Hepatic Protein Metabolism and Amino Acids in Nitrogen Balance

Question 1

What is the Main contributor of Amino acids in a fed state and in a fasting state?

Answer 1

Fed state- diet
Fasting- Bodily protein (80% is skeletal muscle)

Question 2

What three ways is bodily protein degraded?

Answer 2

Lysosomal and Ubiquitin-dependent pathways
Protein re-synthesis

Question 3

What is an essential amino acid?

Answer 3

An amino acid that cannot be produced and needed in diet

Question 4

8 Essential Amino acids

Answer 4

Phenylalanine
Valine
Leucine
Isoleucine
Tryptophan
Methionine
Threonine
Histidine

Question 5

What is a non-essential amino acid

Answer 5

Simpler amino acid that can be produced de novo (from other molecules)

Question 6

Examples of 5 non-essential amino acids

Answer 6

Alanine
Glutamate
Asparate
Asparagine
Serine

Question 7

What is a glucogenic amino acid?

Answer 7

Carbon backbone used in glucogeonesis

Question 8

What is a ketogenic amino acid?

Answer 8

Amino acid which carbon backbone produces acetyl CoA or acetoacetyl coA

Question 9

What should the nitrogen balance be?

Answer 9

+- 4g/day

Question 10

What 3 things are amino acids split between

Answer 10

Metabolic precursors
Free pool in blood
Proteins in body

Question 11

4 Examples of when people have a positive Nitrogen balance (More intake than excretion)

Answer 11

Pregnancy
Lactation
Bodybuilder + steroids
Recovery phase

Question 12

3 Examples of when there is a negative nitrogen balance?

Answer 12

Protein Malnutrition
Severe illness
Corticosteroids

Question 13

What is transamination?

Answer 13

Turning an amino acid into an intermediate in the TCA cycle (Krebs cycle)

Question 14

How does Transamination work?

Answer 14

Taking an amine group (NH2) from an amino acid adding it to an alpha-ketoacid
which turns the amino acid into an alpha-ketoacid itself

Question 15

What is an alpha-ketoacid

Answer 15

Deaminated form of an amino acid

Question 16

What is the universal alpha-ketoacid

Answer 16

Alpha-ketoglutarate

Question 17

What Enzymes catalyse transamination? Give an example

Answer 17

Amino transferase
E.g. pyridoxal phosphate

Question 18

What does Alanine produce during Transamination? with which alpha-ketoacid? Which enzyme?

Answer 18

Pyruvate+glutamate
Alpha-ketoglutarate
Aminotransferase (ALT)

Question 19

What is Deamination?

Answer 19

Removal of an amine group from a molecule

Question 20

What is Glutamate converted into as a result of deamination? Which enzyme is used? What des it produce as a by-product?

Answer 20

Alpha-ketoglutamate
Glutamate dehydrogenase
Ammonium

Question 21

How is ammonium removed?

Answer 21

Via urea cycle

Question 22

What two types of protein does the liver produce?

Answer 22

Albumin and Clotting factors

Question 23

Clotting cascade proteins produced in the liver

Answer 23

1
2
4
5
6
7

Question 24

Name of Factors 1 and 2 in coagulation cascade?

Answer 24

1- Fibrinogen
2-Prothrombin

Question 25

4 functions of Albumin

Answer 25

Binding and transport
Maintenance of osmotic pressure
Free radicals
Anticoagulant effects

Question 26

Two methods of Protein Degradation?

Answer 26

Proteasome
Lysosomal

Question 27

What bond does the ubiquitin protein form and with what Amino acid?
What does this trigger?

Answer 27

Carboxyl group forms isopeptide bond with Lysine residue
Triggers to proteasomes that protein nees to be degraded

Question 28

What 3 enzymes are involved in the formation of the isopeptide bond between ubiquitin and lysine?

Answer 28

E1- Ubiquitin-activating enzyme
E2-Ubiquitin-conjugating enzyme
E3-Ubiquitin-protein ligase

Question 29

What does the formation of an ubiquitin chain binding to multiple lysine residues cause? how many is particularly strong?

Answer 29

Stronger signal to proteasome
4 chains is stronger

Question 30

What does the N-terminal (amine end)residue determine in a protein?

Answer 30

Proteins half life

Question 31

4 types of Lysosomal degradation? which are selective and which are non-selective?

Answer 31

Macroautophagy- non selective
Microautophagy- non selective
Chaperone-mediated autophagy- selective
Endocytosis/phagocytosis

Question 32

What is Macroautophagy?

Answer 32

ER derived autophagosomes engulf cytosolic proteins
Fuses with lysosome to initiate proteolysis

Question 33

What is microautophagy?

Answer 33

Invaginations of lysosomal membrane engulf proteins

Question 34

What protein does Chaperone meediated autophagy involve?

Answer 34

Chaperone protein hsc70

Question 35

What do the proteins in chaperone-mediated autophagy do?

Answer 35

Accompany specific proteins in response to stressors

Question 36

What occurs in a hepatocyte in the Glucose-Alanine cycle?

Answer 36

Alanine is converted into Pyruvate then Glucose via Glucogeonesis

Question 37

What occurs in the Muscle cell in the Glucose-Alanine cycle when in a catabolic state (fast)?

Answer 37

Glucose is converted into pyruvate which then produces alanine via transamination