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BIO2600 Week 1/2 Notes

by: Nausheen Zaman

BIO2600 Week 1/2 Notes BIO2600

Marketplace > Wayne State University > Biology > BIO2600 > BIO2600 Week 1 2 Notes
Nausheen Zaman
GPA 3.3
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About this Document

Notes from lecture during weeks 1 and 2
Intro to Cell Biology
Class Notes
Biology, cellbiology, cellular biology, Wayne State University




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This 5 page Class Notes was uploaded by Nausheen Zaman on Wednesday September 14, 2016. The Class Notes belongs to BIO2600 at Wayne State University taught by in Summer 2016. Since its upload, it has received 77 views. For similar materials see Intro to Cell Biology in Biology at Wayne State University.

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Date Created: 09/14/16
KEY QUESTIONS  ­ What are the relationships between the structure and function of cells?  ­ Cellular compartmentalization (membranes ­ structure and function)  ­ Signalling on intra/extracellular levels ­ flow of information from all different parts  of the cell  ­ Roles of different subcell structures  ­ How a cell copies itself through mitosis/meiosis (cell cycle)  ­ Cell checkpoints to regulate its function  ­ Cell death when it recognizes its damage to avoid copying a sick cell    History of Cell Biology  ­ First seen with invention of compound microscopes (more than one lens) in the late  1500s  ­ Called ‘cells’ because of monastery cells by Robert Hooke    What makes a cell?  ­ Small, membrane enclosed units with the ability to create copies of themselves  1. All living organisms are composed of cells  2. Cells are the basic unit of life  3. Cells can only be duplicated from living cells (not dead ones! Unless you’re into  synthetic bio :))  ­ Come in all different shapes/sizes with different functions  ­ Basic chemistry  ­ DNA (transcribes) → RNA (transcribes) → proteins (Central Dogma of Cell  Biology)  ­ RNA viruses go through a DNA intermediary, challenging Central Dogma  ­ Non­coding RNAs (microRNAs ­ used to fight against foreign viruses ­ inhibit  translation of mRNAs)    Prokaryotic vs Eukaryotic  ­ Prokaryotes: No nucleus and genetic material not enclosed in a membrane  ­ Bacterium  ­ Eukaryotes: Nucleus where genetic material resides  ­ Animal/Plant cells  ­ Cellular compartmentalization  ­ Nucleolus within nucleus is NOT bound to the nucleus  ­ DNA packed in by chromatin into chromosomes  ­ Genome size does not correlate to the size of the animal  ­ Gene sizes may be bigger, junk DNA (not actual junk DNA, they have a  function)  ­ Mitochondria have double membranes because they are protecting a second  genome within  ­ Chloroplasts also have two membranes because   ­ Ribosomes make proteins transported through the endo reticulum into the Golgi  ­ Cytoplasms are NOT static. The organelles are free to move around in the cell  ­ Actin filaments ­ micro filaments  ­ Microtubules ­ motor proteins   ­ Intermediate filament ­ keratin (protein complexes involved in cell  adhesion)    Membranes  ­ No membranes = NO CELL  ­ Prokaryotes = One membrane protecting cell (plasma membrane)  ­ Eukaryotes = Internal (organelle membranes) and external (plasma membranes  ­ Function  ­ Plasma membranes  ­ Cell communication (intra/extracellular signalling) → receptor proteins  allow cells to take note of environment and act according to surrounding  conditions  ­ Import/export of molecular wastes and nutrients for cell growth and  survival→ enter and pass through cells by means of selective channels  and transport chains   ­ Cell movement ­ Membranes are flexible and this allows cell growth and  movement (ex. axons)  ­ ALL FUNCTIONS NEED PROTEINS TO WORK!!! (Without proteins it can  still protect the cells internal organs)  ­ Organelle membranes  ­ Nucleus + mito = two organelles covered with two membranes  ­ These organelles store important genetic information for survival  ­ Both organelle and plasma membranes have a subtle difference in the protein  composition of the membrane structure  ­ Used to differentiate between two functions   ­ Both still share a general structure  ­ Components  ­ 2 main components!  ­ Lipids ­ basic structure and signalling  ­ Proteins ­ required for different functions  ­ Phospholipid structure  ­ Hydrophilic head  ­ Composed of   ­ Hydrophobic tail  ­ Composed of  ­ Amphipathic molecule has both hydrophilic and hydrophobic parts  ­ Hydrophobic = nonpolar  ­ They are caged around by polar molecules (water)  ­ Hydrophilic = polar  ­ Water is polar  ­ Different types of phospholipids  ­ Phospholipid ­ phosphatidylseride  ­ Sterol ­ cholesterol  ­ In an aqueous environment, hydrophobic tails are attracted to each other and hydrophilic  heads are attracted to water  ­ Having only one layer would be unstable  ­ The lipids will bury their tails in the center and make it into a ball of cells (lipid  micelle)  ­ Think of oil and water  ­ Having a bilayer makes it more shielded and cylinder­like  ­ More energetically favorable  ­ If a sheet of bilayer exists…  ­ It will spontaneously collapse on itself and protect the uncovered layer into a  sphere to make itself energetically favorable and stable (liposome)  ­ This behavior is essential for the formation of a living cell  ­ The bilayer is fluid in structure  ­ The aqueous surroundings allow the structure to stay the same  ­ Lipids can move along the bilayer and change places with each other along the  bilayer  ­ Does not require enzymes and is important for membrane function and integrity  ­ Your cells would break if they are too rigid (exocytosis + endocytosis)  ­ Types of phospholipid movement  ­ Lateral diffusion ­ lipids exchange places with each other  ­ Flexion ­ move the hydrophobic tails back and forth  ­ Rotation ­ hydrophilic head rotates around each other  ­ Influences on the fluidity of the lipid bilayer  ­ The number of double bonds in the phospholipid hydrocarbon tails  ­ One tail is usually unsaturated  ­ Number of cholesterol molecules in bilayer  ­ Saturated hydrocarbons makes the bilayer stiffer with more packing (no  double bonding)  ­ Unsaturated hydrocarbons makes the bilayer more fluid (has cis double  bonds) with looser packing   ­ Length of hydroC tails  ­ Colder temperature can shrink the hydrocarbon tails → more fluid bilayers  ­ Hotter temp → longer tails → more fluid bilayers but less stable   ­ Shorter tails = less interactions + more fluid bilayers  ­ Longer tails = more interactions + much stiffer bilayers  ­ Cholesterol contributes to a more rigid bilayer because of the  planar ring structure right under the polar head   ­ The cholesterol fills in space due to the kinks left behind by the  longer tails from hotter temperatures  ­ Cholesterol provides stability to animal lipid bilayer  ­ Hassett and Crockett (2009)  ­ Did a study on crustacea  ­ Lower temps = lower cholesterol levels  ­ Higher temps = higher cholesterol levels  ­ Why is it important for the lipid bilayer be fluid?  ­ Membranes have proteins: a fluid bilayer → easily allows proteins to move  through the layer to interact with other proteins for cellular signaling  ­ Allows membrane proteins and lipids to distribute evenly between mother and  daughter cells during division  ­ Allows membranes to fuse and mix with each other  ­ Necessary for cell expansion, endocytosis and exocytosis  ­ Membrane assembly begins in the ER  ­ Enzymes on surface of ER make: free fatty acid­produced phospholipids,   ­ ER lipid bilayer is symmetrical  ­ Transfer between monolayers need enzymes  ­ Scrambalase = transfers phospholipids from one monolayer to another  and balances it out  ­ Neither monolayer is enriched of a certain phospholipid mor/e than  another one  ­ ER membranes are pinched off to form Golgi membrane  ­ GA lipid bilayer is asymmetrical   ­ Flippase ­ transfers specific phospholipids to GA monolayer  ­ Scrambalases vs. Flippases  ­ Scrambalase ­ ER (if lipid bilayer asymmetry need to be disrupted a.k.a  apoptosis)  ­ Flippases ­ GA (used for monolayer asymmetry)  ­ Hassett and Crockett (2009) continued  ­ Crustacea @ higher temp = HIGHER cholesterol ­ improves stability of the  bilayer  ­ Crustacea @ lower temp = LOWER cholesterol ­ makes the bilayer more fluid  ­ Phospho/glycolipids are asymmetrically distributed in the bilayer  ­ Orientation in the bilayer is crucial to function   ­ PE and PS is more reactive than PC and SP ­ makes them more involved in the  inside of the cell because if they were outside then it would send off too make  signals causing the cell to become engulfed  ­ Golgis are pinched off → added to plasma membrane  ­ Membranes always retain their orientation    PROTEINS  ­ Transporters (pumps)  and channels  ­ K+ ion channel (Potassium ion channel)  ­ Na­/K+ pump (Sodium­Potassium Pump)  ­ Beta barrels composed of beta sheets  ­ Hydrophobic core and hydrophilic outside  ­  


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