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INTRODUCTION TO THE CELL

INTRODUCTION TO THE CELL. Discovery of the Cell. Cell : the smallest unit of matter that can carry on all the processes of life—very organized! Discovery of the cell 1665 by English scientist Robert Hooke He looked at thin slices of cork under a microscope.

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INTRODUCTION TO THE CELL

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  1. INTRODUCTION TO THE CELL

  2. Discovery of the Cell • Cell: the smallest unit of matter that can carry on all the processes of life—very organized! • Discovery of the cell • 1665 by English scientist Robert Hooke • He looked at thin slices of cork under a microscope. • He used the term cells to describe the empty spaces in cork(named after the small rooms that monks lived in). • Hooke actually observed the remains of dead plant cells. • The first person to observe living cells was Anton van Leeuwenhoek, a Dutch microscope maker, in 1673.

  3. Cell Theory • Major ideas of the cell theory: • All living things are made of one or more cells. • Cells are the smallest units of life (basic unit of structure and function in an organism). • All cells come from the reproduction of existing cells. • Evidence for the cell theory from German scientists: • Matthias Schleiden, 1838: plants are composed of cells. • Theodor Schwann, 1839: animals are composed of cells. • Rudolf Virchow, 1855: cells only come from other cells.

  4. Great Diversity of Cells • Cell Diversity: Not all cells are alike! Cells differ in size, shape, and internal organization. However, they are all made of the same basic chemical elements: C, H, O, N, P, and S.

  5. Cell Size • Large: eggs; nerve cells in giraffe legs (up to 2m!) • Small: most cells are only 10-50 micrometers in size (very tiny!) • Most cells are only visible under a microscope. • Why are cells so small? • They are limited in size by the ratio between surface area and volume. Nutrients, oxygen, and other materials must enter the cell through its surface. As a cell grows larger its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell’s needs. • What happens if cells are too big? • Nutrients cannot enter and waste products cannot leave fast enough • Why is this a problem? • Cells will die without nutrients and oxygen. SURFACE AREA TO VOLUME VIDEO

  6. Cell Shape • Different cell structure reflects a different function of the cell. • Nerve cells: long extensions enable the cell to pass on nerve impulses • Skin cells: flat shape to cover body surface • Red blood cells: lack a nucleus and mitochondria because they don’t have to replace themselves or use the oxygen in route to their target

  7. Internal Organization • Cells contain internal parts called organelles. • Organelle: cell part that performs a specific function. • Just as the organs of a multi-cellular organism carry out the organism’s life functions, the organelles of a cell maintain the life of the cell. • Cell membrane: thin membrane that surrounds the cell. • Most organelles inside the cell are surrounded by their own membrane. (called membrane-bound organelles.) • Nucleus: large organelle near the center of the cell—contains the genetic information and is the control center of the cell (not in Prokaryotes)

  8. Two Types of Cells • Eukaryotes: Organisms whose cells contain a membrane-bound nucleus and other organelles • Includes cells of organisms from the following kingdoms: protists, fungi, plants, animals • Prokaryotes: Unicellular organisms without a nucleus and most organelles (very simple) • Includes the single-celled organisms from the following kingdoms: Archaebacteriaand Eubacteria (all bacteria!) • NUCLEUS IS NOT FOUND IN PROKAYOTES! • Prokaryotes contain a Nucleoid: the region of a prokaryotic cell that is currently occupied by the genetic material that makes up the chromosome

  9. Cell Types Eukaryote Prokaryote

  10. Comparison Chart

  11. Viruses Example of a Virus Image Virus Details • NOT made of cells Not considered living or dead • Contain genetic material (DNA or RNA) that is NOT in a nucleus and a protein coat

  12. Viral Infection Cycles • Viruses inject DNA into host cell, then either the lytic or lysogenic cycle begins, depending on certain conditions in the host cell

  13. Lytic Cycle • Virus takes over the cell organelles to make new copies of viral DNA and protein coats (capsids). Viral parts self-assemble, cell lyses, and viruses are released to infect other cells • Shorter cycle

  14. Lysogenic Cycle • Viral DNA becomes incorporated into the host cell’s DNA • viral DNA is called a Prophage • The prophage is replicated with the host cell’s DNA • The cell can enter the lytic cycle at any time (HIV can hide out in the lysogenic cycle for years which is why we don’t see the effects for 5-10 years)

  15. Relationship between Lytic and Lysogenic Cycles

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