Final Review - Ocean o How much of the earth is covered by water? About 75%o How much does pressure increase for every 10 meters? 1 atm o What is the deep sea defined as? The ocean below either 200 or 1,000 meterso What are three characteristics of the deep ocean? Low temperature (approximately 2-4 degrees Celsius) High hydrostatic pressure (up to 1500 atm in the Mindanao Trench) No sunlight (leads to low food availability, affecting adaptations of organisms at these depths)o What are the characteristic depth distribution patterns of deep sea species impacted by? Pressure o What impact does increased pressure have on processes with positive and negative volume changes? Positive: inhibits Negative: accelerates o When is a process unaffected by pressure increases? When there is no net volume change o What are three examples of biochemical processes that can be affected by pressure increases? Rates of catalysts Binding of substrates Assembly of subunits o The volume changes of the above processes may result from what? The interaction of enzymes and substrates with water o The water may be more organized by interactions with Charged substrates or amino acids o How is membrane fluidity affected? High pressure acts like low temperature, causing membranes to freeze o What are free vehicles and what is an example? Not attached to vessel E.g., monster cameras o What are some examples of deep submergence vehicles? Johnson Sea Link, Alvin o Give a description of HOV Alvin Human operated vehicle Owned by the U.S. Navy and operated by Woods Hole Oceanographic Institution Recovered a hydrogen bomb lost in the Mediterranean Sea (1966) Explored the hydrothermal vents, surveyed the Titanico What is the significance of Alvin’s lunch? Sparked interest in metabolic rates in the deep seao What is bioluminescence? Biologically produced light used for species recognition, camouflage and in somecases, hunting o Wavelengths of bioluminescence Different wavelengths penetrate different depths Typical wavelengths are in blue range o What family do rattails belong to? Macrouridae and the teleost (bony) fish family o What is the common name of rattails? Grenadiers o What are rattails a useful model of how organisms adapt to the high pressure of the deep sea? Different species of rattails live at different depths, and since they are so closely related you can compare them better than you could compare two unrelated species at different depths - Cell signaling o What are first messengers? Direct contact; short distance signaling Extracellular molecules that elicit a cellular response when it binds to a receptorprotein E.g., hormones, neurotransmitters o What are two examples of second messengers? Non-protein, water soluble molecules or ions Cyclic adenosine monophosphate (cAMP)- Synthesized from ATP- Activates an enzyme called protein kinase Calcium- Muscle contractions o What is signal amplification and how does it benefit the cell? Signal amplification is amplifying the cells response to a signal by phosphorylating the cascades of enzymes and cAMP molecules Amplify faint signal- Start with a few first messenger molecules- Many second messenger molecules - Each step in the cascade recruits more molecules Elicit a coordinated response o What is the role of phosphorylation cascades in signal amplification? Activated kinase activates a different kinase, etc. At each step more enzymes are recruited o Where are the receptors involved in cell signaling located? On the cell’s surface or inside of the cell May involve a receptor in the plasma membrane- An integral membrane protein May involve an intracellular receptor (inside cell; cytoplasm)- E.g., steroid hormone receptors o Signal amplification in the breakdown of glycogen Epinephrine (adrenaline) activates a GPCR in liver cells Calcium activates a phosphorylation cascade in skeletal muscle (after the Protein Kinase A step, activating the enzyme phosphorylase kinase) As a result of signal amplification, a smaller number of epinephrine molecules binding to receptors on the surface of a liver or muscle cell can lead to the release of hundreds of millions of glucose molecules from glycogen o What reactions do protein kinases and phosphatases catalyze? Protein kinases: phosphorylation reactions- Covalent transfer of phosphate group from ATP to specific amino acids of target protein- Acts as an on or off switch for the target protein Phosphatases: remove phosphate groups o What is the role of cAMP-dependent Protein Kinase A in cell signaling? Catalyze phosphorylation reactionso What are the subunits of Protein Kinase A and what do they do? 2 regulatory subunits (R) 2 catalytic subunits (C)o 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 reactionso What is the subunit composition of the inactive enzyme? R2C2o The relationship of adenylyl cyclase and cAMP Adenylyl cyclase catalyzes the formation of many cAMP molecules from ATPo How is adenylyl cyclase activity regulated? Epinephrine outside the cell binds the receptors on the surface of the cell causing the activation of adenylyl cyclase which in turn can catalyze many molecules of cAMP The enzyme is modulated (positively and negatively) by different G proteins Intracellular cAMP levels go up or down- Depends on the summation of all the positive and negative signals on the cell o G proteins Switch protein- Either on or off Activated by occupied (activated) receptor GDP is bound to the alpha subunit of the inactive G protein hererotrimer (protein made of three different units) Inactive, off: alpha- GDP beta gamma Active, on: alpha- GTP + beta gamma Activation of G proteins - An activated receptor interact with the G protein- GTP replaces GDP on the alpha subunit- The G protein dissociated in alpha-GTP and a beta gamma dimer - The G protein is now ono Then interacts with their target enzymes or ion channels - Turned off when an intrinsic GTPase activity of the alpha subunit hydrolyzes GTP to GDPo Alpha- GDP and the beta gamma dimer reassociate Coupled signaling - Membrane receptor is activated by an intracellular signal- G protein transfers extracellular signal into
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