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2) Biochemistry II > Amino Acid Catabolism > Flashcards

Amino Acid Catabolism Flashcards

1
Q

In uncontrolled diabetes, or a tumor, what is the energy source?

A
  • Glucose cannot be used efficiently

- Fat and, if not available, protein will be degraded

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2
Q

Where are most amino acids metabolized?

A

In the liver

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3
Q

What happens to the ammonia? What happens to the carbon skeleton?

A
  • Ammonia: recycled or excreted

- Carbon skeleton: TCA cycle, gluconeogenesis, ketogenesis

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4
Q

What happens to proteins in the stomach?

A
  • Gastrin –> HCl

- Pepsinogen –> pepsin: protein degradation

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5
Q

What happens to proteins in the duodenum?

A
  • Acidity stimulatse secretin, which stimulates the pancreas to produce bicarbonate
  • pH rises to 7
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6
Q

What does the pancreas secrete for protein degradation?

A

Trypsin and chymotrypsin

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7
Q

What is the general amino acceptor?

A

a-ketoglutarate

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8
Q

Aminotransferases are _____ specific

A

amino acid

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9
Q

What happens when a-ketoglutarate accepts an amino group? What is the amino acid that lost its amino group known as?

A
  • Glutamate

- a-Keto acid

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10
Q

PLP uses _______ as a cofactor in transamination reactions

A

Vitamin B6

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11
Q

Vitamin B6 is a cofactor for _____ and ______

A

PLP

glycogen phosphorylase

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12
Q

What happens in the liver in deamination reactions?

A
  • Glutamate dehydrogenase removes the amino group from glutamate
  • Re-creates a-ketoglutarate
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13
Q

Where does deamination occur?

A

Mitochondria of liver cells

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14
Q

What is the role of glutamine synthase?

A
  • Uses energy to incorporate ammonia, and forms glutamine

- Glutamine is excreted into circulation

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15
Q

What is the role of glutaminase?

A
  • Once glutamine is incorporated into the liver mitochondria

- Converts glutamine to glutamate, which removes the ammonia that is then excreted as urea

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16
Q

Pyruvate accepts an amino group from _____ to form _____

A

glutamate

alanine

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17
Q

In the liver, alanine is degraded by removing an ______ to form ______

A

amino

pyruvate

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18
Q

Pyruvate undergoes ________ to produce glucose

A

gluconeogenesis

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19
Q

What are the steps to the glucose-alanine cycle?

A
  • Glucose –> Pyruvate
  • Pyruvate + Amino group from Glutamate –> Alanine
  • Liver: Alanine – amino group –> Pyruvate
  • Pyruvate –> gluconeogenesis = glucose
  • Glucose can be used for exercise
20
Q

What are the sources of ammonia that contribute to glutamate in the mitochondria?

A
  • Glutamine
  • Alanine
  • Glutamate
21
Q

Glutamate can donate its amino group to form what? How many ammonias does that produce?

A
  • a-Ketoglutarate

- 1 ammonia

22
Q

Glutamine can donate its amino group to form what? How many ammonias does that produce

A
  • Glutamate, which can donate its amino group to form a-Ketoglutarate
  • So, 2 ammonias total
23
Q

Ammonia from the intestines arrives to the liver, and is combined with ____ to form ______ through the enzyme ___________, which utilizes ____ ATPs

A

HCO3
carbonoyl phosphate
carbonoyl phosphate synthetase 1
2

24
Q

Oxaloacetate uses the amino group from __________ to form __________, with the enzyme ___________

A

glutamate
aspartate
Aspartate amino transferase

25
Q

_____, like Glutamate, is an amino group donor

A

Aspartate

26
Q

What are the four cytosolic enzymes of the urea cycle?

A
  1. Ornithine transcarbamylase
  2. Arginosuccinate synthase
  3. Arginosuccinase
  4. Arginase
27
Q

How is citrilline synthesized? What enzyme? Where does it travel to?

A
  • Enzyme: Ornithine transcarbamylase
  • Combining carbonyl-phosphate and ornithine
  • Travels to the cytosol
28
Q

How is arginosuccinate synthesized? What enzyme?

A
  • Enzyme: Arginosuccinate synthase

- Citrilline and aspartate are combined

29
Q

How is arginine formed in the urea cycle? What enzyme?

A
  • Enzyme: Arginosuccinase

- Fumarase is discarded from arginosuccinate, to form arginine

30
Q

How is ornithine synthesized in the urea cycle? Where does it travel to?

A
  • Enzyme: Arginase

- Urea is removed from arginine to synthesize ornithine, which travels to the mitochondria

31
Q

Which enzymes of the TCA cycle contain both cytosolic and mitochondrial isoforms?

A
  • Fumarase

- Malate dehydrogenase

32
Q

Which intermediate of the TCA cycle contributes to the formation of Aspartate?

A

Oxaloacetate

33
Q

Which intermediates link the TCA cycle and the urea cycle?

A
  • Oxaloacetate
  • Fumarate
  • Aspartate
  • Malate
34
Q

What is the carbon skeleton converted to during amino acid catabolism?

A

Intermediates of the TCA cycle

35
Q

What do glucogenic amino acids create? What can that be incorporated into?

A
  • Pyruvate

- Can be incorporated into gluconeogenesis

36
Q

What do ketogenic amino acids create?

A
  • Acetyl-CoA

- Intermediates of ketone body synthesis

37
Q

Which amino acids are both ketogenic and glucogenic?

A
  • Isoleucine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Tyrosine
38
Q

Which amino acids are exclusively ketogenic?

A

Lysine and Leucine

39
Q

Which amino acids are ketogenic?

A
  • Leucine
  • Lysine
  • Phenylalanine
  • Tryptophan
  • Tyrosine
  • Isoleucine
  • Threonine
40
Q

What is glutamate dehydrogenase activated by?

A

ADP

41
Q

What is glutamate dehydrogenase inhibited by?

A

GTP

42
Q

What are the 4 enzymes of the urea cycle and carbamoyl phosphate synthase 1 regulated by?

A

Nutritional status

43
Q

What happens to the enzymes of the urea cycle when an individual is starving?

A

Enzymes are increased since you are metabolizing more amino acids

44
Q

What happens to the enzymes of the urea cycle when an individual is consuming a protein-rich diet?

A
  • Surplus amino acids = more ammonia produced

- Enzymes are upregulated

45
Q

What is the high-energy used by the urea cycle offset by?

A

By the NADH (2.5 ATP) malate-oxaloacetate conversion reaction

46
Q

How many ATPs are utilized in the urea cycle? At which stage(s)?

A
  • 3 ATPs are utilized in the urea cycle
  • 2 ATP at carbamoyl phosphate
  • 1 ATP at the stage of secondary reaction

2) Biochemistry II (23 decks)

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