2.2 Prokaryotic Cells Please use your text to complete the handout on the Prokaryotic cell outcomes 2.2 PROKARYOTIC CELLS 2.3 EUKARYOTIC CELLS AND MICROSCOPE ANATOMY! IB Bio SL 2.3 Eukaryotic Cells Please use your text to complete the worksheet on the Eukaryotic Cell outcomes What is a Prokaryotic Cell? Are cells that lack membrane bound organelles or any type of cells nucleus. They are cells that are much smaller and simpler than Eukaryotic cells. In fact most Prokaryotic cells are less than one micrometre in diameter! The beginning of life Features of Prokaryotic Cells Prokaryotic cells are thought to be the first to have appeared on earth. Prokaryotic cells still play a large role in the world today. Bacteria is a good example. The features of the Prokaryotic cell that you will have to identify are: Cell wall Plasma membrane Pili &Flagella Ribosomes Nucleoid
Cell wall Protects and maintains the shape of the cell. In most prokaryotes the cell wall is composed of a carbohydrate-protein complex called peptidoglycan. Some bacteria have an additional layer outside the cell wall that allows them to stick to teeth, skin and food. Plasma membrane Controls the movement of materials into and out of the cell. It also plays a role in binary fission (stay tuned) Pili Are hair-like growths on the outside of the cell wall. They are used for attachment. Their main function is in joining bacteria cells in preparation for the transfer of DNA. (sexual reproduction) Flagella Are hair-like growths (longer than pili) that are used for cell motility. Ribosomes Nucleoid Region Function as the sites of protein synthesis. Ribosomes typically occur in very large numbers in cells with high protein production. The ribosomes in prokaryotic are small (70s) cells Because bacteria cells are non-compartmentalized and contain a single, long, continuous, circular thread of DNA... This region is involved in the control of the cell as well as reproduction.
Binary Fission Binary Fission Is the simple process by which prokaryotic cells divide. 1. The circular DNA is copied 2. Two daughter chromosomes become attached to different regions on the plasma memberane. 3. The cells divide into two genetically identical daughter cells. The process includes; elongating of the cell, and partitioning of the newly produced DNA. Endosymbiotic Theory Global Connections... http://learn.genetics.utah.edu/content/begin/cells/ organelles/ Prokaryotes and clean water resources Lifesaver bottle with Michael Pritchard http://www.ted.com/talks/lang/eng/michael_pritc hard_invents_a_water_filter.html We ll revisit this idea in the evolution unit! 2.3 Eukaryotic Cells What do you need to know? Draw a diagram of a liver cell including... Free ribosomes rough endoplasmic reticulum lysosome Golgi apparatus mitochondrion nucleus
Free Ribosomes very small structures (about 80S) that carry out protein synthesis in the cell. Free ribosomes are found floating in the cytoplasm and others are found attached to the rough ER. Ribosomes are composed of RNA and protein and are larger in eukaryotic cells than prokaryotic cells. Eukaryotic ribosomes are composed of two subunits. Endoplasmic reticulum an extensive network of channels that stretches from the nucleus to the plasma membrane. Its function is to transport materials through the cell. There are two types of ER, rough ER and smooth ER. The rough ER is distinguished by the ribosomes attached to its exterior surface. The advantage of having ribosomes attached to ER is that as the ribosomes synthesize proteins they can be transported by the ER to become parts of cell membranes, enzymes for the cell or messengers between cells. The smooth ER has many functions such as production of membrane phospholipids, production of sex hormones, breaks down harmful substances, stores calcium ions, transports lipid based compounds, and aid liver cells in releasing glucose into the blood when needed. Lysosome single membrane bound organelles produced by the Golgi apparatus that contain strong hydrolytic enzymes which break down biological molecules. They can contain up to 40 different enzymes and can also break down worn out cell parts that are no longer functioning properly. Lysosomes are involved in breaking down materials brought into a cell via phagocytosis.
Golgi apparatus this organelle is composed of many flattened sacs called cisternae which are stacked on top of each other and it is normally located between the ER and plasma membrane. The Golgi apparatus collects, packages, modifies and distributes materials throughout the cell. It is located close to the ER to receive products transported by the ER and close to the plasma membrane so it can discharge materials needed outside the cell. This organelle is found in high numbers in cell that produce and secrete substances (i.e. pancreas cells). Mitochondrion very large, double membrane bound rod-shaped organelles that are found scattered in the cytoplasm and contain their own DNA. Their outer membrane is smooth while their inner membrane is highly folded into cristae which increase the surface area of the inner mitochondria for cellular respiration, the main function of the mitochondria. Due to its size and ability to produce energy in the form of ATP, mitochondria also have their own ribosomes. Mitochondria are found in high numbers in cells that have high energy needs (i.e. muscle cells). Nucleus eukaryotic DNA is housed inside the double membrane or nuclear envelop of the nucleus. The double membrane allows the DNA to remain separate from the rest of the cell and carry out its functions without interference from the other parts of the cell. The nuclear membrane contains pores that allows for communication with the rest of the cell. DNA is contained in the form of chromosomes within the nucleus. The nucleus is normally located in the center of the eukaryotic cell but is often pushed to the side in plant cells due to the large vacuole. Most cells have one nuclei but some have multiple nuclei while others have none (i.e. red blood cells). If there is no nucleus the cell cannot reproduce. Most nuclei often have a nucleolus a dark area inside the nucleus where ribosomes are manufactured.
See inside a cell! http://learn.genetics.utah.edu/content/begin/cells/ insideacell/ http://www.cellsalive.com/cells/3dcell.htm Comparison between prokaryotic and eukaryotic cells Feature PROKARYOTIC CELLS EUKARYOTIC CELLS Genetic material Location of genetic material Contain a naked loop of DNA. Sometimes referred to as a nucleoid. Naked DNA found in region of the cytoplasm called nucleoid. Contain four or more chromosomes consisting of strands of DNA associated with protein. Located inside the double membrane of the nucleus; sometimes referred to as the nuclear envelop. Cont d Feature PROKARYOTIC CELLS EUKARYOTIC CELLS Mitochondria Ribosomes Membrane bound organelles or internal membranes Prokaryotes do not contain mitochondria. The surface of the cell membrane and the mesosome are used to produce cellular energy. Ribosomes are smaller in prokaryote cells. (70S) Few or none are present. Size Measure less than 10 micrometers. Eukaryotic cells all contain hundreds of mitochondria. Ribosomes are larger in eukaryote cells. (80S) Eukaryotic cells contain several membrane bound organelles such as ER, Golgi apparatus and lysosomes. Measure more than 10 micrometers. Difference between plant and animal cells FEATURE ANIMAL CELL PLANT CELL Cell wall No cell wall. Cells have a plasma membrane only. Contains a cell wall with a plasma membrane just inside. Chloroplasts Not found in animal cells. All plants that carry out photosynthesis contain chloroplasts. Carbohydrate storage Animal cells store carbohydrates in the form of glycogen. Plant cells store carbohydrates in the form of starch.
Cont d FEATURE ANIMAL CELL PLANT CELL Vacuole Not normally present in animal cells. Some small vesicles are sometimes formed. Plant cells contain one large central fluid filled vacuole. Extracellular components Extracellular components are structures outside the plasma membranes of cells. Shape Usually a rounded shape but the plasma membrane is flexible and can change shape. Plant cells have a fixed shape due to the cell wall. Often boxlike or angular in shape. One commonly known example is the cell wall in plant cells. Centrioles Contains centrioles within a centrosome area. Do not contain centrioles within a centrosome area. Another example of an extracellular component is the extracellular matrix of animal cells as well as bone and cartilage. The Cell Wall The cell wall is composed of cellulose microfibrils which form a thick wall surrounding the entire cell. The cell wall grows with the cell, continually adding more cellulose to maintain its thickness. The cell wall protects the plant cell and helps to maintain its shape. The cell wall also protects the cell from too much water entering and helps the cell maintain osmotic balance. Since it is made of cellulose, the plant cell can use the cell wall to store carbohydrates. Extracellular matrix of animal cells The extracellular matrix of animal cells is composed of glycoproteins and collagen fibres. Together they form a fibre-like structure that anchors the matrix to the plasma membrane. The ECM adds strength to the plasma membrane, allows cell to cell interactions, and allows adjacent cells to attach to one another Cartilage is made of cells with a lot of extracellular material which gives cartilage its firm, resilient structure
Light Microscopes The ocular lens in the eyepiece magnifies and transmits the image to your eye The magnification of the ocular lens is 10X To find the total magnification of the microscope you are using, multiply the magnification of the objective lens by the magnification of the ocular lens. For example: 40X (objective lense) x 10X (ocular lense) = 400X magnification The Parts of a Light Microscope Light source: Could be a mirror, but most likely it is a bulb built into the base Diaphragm: Adjusts the amount of light striking an object Objective lens: Gathers light and magnifies image Ocular lens (eyepiece): Magnifies objects and focuses light to your eye Stage: Holds slide Can be moved using the coarse or fine adjustment knobs to bring the object into focus Stage clips: Hold slide in place Base and arm: Structural support for the microscope Can you name the parts? Start on the left side and work from the top down. Then go to the right side and work from the top down. Ocular lens (eyepiece) Images Produced by Light Microscopes Objective Lenses Stage Diaphragm Light Source Arm Stage clip Course adjustment Fine adjustment Amoeba Streptococcus bacteria Anthrax bacteria Nice Job! Base Human cheek cells Plant cells Yeast cells Fun in the lab! Cells that you eat! Yumm! You will examine several plant and animal cells under the light microscope super-fun!