Download Cells fall into two major categories: 1-prokaryotes 2

Cells fall into two major categories:
1-prokaryotes
2-eukaryotes
1. Prokaryotes are cellular organisms that don’t have a “true” nucleus. They do not
have a nuclear membrane. (i.e. bacteria, blue-green algae)
Remember a nucleus is the control center of the cell. It contains the genetic material
packed into chromosomes, and it is associated with other organelles that function in
the production of amino acids and proteins based upon what the genetic material
dictates.
Prokaryotes have some genetic material, but it is not as well organized as it is in
eukaryotes. Still, prokaryotes are able to reproduce.
2. Eukaryotes are organisms that contain chromosomes including plants, animals,
fungi (like mushrooms), protozoa, and most algae. Eukaryotes have the following
characteristics:
1. Have a nucleus that stores their genetic material.
2. Animal cells have an organelle called mitochondria that effectively
combines oxygen and food to convert energy to a useable form.
3. Plant cells have chloroplasts, which use energy from sunlight to create
food for the plant.
4. Eukaryotic cells have internal membranes, which created compartments
inside the cells that have different functions.
5. Plant cells have a cell membrane and a cell wall, which is rigid; animal
cells have only a cell membrane, which reinforces the cytoplasm of the cell,
controls cellular movements.
6. The cytoskeleton, which reinforces the cytoplasm of the cell, controls
cellular movements.
Eukaryotic cells are primarily distinguished from prokaryotic cells by having
a true nucleus.
Typically eukaryotic cells are larger than prokaryotic cells.
Eukaryotic cells contain many membrane-bounded organelles, prokaryotic cells do
not.
Eukaryotic cells contain many internal compartments, prokaryotic cells do not.
Eukaryotic cells have a membrane-surrounded nucleus, prokaryotic cells do not.
Prokaryotic DNA exists a circular molecule and contains mesosomal spheres that
attached at regular intervals along its length.
In some prokaryotic cells this membrane structure has been observed to exist only
as a preparation artifact, a pattern that looks like a structure but is actually
produced by the process of fixing the cell for microscopy.
Animal cells have these organelles and suborganelle structures:
-Centrioles
-Cell membrane
-Nucleus
-Nucleolus
-Mitochondria
-Golgi body, Golgi apparatus or Golgi complex
-Small vacuoles
-Lysosomes
-ER (endoplasmic reticulum)
-Ribosomes
Plant cells have all the organelles an animal cell has plus
Cell wall
(Cellulose in cell wall provides structure and rigidity)
Large vacuole
(largest organelle in the plant used for storage of large molecules of starch)
Chloroplasts
which contain chlorophyll (the green pigment in plants)
ER-Endoplasmic Reticulum
Main function is to make and transport proteins. It is a series of canals that connects
nucleus to cytoplasm of cell.
(Rough ER) has dots lining its canals. They make proteins that will be secreted from
cell.
(Smooth ER) has no dots, no ribosomes. Its principle function is steroid synthesis
and detoxification of harmful substances.
Here patches of the ER membrane bud off and form transport vehicles carrying
proteins from ER to Golgi, where the proteins are further modified then repackaged
into vesicles and released by exocytosis.
Golgi:
Consists of a stack of flattened, closed membranous sacs-it looks like a maze with
water droplets splashing off it. The “water droplets” are transport vehicles bringing
material from the ER.
-Inside the Golgi, products produced by the cell (enzymes or hormones) are
packaged for export to other organelles or to the outside of the cell.
Golgi surrounds the product to be secreted with a sac called a vesicle. Vesicle finds
its way to plasma membrane (cell membrane), where certain proteins allow a
channel to be produced so that the products inside the vesicle can be secreted
outside of the cell. Once outside the cell, the product (hormone or enzyme) can
enter the bloodstream and be transported throughout the body where ever it is
needed.
-
So the major function is to modify, sort and package molecules such as
proteins (and glycoproteins)
Nucleus:
1. Located in the center of the animal cell.
2. There is chromatin, nuclear pores, and karyosomes in the nucleus.
Chromatin: is genetic material in the nucleus that exists as loose threads.
Nuclear pore: these are holes in the nuclear membrane that allows proteins
and RNA to pass into and out from the nucleus via these pores.
Karyosome: is a dense mass of RNA and protein located within the nucleus.
Ribosomes:
1. are the site of proteins synthesis in the cells.
2. Consist of large and small subunits.
3. Are attached to ER to form a rough ER.
Lysosomes:
1. This organelle is found only in an animal cell not in a plant cell. These
are special vesicles formed by the Golgi to “clean up” the cell (i.e. intracellular
digestion). They are the garbage people of the cell.
2. They are found in unicellular eukaryotic cells and animal cells.
3. They contain digestive enzymes used to breakdown products that may be
harmful to cell and “spit” them back out into the extracellular fluid.
4. Lysosomes also remove dead organelles by surrounding the dead
organelle, breaking down its proteins and releasing them to reconstruct a
new organelle.
5. Since lysosomes act upon its won cell, process is called autodigestion.
Peroxisomes:
1. These are little sacs of enzymes produced by smooth ER to help
protect cell form toxic products.
2. You know how H2O2 is normally produced in some metabolic
reactions, so it is inside of you.
3. However H2O2 becomes harmful to the cells of the body if too much
accumulated, so the key is to keep breaking it down to keep it from
accumulating.
4. Perioxisomes break down excess H2O2 into H2O. The
enzyme catalase is abundant in the peroxisomes and used H2O2 to
detoxify substances especially in liver and kidneys.
Mitochondria:
1. Contain their own DNA
2. Produce some if its own lipids and proteins.
3. Produce most of the cells ATP.
Plastids:
1. Plastids are organelles that resemble some prokaryotic cell, they like
mitochondria, contain DNA, RNA, ribosomes, and they reproduce.
2. Are not found in animal cells, they are found in photosynthetic eukaryotic cellsplants and algae.
3. May develop into a chloroplast, chromoplast or leucoplast depending on the type
of cell in which it occurs.
4. Chloroplasts are green plastids that carry out photosynthesis.
5. Chromoplast makes and store yellow/orange pigments of flowers and fruits, and
roots.
6. Leucoplasts are colorless pigments, which serve as storage areas and classified by
material stored; carbohydrates, fats, proteins or combo amyloplasts take in
sugar and store it as a starch.
Cell wall:
1. Composed of cellulose and other fibers and porous to allow water and small
dissolved substances through and tough enough to give the plant structure
and support and flexible enough to allow plant to bend without breaking.
2. Each plant cell builds an elastic primary cell wall.
3. Many plants have a more rigid secondary wall when fully grown in this wall
the cellulose has been reinforced by a strengthening material called lignin.
Cytoskeleton:
1. Skeleton of the cell. It is composed of thin tubules and contractile
filaments in cytoplasm.
2. Provides a framework for the cell shape and movement. Its components
can be dissembled, moved to new locations, and used in new structures.
3. Made up of at least 3 types of fibers;
microtublules, intermediate filaments, and microfilaments.
4. Exist as protein fibers in muscle cells and some unicellular organisms
(like amoebas).
Microtubules
1. support cellular activities
2. provide motility
3. formed from a globular protein tubulin always present in cytoplasm
Intermediate filaments
1. help to maintain shape of the cell
2. contributes to the mechanical strength
3. Keratins ( found in epithelial cells, covering the surface of various organs;
found in epidermal cells in skin hair, fingernails and feathers).
Microfilaments:
1. Contain actin which is involved in contraction of muscles.
2. Helps unicellular organisms like amoeba change their shape.
3. Assist in both exocytosis and endocytosis.
4. Form actin subunits found near plasma membrane;
5. Responsible for much of the movement with in a eukaryotic cell.
6. Plays an important role in cytoplasmic streaming in plant cells.
Centrioles:
1. Found only in animal cells.
2. They organize microtubules.
3. Exist in the cytoplasm outside of nuclear envelope that produces
microtubules.
4. Form spindle tubules, which help cells, divide during cell
division.
5. Exist in pairs.
6. Form flagella and cilia.
Organization of Cells:
The cell is the basic unit of life.
Tissues: are groups of cells that perform a specific task in an organism.
Organs: groups of tissues assembled to perform a specific task.
4 types of Animal tissues:
Epithelial- forms covering and linings of the outside of the body.
Connective: contains numerous fibers.
Nervous: nerve cells that conduct electrical impulses in response to stimuli.
Muscle: calls that conduct electrical impulses and contract.
4 types of Plant tissues:
Dermal: covers the outside of plants.
Vascular: transport water and nutrients and hormones between different
parts of a plant.
Ground tissue: fills spaces between epeidermis and vascular tissue inside the
leaves and stems.
Meristems: tissues made up of cells that divide and develop into 3 parts of
new growth in a plant.