1. Chapter 7: A View of the Cell
7.1. The Discovery of Cells

2. The Cell Theory (History)
The microscope was invented by Anton van Leeuwenhoek.
The first person to see a cell (in cork) was Robert Hooke.
Matthias Schleiden concluded that all plants have cells
Theodore Schwann observed that animals were also composed of cells

3. The Cell Theory 3 main ideas:
All living things are composed of one or more cells
The Cell is the basic unit of organization of organisms
All cells come from cells

4. The Light Microscope Uses light and lenses
The Simple light Microscope used one lens and natural light (Leeuwenhoek)
The Compound light microscope: Uses multiple lenses
Magnifies up to 1500 times

5. The Electron Microscope
Invented in the 1940s
Uses a beam of electrons
Magnifies up to 500,000 times
Two Kinds:
Scanning electron microscope (SEM): Scans the surface of cells.
Transmission electron microscope (TEM): Allows for study of structures inside cells.

6. The Electron Microscope
SEM
TEM

7. Two Basic Cell Types
Prokaryotes: Cells lacking internal membrane-bound structures
Eukaryotes: Cells containing internal membrane-bound structures
The membrane-bound structures are called organelles
Contains a nucleus: organelle that manages cellular function. First observed by Robert Brown. Rudolf Virchow concluded that it was responsible for cell division.

8. Chapter 7: A View of the Cell
7.2 The Plasma Membrane

9. Maintaining a Balance
The Plasma membrane is the boundary between the cell and it’s environment
Needs to let the good stuff (e.g. nutrients) in and the bad stuff (waste) out
The plasma membrane maintains homeostasis.

10. Plasma Membrane

11. The Plasma Membrane
Maintains Homeostasis: regulates internal environment [Good in (but not too much), Bad Out]
Selective permeability: Allows some molecules into the cell and keeps some out.
Some molecules can cross the plasma membrane (i.e. water). Others must go through channels (i.e. Na, Ca, etc)

12. Structure of the Plasma Membrane
Composed of a phospholipid bilayer.
A Lipid with a phosphate group attached
Has only 2 fatty acid tails
Forms a sandwich
The phosphate group forms the polar head
The fatty acid tails form the nonpolar tail

13. Fluid Mosaic Model
The membrane is fluid: It is flexible and phospholipids can move in the membrane like water in a lake.
The membrane is mosaic: There are proteins embedded in the membrane that also move (like boats in the lake)

14. Other components
Cholesterol: Helps stabilize the plasma membrane, and prevents the phospholipids from sticking together.
Transport Proteins: Proteins that span the entire membrane and form channels for specific molecules to enter and leave (like a door).
Other Proteins and carbohydrates on the external surface: Helps with identification.
Proteins on internal surface: Provides flexibility by attaching the plasma membrane to the cell’s internal structure.

15. Chapter 7: A View of The Cell
7.3 Eukaryotic Cell Structure

16. Cellular Boundaries Plasma membrane surrounds the cell
In plants, fungi, most bacteria and some protists, the cell wall surrounds the plasma membrane
Fairly rigid
Provides support and protection
Made up of the carbohydrate cellulose
Has pores to allow molecules through

17. Nucleus and cell control
The Nucleus is the leader of the cells
Gives directions for the making of proteins
The master set of directions is in chromatin
During cell division, chromatin condenses to form chromosomes.

18. Nucleus and Cell Control
Inside the nucleus there is also the nucleolus
Makes ribosomes
Ribosomes are sites where proteins and other enzymes are made, according to instructions from DNA
Ribosomes leave the nucleus, into the cytoplasm in order to make proteins
Cytoplasm: The fluid inside the cell

19. Nucleus and cell control
The Nuclear envelope is a double membrane that surrounds the nucleus.
Made up of 2 phospholipid bilayers
Contains small nuclear pores

20. Assembly and Transport
The endoplasmic reticulum: A series of highly folded membranes
Where cellular chemical reactions take place
Like a large workspace
Some parts have ribosomes attached (rough endoplasmic reticulum - RER)
Others don’t (smooth endoplasmic reticulum – SER)

21. Assembly and Transport
RER: Proteins made in the RER may:
form part of the plasma membrane
be released from the cell
transported to other organelles
SER: involved in production and storage of lipids.

22. Assembly and Transport
The Golgi apparatus: flattened system of tubular membranes and vessicles
Modifies proteins
Sorts and packages proteins
It’s kind of like the post office: Sorts the mail and sends it to the right place

23. Assembly and Transport
RER
Golgi apparartus
vessicles

24. Vacuoles A vacuole is a sac surrounded by membrane
Used for temporary storage of
Food
Enzymes
Waste
Plant cells usually have one large vacuole, animal cells have many smaller ones

25. Lysosomes and recycling
Lysosomes are organelles that contain digestive enzymes
They digest food particles, organelles and engulfed viruses or bacteria
Can fuse with vacuoles and digest the contents.
Can also digest cells that contain them.
i.e. tadpole’s tail

26. Energy Transformers
For all the cellular processes to happen, energy is needed
Two organelles provide that energy:
Choloroplasts (in plants)
Mitochondria (in animals and plants)

27. Chloroplasts
Chloroplasts are organelles that captures light energy and produces food to store for later
Has a double membrane (like the nucleus)
The inner membrane folds in to form stacks of membranous sacs called grana/thylakoids.

28. Chloroplasts
In the thylakoid membrane there is the green pigment called Chlorophyll
Traps light energy
Gives leaves and stems their green color

29. Mitochondria
Mitochondria produces energy in a form that can be used by the cell when necessary.
Has an outer membrane and a highly folded inner membrane.
Provides large surface area.

30. Structures for Support and Locomotion
Cytoskeleton: forms the framework of the cell
Maintains shape
Composed of:
Microtubules: thin hollow cylinders made of protein
Microfilaments: thin, solid protein fibers

31. Structures for Support and Locomotion
Cilia and flagella : Structures that aid in locomotion and feeding.
Composed of pairs of microtubules, with a central pair surrounded by 9 additional pairs.
Cilia are short, numerous, hair-like projections that move in a wavelike motion
Flagella are longer projections, move in a whip-like motion.