LSU BIOL 1201 - Learning Objectives Number 4

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Learning Objectives Number 4 Ocean The Ocean Deep sea Three quarters of the planet is covered with water The average depth of the ocean is 3800 meters For every 10 meters depth increase pressure increases 1 atm Defined as the ocean below either 200 or 1000 meters Characterized by low temperature high hydrostatic pressure and no sunlight o Approximately 2 4 C o Up to 1 500 atm in the Mindanao Trench Sunlight necessary for photosynthesis does not penetrate to these depths and thus there is low food availability and this affects the adaptations of organisms at these depths Have characteristic depth distribution patterns which may be affected by Deep sea species pressure Pressure Acts on volume changes o Of the entire solute solvent system Increased pressure inhibits a process that proceeds with a positive volume change and accelerates a process that proceeds with a negative volume change o Only if there is no net volume change is a process unaffected by pressure increases Biochemical processes can be affected o Examples of what can be affected Rates of catalysis binding of substrates assembly of subunits The volume changes associated with these processes may result from the interaction of enzymes and substrates with water o The water may be more organized by interactions with charged substrates or amino acids o Membrane fluidity is also affected High pressure acts like low temperature causing membranes to freeze Free vehicles Not attached to vessel o E g monster cameras Deep Submergence Vehicles E g Johnson Sea Link Alvin HOV Alvin Human Occupied Vehicle Owned by the U S Navy and operated by Woods Hole Oceanographic Institution 1 1966 recovered a hydrogen bomb lost in the Mediterranean Sea Explored the hydrothermal vents surveyed the Titanic The Story of Alvin s Lunch In the fall 1969 Alvin sank in 1540 m water temperature 3 C and was recovered 11 months later On board were lunches for pilot and 2 scientists o Bullion soup bologna sandwich with mayonnaise apples o Samples were eaten and they were okay o Some put back in refrigerator at 3 C o Decayed in 3 weeks Sparked interest in metabolic rates in the deep sea which Bioluminescence continues to today Rattails Biologically produced light used for among a number of roles species recognition camouflage and in some cases hunting Bioluminescence and color play role in being invisible o Different wavelengths of light penetrate to different depths o Typical wavelengths of bioluminescence are in the blue range These fish belong to the family Macrouridae and are the predominant deep sea teleost boney fish family o Also have the common name of grenadiers If one is interested in examining how organisms adapt to the high pressures of the deep sea this family of fishes provides a useful model Different rattail species occupy different depths and thus experience different pressure regimes One can compare species that differ primarily in the variable of interest hydrostatic pressure without possible confounding variables such as phylogenetic distance or different lifestyles or body temperatures Cell Signaling What are first messengers Extracellular messengers that elicits a cellular response when it binds to a receptor protein Hormones neurotransmitters What are two examples of second messengers cAMP cyclic adenosine monophosphate o Synthesized from ATP o Activates an enzyme called protein kinase Calcium o Muscle contractions Amplify faint signal What is signal amplification and how does it benefit the cell o A few first messenger molecules o Many second messenger molecules 2 o Each step in the cascade recruits more molecules Elicit a coordinated response What is the role of phosphorylation cascades in signal amplification Activated kinase activates a different kinase At each step more enzymes are recruited Where are the receptors involved in cell signaling located May involve a receptor in the plasma membrane o An integral membrane protein May involve an intracellular receptor o Steroid hormone receptors Signal amplification in the breakdown of glycogen Epinephrine adrenaline activates a GPCR in liver cells e g Fig 11 10 11 16 45 7 and 45 9 Calcium activates a phosphorylation cascade in skeletal muscle after the Protein Kinase A step in Fig 11 16 activating the enzyme phosphorylase kinase The relationship of adenylyl cyclase and cAMP Adenylyl cyclase produces cAMP How is adenylyl cyclase activity regulated The enzyme is modulated positively and negatively by different G proteins Intracellular cAMP levels go up or down o Depends on the summation of all the positive and negative signals on that cell What reactions do protein kinases and phosphatases catalyze Protein kinases phosphorylation reactions o Covalent transfer of phosphate group from ATP to specific amino acids of target proteins o Acts as an on or off switch for the target protein Phosphates remove phosphate groups What is the role of cAMP dependent Protein Kinase Protein Kinase A in cell signaling Catalyze phosphorylation reactions What are the subunits of Protein Kinase A and what do they do Two regulatory subunits Two catalytic subunits What is the subunit composition of the active enzyme In the cytoplasm cAMP binds to the R subunit R2C2 dissociates into an R dimer and 2 C monomers C monomers catalyze phosphorylation reactions Of the inactive enzyme R2C2 What is G protein cycle Be sure you know all of the steps in the cycle and can reproduce it from memory G proteins o Switch proteins 3 o Either on or off o Activated by occupied activated receptor o GDP is bound to the alpha subunit of the inactive G protein heterotrimer o Inactive off alpha GDP beta gamma o Active on alpha GTP beta gamma Alpha subunit with GTP bound and a beta gamma dimer Activation of G proteins o An activated receptor interacts with the G protein o GTP replaces GDP on the alpha subunit o The G protein dissociates into alpha GDP and a beta gamma dimer o The G protein is now on Activated G protein subunits o Interact with their target enzymes or ion channels Inactivating G proteins o Turned off when an intrinsic GTPase activity of the alpha subunit hydrolyzes GTP to GDO o Alpha GDP and the beta gamma dimer re associate G protein coupled signaling o Membrane receptor is activated by an extracellular signal o G protein transfers the extracellular signal into the intracellular compartment by interacting with a target o Target enzyme produces an intracellular second messenger What are examples of the types of G


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LSU BIOL 1201 - Learning Objectives Number 4

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