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BIOC192 2024 > Lecture 28 > Flashcards

Lecture 28 Flashcards

1
Q

How are amino acids consumed in the diet?

A

As proteins

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2
Q

What does protein digestion involve?

A

Hydrolysis of peptide bonds by different proteases / peptidases

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3
Q

What are the two types of peptidases?

A

Endopeptidase and exopeptidase

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4
Q

What do endopeptidases do?

A

Attack peptide bonds within the protein polymer

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5
Q

What do exopeptidase do?

A

Attack the last peptide bond near the end of the protein polymer

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6
Q

How do endopeptidases work?

A

Different endopeptidases act sequentially to produce smaller peptides each round

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7
Q

What is endopeptidase specificity determined by?

A

Adjacent amino acid side chain in the protein substrate

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8
Q

Where do carboxypeptidases cut?

A

Near the carboxyl-terminal residue

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9
Q

Where do aminopeptidases cut?

A

Near the amino-terminal residue

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10
Q

What are proteases produced as?

A

Zymogens

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11
Q

What are zymogens?

A

Inactive precursors to the peptidase / protease

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12
Q

Why are zymogens needed?

A

To prevent peptidase activity before reaching the GIT and breaking down the proteins within cells

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13
Q

How are zymogens activated?

A

Through cleavage of peptides from their structure

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14
Q

What are the two forms of zymogen activation?

A

Autolytic activation and catalytic activation

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15
Q

What is autolytic activation?

A

Change in chemical composition (e.g. pH) causing self activation (cleavage)

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16
Q

What is catalytic activation?

A

An active form acting as a catalyst to activate the inactive form

17
Q

How are di- and tri-peptides absorbed into the SI?

A

By co-transport with H+ ions via a membrane transporter

18
Q

How are amino acids absorbed into the SI?

A

Through an amino/Na+ cotransporter as amino acids are moving against their concentration gradient

19
Q

What happens to absorbed di- and tri-peptides?

A

They are further digested into individual amino acids by cytoplasmic peptidases

20
Q

How do amino acids enter the blood?

A

Through a facilitative transporter into the interstitial fluid and then to the blood

21
Q

What are the different Na+ dependent carriers for amino acids across the SI?

A

Neutral AA, proline & hydroxyproline, acidic AA and basic AA & cysteine

22
Q

What is deamination of amino acids?

A

The process of removing an amino group

23
Q

What does deamination of amino acids generate?

A

A carbon skeleton and a free amino group

24
Q

What can a carbon skeleton be used for?

A

Energy capture

25
Q

What happens to a free amino group?

A

Is generally excreted

26
Q

What are the two way amino acids can be deaminated?

A

Through releasing their amino group to solution or transferring it to a keto acid

27
Q

What is the transfer of amino group to a keto acid known as?

A

Transamination

28
Q

What is transamination catalysed by?

A

Aminotransferase enzymes

29
Q

What is PLP?

A

Pyridoxal phosphate derived from vitamin B6, a co-enzyme required for transamination reactions

30
Q

What are the two forms PLP exists as?

A

Pyridoxal phosphate with no amino group and pyroxamine phosphate with an amino acid

30
Q

What is the first step of transamination?

A

Amino group is transferred from the amino acid to the PLP to form pyridoxamine phosphate

31
Q

What is the second step of transamination?

A

Amino group is transferred from the pyridoxamine phosphate to the keto acid to form pyridoxal phosphate

32
Q

What is the keto acid pair for glutamate?

A

alpha-ketoglutarate

33
Q

What is the keto acid pair for aspartate?

A

Oxaloacetate

34
Q

What is the keto acid pair for alanine?

A

pyruvate

35
Q

What can happen to keto acids?

A

They can be fed into metabolic pathways either directly or after modification

36
Q

Why are transamination reactions required in the liver?

A

To remove excess nitrogen through converting it to urea

BIOC192 2024 (36 decks)

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