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Biochemistry II > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

what rxns are unique to gluconeogenesis?

A
  • pyruvate carboxylase
  • PEPCK
  • F16BiPhosphate
  • G-6-phosphatase
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2
Q

list the roles of the pentose phosphate pathway

A
  • generates NADH
  • prevents oxidative stress
  • glucose metabolism
  • xenobiotic metabolism
  • scrambling of carbons
  • production of nucleotides
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3
Q

what enzyme catalyzes the oxidative decarboxylation step in the pentose phosphate pathway?

A

6-phosphogluconate dehydrogenase

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4
Q

what is the regulatory step of the pentose phosphate pathway and how is it regulated?

A

G-6-P

regulated by dehydrogenase (NADP+/NADPH ratio & hormones)

inactivated: increase NADPH activated: decrease in ratio

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5
Q

explain the role of glycogenin in glycogen synthesis

A
  • glycogenin attaches glucose molecule to tyrosine residue
  • complex is formed between glycogenin and glycogen synthase (allows attachment of glucose molecules)
  • finally glycogen synthesis forms a large chain
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6
Q

what are the 3 sources of NADPH for fatty acid synthesis?

A
  1. PPP
  2. malic enzyme
  3. isocitrate dehydrogenase
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7
Q

what molecule is used as the building block for every round of fatty acid synthesis? which one is used for the first round?

A

every round: malonyl CoA
1st round: acetyl CoA

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8
Q

How can PEPCK function differ between animals?

A
  • PEPCK can be found in the MTCH or cytosol
  • if found in the cytosol it involves moving reducing equivalents out of the MTCH into the cytosol
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9
Q

describe 3 major steps that fatty acid synthase uses to produce fatty acids and name one enzyme associated with each step

A
  1. entry/condensation
    - acetyl transferase
    - B-ketoacyl synthase
  2. reducing = bonds (master step)
    - B-ketomalonyl transacylase
    - dehyrotase
    - enoly reductase
  3. release of molecule
    - thioesterase
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10
Q

what are the 2 modifications that can be made to fatty acids? what are the enzymes responsible for this?

A
  • elongate ———–elongase
  • desaturation —————desaturase
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11
Q

what determines the ratio between acetoacetate and B-hydroxybutyrate during ketogenesis?

A

NAD+/NADH ratios

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12
Q

provide 3 ways that organisms can deal w/ ammonia/ excess nitrogen

A

ammonia
- ammoneotelic
- uricotelic
- ureotelic

nitrogen
- urea cycle

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13
Q

what molecule links the TCA cycle to the urea cycle?

A

fumerate

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14
Q

Describe how glutamate (GLU) and glutamine (GLN) metabolism are involved in pH homeostasis.

A
  • At normal pH: Gln = Glu production
  • At acidic pH: there’s a decrease in the production of Gln -> Glu + NH4+
  • At basic pH: there is a increase in the production of Gln -> Glu+ NH4+
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15
Q

what ultimately decides if a molecule is glucogenic or ketogenic?

A

whether the carbon backbone is formed into pyruvate for glycolysis or acetyl CoA for fatty acid synthesis

glucogenic molecules have to be conserves throughout a cycle

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16
Q

describe hoe acetyl CoA carboxylase is regulated through covalent modification

A
  • inactivated by dephosphorylation of insulin: increases polymerization
  • activated by phosphorylation of glucagon: decrease acetylCoA carboxylase (AMP dependent kinase, PKA)
17
Q

what role does vitamin B12 play in fatty acid metabolism?

A

allows for mutase to generate succinyl CoA

18
Q

provide 3 reasons why sugar nucleotides are used in metabolism.

A
  • irreversible
  • increase enzyme interactions
  • good leaving group: nucleotide
  • resource allocation
19
Q

what mode of the PPP would a rapidly dividing cell opt for and why?

A

scrambling phse
- attempts to generate increased ribose and deoxyribose

20
Q

what are the 4 steps in the mechanism of glycogen phosphorylase?

A

removes end glucose on glycogen to generate G-1-P

  1. donates proton to 4C on glycogen chain
  2. donates protein to inorganic phosphate
  3. forms carbonium ion intermediate
  4. Pi attacks intermediate forming G-1-P

proton is given back to pyridoxal phosphate

21
Q

in amino acid catabolism, the first reaction for many amino acids is a

A
  • transamination requiring pyridoxal phosphate
22
Q

what 2 molecules play an important role in getting fatty acids into the mitochondria?

A
  1. compound: carnitine
  2. protein: translocase
23
Q

what is the role of phosphorylase kinase in glycogen metabolism

A

regulate glycogen metabolism
- phosphorylate glycogen phosphorylase leads to activation

Biochemistry II (6 decks)

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