Chapter Four:

1. Chapter Four: Cell Structure and Function

2. The Cell • the basic unit of life and organisms • discovery made possible by the invention of the microscope

3. Brief History: Galileo Galilei • arranged two glass lenses within a cylinder, he was the first to record observations through a microscope.

4. Robert Hooke • He took slices of cork from a tree, observed the tiny compartments, and gave them the name, cellulae (cell).

5. Antony van Leeuwenhoek • Used a microscope to view pond water and discovered what we know today as single-celled organisms.

6. Robert Brown • Notices opaque spots in cells and named them nucleus.

7. Matthias Schleiden • Botanist • Concluded that all plants are made of cells. • Plant cells develop as independent units even though they are part of a plant.

8. Theodor Schwann • Zoologist • Concluded that all animals were made of cells. • Animal cells develop as independent units even though they are part of the animal.

9. Rudolf virchow • Physician • Determined that cells come from other cells.

10. The observations of Schleiden, Schwann, and Virchow formed the Cell Theory.

11. Cell Theory All organisms are made of cells. The cell is the most basic unit of life. All existing cells are produced from other living cells.

12. Common Features of cells All cells have 1. Cell membrane (plasma membrane): • A phospholipid bilayer that serves as an outer boundary that regulates what enters and leaves the cell. 2. Cytoplasm: • Fluid substance between the cell membrane and the DNA region.

13. DNA containing region. • Prokaryote cells-a circular piece of DNA called plasmid. • Eukaryote cells-genetic material is in the nucleus. • Cytoskeleton: • network of protein fibers in the cytoplasm that give structure and support to the cell. • Ribosome: • cell structures that make proteins.

14. Two Basic Cell Types Prokaryote Eukaryote

15. Prokaryotes Characteristics • DO NOT HAVE A NUCLEUS • DO NOT HAVE internal compartments, structures, or organelles. • Have a cell wall • Single-celled organisms • Relatively small and simple • Can not carry out many specialized functions. Bacteria are the only Prokaryotes!

16. Eukaryotes Characteristics HAVE a nucleus HAVE internal compartments, structures, and organelles. Single-celled (Protists) and multicellular organisms Plants and Fungi – have a cell wall; Animals – do not have a cell wall; Protist - mixed (some have cell walls and others do not) Organelles allow cells to carry out specific (specialized) functions. Animals, Fungi, Plants, and Protists are Eukaryotes!

18. Cell Membrane

19. Cell Membrane • Function: controls the passage of materials into and out of a cell. • Location: surrounds the cell; inside of the cell wall if one is present.

20. Fluid Mosaic model • Cells are surrounded by fluids, inside the cell itself and around it. • The membrane is flexible not rigid or solid • Have a mixed composition “mosaic” of diverse and colorful phospholipids, proteins, sterols, and carbohydrates incorporated within.

21. Structure: • consists of a double layer of phospholipids. Phospholipid-a molecule composed of three basic parts: a charged phosphate group, glycerol, and two fatty acid chains.

22. Phospholipid PO4- -Polar -Hydrophilic (Water-loving) -Phosphorus Head Fatty Acid Chain -Nonpolar -Hydrophobic (Water-fearing)

23. -The tails point toward each other in the center of the membrane -The heads point to the fluid cytoplasm and the fluid outside of the cell. -Head- -Tail- -Tail- -Head- Sandwich concept (Bread) = Head (Meat) = Tails (Bread) = Head

24. The hydrophilic head of a phospholipid is polar and composed of glycerol and a phosphate group. • The two hydrophobic tails are nonpolar and are composed of two fatty acids. • Because of the properties of polar heads and nonpolar tails, the phospholipids arrange themselves in layers.

25. There are other molecules embedded within the phospholipid layers. These molecules have several functions: • Cholesterol molecules strengthen the cell membrane. • Some proteins help materials cross the membrane. • Carbohydrates serve as identification tags. All of these components are working together for the membrane to function properly.

26. Passive Transport Ch 4

27. Passive Transport • movement of substances across the cell membrane that does not require energy.

28. A. Diffusion • movement of substances from an area of greater concentration to an area of lower concentration. • substances diffuse down their concentration gradient.

29. B. Osmosis • the diffusion of water through a selectively permeable membrane (cell membrane). • involves the movement of a substance –water- down its concentration gradient.

30. The direction of water movement across the cell membrane depends on the concentration of free water molecules in the cytoplasm and in the fluid outside the cell.

31. There are three possibilities for the direction of water movement. 1) Water moves out ⇒ Cell shrinks ⇒ Hypertonic solution The fluid outside the cell has a lower concentration than the fluid inside the cell (cytoplasm). 2) Water moves in ⇒Cell Swells ⇒ Hypotonic solution The fluid inside the cell (cytoplasm) has a lower concentration than the fluid outside the cell.

32. 3) No movement of water ⇒Cell Stays the same ⇒Isotonic solution The cytoplasm and the fluid outside the cell has the same concentration. • Hypertonic Solution • Hypotonic Solution • Isotonic Solution

33. C. Facilitated Diffusion transport of substances through a cell membrane down a concentration gradient aided by carrier proteins.