EK 2.B.c.3 LO 2.14 EK 2.B.c.3 LO 2.14

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1 EK 2.B.c.3 LO 2.14 EK 2.B.c.3 LO 2.14 Cell Theory Cell Theory 1. The cell is the basic unit of life. 2. All living things are composed of cells 3. Cells only come from preexisting cells. Types of Cell Prokaryotic: Cells without a nucleus or membrane bound organelles. Eukaryotic: Cells with a nucleus and membrane bound organelles.(larger more evolved) Cells are limited in their size. 2 Notes Prokaryotic cells in general are smaller and consideredd more primitive Genomic DNA is smaller with no histone proteins and forms a circle of DNA. These cellss are found in the domains Archaea and Bacteria 3

2 EK 2.B.c.3 LO EK 2.A.3.b LO 2.6 Relative Size of Cells The size of a cell is limited by two factors: 1. The surface area increases at a slower rate than the volume for a sphere or cube shape. 2. The larger the cell the longer it takes for materials to diffuse to the center of the cell. 5 EK 2.A.3.b LO 2.6 Surface Area to Volume Ratio Point out how increasing the number of cells in a given volume will increase the overall surface area that can be used for the exchange of material. 6

3 EK 2.B..3.c LO 2.14 Prokaryotes Prokaryotes were the first cells to evolve. This is an electron micrograph of an actual prokaryotic cell. It has a rod shape Other characteristics of prokaryotic cells Cell wall peptidoglycan, 3 basic shapes cocci, bacilli, and sprilla. Used to prevent cells from bursting. Capsule Some prokaryotes have these outside the cell wall. Allows cells to adhere to substrates and additional protection 7 Plasma membrane regulates what crosses the cell membrane. Nucloid region Area where the circular DNA is found. Mode of nutrition can vary decomposing heterotrophs, pathogenic heterotrophs, phototrophic autotrophs or chemotrophic autotrophs. Biochemical pathways can vary Photosynthesis Obligate anaerobic respiration Facultative aerobic respiration Aerobic respiration

4 EK 2.B..3.c LO 2.14 EK 2.B.3 LO 3.33 Prokaryote Eukaryotic Animal Cell 8 Ribosomes Workbench where proteins are made, smaller than eukaryotic ribosomes. Flagella made from a solid core of protein. They rotate like a helicopter rotor. Not all prokaryotes have flagella Pili Extensions that allow prokaryotes to adhere to one another for DNA exchange. Lamella If cell is photosynthetic, membrane where photosynthetic pigments are attached. Capsule Extra layer on top of cell wall for certain prokaryotes. Seems to add additional protection. Plasmid Small circle of DNA not included in the genome that can contain genes. Eukaryotic cells are more highly evolved. They have evolved with membrane bound organelles. These organelles allows for division of labor. Organelles evolved from the following: 1. The involution of cell membrane which gave rise to the nucleus, endoplasmic membrane, Golgi apparatus, and lysosome 9 2. When prokaryotic cells were engulfed by other prokaryotic cells and instead of being destroyed, took up residence within the cell. This gave rise to the mitochondrion, the chloroplast and perhaps the flagellum.

5 EK 2.B..3 LO 2.14 EK 2.B..3 LO 2.14 Eukaryotic Plant Cell Cheek Cells with Different Stains 10 Differences between plant cells and animal cells. Organelle Plant Animal Cell wall Yes No Chloroplasts Yes No Central Vacuole Yes No Lysosome No Yes Centrioles No Yes Flagella No Yes (some lower plants) 11

6 EK 2.B..3.b LO 2.13 Nucleus The nucleus is surrounded by a double membrane called the nuclear envelope and is pitted with protein pores allows materials in and out. For example, the pores regulate which pieces of RNA can be transported out to the cytosol. Contained in the nucleus 12 Nucleolus DNA (chromatin)which is the blue print for proteins. The photo is an actual electron micrograph of nuclear pores. Proteins RNA Other materials needed for DNA replication and translation in which DNA is used as a template to make an RNA molecule. EK 2.B..3.b LO 2.13 Nucleolus The nucleolus is dark staining object in the nucleus. It contains DNA which codes for the production of ribosomal RNA. 13

7 EK 2.B. 3.b, 4.A.2.b LO 2.13, 4.5 EK 2.B. 3.b, 4.A.2.b LO 2.13, 4.5 Nuclear Envelope and E.R. Connection. Smooth ER Continuous with rough ER is the smooth ER. It is different from the rough ER in that it that lacks ribosomes Continuous with the nuclear membrane is the endoplasmic reticulum. There are two types of E. R. and they are rough and smooth. Rough E.R. is pitted with ribosomes. The attached ribosomes are making proteins and threading them into to the internal part of the E.R. These proteins will be packaged later on by the E.R. and shipped to the Golgi apparatus for modification before being exported or becoming part of the cell membrane. The ribosomes on the E.R. are only attached when synthesizing proteins. Once done the ribosomes are detached from the E.R. Functions of smooth E.R. are 1. Synthesis of lipids and phospholipids 2. Involved in the breakdown of glycogen. 3. Detoxification of drugs by adding a OH to them making them more soluble. 4. Storage of calcium in muscles needed for contractions. EK 2.B. 3.b, 4.A.2.c LO 2.13, 4.5 Golgi Apparatus 16 The Golgi apparatus receives vesicles from the cell and its ER Proteins from the ER are modified and then sent out for export from the cell membrane. It is made of flattened membranes. It has a polarity in that there is a receiving face, cis face and an exporting face, trans face. Once the vesicle has deposited its material, the molecules may go through a series of membranes as they are modified. The Golgi apparatus is derived from membrane on the ER.

8 EK 2.B. 3.b, 4.A.2.c LO 2.13, D Illustration of the Golgi Apparatus 17 See a three dimensional image of the Golgi complex in a rat kidney cell created using a new imaging technique known as EM tomography. This technique produces a 3D image of a thick (250 nm) section of tissue by combining a series of confocal 2D images from various depths in the section. The cis Golgi is shown in dark blue and the trans Golgi in light brown, with the medial cisternae in various other colors. Notice the extensive convolutions of the Golgi membranes. Credit: Courtesy of W.J.C. Geerts EK 2.B. 3.b, 4.A.2.c LO 2.13, 4.5 Electron Micrograph of the Golgi Appratus Functions of the Golgi apparatus 1. Modifying proteins from ER. 2. Manufacturing certain polysaccharides 3. Contributing to the plasma membrane 18 EK 2.B. 3.b, 4.A.2.c LO 2.13, 4.5 Golgi Apparatus Directing Secretions 19

9 EK 2.B.3, 4.A.2.e LO 2.13, 4.5 Lysosomes There is flow or connection of organelle membranes in the formation of lysosomes. 20 Lysosomes membrane bound organelles that contain hydrolytic enzymes to break down materials (proteins, fats, polysaccharides, nucleic acids). These enzymes work best in a low ph. The lysosome pumps H+ into the interior. So if one breaks open, the high ph of the cell will denature these enzymes, but if a number of them break open, the cell will die. Lysosomes are used in the process of digestion of food particles and autophagy breaking down and recycling old organelles. EK 2.B.3, 4.A.2.f LO 2.13, 4.5 EK 2.B.3, 4.A.2.f LO 2.13, 4.5 Vesicles and Vacuoles Contractile Vacuoles Vacuoles and vesicles are membrane bound compartments used for storage. Vacuoles are larger than vesicles. Plants use a large central water vacuole to maintain their turgor and structure There are water vacuoles found in certain freshwater protist that will expel excess water. Chlamydomonas Video left side Chlamydomonas is a unicellular green alga with two anterior flagella and a single cupshaped chloroplast. Each cell is about 10 micrometers across. This cell is viewed with Nomarski optics, which gives an image that appears three dimensional. The smooth space at the anterior end is the contractile vacuole, which you can see contract in this clip. This organelle is involved in water regulation in Chlamydomonas. By expelling a solution hypotonic to that in the cell, the contractile vacuole counters the osmotic movement of water into the cell. The slightly larger circular structure within the chloroplast at the other end of the cell is the pyrenoid, where starch is deposited. The 3D appearance around the pyrenoid is due to the view of the thylakoid membrane stacks in the chloroplast. Credit: Michael Clayton, University of Wisconsin, Madison

10 EK 1.B.1.b LO 1.16 Endomembrane or Cytomembrane Sytems The endomembrane system or cytomembrane system refers to the organelles that are at some point in time continuous or arise from one another. Nuclear envelope is continuous with the rough ER and the smooth ER. 23 The rough ER gives rise to the Golgi apparatus. It receives vesicles from ER at the cis face. Materials are modified and moved from one compartment to another. Once completed materials are repackaged in vesicles and shipped to the plasma membrane. EK 4.A.2 LO 4.5 EK 2.B.3, 4.A.2.d LO 2.13, 4.5 Microbodies Peroxisomes and Glyoxysomes Mitochondiron and ATP Production The mitochondrion is used to phosphorylate ADP to ATP (energy). 24 Microbodies Collection of membrane bound organelles that contain enzymes that function in a certain manner. Ex. Peroxisomes will remove hydrogen from toxic substances and then combine the hydrogen with oxygen forming hydrogen peroxide. Hydrogen peroxide is toxic but peroxisomes contain catalase to break it down. Ethanol is detoxified in this way. Ex. Glyoxysomes are microbodies in plant cells that convert fatty acids to sugars. Microbodies are made from proteins and lipids from the cytosol. Cells may have only one or many depending upon the function of the cell. They have two membranes: the outer is smooth, and the inner is folded forming the cristae (increased surface area for enzymatic pathways embedded here). The inside of the cristae is the inner matrix which contain enzymes for cellular respiration. 25

11 EK 2.B.3, 4.A.2.d LO 2.13, D Illustration of the Golgi Apparatus In cells, a higher the energy demand, corresponds with an increase in the number of mitochondria in the cell. 26 Mitochondria in 3D Video See a 3D representation of the internal structure of a mitochondrion, made using EM tomography, a technique much like a CAT scan. This model was constructed using a series of confocal 2D images taken at various depths through an intact mitochondrion. Notice the extensive surface area of the cristae. EK 2.B.3, 4.A.2.d LO 2.13, 4.5 Mitochondria and Endosymbiosis Mitochondria evolved from ancient prokaryotic cells through endosymbiosis. The evidence includes: 1. Has its own DNA that is circular like prokaryotes 2. Has prokaryotic like ribosomes 3. Replicates like a prokaryote 4. Does protein synthesis like a prokaryote 27 The mitochondria, chloroplasts and the flagella evolved from prokaryotic cells engulfing other prokaryotic cells. Instead of being destroyed, the prokaryotic cell took up residence replicating and dividing inside the host cell. Over time some of the genes of the engulfed cell were transferred to the host cell making them dependent on the host and becoming an organelle. This is the endosymbiosis hypothesis.