Chapter 3 Cell Structure by linzhengnd



Chapter 3 Cell Structure
1. You will distinguish eukaryotic and prokaryotic cells.
2. You will learn the structure and function of the
    plasma membrane.
3. You will relate the structure of cell parts to their
4. You will recognize the 5 scientists that discovered the
    nature of cells.

CH. 3.1 Looking at Cells
1. All living things are made of cells.
2. Cells are often too small to be seen with the naked eye.

Discovery of Cells
1. Prior to the discovery of microscopes people believed
    that curses and supernatural forces caused diseases.
2. The invention of microscopes in the early 1600s
   allowed people to start seeing things too small to be
   observed by the naked human eye.
3. A compound light microscope uses a series of lenses
    to magnify objects in steps.
4. 1665 – Robert Hooke used a compound microscope to look
    at cork. He described the tiny box-like structures as cells.
(They reminded him of the cells in a monastery. His
microscope had multiple lenses but the lens quality was poor
allowing him to only see things about 20 times bigger.)

5.   Anton van Leeuwenhoek described cells seen through
      a simple light microscope from 1668 to 1700. His
     microscope had only one lens. (He was a lens maker and his
     single lens could see things up to 200 times bigger.)
     He was the first person to see unicellular organisms (He was
      the first person to see single cell organisms like protists.
      He was the first person to see sperm and blood cells.)

6.  By the 1800’s microscopes and lenses had been perfected so
   scientists could see things up to 1500 times bigger.
7. 1830’s – Matthais Schleidan observed a variety of plants and
    concluded they were made of cells.
8. 1830’s – Theodore Schwann made similar observations
   about animals.
9. 1858 – Rudolf Virchow determined that cells come from
   other cells.
10.The work of Schleidan, Schwann, and Virchow formed the
    modern cell theory.

Cell Theory
1. All organisms are composed of cells.
2. The cell is the basic unit of organization of organisms.
3. All cells come from pre-existing cells. Cells divide to
   form two identical cells (mitosis or binary fission).

Types of microscopes
1. A compound light microscope uses light passing through
   two or more lenses to enlarge an image of a specimen.
2. Developed in the 1600’s and perfected over 200
    years the CLM can magnify objects up to 1500 times.
3. An electron microscope uses a beam of electrons instead of
   light to produce pictures of the specimen.
   Developed in the 1940’s, the electron microscope can
       magnify objects 500,000 times their original size.
   Object must be in a vacuum. Organisms cannot survive
       in the vacuum of an EM.

Cells must be small
1. Small cells work more efficiently than large ones.
2. The human body is composed of 100 trillion cells.
3. Small cells exchange substances more readily than
    large cells because of surface-area-to-volume ratio.
4. The higher the surface-area-to-volume ratio the
    shorter the distance an object has to travel to reach
    the center of the cell.
5. Small things and flat things have more surface area
       compared to the volume inside.

Common features of the cell (all cells have these)
1. All cells share some common features.
2. All cells have a plasma membrane that is an outer
    boundary of the cell. (plasma membrane is also
   called the cell membrane)
3. The plasma membrane regulates what comes in and
    goes out of the cell.
4. All cells contain cytoplasm that is the “interior fluid”
    of the cell.
5. All cells have a cytoskeleton that acts like a scaffold
   and supports the cell as well as the interior structures.
6. All cells have ribosomes which are the structures on
    which proteins are made.
7. All cells have DNA and RNA which contain all the
    instructions for making proteins, regulating cellular
   activities, and reproduction.

Prokaryotes do not contain internal compartments
1. The smallest and simplest cells are prokaryotes or bacteria.
2. Prokaryotes do not have a nucleus. They also do not have
     endoplasmic reticulum, mitochondria, chloroplasts, vacuoles,
     Golgi apparatus, or any other membrane bound structures.
3.   The genetic material in bacteria is a single circular
      strand of DNA.
4.   Bacteria grow and divide very rapidly.
5.   Some bacteria cause human disease.
6.   Bacteria have a cell wall made of simple polysaccharides
     that surrounds the plasma membrane.
7.   Antibiotics break down the cell wall causing the
     bacteria to explode.
8.   Many bacteria have long flagella that enable them to move.

Eukaryotic Cells are organized
1. Eukaryotic cells have a nucleus.
2. The nucleus is an internal membrane bound structure
   that contains the cell’s DNA.
3. The DNA is in open ended strands.
4. Eukaryotic cells have many other membrane bound
    structures that enable them to function in ways bacteria
5. Some single celled eukaryotes have flagella or cilia that
        allows them to move.
6.   Flagella are long whip-like projections.
7.   Cilia are short hair-like projections.
8.   Some cells have cilia designed to move other materials from
     place to place.

Cell Membranes
1. Are selectively permeable meaning some things can pass
     through while others cannot.
2. Are flexible instead of being hard like a shell.
(like a water balloon)
3. Are primarily composed of phospholipids.
4. A phospholipid is composed of a polar head and two
    non-polar tails.
5. The polar head is a phosphate group and is hydrophilic.
6. The non-polar tails are fatty acids and are hydrophobic.
7. This hydrophilic / hydrophobic nature creates an inner
     non-polar layer to the membrane with two polar
    layers on the outside of the membrane.

Proteins are embedded in the lipid bilayer
1. Surface marker proteins often have a carbohydrate head that
       allows cells to recognize each other.
2. Receptor proteins recognize and bind to specific substances.
3. Enzymes assist chemical reactions inside the cell.
4. Transport proteins help substances move across the

Cell Organelles are membrane bound structures with
specialized functions.

The Nucleus
1. The nucleus houses the DNA and controls most functions of
   the cell. (This is the boss’ office and the Boss DNA has all
               the information needed make proteins)
2. The DNA in eukaryotic cells is shaped like elongated thin
3. The nuclear membrane has pores called nuclear pores which
   allow the RNA to pass from the nucleus into the cytoplasm.
4. The RNA carries a message from the DNA to the ribosomes
   where the message is translated and turned into proteins.
    (The RNA is the supervisor who carries the message to the
    Ribosome Workers who make the protein)

The Endoplasmic Reticulum
1. In addition to free floating ribosomes found in all cells,
      eukaryotic cells have ribosomes attached to the
      endoplasmic reticulum.
2. The ER moves proteins through the cell.
3. The two main parts of the ER are Rough ER and Smooth ER.
4. The rough ER contains ribosomes.
5. The smooth ER does not contain ribosomes.
6. After the proteins are made, a part of the ER pinches off
   forming a vesicle (little bag) containing the proteins.
   (The ER is the conveyor belt in the protein factory)

Golgi Apparatus
1. The Golgi apparatus packages and distributes proteins.
     (Fed Ex) (Pimped Out)
2. Vesicles from the ER travel to the Golgi apparatus
     delivering crude proteins.
3. Enzymes in the Golgi apparatus modify these proteins.
4. The proteins are then repackaged into new vesicles and then
       ships them out to other parts of the cell or to the outside
       of the cell.
5. Lysosomes are vesicles produced by the Golgi apparatus
       that contain digestive enzymes. (Recycle Bin)

1. The mitochondria make ATP, the energy currency
    of the cell. (Power Plant)
2. Mitochondria are a unique organelle in that they contain a
       separate nucleus with separate DNA and free floating
3. The mitochondrial DNA allow them to reproduce
       independent of cell division.
4. This is one piece of evidence in the theory on the origin of
       eukaryotic cells from prokaryotic cells.

Specialized Plant Structures and Organelles
1. Cell Wall
2. Chloroplasts
3. Central Vacuole

Cell Wall
1. Plant cells have a thick cell wall that surrounds the cell
       membrane and gives the cell support and protection.
2.   The cell wall is made of a complex polysaccharide
       called cellulose.
3.   Most animals cannot digest cellulose without the help of
       symbionts. (mutualism)
1. Chloroplasts are organelles that trap light energy to
      make carbohydrates from CO2 and H2O.
2. Chloroplasts, like mitochondria, contain their own DNA and
      are thought to be descendants of prokaryotic cells.
Central Vacuole
1. The central vacuole is the largest organelle in the plant cell.
2. The central vacuole stores water, nutrients, ions, and waste.
3. When the central vacuole is full of water, it presses tight
   against the cell wall making the cell rigid.
4. This rigidity is called turgor pressure and allows soft
    tissue plants to stand upright.

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