonly cause a change in the activity of preexisting proteins or in the amounts and types of proteins that cells produce.
29. During growth, eukaryotic cells continually progress through the four stages of the cell cycle, generating new daughter cells.
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31. Apoptotic cells break apart without spewing forth cell constituents that might harm neighboring Cells
32. During the later stages of mitosis, microtubules (red) pull the replicated chromosomes (black) toward the ends of a dividing cell.
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42. ATP is the most common molecule used by cells to capture and transfer energy. ATP is formed from ADP and inorganic phosphate (Pi) by photosynthesis in plants and by the breakdown of sugars and fats in most cells. The energy released by the splitting (hydrolysis) of Pi from ATP drives many cellular processes.
