Cells

1. Cells

2. I. Introduction – “What is a cell?” • A cell is the smallest unit that can carry out all the activities necessary for life. (i.e. homeostasis, metabolism, reproduction, heredity, cellular organization) • Most microscopic organisms are made up of a single cell.

3. II. Cell Discovery – “Who discovered the cell?” • New information was due largely to the advancement of the microscope. • From a simple magnifying glass to more complex compound light microscopes to the latest technology of transmission electron microscopes and scanning electron microscopes.

4. a. Robert Hooke (1635-1703) • In 1665, the English scientist and monk, observed a thin slice of cork. • He described what he saw as “a great many little boxes,” which he then termed the cell.

5. b. Anton van Leeuwenhoek (1632-1723) • In 1675, the Dutch microscope maker, was the first person to observe living cells. • For the next 150 years very little research was done on cells.

6. c. Robert Brown (1773 - 1858) • In 1827, the English botanist, was the first person to see the nucleus inside cells. • However, by the time he died no one really understood the importance of his discovery.

7. d.Matthias Schleidan (1804-1881) • In 1838, the German botanist, observed thousands of plant cells and concluded that all plants were composed of cells.

8. e. Theodor Schwaan (1810-1882) • In 1839, the German zoologist, came to the same conclusion, that all animals were composed of cells.

9. f. Rudolph Virchow (1821-1902) • In 1855, the German physician, while studying diseases, determined that cells come only from other cells. (i.e. cells produce more cells)

10. III. The Cell Theory – “Why are cells important?” The observations of these scientists, taken together are known as the cell theory: 1) All living things are composed of one or more cells. 2) Cells are organisms’ basic units of structure and function. 3)   Cells come only from existing cells.

11. IV. Basic Materials in a Cell – “What is a cell made up of ?” The 4 Major Organic Molecules 1) Carbohydrates 2) Lipids 3) Proteins 4) Nucleic Acids

12. V. Levels of Cellular Organization - “How are cells organized?” i)       Cells ii)      Tissues iii)     Organs iv)     Organ systems v) Organisms

13. VI. Organelles Found in a Typical Cell - “What is in cell?” • Organelles (little organs) are specialized compartments that carry out specific functions within a cell. • BY UNDERSTANDING THE STRUCTURES IN A CELL, YOU CAN PREDICT THEIR FUNCTIONS.

14. A. Nucleus 1. Termed the “brain” of the cell. 2. Used to direct all cell activities and serves as the storage center for the cell’s DNA. 3. Contains the chromosomes (genes).

15. B1. Stores genetic material such as RNA.. B2. Site where ribosomes are synthesized (made). C1. Double membrane around the nucleus is used to protect it and allow nucleic acids to enter and leave the nucleus. B. Nucleolus and C. Nuclear Envelope

16. D. Cell Membrane 1. The semipermeable membrane allows specific molecules to come in and out of the cell. 2. They also protect the cell and give it support. 3. The lipid bilayer is made of hydrophilic heads and hydrophobic tails.

17. E. Cytoplasm 1. A jellylike fluid within the cell that helps to cushion the cell and other organelles. 2. Cytosol is the liquid portion, which is in constant motion as the particles move around.

18. F. Mitochondria 1. Often called the “powerhouse” of the cell because it is the place where energy/ATP is converted. (i.e. site where cellular respiration occurs) 2. The number of mitochondria in a cell will vary. (i.e. muscle cells have more mitochondria)

19. G.Ribosomes 1. These are the most numerous of the cells organelles because they are they sites where proteins are created (synthesized).

20. H. Endoplasmic Reticulum (ER) • The ER directs the traffic of the many molecules by creating a series of channels that act as a “highway system” though the cytosol. 1. Rough (has ribosomes on it) – synthesizes proteins. 2. Smooth (no ribosomes) – synthesizes lipids.

21. I. Golgi Apparatus 1. Labels the proteins that are to be used inside and outside of the cell. 2. Also packages and distributes the proteins to specific destinations.

22. J. Lysosome 1. A type of vacuole that contains digestive enzymes to break down food particles and disease-causing bacteria that enter the cell. 2. “Recycling centers” of the cell.

23. K. Vacuoles 1. Fluid filled space that aids in digestion, storage, support, and helps maintain water balance. 2. Often stores enzymes and waste products.

24. L. Cilia and Flagella 1. They are hair-like projections out of the cell membrane. 2. Used for locomotion in unicellular organisms and movement of materials in multi-cellular organisms.

25. M. Centrioles (Animal only) 1. Organizes fibers during cell division. (i.e. mitosis) 2. Always found in pairs.

26. N. Chloroplasts (Plants only) 1. These organelles make chemical energy in the form of sugars, using air, water, and energy from sunlight. (i.e. photosynthesis) 2. Found mostly in algae such as seaweed and green plants.

27. O. Cell Wall (Plants only) 1. Thick outer layer that provides strength by making the cell rigid. 2. Mostly made of cellulose but with some pores to allow ions and molecules to pass through.

28. P. Large Central Vacuole(Plants only) 1. Holding tank – stores waste products, nutrients, and water. 2. May occupy between 30% and 90% of the cells volume.

29. VII. Categories of Cells – “How do cells differ? 1. Prokaryotic (First Cells) a. Small, simple cells that lack a nucleus. b. Bacteria are living prokaryotes and are the most numerous.

30. VII. Categories of Cells – “How do cells differ? 2. Eukaryotic (True Cells) a. Large, complex cell that contain a membrane-bound compartment called the nucleus. b. Both plant cells and animal cells, although different themselves, are considered eukaryotic since they have a nucleus.

31. Prokaryote vs. Eukaryote A. Nucleus none yes B. Membrane bound organelles none yes C. Size (microns) 1-10µm 2-1,000µm D. Evolved 3.5bya 1.5bya (billion years ago) E. Types of cells bacteria plants/animals/fungi

32. VIII. Theory of Endosymbiosis – “Why do cells differ?” • Mitochondria and chloroplasts are descendants of prokaryotic cells so it is believed that 1.5 billion years ago some prokaryotic cells were “swallowed” by larger cells but were not digested. Thus the prokaryotic cells remained inside the larger cells and gradually lost the ability to live alone. The partnership that the two cells formed is called endosymbiosis.

33. IX. Limits of Cell Size – “Why are all cells so small?” 1. Since cells are continuously in contact with their surroundings their parts cannot be to far from the membrane. 2. Cell volume increases faster than surface area. (i.e. ratio of surface area to volume limits how large a cell can get): a. Surface area = measurement of exterior of cell b. Volume = measurement of interior of cell

34. Any Questions? • An education is not how much you have committed to memory. It is knowing where to go to find out what you need to know and it is knowing how to use the information that you get. --William Feather