Download Unit A Notes #1 Cell Intro - Mr. Lesiuk

CELL STRUCTURE : PART ONE
Cell Theory:
- The study of cells had its birth with the invention
of the microscope. Advances in Cytology (study of
cell) took place in the 1900’s with the invention of
better scanning microscopes.

- In the late 1830’s two German biologists,
Schleiden (a botanist) and Schwann, (a zoologists)
made similar claims. They found that all
organisms they had studied were composed of
cells. Their discoveries were generalized in the
following statement:
1. “ The cell is the basic building block of all
organisms.”
2. "All organisms consist of one or more cells"
- A few years later, Rudolph Virchow added the
following observation:
3. “ All cells come from pre-existing cells.”
Virchow:
- These three statements comprise what is now
known as the “CELL THEORY”.
Cell Types:
A) Prokaryotic Cells – (Pro = First, Karyo =
Nucleus) Primitive (simple) cells.
- Do not contain a nucleus or any membrane
bound organelles.
- Lack internal membranes.
- Only Kingdom Monera (bacteria) have
Prokaryotic cells.
- In Prokaryotic cells, the reactions occur all over
the cytoplasm, and reactions are less efficient.
B) Eukaryotic Cells – (Eu =True, Karyo = Nucleus)
Complex cells
- Have a nucleus and many membrane bound
organelles.
- Contains internal membranes.
- Each organelle carries out a certain function.
- Eukaryotic cells make up Plants, Animals,
Protists, and Fungi.
Cellular Organelles and Other Cellular
Components:
Nucleus
- Largest organelle.
- Surrounded by a double-layered membrane
(the nuclear envelope).
- Membrane has pores through which larger
molecules pass. (Nuclear Pores)
- Control centre for the cell’s functions. (The
brain).
- Contains a fluid called the nucleoplasm.
- Contains chromatin (DNA strands which form
chromosomes during cell division).
Nucleolus
- Dark region in the Nucleoplasm.
- One or more found in the nucleus.
- Site where ribosomal RNA (rRNA) is produced
or stored and ribosomes are made.
- Involved in interactions between the nucleus and
the cytoplasm.
Chromatin:
- The hereditary material of the cell.
- Condenses to form chromosomes during cell
division.
- Composed of Protein (Histones) and DNA
PROTEIN
HISTONE
Chromosomes
- Rod-shaped bodies in the nucleus, only visible
during cell division.
- Contains the hereditary information. (genes)
- Condensed (bunched up) chromatin.
23 pairs of
chromosomes in
a healthy human
= 46
Cytoplasm = (Cytosol and cytoplasmic organelles)
- A colloidal substance, which can change from a
solid (gel) to a liquid (solution) state with the
addition of heat or change in metabolic activity.
- It contains and supports all the cells organelles.
Cell Membrane or Plasma Membrane
- Composed of proteins and phospholipids (fats
containing a phosphate group).
- Acts as skin around the cells contents.
- Acts as a selectively permeable membrane to
allow movement of materials in and out of the cell.
- Located around the outside of the cell.
- Single- layered membranes are located around
the vacuoles, lysosomes, E.R., Golgi Apparatus.
- Double-layered membrane around the nucleus
and mitochondria.
- Hydrophilic (water-loving) polar phosphate
heads sticking out, with Hydrophobic (water
fearing) fatty acid tails sticking in.
Smooth Endoplasmic Reticulum
- System of interconnected flattened tubes, sacs, or
canals.
- Begins at the nuclear envelope and branches
throughout the cytoplasm to the cell membrane.
- Moves molecules from one area to another.
- It is the site of phospholipid (and steroid)
manufacturing.
- Cells that produce steroid hormones, have an
abundant amount of smooth ER.
- Section of both types of ER can break free
“blebbing” to produce small membrane bound
sacs of either proteins or lipids called vesicles.
- Often these vesicles contain enzymes that
synthesize lipids and related products such as
steroids.
- Some contain enzymes that detoxify drugs.
- Amount of E.R. in a cell increases or decreases
depending on the cell’s activity.
Rough
ER
Rough Endoplasmic Reticulum
- Like Smooth E.R., but with attached ribosomes.
- Abundant in cells that produce large amounts of
protein for export from the cell.
The combination of phospholipid-membranous
structures including the Nuclear Envelope,
Endoplasmic Reticulums, Cell Membrane and
Golgi Apparatus; collectively work together to
form what is known as the Endomembrane
System.