Chapter 2

Cells – are the smallest unit that is capable of performing life functions.

          They come in many different sizes and shapes.

          Often the shape of a cell tells you something about its job.

 There are three characteristics in common for all cells:

        1. cell membrane

        2. hereditary material

        3. cytoplasm

All cells can be divided into 2 groups: Prokaryotic and Eukaryotic

·        Prokaryotic cells do not contain membrane bound organelles. (cooler without baggies)

·        Eukaryotic cells do have membrane bound organelles.  Animal and plant cells are all Eukaryotic. (cooler with baggies)

Cell Parts:

Cell Membrane – is a protective layer that surrounds the cell.  Let certain things pass in or out.

Cytoplasm– is the gel-like material inside the cell membrane.

Nucleus – is the largest organelle in most cells.  It directs all the activities of the cell and contains instructions for everything the cell does (DNA). 

The nucleus may contain a nucleolus which is darkened area of nucleus that makes ribosomes.

Chloroplasts – are not in animal cells.  This is where chlorophyll is found and light energy is changed into glucose (sugar).

Mitochondria – are the power source for cells.  Food is broken down here into carbon dioxide, water, and energy.

Ribosomes – make proteins.  Some ribosomes float freely in the cytoplasm and other are attached to the ER.  DNA directs the what, when and how much protein to make.

Endoplasmic Reticulum (ER) – is a folded membrane that moves material around in the cell.  The ER may be smooth or rough.  Rough ER contains ribosomes.

Golgi bodies – are stacks of membrane-covered sacs that package and move proteins to the outside of the cell.

Vacuoles – are storage areas in the cell.  They may contain water, food, or anything else the cell needs to store.

Lysosomes – contain chemicals that digest wastes and worn-out parts of the cell.  The lysosome may break down the entire cell itself if it is damaged or dead. 

Systems work together to make organisms. Organs work together to make systems. Tissues work together to make organs. Cells work together to make tissues.

Section 2

 Microscopes – have one or more lenses that make an enlarged image of an object.

 Zacharias Janssen – a glasses maker in 1590, put two magnifying glasses together in a tube.  This was the first microscope.

 Anton Van Leeuwenhoek – a scientist in 1600s, put a tiny glass bead into a tube and made a simple microscope.  He looked at pond water and saw many things.  It was 270 xs larger.

Simple microscopes – have only one lens.  (like a magnifying glass)

Compound – have more than one lens. (eyepiece lens and objective lens)

·        The power of the microscope is found by multiplying the strengths of each lens individually.  Some may be as powerful al 2000x!!!

Electron microscopes – use fast speed electrons bouncing off an object to see it. These have a power of 1,000,000 xs.

·        Scanning electron microscope (SEM) – see whole objects that could be living.

·        Transmission electron microscope (TEM) – see a small slice of an object.

·        Scanning tunneling microscope (STM) – shows arrangements of atoms on the surface of a molecule.

Cell Theory

·        Robert Hooke (1665) called ‘little boxes’ he saw in cork CELLS.

·        Matthias Schleiden (1838) stated that all plants are made of cells.

·        Theodor Schwann (1839) stated that all animals were made of cells.

·        Rudolph Virchow (1854) stated that cells divide to form others.

With all this work and more, the cell theory was written and is a basis for scientists.

The Cell Theory states:

1.     All organisms are made of one or more cells.

2.     Cells are the basic units of life.

3.     All cells come from cells that already exist.

Section 3

Virus – a nonliving particle consisting of a core of hereditary material surrounded by a protein coat

Characteristics of viruses are

·        Microscopic – small!!!

·        Can only reproduce inside another cell – called host cell

·        Nonliving

·        Protein coat – gives shape (they come in all shapes)

·        Has hereditary material (DNA or RNA)

Some can be made into crystals and stored for years

Viruses are named for diseases they cause or organ/tissues they infect.

Reproduction of Viruses –

          Viruses get into the nucleus of a cell and attach to its DNA.  They then cause the cell to make many more copies of the virus.  The cell continues to make more viruses until it pops and dies.

 Active Viruses – begin making new viruses as soon as they enter the cell.

Latent Viruses – hang out for a while first after they enter the cell.  They later become active.  Nobody knows what triggers many latent viruses to become active.

Viral diseases – are caused by viruses.  There is no cure or antibiotic that can help this disease.  These diseases can be prevented however.

Vaccines are used to prevent viral diseases.  They are injections of modified virus particles that cannot cause the disease anymore.

Edward Jenner in 1796 developed a vaccine for smallpox.  He noticed that people that had cowpox did not get smallpox.  He did this not knowing what a virus was and had never seen one.

Many vaccines are now mandatory for children.  The following are some vaccines available.

          Smallpox, rabies, polio, mumps, measles, flu, chicken pox

Doctors are working on a cold and AIDS vaccine.

Viruses can also do well. 

Gene therapy – is the use of a virus to infect cells that are defective.  It is used in treating sickle-cell anemia and others.