I. The Cell- The basic unit of structure and function

A. Discovery of Cells 1. Early Microscope Observations

Antoni van Leeuwenhoek (1632-1723). Robert Hooke 1665

a) Robert Hooke (1660) observed cork under a compound microscope and named the box-like structures cells

b) Matthias Schleiden

• 1838

• Concluded all plants and plant parts are made of cells

c. Theodor Schwann

• 1839

• Concluded all animal and animal parts are made of cells

d. Rudolf Virchow

• 1855• Concluded that

all cells come from previously existing cells

• "Omnis cellula e celula"

2. Cell Theory (Schleiden, Schwann and Virchow)

a) All organisms are composed of cells

b) Cells are the basic unit of structure and function in organisms

c) All cells come from previously existing cells

B. Types of Cells:Prokaryotic Vs. Eukaryotic Cells

1. Prokaryotic Cells

• small cells with no nucleus and membrane bound organelles.

• Examples: Bacteria and Blue-green algae

2. Eukaryotic Cells- Cells that have a nucleus and membrane bound organelles.

Plant

Animal

Fungus

Protist

C. Cell Size Limitations

1. Based on the ability of the cell to obtain oxygen, nutrients and to get rid of wastes.

2. Surface area to volume ratios are extremely important

Sammy Cell

Surface Area Vs. Volume

Surface Area (Cell membrane)- place where all oxygen, food and wastes must enter and exit the cell

Volume (cytoplasm)- substance that uses up food, oxygen and produces waste

1 μm1 μm

1 μm

Surface area = length X width X number of sides

Volume = length X width X height

Surface area = 1 μm X 1 μm X 6

Surface area = 6 μm2

Volume = 1 μm X 1 μm X 1 μm

Volume = 1 μm3

Surface Area to Volume Ratio = 6 : 1

Surface area = 24 μm2

Volume = 2 μm X 2 μm X 2 μm

Volume = 8 μm3

Surface Area to Volume Ratio = 3 : 1

Cell Double Size

Surface area = 2 μm X 2 μm X 6

2 μm2 μm

2 μm

Surface area = 54 μm2

Volume = 3 μm X 3 μm X 3 μm Volume = 27 μm3

Surface Area to Volume Ratio = 2 : 13 μm

3 μm

3 μm

Cell Triples Size

Surface area = 3 μm X 3 μm X 6

3. As a cell grows, its need for oxygen increases faster than its ability to get oxygen. So the cell must divide or suffocate

4. The Importance of Compartmental organization

a) Eukaryotic Cells are surrounded by a plasma membrane and are partitioned into organelles which provide correct environments for specific metabolic processes

b) Many enzymes are built into the membranes

D. Cells are shaped to perform their function

                                        

1. Nerve Cells are long and thin and highly branched to transmit messages throughout the body

2. Red Blood Cells are round for moving through small blood vessels

E. Organelles of the Eukaryotic Cell

1. Nucleus- organelle responsible for the

control of all cellular processes a) A nuclear membrane

determines what materials enter and exit the nucleus through the nuclear pores

b) While the cell is not dividing, loose strands of DNA appear grainy and are called chromatin

c) Nucleolus- dark spherical structure in the nucleus that is rich in RNA and is responsible for the production of ribosomes

Nuclear pore

Nuclear Membrane

Chromatin

Nucleolus

Which is the SEM and which is the TEM?

Chromosomes

Chromosome Vs ChromatinDNA Packing

2. Endoplasmic Reticulum- network of internal membranes extending through the cell

a) The ER transports materials in the cell

b) The Smooth ER (SER) produces lipids, stores calcium and detoxifies certain poisons

c) The Rough ER (RER) has ribosomes along its length. Transports many proteins

3. Ribosomes The site of protein synthesis

4. Golgi Apparatus- layers of plate-like membranes which store and package cell products usually for transport out of the cell

5. Lysosome- golgi vesicle containing digestive enzymes that fuse with vacuoles and

digest food

Organelles work together to carry out life processes

6. Mitochondria- power plant of the cell in which most of the reactions of cellular

respiration occur

7. Plastids- organelles found only in plant cells that are involved in the synthesis or storage of food

a) Chloroplast- contain chlorophyll and carotenoids which trap light energy for photosynthesisb) Leucoplast- plastid used in the storage of starch and other materialsc) Chromoplast- contains pigments that give flowers and Fruits their characteristic colors

8. Cytoskeleton- interlinked microfilaments that form the framework of the cell

9. Centrioles- Found in animal cells Anchor spindle fibers during cell division

10. Vacuoles- membrane bound area for digestion food storage, water storage and waste disposal

11. Cilia and Flagella- specialized microtubules used for movement

12. Plasma Membrane- fluid , phospholipid bilayer which determines what materials enter and exit the cell

13. Cell Wall-ridged outer layer of plant cells for support and protection