Download Cells and Their Organelles Notes

Cells and Their Organelles Notes
The cell is the basic unit of life. Cells come in different sizes and shapes. A cell’s shape might tell you something
about its function. A nerve cell has many branches that send and receive messages to and from other cells. A nerve cell in
your leg could be a meter long. A human egg cell is no bigger than the dot on this i. A human blood cell is much smaller than
the egg cell. A bacterium is even smaller---8,000 of the smallest bacteria can fit inside one red blood cell.
A nerve cell cannot change its shape. Muscle cells and some blood cells can change shape. Some cells in plant stems
are long and hollow and have openings at their ends. These cells carry food and water throughout the plant.
There are two types of cells, prokaryotes and eukaryotes. Prokaryotes
are the simplest of all cells, they lack membrane bound organelles (like a nucleus
or mitochondrion). Prokaryotes are microorganisms that do everything from
make cheese to cause strep throat. Eukaryotes are structurally more complex,
larger in size, and have a nucleus. Eukaryotes are broken down into plant and
animal cells.
Common Cell Traits
Living cells have many things in common. A cell is the smallest unit that can
perform life functions. All cells have an outer covering call the cell membrane. The
cell membrane is semipermeable, allowing some substances to pass into the cell and
blocking others. It is composed of a double layer of phospholipids and embedded
proteins. Inside every cell is a gelatin like material called cytoplasm in which the
organelles are located. The cytoplasm has a framework called the cytoskeleton, which
helps the cell keep or change its shape.
Cell Organization
Just as restaurant workers have specific jobs, each cell in your body has a certain job to do. Cells take in nutrients,
release and store chemicals, and break down substances 24 hours a day.
Plant cells, algae, fungi, and some prokaryotes have an additional layer surrounding
them called the cell wall, which is a tough, rigid outer covering that protects the cell and gives
it shape. A plant cell wall is mostly made up of a substance called cellulose. The long,
threadlike fibers of cellulose form a thick mesh. The mesh allows water and dissolved
materials to pass through the cell wall.
Cell walls may contain pectin, which is used to thicken jams and jellies. Cell walls also
contain lignin, which is a compound that makes cell wall rigid.
Structure & Function Organelles
Most of a cell’s life processes happen in the cytoplasm. Within the cytoplasm of eukaryotic
cells are structures called organelles. Some organelles process energy. Others make materials needed
by the cell or other cells. Some organelles move materials. Others store materials. Membranes
surround most organelles.
The centrioles are a small body located near the nucleus in animal cells. The centrioles are
where microtubules are made. During cell division (mitosis), the centrioles divide and the two parts
move to opposite sides of the dividing cell. Microtubules are shaped like soda straws and give the
nucleus and cell its shape.
The nucleus in the center of a eukaryotic cell is a spherical body containing the
nucleolus that makes ribosomes. The nucleus controls many of the functions of the cell (by
controlling protein synthesis). It also contains DNA assembled into chromosomes. The
nucleus is surrounded by the nuclear membrane. Materials can move from the nucleus to the
cytoplasm through nuclear pores in the membrane around the nucleus. Prokaryotes have a
nucleoid region instead of a nucleus, but still contain DNA.
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Protein takes part is almost every cell activity. Cells make their own proteins on
structures called ribosomes. Ribosomes are considered organelles, even though they are
not membrane bound. Hereditary material in the nucleus tells ribosomes how, when,
and in what order to make proteins by a process called protein synthesis. Some
ribosomes are free-floating in the cytoplasm and some are attached to the rough
endoplasmic reticulum.
Rough endoplasmic reticulum (rough ER) is a vast system of interconnected,
membranous, infolded and convoluted sacks that are located in the eukaryotic cell's
cytoplasm. The ER is continuous with the outer nuclear membrane. Rough ER is
covered with ribosomes that give it a rough appearance. Rough ER transports materials
through the cell and produces proteins in sacks called cistern, which are sent to the
Golgi body, or inserted into the cell membrane. The Golgi
apparatus or Golgi complex is a flattened, layered, sac-like
organelle that looks like a stack of pancakes. The Golgi body
modifies & packages proteins and carbohydrates into membranebound vesicles for "export" from the cell. Smooth ER does
NOT have ribosomes on its surface. It makes proteins and lipids
that will be exported by the cell. It also controls the Calcium level in muscles and detoxifies poisons,
alcohol, and drugs.
Mitochondria are spherical to rod-shaped organelles with a double membrane. The inner
membrane is infolded many times, forming a series of projections called cristae. The mitochondrion
converts the energy stored in glucose into ATP (adenosine triphosphate) for the cell. Both plant and
animal cells have double membranes and their own DNA.
Energy enters the food chain through the chloroplasts. Chloroplasts do not exist in
animal cells; they are present only in plants and some protists. Chloroplasts are elongated or discshaped organelles containing chlorophyll that trap sunlight for energy into the chemical bond
energy of sugar. Living things use sugars as their primary energy source. Photosynthesis (in
which energy from sunlight is converted into chemical energy - food) takes place in the
chloroplasts. Only plant cells, not animal cells, can make their own food.
Plant cells also contain one large fluid-filled sac called a vacuole. Animal cells have a few tiny vacuoles. The vacuole
fills with food being digested and waste material that is on its way out of the cell. In plant cells, a large central vacuole takes
up most of the space in the cell.
The word "lysosome" is Latin for "kill body." This is a very colorful description for
some of the most unusual organelles in the cell. Lysosomes are organelles produced by the
Golgi apparatus that contain powerful protein digesting enzymes. Lysosomes are responsible
for the breakdown and absorption of materials taken in by the cell. Nutrients are digested by
the cell here, as well as, old cell organelles that are going to be recycled.
Flagella and cilia are flexible membranes extensions of a cell that help prokaryotic cells move.
Flagella are long, thick tails that will whip around and sometimes twirls, pushing the cell along. For example, flagella can be
found at the end of a sperm or Euglena (pictured below), which allows it to swim. Cilia are little hairs that you might see on
the outside of a paramecium (pictured below) to aid in movement or in the lining of our air passages in which the cilia will
allow liquid to move over the surface of the cell to sweep mucus and dirt out of the lungs.
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Part I. Cell wall, Cell membrane, cytoplasm
1. What surrounds only plant cells and some prokaryotes?
2. From the answer to question #1, what is its function?
3. What is a plant cell wall made up of mostly?
4. What other two substances might a cell wall contain?
5. The cell membrane or plasma membrane is considered semi-permeable in its function. What does this mean?
6. What 2 things make up the cell membrane?
7. Where are organelles located?
8. Centrioles are found in what type of cell?
9. What are the centrioles functions?
10. In your own words, explain what the cell wall, cell membrane, cytoplasm, and centrioles structures and
functions are.
Part II. Nucleus, Nucleolus, & Ribosomes
1. Where is the nucleus located and what is its function?
2. What does the nucleus contain?
3. Where are ribosomes made?
4. The nucleus is surrounded by the ____________________ ____________________.
5. Do prokaryotic cells have a nucleus? If not, what do they have instead?
6. Where do cells make their own proteins?
7. Explain what protein synthesis is.
8. Where are two places within a cell that you can find ribosomes?
9. In your own words, explain what the nucleus, nucleolus, and ribosomes structures and functions are.
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Part III. Rough & Smooth Endoplasmic Reticulum, Golgi Apparatus, & Mitochondira
1. What does the Rough ER look like?
2. What is the Rough ER’s function?
3. What does the Smooth ER look like?
4. What is the Smooth ER’s function?
5. What does the Golgi apparatus look like?
6. What is its function?
7. What does the Mitochondria look like?
8. What is unique about its inner membrane?
9. What is its function?
10. In your own words, explain what the Rough ER, Smooth ER, Golgi apparatus, and mitochondria structures and
functions are.
Part IV. Chloroplast, Vacuoles, Lysosomes, Flagellum, and cilia (pili)
1. Where do you find chloroplasts?
2. What does the chloroplast look like?
3. What is its function?
4. What type of cells do you find vacuoles present? Describe what a vacuole looks like in these cells.
5. What is the function of the vacuole?
6. Lysosomes are produced by what organelle and what do they contain?
7. What is the function of the lysosome?
8. What does the flagellum look like?
9. What is the function of the flagellum? Provide two examples.
10. Describe where you can find cilia.
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11. In your own words, explain what the Chloroplast, vacuoles, lysosomes, flagellum, and cilia structures and
functions are.
Structure & Function of Organelles: Fill in the blanks with the correct organelle.
The 1. ________________, like the boss in a factory, is part of the cell that controls all the cell’s functions.
This cell part controls the cell because it contains the cell’s entire DNA (deoxyribonucleic acid). Without the help
of 2. ________________, very small structures that help assemble proteins, the DNA that controls the cell would
be of no use. Proteins and other molecules are transported throughout the cell on the 3. ________________
________________ like the assembly lines of a factory. Once the proteins are assembled, they are stored and
packaged by the 4. ________________ ________________ so that they can be sent out of the cell to other parts
of the organism that need them. If any molecules are no longer needed by the cell, the 5. ________________ will
take care of them by digesting and breaking them down, like the trash center of a factory. If the cell wants to save
the materials for later, it can store them in the 6. ________________.
In order to stay healthy, cells need to be able to control what exists and enters the cell from the surrounding
environment. Cells need to bring in materials, like oxygen, water, and food, and get rid of waste. In both plant and
animal cells, the 7. ________________ ________________ helps the cell accomplish this task.
The cell itself needs support and structure. In plant cells, the 8. ________________ ________________
also provides structure and support, making plant cells very boxy, and is located just outside the cell membrane.
No cell can do all these things without some energy! Plant cells have an important organelle call a 9.
________________ that turns sunlight into food for the plant. Animals can’t make their own food, but instead eat
other organisms to get food. Then, in both plant and animal cells, the 10. ________________ converts food into
energy for the cell!
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