Bmgy1Ht8 - Amino Acid Metabolism

Front 1

How are excess amino acids broken down by the body?

Back 1

They are separated into a nitrogen group, which is excreted via urea, and a carbon skeleton, which is used for energy production

Front 2

Which organ is the nitrogen group from the breakdown of amino acids transported to?

Back 2

The liver, where it is converted to urea for excretion via the kidneys

Front 3

What happens to the carbon skeleton produced by amino acid breakdown?

Back 3

It is fed into the TCA cycle at various points

Front 4

What are 'inborn errors of metabolism'?

Back 4

Errors in amino acid metabolism

Front 5

How much protein is broken down by our bodies per day?

Back 5

~300g

Front 6

How much protein should we consume in a day? How much is excreted per day?

Back 6

~100g for both, as a balance is required

Front 7

Where do we store proteins for use as an energy supply?

Back 7

We don't, any excess amino acids are immediately used as a form of energy

Front 8

What are the two sources of amino acids in our body?

Back 8

Dietary metabolism

Protein breakdown

Front 9

How can amino acids be classified according to availability?

Back 9

Essential, non-essential, conditionally essential

Front 10

What is a 'conditionally essential' amino acid?

Back 10

One that we can produce, but not necessarily in sufficient quantities

Front 11

Describe histidine (His/H) according to all 3 classifications

Back 11

Essential, polar basic, glucogenic

Front 12

Describe isoleucine (Ile/I) according to all 3 classifications

Back 12

Essential, non-polar alkyl, gluco/ketogenic

Front 13

Describe leucine (Leu/L) according to all 3 classifications

Back 13

Essential, non-polar alkyl, ketogenic

Front 14

Describe lysine (Lys/K) according to all 3 classifications

Back 14

Essential, polar basic, ketogenic

Front 15

Describe methionine (Met/M) according to all 3 classifications

Back 15

Essential, non-polar alkyl, glucogenic

Front 16

Describe phenylalanine (Phe/F) according to all 3 classifications

Back 16

Essential, non-polar aromatic, gluco/ketogenic

Front 17

Describe threonine (Thr/T) according to all 3 classifications

Back 17

Essential, polar neutral, glucogenic

Front 18

Describe tryptophan (Trp/W) according to all 3 classifications

Back 18

Essential, non-polar aromatic, gluco/ketogenic

Front 19

Describe valine (Val/V) according to all 3 classifications

Back 19

Essential, non-polar alkyl, glucogenic

Front 20

Describe arginine (Arg/R) according to all 3 classifications

Back 20

Semi-essential, polar basic, glucogenic

Front 21

Describe cysteine (Cys/C) according to all 3 classifications

Back 21

Semi-essential, polar neutral, glucogenic

Front 22

Describe glutamine (Gln/Q) according to all 3 classifications

Back 22

Semi-essential, polar neutral, glucogenic

Front 23

Describe glycine (Gly/G) according to all 3 classifications

Back 23

Semi-essential, non-polar alkyl, glucogenic

Front 24

Describe proline (Pro/P) according to all 3 classifications

Back 24

Semi-essential, non-polar alkyl, glucogenic

Front 25

Describe serine (Ser/S) according to all 3 classifications

Back 25

Semi-essential, polar neutral, glucogenic

Front 26

Describe tyrosine (Tyr/Y) according to all 3 classifications

Back 26

Semi-essential, polar neutral, gluco/ketogenic

Front 27

Describe alanine (Ala/A) according to all 3 classifications

Back 27

Non-essential, non-polar alkyl, glucogenic

Front 28

Describe asparagine (Asn/N) according to all 3 classifications

Back 28

Non-essential, polar neutral, glucogenic

Front 29

Describe aspartic acid (Asp/D) according to all 3 classifications

Back 29

Non-essential, polar acidic, glucogenic

Front 30

Describe glutamic acid (Glu/E) according to all 3 classifications

Back 30

Non-essential, polar acidic, glucogenic

Front 31

Which class of enzymes breaks down dietary protein into amino acids and oligopeptides? Give two examples

Back 31

Proteolytic enzymes - pepsin and pancreatic enzymes

Front 32

How are oligopeptides further broken down into tri/dipeptides?

Back 32

By aminopeptidases from their amino-terminal end

Front 33

How are tri/dipeptides broken down into amino acids

Back 33

By peptidases

Front 34

How do many amino acid transporters work?

Back 34

They co-transport Na+ along with the amino acid, and rely on Na/K-ATPase to restore extracellular Na+

Front 35

What might cause a protein to be degraded?

Back 35

- If it is damaged or incorrectly folded

- if its production has been downregulated due to transcriptional activity

- if it acts as a signalling protein that needs to be removed

Front 36

Where does most protein turnover occur?

Back 36

Skeletal muscle (41%) followed by liver (25%)

Front 37

How are proteins labelled for breakdown? Which organelle breaks the protein down?

Back 37

They are tagged with ubiquitin and broken down by the proteosome

Front 38

Describe the structure of the proteosome

Back 38

A barrel structure with its active site buried in the middle to prevent accidental breakdown of amino acids. It is also surrounded by regulatory particles to ensure only ubiquitinited proteins can get inside it

Front 39

Which enzyme tags proteins with ubiquitin? Describe how it works

Back 39

- Ubiquitin ligase has 3 subunits, E1/2/3

- E1 carries the ubiquitin and E2 activates it

- E3 recognises the protein to be ubiquinated and binds to it, allowing E1 and E2 to pass the ubiquitin onto it

Front 40

What is Angelman's syndrome?

Back 40

A genetic disease caused by mutations in ubiquitin ligase, leading to severe motor and intellectual disability

Front 41

Is insulin a catabolic or anabolic hormone?

Back 41

Anabolic

Front 42

Are thyroid hormones/glucocorticoids catabolic or anabolic hormones?

Back 42

Catabolic

Front 43

How can amino acids be classified according to their side chain?

Back 43

Either polar or non-polar

Polar can be further divided into acidic, neutral or basic

Non-polar can be divided into alkyl or aromatic

Front 44

What is deamination? What are the 3 types?

Back 44

The removal of a nitrogen group from amino acids. The three types are oxidative, non-oxidative and hydrolytic

Front 45

Which is the only amino acid that undergoes rapid oxidative deamination? Describe the reaction

Back 45

Glutamate + NAD(P)+ => @-ketoglutarate + NAD(P)H + H+ + NH4+

Catalysed by glutamate dehydrogenase

Front 46

Describe glutamate dehydrogenase, including its location, coenzymes and allosteric regulation

Back 46

- Mostly expressed in liver/kidney

- Can use either NAD+ or NADPH as a coenzyme

- NAD+ used in oxidative deamination

- NADPH used in reductive amination

- deamination stimulated by ADP/GDP (low energy signals)

- amination stimulated by ATP/GTP (high energy signals)

Front 47

If the amino acid is not glutamate, but needs to undergo oxidative deamination, what happens to it?

Back 47

It is transaminated, transferring its amino group to @-ketoglutarate, making glutamate and the amino acids corresponding a-ketoacid. The glutamate can then undergo deamination to remove the NH3 group

Front 48

Write the transamination reaction for alanine

Back 48

Alanine + @KG => glutamate + pyruvate

(pyruvate is the @ketoacid for alanine)

Catalysed by alanine transaminase

Front 49

Write the transamination reaction for aspartic acid

Back 49

Aspartic acid + @KG => glutamate + OAA

(OAA is the @-ketoacid for aspartic acid)

Catalysed by aspartate transaminase

Front 50

What do all transaminases require as a cofactor?

Back 50

Pyroxidal phosphate

Front 51

What is the ketoacid of alanine?

Back 51

Pyruvate

Front 52

What is the ketoacid of aspartate?

Back 52

OAA

Front 53

What is the ketoacid of leucine?

Back 53

2-oxo-3-methyl valerate

Front 54

What is the ketoacid of isoleucine?

Back 54

2-oxo-4-methyl valerate

Front 55

What is the ketoacid of valine?

Back 55

2-oxo-3-methyl butyrate

Front 56

Which two amino acids undergo non-oxidative deamination and why? Which enzymes carry this out?

Back 56

Serine and threonine because of the OH in their side chain. Serine/threonine dehydratase

Front 57

Which amino acids undergo hydrolytic deamination?

Back 57

Glutamine and asparagine

Front 58

Write out the reaction for the hydrolytic deamination of glutamine (the one for asparagine will be the same)

Back 58

Glutamine + H2O => glutamate + NH4+

Catalysed by glutaminase (asparaginase for asparagine)

Front 59

Describe the different locations where glutaminase is expressed and why

Back 59

Liver to generate urea

Kidneys to generate NH4+ for acid base balance

Neurons to assist in neurotransmission

Front 60

Write out the reverse reaction of the hydrolytic deamination of glutamine. Where does this process take place?

Back 60

Glutamate + NH4+ + ATP => Glutamine + ADP + Pi

Takes place in muscle via glutamate synthase

Front 61

Describe the urea cycle

Back 61

- Carbamoyl phosphate + ornithine => citrulline

- citrulline + aspartate => argininosuccinate

- argininosuccinate => fumarate + arginine

Arginine + H2O => urea + ornithine

Front 62

Write out the equation for Carbamoyl phosphate synthesis

Back 62

HCO3- + NH4+ + 2ATP => Carbamoyl phosphate + 2ADP + 2Pi

Catalysed by Carbamoyl phosphate synthetase 1

Front 63

How is Carbamoyl phosphate synthetase 1 allosterically regulated?

Back 63

Activated by N-acetylglutamate

Front 64

What can cause a blockage of Carbamoyl phosphate synthesis and what does it lead to?

Back 64

Genetic defects in Carbamoyl phosphate synthetase 1, leads to hyperammonaemia

Front 65

What are glucogenic amino acids?

Back 65

Amino acids which are fed into the TCA cycle upon breakdown, they have side chains 3 carbons long or greater

Front 66

What are ketogenic amino acids?

Back 66

Amino acids with side chains of 2 carbons, which can be used to form Ketone bodies

Front 67

How can amino acids be classified according to their metabolic fate?

Back 67

Glucogenic

Ketogenic

Both

Front 68

Which 7 molecules are end-products of amino acid C-skeleton breakdown? Which are glucogenic and which are ketogenic?

Back 68

Pyruvate

Fumarate

OAA

succinyl-coA

@-ketoglutarate are glucogenic

AcCoA

Acetoacetyl-coA are ketogenic

Front 69

Which amino acids breakdown into pyruvate?

Back 69

Tryptophan

Alanine

Serine

Glycine

Cysteine

Threonine

Front 70

Describe breakdown of deaminated tryptophan into pyruvate

Back 70

- Tryptophan => alanine + AcAcCoA

- Alanine + @KG => Glutamate + pyruvate (alanine transaminase)

Front 71

Describe breakdown of deaminated alanine to pyruvate

Back 71

Alanine + @KG => glutamate + pyruvate (alanine transaminase)

Front 72

Describe the breakdown of deaminated glycine to pyruvate

Back 72

- Glycine + methylene-tetrahydrofolate => serine + tetrahydrofolate (serine hydroxymethyltransferase)

- serine => Pyruvate + H2O + NH4 (serine dehydratase)

Front 73

Describe the breakdown of deaminated serine to pyruvate

Back 73

Serine => Pyruvate + H2O + NH4 (serine dehydratase)

Front 74

Describe the breakdown of deaminated cysteine to pyruvate

Back 74

Cysteine + H2O => Pyruvate + NH4 + thiocysteine (cystathionase)

Front 75

Describe the breakdown of deaminated phenylalanine to fumarate

Back 75

- Phenylalanine + tetrahydro-biopterin + O2 => Tyrosine + dihydro-biopterin + H2O (phenylalanine hydroxylase)

- tyrosine => fumarate (tyrosine amino transferase)

Front 76

Phenylketonuria is caused by a deficiency in which enzyme?

Back 76

Phenylalanine hydroxylase

Front 77

Describe the breakdown of deaminated asparagine to OAA

Back 77

- asparagine + H2O => Aspartate + NH3 (asparaginase)

- aspartate + @KG => OAA + glutamate (aminotransferase)

Front 78

Describe the breakdown of deaminated leucine to acetoacetate + AcCoA

Back 78

- Leucine => @ketoisocaproic acid (BCAA aminotransferase)

- @ketoisocaproic acid => isovaleryl-coA (BC@ketoacid dehydrogenase)

- isovaleryl-coA => Acetoacetate + AcCoA (dehydrogenation)

Front 79

Describe the breakdown of deaminated valine to succinyl-coA

Back 79

- Valine => @ketoisovaleric acid (BCAA aminotransferase)

- @ketoisovaleric acid => isobutyryl-coA (BC@ketoacid dehydrogenase)

- isobutyryl coA => propionyl-coA (dehydrogenation)

- propionyl-coA => methylmalonyl-coA (biotin)

- methylmalonyl-coA => succinyl-coA (5'deoxyadenosyl cobalamin)

Front 80

Describe the breakdown of deaminated isoleucine to acetyl-coA and succinyl-coA

Back 80

- Isoleucine => @keto-beta-methyl valeric acid (BCAA aminotransferase)

- @keto-beta-methyl valeric acid => @-methyl-butyryl coA (BC@ketoacid dehydrogenase)

- @-methyl-butyryl coA => AcCoA + propionyl coA (dehydrogenation)

- propionyl-coA => methylmalonyl-coA (biotin)

- methylmalonyl-coA => succinyl-coA (5'deoxyadenosyl cobalamin)

Front 81

Describe the breakdown of deaminated threonine to pyruvate

Back 81

Threonine => Pyruvate + CO2 (threonine dehydrogenase)

Front 82

Describe the breakdown of deaminated threonine to succinyl-coA

Back 82

- Threonine => @-ketobutyrate + NH4 (threonine dehydratase)

- @ketobutyrate => succinyl-coA

Front 83

Describe the breakdown of deaminated methionine to succinyl-coA

Back 83

- Methionine => homocysteine ( via S-adenosyl-methionine)

- homocysteine => @ketobutyrate (homocysteine desulphydrase)

- @ketobutyrate => succinyl-coA

Front 84

Describe the breakdown of deaminated arginine to @KG

Back 84

- Arginine => ornithine (arginase)

- ornithine => @KG (via urea cycle)

Front 85

Describe the breakdown of deaminated proline to @KG

Back 85

- Proline => glutamate (oxidation)

- glutamate => @KG (glutamate dehydrogenase)

Front 86

Describe the breakdown of deaminated histidine to @KG

Back 86

- Histidine => glutamate (via histidase)

- glutamate => @KG (glutamate dehydrogenase)

Front 87

Describe the breakdown of deaminated glutamine to @KG

Back 87

- glutamine => glutamate (glutaminase)

- glutamate => @KG (glutamate dehydrogenase)

Front 88

Draw a map of the Krebs cycle, showing the entry points for all 20 amino acids

Back 88