Lecture Exam 2 Flashcards
What is a zymogen?
-Zymogen: an inactive substance which is converted into an enzyme when activated by another enzyme
How is pepsinogen activated?
-pepsinogen: zymogen that is converted to active pepsin by autocatalytic cleavage at low pH
How is trypsin activated?
Enteropeptidase: a proteolytic enzyme that converts trypsinogen to trypsin
What is the role of PLP? Which vitamin is it?
-PLP carries the amino groups at the active site
-Vitamin B6
What is a transanimation reaction?
-Transanimation Reaction: forms a new amino acid from the transfer of an amino group
What is the Glucose-Alanine cycle? What tissues are involved? What are the main molecules?
-Glucose-Alanine Cycle: pathway by which alanine carries ammonia and the carbon skeleton from pyruvate to the liver
-Muscle and Liver tissues are involved
-Main Molecules: Glutamate, alpha-ketoglutarate, alanine, pyruvate
What is the urea cycle? What are the main products? Where do those molecules go?
-pathway by which the ammonia deposited in the mitochondria of hepatocytes is converted to urea
-Main Products: urea, AMP, fumarate
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How does the aspartate-argininosuccinate shunt connect the urea cycle and the citric acid cycle?
-Aspartate-arginosuccinate shunt: pathways linking the citric acid and urea cycles
-aspartate donates an amonnia to the carbanoly phosphate to be released as urea
What is a ketogenic amino acid? What is a glucogenic amino acid?
-Ketogenic Amino Acid: produces ketone bodies (phenylalanine, tyrosine, tryptophan, lysine, leucine, isoleucine, threonine)
-Glucogenic Amino Acids: can be converted to glucose or glycogen (all amino acids, except for leucine and lysine)
What vitamin is used to make tetrahydrofolate? What types of reactions can tetrahydrofolate participate in?
-Tetrahydrofolate: transfers intermediate oxidation states
-H4 folate is the vitamin
What is S-adenosylmethionine? What types of reactions does it participate in?
-S-adenosylmethionine: transfers methyl groups
-has a 1000x more reactive methyl group than the methyl group of N5-methyltetrahydrofolate
What is megaloblastic anemia? How does it related to vitamin deficiency?
-Megaloblastic anemia: observed in vitamin B12 deficiency due to the decline in the production of mature erythrocytes
What are the key breakdown products of amino acid degradation?
-They are converted in whole or in part to pyruvate, then it is either converted to acetyl-CoA for oxidation via the citric acid cycle, oxaloacetate to enter gluconeogenesis
What is a phenylketonuria (PKU)?
-disease caused by a genetic defect in phenylalanine hydroxylase
-most common cause of elevated levels of phenylalanine in the blood
What is a chemiosmotic theory?
-Chemiosmotic Theory: transmembrane differences in proton concentration are the reservoir for the energy extracted from biological oxidation reactions
What is the structure of the mitochondria? How does the inner membrane and matrix help facilitate metabolism?
-Outer membrane is readily permeable to small molecules and ions
-transport occurs through porins
-Inner membrane is impermeable to most small molecules and ions
-transport requires specific transporters
-The mitochondrial matrix contains: PDH complex, enzymes of the citric acid cycle, enzymes of the fatty acid beta oxidation pathway, and enzymes of the pathways of amino acid oxidation
-The inner mitochondrial membrane segregates the intermediates and enzymes of cytosolic and matrix metabolic pathways
What is the respiratory chain? What key molecules are used to carry electrons through the respiratory chain?
-Respiratory Chain: series of electron carriers
-dehydrogenases collect electrons from catabolic pathways and funnel them into universal electron acceptors
-NAD
-flavoproteins
-ubiquinone (coenzyme Q or Q)
-cytochromes
-iron-sulfur proteins
How are electron flow, proton pumping, and ATP synthesis connected?
-The electron-transport pumps H+ out of the cell and thereby establishes a proton-motive force across the plasma membrane that drives the ATP synthase to make ATP.
What are the main complexes of the electron transport chain? Which ones pump protons and which do not?
-Complex I (NADH to ubiquinone)
-Pumps Protons
-Complex II (from succinate to ubiquinone)
-no proton pumping
-Complex III (from ubiquinone to cytochrome c)
-pumps protons
-Complex IV (from cytochrome c to O2)
-pumps protons
Which complex receives electrons from NADH? Which complex receives electrons from FADH2?
-Complex I receives electrons from NADH
-Complex II receives electrons from FADH2
How does the ATP synthase work to make ATP?
-In the absence of an oxidizable substrate, the proton-motive force alone drives ATP synthesis
What factors regulate ATP synthesis?
-Inhibit: glucose-6-phosphate, ATP, citrate, NADH
-Producing: phosphate,
What do the Malate-Aspartate and Glycerol-3-phosphate shuttles do? How do these shuttles interface with electron transport?
-Malate-Aspartate Shuttle: moves NADH equivalents into the respiratory chain at Complex I and yield a P/O ratio of 2.5
-Glycerol 3-phosphate: NADH enters the respiratory chain at Complex III and yield a P/O ratio of 1.5
What is thermogenesis?
-Thermogenesis is defined as the dissipation of energy through the production of heat and occurs in specialised tissues including brown adipose tissue and skeletal muscle.
What are the main genes encoded in the mitochondria?
-13 mitochondrial proteins are encoded by the mitochondrial genome and synthesized in the mitochondria
-Respiratory Proteins, NADH dehydrogenase, succinate dehydrogenase, ubiquinone, cytochrome c oxidoreductase, cytochrome oxidase, ATP synthase, proteins for complex I, II, and III, and IV, ATP synthase, tRNA, rRNA, control region of DNA
What is the naturalistic theory behind the origin of mitochondria?
-Mitochondria arose from aerobic bacteria that entered into an endosymbiotic relationship with primitive eukaryotes and those endosymbiotic bacteria eventually became mitochondria
Photophosphorylation
ATP synthesis driven by light; electron flow through a series of membrane carriers is coupled to proton pumping; H2O is the electron donor; NADPH is formed
Photosynthesis
encompasses two processes: light dependent reactions, CO2-assimilation reactions to produce energy
Calvin Cycle
uses CO2-assimilation reactions (ATP and NADPH are used to reduce CO2 to form triose phosphate)
CO2 Assimilation
ATP and NADPH are used to reduce CO2 to form triose phosphate
Photon
a quantum of light
Quantum
a quantity of energy in a photon equal to the energy of the electronic transition to a higher energy level
-to be absorbed, a photon must contain a quantum
Fluorsecenece
light emission accompanying decay of excited molecules
-always at a longer wavelength (lower energy) than that of the absorbed light
Exciton
quantum of energy passed from an excited molecule to another molecule through exciton transfer
Chlorophylls
green light-absorbing pigments in the thylakoid membranes
In what ways do chloroplasts and mitochondria differ?
-Chloroplasts: Light converts H20 to a good electron donor and NADP+ is the electron acceptor, H+ pumps into the chloroplast
-Mitochondria: Reduced substrate (fuel) donates electrons and O2 accepts them, H+ pumps electrons out of the mitochondria
In what ways are chloroplasts and mitochondria similar?
-Energy of electron flow is stored as electrochemical potential
-ATP synthase uses electrochemical potential to synthesize ATP
What are photopigments and how do they differ between plants, cyanobacteria, and algae?
-Photopigments: unstable pigments that undergo a chemical change when they absorb light
-I have no idea where the other stuff is
What is a photosystem?
functional arrays of light-absorbing pigments located in the thylakoid or bacterial membrane
How do electrons flow in a type I and type II photosystems?
-Type II Photosystem: contains a single P870 reaction center, a cytochrome bc, electron-transfer complex, and an ATP synthase
-Type I Photosystem: can send electrons through a cyclic electron transfer path or through a linear path that reduces NAD+ to NADH
What is the overall process and purpose of CO2 assimilation and CO2 fixation?
-CO2 Assimilation: the process of converting CO2 to simple (reduced) organic compounds via the Calvin cycle
-CO2 fixation: the process of incorporating (fixing) CO2 into the triose phosphate 3-phosphoglycerate
What is rubisco and what role does it play in CO2 assimilation?
-Rubisco: catalyzes the covalent attatchement of CO2 to ribulose 1,5-bisphosphate and the cleavage of the unstable six-carbon intermediate to form two molecules of 3-phosphoglycerate
What effect does light have on disulfide bonds in some photosynthetic enzymes?
-enzymes are activated by light driven reduction of disulfide bonds between critical Cys residues
-reduced thioredoxin donates electrons for the reducation of the disulfide bonds of the light-activated enzymes
What is the purpose of the glyoxylate cycle? What pathways does it tie together?
-Glyoxylate Cycle: converts acetate to succinate or another four-carbon intermediate of the citric acid cycle
-It ties togther the Citric Acid Cycle and Glycolysis?
What is cellulose synthesis? Describe the general process.
-Cellulose: must be synthesized from intracellular precursors but deposited and assembled outside the plasma membrane
-Cellulose Synthase: catalyzes the assembly of cellulose chains
-has a glycosyl transferase activity in its cytoplasmic domain
-forms a transmembrane channel through which the growing cellulose chain is extruded
