Download Note 2.1 Cell Structures

UNIT 1: Biochemistry
Chapter 2: Cell Structure and Function
pg. 70 - 107
Organelles are internal structures that carry out specialized functions,
interacting and complementing each other.
Animal and plant cells have the same organelles in common, but plant cells
also have a cell wall and chloroplasts, not found in animal cells.
Plasma membrane – is a dynamic barrier that surrounds the cytosol of the
cell.
The plasma membrane creates a barrier that separates the external
environment from the internal environment, cytosol. The plasma membrane
regulates the movement of material into and out of the cell. Maintaining the
internal environment allows the organelles to do their jobs.
Organelles work in conjunction with each other to keep the cell healthy and
functioning.
Cell Theory:
a. all living things are made up of cells
b. All cells come from pre existing cells
c. the cell is the smallest entity that expresses the characteristics of life.
2.1: Cell Structures
pg. 72 – 80
The Nucleus
All eukaryotic cells have a true nucleus and membrane bound organelles.
The nucleus contains the DNA (genetic material), protects it, of the cell.
DNA can also be found in two other organelles, mitochondria and the
chloroplasts.
Nuclear Envelope
Nuclear envelope – is a bi-layer membrane that encloses the nucleus of a
eukaryotic cell.
The nuclear membrane is a bi-layer of phospholipids, which continues into a
second organelle. The endoplasmic reticulum is attached to the nucleus.
The membrane has proteins, receptors and transport, embedded into it,
which allows materials to pass into and out of the nucleus.
Table 1: Organelles of Eukaryotic Cells, pg. 73
Nucleolus
The nucleolus is found within the nucleus, floating in the nucleoplasm of the
nucleus. The nucleolus is responsible for producing a ribosome from protein
and RNA.
The Endo-membrane System
Endo-membrane system – is a group of interacting organelles between the
nucleus and the plasma membrane.
These organelles are responsible for the production of lipids, enzymes, and
other proteins, along with the removal, recycling, and destroying toxins.
Endoplasmic Reticulum
Endoplasmic reticulum (ER) – is a membrane bound organelle that is
folded into flattened sacs and tubes, and is often an outgrowth of the nuclear
envelope in a eukaryotic cell.
Smooth ER – is an area of the endoplasmic reticulum without attached
ribosomes.
Rough ER – is an area of the endoplasmic reticulum with attached
ribosomes.
The endoplasmic reticulum is a direct extension of the nuclear envelope. It
forms a continuous compartment of tubes and flattened sacs. There are two
kinds of endoplasmic reticulum, rough and smooth.
The rough endoplasmic reticulum has ribosomes attached, and is the site of
polypeptide chains. These proteins are then folded, into their complex
structures.
Smooth endoplasmic reticulum store enzymes, which produce lipids, and
break down carbohydrates, fatty acids, drugs and some poisons.
Vesicles
Vesicle – is a small, membrane bound organelle that may transport, store, or
digest substances within a cell.
There are a many different types of vesicles that form from organelles or
from the plasma membrane. Some transport proteins, some contain enzymes
(peroxisomes), that digest fatty acids, hydrogen peroxide (by product of fatty
acid digestion) into water and oxygen.
Vacuole – is a liquid-filled organelle that stores waste and aids in cellular
metabolism and water balance.
Vacuoles perform an important function; they isolate, and dispose of wastes,
debris, and toxic materials.
Plants have large central vacuoles, which contain amino acids, sugars, ions
wastes and toxins, dissolved in water. These central vacuoles take up 50% to
90% of the cell.
Lysosome – is a small, membrane bound organelle that contains digestive
enzymes that aid in waste disposal.
Golgi Body
Golgi body – is an organelle with folded membranes where the final
packaging of proteins occurs.
Golgi body looks like a stack of pancakes, and are responsible for modifying
polypeptide chains and lipids that have be delivered by the vesicles from the
endoplasmic reticulum. The finished products, membrane proteins, and
enzymes are sorted and packaged into new vesicles to be shipped to the
plasma membrane or lysosomes.
Other Organelles
Mitochondria – is an organelle with two membranes, the site of most ATP
synthesis during aerobic cellular respiration.
All eukaryotic cells have mitochondria, which is responsible for the
production of ATP through cellular respiration, in the presence of oxygen.
The number of mitochondria found in a cell is dependent on the function of
the cell. If the cell has a high demand for energy, then it will have a large
number of mitochondria.
The mitochondrion has two membranes, outer and inner mitochondrial
membranes (cristae), which creates two different compartments. The intermembrane space is found between the outer and inner membrane and the
second is found inside the cristae and is called the matrix.
The mitochondrion has its own DNA and is similar size to a bacterium.
Mitochondrion is able to independently divide, and have their own
ribosomes. It is theorized that the mitochondrion evolved from an aerobic
bacteria and formed a symbiotic relationship in the eukaryotic cell,
endosymbiosis.
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Plastids
Photosynthetic cells of plants and algae contain chloroplasts, which are
organelles responsible for the metabolic process of photosynthesis.
The chloroplast has two outer membranes and semi-fluid interior called a
stroma. The stroma contains enzymes, the chloroplast’s DNA, a series of
folded membranes called Thylakoid discs.
Plastid – is a membrane bound organelle that is involved in photosynthesis
and storage in plants and algae.
Chloroplast – is a double membrane bound organelle that contains enzymes
and pigments that are used to perform photosynthesis in eukaryotic cells.
Chromoplast – is an organelle that makes and stores pigments other than
chlorophyll.
Amyloplast – is an organelle that stores starch.
The Dynamic Cytoskeleton
Microtubules and Microfilaments
Cilia, flagella, and Pseudo pods
The Cell Surface
Cell wall – is the outer barrier of a plant cell; the cell wall surrounds the
plasma membrane and gives structure to the plant.
Primary wall – is a cellulose coating that surrounds the plant cell.
Secondary wall – is a coating that is added to plant cell wall; it is more rigid
and often thicker than the primary cell wall.
Extra-cellular matrix (ECM) – is a molecular system that supports and
protects a cell; a cell’ environment.
Cell Junction – is a structure that allows cells to interact with each other and
the surrounding environment.