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Transcript of Cells
Have a nucleus.
Are 10-100 um in size.
Are most often multicellular.
What are Cells?
Cells are the basic building blocks of life. All cells come from other cells.
There are two different types of cells:
Lack a nucleus.
Have free floating DNA.
Lack nucleus-bound organelles.
Lack most other organelles.
Plant Cells vs. Animal Cells
Rough Endoplasmic Reticulum (E.R.)
Smooth Endoplasmic Reticulum (ER)
How do Molecules Travel Across the Membrane?
The Cell Cycle & Mitosis
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Telophase & Cytokinesis
Only have one, circular chromosome.
Are 0-10 um large.
Are usually unicellular, either blue or green algae or bacteria.
Often have a cell wall.
DNA and other organelles are membrane-bound.
Have numerous, linear chromosomes.
Only plants will have a cell wall.
Both Prokaryotes and Eukaryotes:
Have a plasma membrane.
Both plants and animals are Eukaryotic.
Have a cell wall, outside the plasma membrane.
Have chloroplasts, which are essential for photosynthesis.
Often has a large, central vacuole.
Most often won't have centrioles.
The nucleus controls all the actions of the cell. It is made up of the:
Nucleolus, which assembles ribosomes and RNA.
Chromatin, a mass of wound up DNA strands.
Nuclear Membrane and Envelope, which contain the DNA, separate from the rest of the cell to keep it safe and undamaged.
Chromosomes, an X shaped structure of wound up DNA.
Have neither a cell wall, nor chloroplasts.
May have smaller vacuoles, but are often absent.
Both plant and animal cells:
Have most organelles in common: mitochondria, plasma membrane, nucleus, cytoskeleton, ribosomes,
endoplasmic reticulum, golgi
apparatus, and lysosomes.
Ribosomes are small units of RNA and proteins that convert RNA into proteins for the cell to use. They are either free-floating or attatched to the Rough ER.
The Rough ER is a membrane studded with ribosomes, hence the "rough." It is attached to the nuclear envelope, and is where many proteins are synthesized, as well as the lysosome enzymes.
The Smooth ER is another membrane, but is lacks the ribosomes of the Rough ER. It is the area where lipids and steroids are synthesized and it breaks down toxin in the cell.
Golgi apparatus is a sac surrounded by a membrane which receives, modifies and sorts proteins into vesicles for secretion or transport. These vesicles then deliver the proteins to other cell organelles and to the plasma membrane to be sent to other parts of the body.
Vesicles are little, pouch-like sections of plasma membrane that can encase a substance, pinch off into a bubble shape, then release the substance in another area.
Lysosomes maintain the cell's chemical balance and remove unwanted debris. Lysosomes are membrane bound organelles which contain digestive enzymes that break down bacteria and cell debris.
Mitochondria are the powerhouse of the cell. They convert raw chemical energy(glucose) into usable ATP through cellular respiration. Mitochondria are surrounded by two membranes: a smooth outer membrane and a folded inner membrane.
"Biology Exams 4 U." Difference between Prokaryotic and Eukaryotic Cells ~. N.p., n.d. Web. 15 Apr. 2015. <http://www.biologyexams4u.com/2012/10/difference-between-prokaryotic-and_21.html#.VS8o8pP4WSo>.
Campbell, Neil A., Brad Williamson, and Robin J. Heyden. "Chapter 9." Biology Exploring Life. Needham, MA: Pearson, 2004. N. pag. Print.
"Characteristics of Prokaryotic Cells." Characteristics of Prokaryotic Cells. N.p., n.d. Web. 15 Apr. 2015. <http://krupp.wcc.hawaii.edu/BIOL101/present/lcture16/sld015.htm>.
"Eukaryotic Cell vs Prokaryotic Cell." Difference and Comparison. N.p., n.d. Web. 13 Apr. 2015. <http://www.diffen.com/difference/Eukaryotic_Cell_vs_Prokaryotic_Cell>.
Kerstin67. "Organelles of Cells and Their Functions." Bright Hub. N.p., 21 Mar. 2011. Web. 16 Apr. 2015. <http://www.brighthub.com/science/medical/articles/111027.aspx>.
Chloroplasts have a similar role in plant cells. They convert sun energy into glucose through photosynthesis, which is then converted by the mitochondria into APT. They also release oxygen and contain chlorophyll, the pigment that makes plants green.
Vacuoles are fluid-filled sacs that store food, water, metabolic & toxic wastes. Plant cells will often have a very large central vacuole,which stores large amounts of food or sugars.
Cytoplasm is a clear, thick, jellylike material that fills the interior area of the cell and contains and supports all the other organelles.
The cytoskeleton is a system of microtubles, microfiliments, and intermediate filiments that strengthen the cell and maintains it's shape.
The plasma, or cellular, membrane is a phospholipid bilayer. In other words, it is two layers of phosolipids, with various types of proteins embedded within it. The membrane does many things, such as provide support, protection, acts as a barrier between the cell and its environment, controls movement of materials in and out of the cell and maintains homeostasis.
Molecular Travel Across the Membrane Crash Course
The cell wall is a strong and rigid layer outside the cellular membrane. In plant cells, it is made of cellulose, but it is made of other materials in prokaryotic cells. It also allows materials to pass in and out of the cell, and provides protection and the support plants need to grow tall.
There are several traits that help the cellular membrane do its job:
Fluidity & Flexibility- This allows the membrane maintain homeostasis, by allowing the cell to grow and adapt to its environment.
Selective Permeability- Only some things can pass easily through the membrane, allowing it to control the chemical balance within the cell.
Channel Proteins- Proteins embedded within the membrane that allow molecules to cross the membrane that not normally wouldn't be able to do so. This also contributes to maintaining the cell's chemical balance and overall homeostasis.
So how do molecules travel across the membrane?
Molecules will naturally move around randomly from areas of high concentration to low concentration until they are evenly spread out; this is called
. When they are all spread out equally, it is called
. Some molecules, typically small, non-polar ones such as oxygen and carbon dioxide can move easily across a semipermeable membrane. This is called
, because it requires no assistance from the cell. Some other molecules can cross with the help of
, which simply act like pores in the membrane, but only for a specific type of molecule. This is
Osmosis is a type of diffusion, but is has to do with water. If there is a high concentration of a solute, water will move to that area to disperse the molecules and dilute the solute, thus reaching equilibrium. In this way, water will move across a semipermeable membrane, in and out of a cell, depending on how much solute is in the solution around it. A solution with a higher solute concentration is
. A solution with a lower solute concentration is
. A solution with a balanced solute concentration is
and in equilibrium.
Some types of molecules cannot get across the semipermeable plasma membrane on their own and therefore need help from the cell. They get across through active transport, which requires the cell to spend energy (ATP). Carrier proteins embedded in the membrane transport the molecules across.
Mitosis is the asexual reproductive process that cell go through to replicate. The result is two identical "daughter" cells.
Interphase is the longest part of the cell cycle, and is when the cell is doing it's cell function. It consists of the G(Gap)0, G1, G2 and S(Synthesis) phases. During this Gap phases, the cell is gathering nutrients and growing in preparation for mitosis. During the S phase, the cell replicates is genes (DNA), so it has two identical sets. There are several, vital checkpoints throughout, so the cell can be sure it's ready for mitosis.
Prophase is the first phase of mitosis. During prophase, the chromatin winds tightly into the chromosomes, each one of which is a pair of identical "sister" chromatids, which are attached by the centromere. The nucleus disappears, so as not to be in the way of the splitting, and the centrioles(another organelle) appear. The spindle(a structure of microtubles that guides the chromosomes through mitosis) begins to form.
During metaphase, the microtubles of the spindle attach to the centromeres of the chromosomes, and guide them into alignment along the mitotic(or metaphase) plate, a region across the center of the cell. It is very important that the chromosomes be
During anaphase, some of the microtubles of the spindle retract, pulling apart the chromosomes into separate chromatids. Other microtubles actually extend, connecting to each other and pushing the centrioles farther apart. The cleavage furrow forms.
Telophase is the final step of mitosis. The nucleus reforms around the two new sets of DNA, and the chromatids relax back into chromatin. The spindle and centrioles disappear, and cytokinesis occurs. Cytokinesis is when the cytoplasm of the original cell splits between the two new daughter cells. The cleavage furrow pinches off the new cells like a drawstring. Mitosis is finished.
Mitosis Crash Course Video