1. Chapter 3
Cell Structure

2. I. History of Cells
Cells were first observed only after microscopes were invented in the 1600s
Robert Hooks, “The Cell Guy” used a microscope to observe a thick slice of cork in 1665
- He saw a lot of little boxes that reminded him of the small cells in which monks lived, so he called them cells

3. Anton van Leeuwenhoek used a microscope to view water from a pond
- discovered many living creatures; first single-celled organisms
Ameoba
Yeast
Bacteria

4. II. The Cell Theory
3 parts
1. All living things are made of one or more cells
2. Cells are the basic units of structure and function in organisms
3. All cells arise from existing cells

5. A. Cell size
Small cells function more efficiently than large cells because of the higher surface are-to volume ratio
- substances do not need to travel as far to reach the center of a small cell, therefore they can enter and leave the cell in numbers large enough to meet the cell’s needs

6. B. Common Features of Cells 1. Cell membrane: outer boundary
Encloses the cell and separates the cell interior from its surrounding
Regulates what enters and leaves a cell
2. Cytoplasm: cell interior
3. Cytoskeleton
Microscopic fibers that support a cells structures in the cytoplasm
Outside of Cell
Inside of Cell
Cytoplasm

7. 4. DNA
Provides instructions for making proteins
Regulates cellular activities
Enables cells to reproduce
5. Ribosomes: one type of cellular structure
Makes proteins

8. III. Prokaryotes
Single-celled organisms that lack a nucleus and other internal compartments
Characteristics of Prokaryotes
A prokaryote’s enzymes and ribosomes are free to move around in the cytoplasm because there are no internal structures that divide the cell into compartments

9. Genetic material is a single, circular molecule of DNA, often located near the center of the cell
Prokaryotic cells have a cell wall surrounding their cell membrane that provides structure and support
Some prokaryotic cell walls are surrounded by a capsule
Many have flagella, which are long, threadlike structures that enable movement

10. IV. Eukaryotic Cells
Eukaryotes are organisms whose cells have a nucleus
The nucleus houses the cell’s DNA
Organelles are structures that carry out specific activities allowing eukaryotic cells to function in ways different from prokaryotes

11. Some eukaryotic cells have hair like structures called cilia that help some cells propel them through their environment and others move substances across their surfaces
Concept Map Prokaryotes vs. Eukaryotes

12. V. The Cytoskeleton
Provides the internal framework and the shape of an animal cell
Composed of an intricate network of protein fibers anchored to the inside of the plasma membrane
Some fibers attach the nucleus and other organelles to fixed locations in the cell

13. A. Microfilaments (Actin Fibers)
Three types
A. Microfilaments (Actin Fibers)
Form a network just beneath the cell surface attached to membrane proteins embedded within the cell membrane
By contracting or expanding, actin fibers control the shape of animal cells
Cell membrane
Microfilaments

14. B. Microtubules
Hollow tubes made of the protein tubulin
Act as “rails” for motor proteins to move along that carry RNA molecules

15. C. Intermediate Fibers
Thick ropes that anchor particular enzymes and ribosomes near one another

16. VI. The Cell Membrane
Cell membranes are fluid because of the lipids that form them
The cell membrane only allows certain substances in the cell’s environment to pass through; it is selectively permeable

17. The Cell Membrane as a Barrier
The cell membrane has a double layer of phospholipids called a lipid bilayer
- a phospholipid is made of a phosphate group and two fatty acids

18. the phosphate group acts as a polar “head,” it is attracted to water, or hydrophilic
the fatty acids act as nonpolar “tails,” they are repelled by water, or hydrophobic

19. B. Membrane Proteins
Some proteins are located in the lipid bilayer to indicate cell type, bind specific substance, and move substances into and out of the cell with the help of enzymes

20. Proteins are made of amino acids that anchor the proteins in the bilayer
- polar amino acids are attracted to the polar “head” groups and water on either side of the cell membrane
- nonpolar amino acids are attracted to the nonpolar “tail” groups on the inside of the lipid bilayer

21. Nuclear pores are scattered over the surface of the nuclear envelope
VII. Nucleus
The nucleus is surrounded by two lipid bilayers called the nuclear membrane, or nuclear envelope
Nuclear pores are scattered over the surface of the nuclear envelope
Ribosomes are assembled in a region of the nucleus, called the nucleolus
Eukaryotic Organelle Concept Map during lecture

22. Ribosomes and RNA are moved out of the nucleus to the cytoplasm through the nuclear pores
Hereditary information is coded in the cell’s DNA which is stored in the nucleus

23. VIII. Ribosomes and the Endoplasmic Reticulum
Ribosomes make proteins
Ribosomes themselves are made of proteins as well as RNA
Production of Proteins
1. Some ribosomes are suspended in the cytosol and make proteins that remain inside the cell

24. 2. Other ribosomes are attached to the endoplasmic reticulum and make proteins that are exported from the cell
The endoplasmic reticulum, or ER, helps move proteins and other substances through the cell
- it too is made of a lipid bilayer

25. ER with ribosomes attached to its surface is called rough ER
Helps transport proteins that are made by the attached ribosomes by pinching them off into vesicles and moving them to the Golgi apparatus
b. ER without ribosomes is called smooth ER
Helps make lipids and break down toxic substances

26. B. Packaging and Distribution of Proteins 1
B. Packaging and Distribution of Proteins 1. Ribosomes make proteins on the rough ER; the proteins are packaged into vesicles 2. The vesicles transport the newly make proteins from the rough ER to the Golgi apparatus

27. 3. In the Golgi apparatus, proteins are processed and then packaged into new vesicles
Many of these vesicles move to the cell membrane and release their contents outside the cell
Other vesicles, including lysosomes, remain within the cytoplasm; Lysosomes digest and recycle the cell’s used component by breaking down proteins, nucleic acids, lipids, and carbohydrates

28. IX. Mitochondria
Mitochondria harvests energy to make ATP, the main energy of cells
Mitochondria has two membranes
1. an outer, smooth membrane
2. an inner, folded membrane
Chemical reactions occur in between the two membranes that produce ATP

29. Mitochondrial DNA
Mitochondria has its own DNA and ribosomes that make their own proteins
Mitochondrial DNA comes from your mother

30. X. Structures of Plant Cells A. Unique Features of Plant Cells
1. Cell Wall
Composed of proteins and carbohydrates, including the polysaccharide cellulose
Helps support and maintain the shape of the cell
Plant Specific Organelles Concept Map during lecture

31. 2. Chloroplasts
Use light energy to make carbohydrates from carbon dioxide and water
Found in a variety of eukaryotic algae
Also contain two membranes, supply energy to the cell, and contain their own DNA like mitochondria

32. 3. Central Vacuole
Stores water and can contain other substances including ions, nutrients, and wastes
When full, it makes the cell rigid allowing for the plant to stand upright