1. Chapter 7
A View of the Cell

2. Cell Theory
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Before microscopes, people thought diseases were caused by curses and supernatural spirits
They had no idea microorganisms, such as bacteria and viruses existed
When the microscope was invented, scientists discovered cells exist
Cells are the basic units of living organisms

3. Cell Theory
Anton van Leeuwenhoek (Dutch) used the first simple light microscope in the 1600s
It had one lens (page 1064)
Gradually, lenses got better
Compound light microscopes use a series of lenses to magnify objects in steps
Can magnify up to 1500 times
The microscopes we use in the lab

5. Cell Theory
Robert Hooke (1600s, English) used a compound light microscope to study cork, the dead cells of oak bark
He saw small, geometric shapes that reminded him of the small rooms monks lived in called cells
Cells are the basic units of all living things

6. Cell Theory
Matthias Schleiden (1830s, German) discovered that all plants are made of cells
Theodor Schwann (German) discovered that all animals are made of cells
Rudolf Virchow discovered that all cells come from existing cells
All these scientists (plus others) contributed ideas that are now summed up in what we call the cell theory

7. Cell Theory All organisms are composed of one or more cells.
The cell is the basic unit of structure and organization of organisms.
All cells come from preexisting cells.

8. Electron Microscopes
Electron Microscopes let us see a much greater magnification than light microscopes
They use beams of electrons to produce images
Scanning Electron Microscope
Used for scanning 3-D surfaces

9. Electron Microscopes Transmission Electron Microscope
Used for scanning interior structures of cell

10. Types of Cells
Organelles are small, specialized structures within cells
Many, but not all are surrounded by membranes
Prokaryotes are organisms that do not have membrane-bound organelles (biology.arizona.edu)
Kingdom Monera ( now split into Eubacteria & Archaebacteria)
Eukaryotes are organisms that do have membrane-bound organelles
Kingdoms Animalae, Plantae, Fungi, Protista

11. Types of Cells
Robert Brown (Scottish) observed that eukaryotic cells have a prominent structure, the nucleus
the nucleus manages cellular functions
Rudolf Virchow concluded that this prominent structure was responsible for cell division

12. Section 1 Review
How has the history of microscopes influence the study of cells?
What are the three parts of the cell theory?
What is the difference between a light microscope and an electron microscope?
What is the difference between a prokaryote and a eukaryote?

13. The Plasma Membrane
Cells must maintain proper conditions within itself to function
The plasma membrane is a flexible boundary between the cell and its environment
It allows a steady supply of nutrients into and out of the cell at the appropriate levels
The plasma membrane is selectively permeable
This means that it allows some molecules to pass through while keeping others out.
Like a screen in a window

14. The Plasma Membrane Phospholipids
The “head” is polar, or slightly charged
It is hydrophilic (likes water)
The “tail” is nonpolar, or not charged
It is hydrophobic (repels water)
The phospholipids arrange themselves form a bi-layer with the fatty acid tails forming the interior and the heads facing the watery environments outside and inside the cell

15. Plasma Membrane The plasma membrane is called a phospholipid bilayer
Arranged in this manner, a barrier is created that is water-soluble at its outer surfaces and water-insoluble in the middle
Keeps out both water soluble and water insoluble molecules

16. Plasma Membrane
The current model of the plasma membrane is called the fluid mosaic model.
The phospholipids actually move around like a fluid.
The other components of the membrane (proteins, carbohydrates, cholesterol, etc.) move around as well

18. Plasma Membrane
Cholesterol helps to stabilize the phospholipids by preventing their fatty acid tails from sticking together
Transport proteins move span the membrane and move needed substances or waste materials through the plasma membrane
Other proteins and carbohydrates that stick out help cells to identify surface signals and other cells
These proteins play an important part in protecting cells from infection

19. Section 2 Review What is a phospholipid?
Why is the cell membrane a bilayer?
What does polar and nonpolar mean?
What are the specialized parts of the cell membrane?
Why is the cell membrane referred to as fluid mosaic?

20. Cell Wall
Fairly rigid structure located outside the plasma membrane of some cells that provides additional support and protection
Plants, fungus, most bacteria
The cell wall is very porous, made of a tough mesh of fibers
Like framing of a house

21. Nucleus
Membrane-bound (called nuclear envelope) organelle that contains the directions to make proteins
Nuclear pores allow passage through the nuclear envelope
Chromatin - uncondensed strands of DNA
When cell is dividing, DNA condenses into chromosomes
Nucleolus - organelle within the nucleus that make ribosomes

22. Organelles
Ribosomes are the sites where the cell produces proteins according to the directions of DNA
One organelle without a membrane
Cytoplasm is the clear, gelatinous fluid inside the cell
Acts as a medium for things to move around in the cell
“Organelles can’t fly”

23. Organelles
The endoplasmic reticulum (ER) is arranged in a series of highly folded membranes suspended in the cytoplasm
In general, ER is involved in the movement of materials throughout the cell
Rough ER has ribosomes, which is where protein synthesis takes place
Smooth ER has no ribosomes and is involved in numberous biochemical activities, including the production and storage of lipids

24. Organelles
The Golgi apparatus is a flattened stack of tubular membranes that modifies the proteins
The Golgi sorts proteins into packages and packs them into membrane-bound structures called vescicles for later transport (like UPS)

25. Organelles
Vacuoles are membrane-bound compartments for temporary storage of materials
Store food, enzymes, water, waste
Plant cells have one very large vacuole

26. Organelles Lysosomes are organelles that contain digestive enzymes
Digest old organelles, food, viruses, bacteria, etc.
Can fuse with a vacuole to dump waste or give enzymes
Lysosomes digest a tadpole’s tail

27. Organelles Plastids are a group of organelles used for storage
Named for the color or pigment they contain
Chloroplasts are organelles that capture light energy and convert it to chemical energy (photosynthesis occurs here)
Plastid containing chlorophyll, which actually traps the light and gives plants green color

28. Organelles
Mitochondria are membrane-bound organelles in plant and animal cells that transform stored chemical energy into a usable form for the cell (ATP)
Has an outer and inner highly folded membrane
ATP produced on inner folds

29. Organelles The cytoskeleton forms a framework for the cell
A network of tiny rods and filaments
Cytoskeleton is constantly changing its shape
Microtubules are thin, hollow cylinders made of protein
Microfilaments are smaller, solid protein fibers
Give support for cell
Provide “highway system” for organelles to move throughout cell

31. Organelles
Centrioles are organelles made up of microtubules that play a part in cell division
In animals and most protists
Cilia are short, numberous projections that look like hairs
Made of microtubules and help organelles move and feed
Flagella are longer projections that move in a whip-like motion
Made of microtublules - help with movement
Cells usually only have 1 or 2

32. Animal Cell

33. Plant Cell

34. Section 3 Review
How are highly-folded membranes an advantage for the functions of cellular parts?
Name an organelle that has highly-folded membranes.
If a cell synthesizes large quantities of protein molecules, which organelles might be numerous in that cell?
A cell’s digestive enzymes are enclosed in a membrane-bound organelle. How can these molecules function in the cell?
Compare and contrast the functions of a cell wall to the functions of a plasma membrane.
What are the functions of the cytoskeleton?
Why are mitochondria and chloroplasts referred to as energy transporters?