Biology 107 - Cell IBiology 107 - Cell ISeptember 24, 2003September 24, 2003

Cell ICell I

Student Objectives:Student Objectives: As a result of this lecture and the assigned As a result of this lecture and the assigned reading, you should understand the following:reading, you should understand the following:

1.1. The basic structural and functional unit of life is the cell. The basic structural and functional unit of life is the cell.

2.2. Cells may be classified as Cells may be classified as prokaryoticprokaryotic or or eukaryoticeukaryotic, depending , depending upon their internal organization.upon their internal organization.

3.3. Prokaryotic cells are typically smaller than eukaryotic cells, while Prokaryotic cells are typically smaller than eukaryotic cells, while eukaryotic cells generally are structurally and functionally more eukaryotic cells generally are structurally and functionally more complex than prokaryotic cells.complex than prokaryotic cells.

Cell ICell I

4.4. A eukaryote ("true nucleus") has a membrane-bounded nucleus, A eukaryote ("true nucleus") has a membrane-bounded nucleus, and possesses membranous organelles, each of which has a and possesses membranous organelles, each of which has a particular function in the cell.particular function in the cell.

5.5. Organelles are structures essential for the functioning of a cell. Organelles are structures essential for the functioning of a cell. Not all organelles are membranous. Examples of non-Not all organelles are membranous. Examples of non-membranous organelles are microtubules and ribosomes.membranous organelles are microtubules and ribosomes.

6.6. The advantages of membranous organelles (compartments) The advantages of membranous organelles (compartments) include: 1) metabolic processes in the cell that require different include: 1) metabolic processes in the cell that require different specific chemical conditions may occur simultaneous and 2) an specific chemical conditions may occur simultaneous and 2) an increase in the cell's total surface area.increase in the cell's total surface area.

Cell ICell I

7.7. Organization of Cells - Common Structures and FunctionsOrganization of Cells - Common Structures and Functions a.a. Cells are microscopic is size because of the surface area Cells are microscopic is size because of the surface area to to volume relationshipsvolume relationships

b.b. Membranes enclose and delimit cellsMembranes enclose and delimit cells

c.c. Cells have a “genetic control center” containing DNACells have a “genetic control center” containing DNA

d.d. Cells have Cells have cytoplasmcytoplasm. The cytoplasm includes the . The cytoplasm includes the organelles organelles (membranous and non-membranous) and the (membranous and non-membranous) and the fluids and fluids and dissolved substances; it excludes the nucleus of dissolved substances; it excludes the nucleus of eukaryotic eukaryotic cells.cells.

Cell ICell I

8. The DNA genetic material in prokaryotes is concentrated in a region called the nucleoid region. In eukaryotes the DNA is enclosed in the nucleus.

9. Most of the DNA is attached to proteins, forming chromatin. The proteins associated with DNA assist in either the structural organization of the genetic material and/or the regulation of the use of the DNA.

Cell I

10. The eukaryotic nucleus:

a. The nuclear material is enclosed by the nuclear envelope, a double membrane structure with pores that allows the passage of material into and out of the nucleus. Through the pores travel mRNA, ribosomes, and various proteins used in gene regulation and DNA maintenance.

b. Contains is a mass of fibers and granules called the nucleolus. The nucleolus is a combination of DNA, RNA and proteins, and it is where ribosomal subunits are assembled.

Prokaryotic Cell

Eukaryotic Cell - Animal

Eukaryotic Cell - Plant

Surface area to Volume Relationship

Relationship Between Surface Area and Volume

Eukaryotic Nuclei

NucleusNucleus

Chromatin

Chromatin – DNA + Proteins

Eukaryotic Nucleus

Nuclear Envelope – Nuclear Envelope – Double-membrane Double-membrane structure with poresstructure with pores

NucleolusNucleolus