BIOL 160 Lipids and Membranes Notes
BIOL 160 Lipids and Membranes Notes BIOL 160 - 021
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BIOL 160 - 021
Mary Alison Bennett
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This 3 page Class Notes was uploaded by Mary Alison Bennett on Friday September 25, 2015. The Class Notes belongs to BIOL 160 - 021 at University of Tennessee - Knoxville taught by Purnima D Pinnaduwage in Fall 2015. Since its upload, it has received 32 views. For similar materials see Cellular and Molecular Biology in Biology at University of Tennessee - Knoxville.
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Date Created: 09/25/15
Inside the Cell Prokarvotic Cells 0 Prokaryotes do NOT have a membranebound nucleus 0 Their DNA is kept in a single chromosome nucleoid o Prokaryotes DO almost always have a plasma membrane stiff cell wall and ribosomes Eukarvotic Cells 0 Considerany larger than prokaryotic cells 0 Size can make it difficult for molecules to diffuse across the entire cell 0 A problem partly solved by membranebound organelles Origin of Eukarvotic Cells 0 Endosymbiosis Theory cells engulfed other cells that became mitochondria and chloroplasts explains the double membranes surrounding these organelles o Eukaryotes likely evolved form prokaryotes same 20 amino acids and nucleic acids as hereditary material Parts of Eukarvotic Cells Ribosomes 0 not technically considered organelles 0 Structure large and small subunits containing LOTS of protein molecules may be attached to ER or free in the cytoplasm 0 Function Synthesize proteins Nucleus 0 Structure double membrane nuclear envelope contains many openings nucleolus manufacturing RNA and ribosome subunits 0 Function stores hereditary information synthesizes RNA and ribosome parts Endoplasmic Reticulum 0 Structure single membrane branching sacs rough ER has ribosomes attached smooth ER does not part of the endomembrane system 0 Endomembrane System composed of the ER Golgi and lysosomes primary system for protein and lipid synthesis 0 Function Rough ER creates and processes proteins smooth ER creates and processes lipids Golgi Apparatus 0 Structure single membrane stack of flattened membrane sacs 0 Function protein lipid and carbohydrate processing Lysosomes 0 Structure single membrane contains protein pumps contain around 40 different digestive enzymes low pH found only in animal cells 0 Function digestion and recycling Protein Transport in the Cell 0 Most proteins are found in the nucleus peroxisomes mitochondria and chloroplasts 0 Proteins will have a target sequence that sends them to the appropriate organelles 0 Moving proteins in and out of the nucleus requires energy 0 Proteins that need to enter the nucleus will have a nuclear localization signal NLS that allows them in Transport and the Endomembrane System 0 The endomembrane system ER golgi and lysosomes manufactures and ships proteins 0 PulseChase experiments have been used to track protein movement 0 Label proteins with radioactive amino acids 0 Wash away excess amino acid leaving labeled proteins 0 Follow the tagged proteins to find their path 0 Pulsechase found that proteins move from Rough ER to Golgi to vesicles The Signal Hypothesis 0 Proteins headed for the endomembrane system have a signal sequence that sends them in the right direction 20 amino acids long 0 Protein synthesis begins on a free ribosome 0 Signal sequence sends the building protein to the appropriate location on the rough ER thanks to a signal recognition particle SRP 0 Protein synthesis continues into the rough ER 0 When synthesis is complete the signal sequence is removed and the ribosome and protein detach from the lumen of the rough ER 0 After the ER proteins move to the golgi in vesicles 0 Vesicle buds off the ER and travels to the golgi where it binds on the cis side and dumps its contents o If the protein is to stay within the ER it will have a special retention tag 0 Once proteins reach the golgi they are tagged sorted and sent in vesicles and delivered to their specific sites Delivery to Lysosomes o Autophagy the lysosome binds to a damaged organelle to be recycled o Phagocytosis the phagosome is engulfed by the cell and sent to the lysosome to extract necessary molecules 0 ReceptorMeditated Endocytosis macromolecules bind to receptors and are engulfed by the cell the vesicle formed fuses with an early endosome and the pH lowers after receiving digestive enzymes the endosome becomes a lysosome Cvtoskeleton o The cytoskeleton is composed of protein fibers and gives the cell shape and stability Also aids in movement of the cell and materials within the cell Very helpful with organization of the cell 0 Microfilaments made of actin resist tension move cells divide cells move organelles o Microtubules made of alpha and beta tubulin dimers resist compression move cells cilia and flagella move chromosomes assist cell division move organelles tracks for intracellular transport 0 Intermediate Filaments make of keratin among other things resist tension and anchor some organelles