Download EK 2.Bc3 LO 2.14 EK 2.Bc3 LO 2.14 Notes Prokaryoti

 EK 2.B.c.3 LO 2.14 Cell Theo
ory
Cell The
eory
1. The cell is the basic unit of life.
2. All livin
ng things are composed off cells
3. Cells only come from
m preexistingg cells.
2
EK 2.B.c.3 LO 2.14 Notes Types o
of Cell
• Prokaryo
otic: Cells witho
out a nucleus o
or membran
ne bound organ
nelles. Prokaryotiic cells in gen
neral are smalller and considered
d more primitive • Eukaryottic: Cells with a nucleus and membran
ne bound organ
nelles.(larger m
more evolved)
Genomic D
DNA is smalleer with no histtone proteins and forms a ciircle of DNA.
• Cells are limited in theirr size.
These cellss are found in
n the domains Archaea and Bacteria 3
EK 2.B.c.3 LO 2.14 4
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.
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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
EK 2.B..3.c LO 2.14 Prokaryotes
Other characteristics of prokaryotic cells Prokaryotes
were the first
cells to evolve.
This is an
electron
micrograph of
an actual
prokaryotic
cell. It has a
rod shape
•
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 •
Plasma membrane‐regulates what crosses the cell membrane. •
Nucloid region‐ Area where the circular DNA is found. 7
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 EK 2.B..3.c LO 2.14 Prokaryote
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. 8
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. EK 2.B.3 LO 3.33 Eukaryotic Animal Cell
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. EK 2.B..3 LO 2.14 Eukaryotic Plant Cell
Differences between plant cells and animal cells. 10
Organelle Plant Animal Cell wall Yes No Chloroplasts Yes No Central Vacuole Yes No Lysosome No Yes Centrioles No Yes Flagella No Yes EK 2.B..3 LO 2.14 Cheek Cells with Different Stains
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(some lower plants) 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 Nucleolus 12
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
EK 2.B. 3.b, 4.A.2.b LO 2.13, 4.5 Nuclear Envelope and E.R. Connection. 14
EK 2.B. 3.b, 4.A.2.b LO 2.13, 4.5 Smooth ER
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 Continuous
with rough ER
is the smooth
ER. It is
different from
the rough ER in
that it that
lacks
ribosomes.
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. 15
EK 2.B. 3.b, 4.A.2.c LO 2.13, 4.5
Golgi Apparatus
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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. EK 2.B. 3.b, 4.A.2.c LO 2.13, 4.5 3‐D Illustration of the Golgi Apparatus
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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 poly‐
saccharides
3. Contributing to the plasma membrane
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EK 2.B. 3.b, 4.A.2.c LO 2.13, 4.5
Golgi Apparatus Directing Secretions
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Lysosomes
EK 2.B.3, 4.A.2.e LO 2.13, 4.5 There is flow or connection of organelle membranes in the formation of lysosomes. 20
EK 2.B.3, 4.A.2.f LO 2.13, 4.5 Vesicles and 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. 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. There are water vacuoles found in certain freshwater protist that will expel excess water. 21
EK 2.B.3, 4.A.2.f LO 2.13, 4.5 Contractile Vacuoles
Chlamydomonas Video left side 22
Chlamydomonas is a unicellular green alga with two anterior flagella and a single cup‐
shaped 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 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. 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. 23
EK 4.A.2 LO 4.5 Microbodies‐ Peroxisomes and Glyoxysomes
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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. EK 2.B.3, 4.A.2.d LO 2.13, 4.5 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. Mitochondiron and ATP Production
The mitochondrion is used to phosphorylate ADP to ATP (energy). 25
EK 2.B.3, 4.A.2.d LO 2.13, 4.5 3‐D Illustration of the Golgi Apparatus
Mitochondria in 3D Video In cells, a higher the energy demand, corresponds with an
increase in the number of mitochondria in the cell.
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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
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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. 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.