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Biochemistry II > Lecture Exam 2 > Flashcards

Lecture Exam 2 Flashcards

1
Q

What is a zymogen?

A

-Zymogen: an inactive substance which is converted into an enzyme when activated by another enzyme

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2
Q

How is pepsinogen activated?

A

-pepsinogen: zymogen that is converted to active pepsin by autocatalytic cleavage at low pH

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3
Q

How is trypsin activated?

A

Enteropeptidase: a proteolytic enzyme that converts trypsinogen to trypsin

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4
Q

What is the role of PLP? Which vitamin is it?

A

-PLP carries the amino groups at the active site
-Vitamin B6

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5
Q

What is a transanimation reaction?

A

-Transanimation Reaction: forms a new amino acid from the transfer of an amino group

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6
Q

What is the Glucose-Alanine cycle? What tissues are involved? What are the main molecules?

A

-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

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7
Q

What is the urea cycle? What are the main products? Where do those molecules go?

A

-pathway by which the ammonia deposited in the mitochondria of hepatocytes is converted to urea
-Main Products: urea, AMP, fumarate
-

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8
Q

How does the aspartate-argininosuccinate shunt connect the urea cycle and the citric acid cycle?

A

-Aspartate-arginosuccinate shunt: pathways linking the citric acid and urea cycles
-aspartate donates an amonnia to the carbanoly phosphate to be released as urea

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9
Q

What is a ketogenic amino acid? What is a glucogenic amino acid?

A

-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)

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10
Q

What vitamin is used to make tetrahydrofolate? What types of reactions can tetrahydrofolate participate in?

A

-Tetrahydrofolate: transfers intermediate oxidation states
-H4 folate is the vitamin

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11
Q

What is S-adenosylmethionine? What types of reactions does it participate in?

A

-S-adenosylmethionine: transfers methyl groups
-has a 1000x more reactive methyl group than the methyl group of N5-methyltetrahydrofolate

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12
Q

What is megaloblastic anemia? How does it related to vitamin deficiency?

A

-Megaloblastic anemia: observed in vitamin B12 deficiency due to the decline in the production of mature erythrocytes

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13
Q

What are the key breakdown products of amino acid degradation?

A

-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

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14
Q

What is a phenylketonuria (PKU)?

A

-disease caused by a genetic defect in phenylalanine hydroxylase
-most common cause of elevated levels of phenylalanine in the blood

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15
Q

What is a chemiosmotic theory?

A

-Chemiosmotic Theory: transmembrane differences in proton concentration are the reservoir for the energy extracted from biological oxidation reactions

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16
Q

What is the structure of the mitochondria? How does the inner membrane and matrix help facilitate metabolism?

A

-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

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17
Q

What is the respiratory chain? What key molecules are used to carry electrons through the respiratory chain?

A

-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

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18
Q

How are electron flow, proton pumping, and ATP synthesis connected?

A

-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.

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19
Q

What are the main complexes of the electron transport chain? Which ones pump protons and which do not?

A

-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

20
Q

Which complex receives electrons from NADH? Which complex receives electrons from FADH2?

A

-Complex I receives electrons from NADH
-Complex II receives electrons from FADH2

21
Q

How does the ATP synthase work to make ATP?

A

-In the absence of an oxidizable substrate, the proton-motive force alone drives ATP synthesis

22
Q

What factors regulate ATP synthesis?

A

-Inhibit: glucose-6-phosphate, ATP, citrate, NADH
-Producing: phosphate,

23
Q

What do the Malate-Aspartate and Glycerol-3-phosphate shuttles do? How do these shuttles interface with electron transport?

A

-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

24
Q

What is thermogenesis?

A

-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.

25
Q

What are the main genes encoded in the mitochondria?

A

-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

26
Q

What is the naturalistic theory behind the origin of mitochondria?

A

-Mitochondria arose from aerobic bacteria that entered into an endosymbiotic relationship with primitive eukaryotes and those endosymbiotic bacteria eventually became mitochondria

27
Q

Photophosphorylation

A

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

28
Q

Photosynthesis

A

encompasses two processes: light dependent reactions, CO2-assimilation reactions to produce energy

29
Q

Calvin Cycle

A

uses CO2-assimilation reactions (ATP and NADPH are used to reduce CO2 to form triose phosphate)

30
Q

CO2 Assimilation

A

ATP and NADPH are used to reduce CO2 to form triose phosphate

31
Q

Photon

A

a quantum of light

32
Q

Quantum

A

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

33
Q

Fluorsecenece

A

light emission accompanying decay of excited molecules
-always at a longer wavelength (lower energy) than that of the absorbed light

34
Q

Exciton

A

quantum of energy passed from an excited molecule to another molecule through exciton transfer

35
Q

Chlorophylls

A

green light-absorbing pigments in the thylakoid membranes

36
Q

In what ways do chloroplasts and mitochondria differ?

A

-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

37
Q

In what ways are chloroplasts and mitochondria similar?

A

-Energy of electron flow is stored as electrochemical potential
-ATP synthase uses electrochemical potential to synthesize ATP

38
Q

What are photopigments and how do they differ between plants, cyanobacteria, and algae?

A

-Photopigments: unstable pigments that undergo a chemical change when they absorb light
-I have no idea where the other stuff is

39
Q

What is a photosystem?

A

functional arrays of light-absorbing pigments located in the thylakoid or bacterial membrane

40
Q

How do electrons flow in a type I and type II photosystems?

A

-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

41
Q

What is the overall process and purpose of CO2 assimilation and CO2 fixation?

A

-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

42
Q

What is rubisco and what role does it play in CO2 assimilation?

A

-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

43
Q

What effect does light have on disulfide bonds in some photosynthetic enzymes?

A

-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

44
Q

What is the purpose of the glyoxylate cycle? What pathways does it tie together?

A

-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?

45
Q

What is cellulose synthesis? Describe the general process.

A

-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

Biochemistry II (5 decks)

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