Lesson 11 Digestion and absorption of proteins. Special roles of aminoacids
and important metabolites derived from them. Metabolic fates of amino acids
and gluconeogenesis.
Concepts and terms
a.Different origins of amino acids in humans
b. Digestion of dietary proteins and absorption mechanisms of amino acids.How
proteolytic enzymes are activated and luminal and cell-surface proteases action?
c. Intestinal mechanism of amino acid and peptide transport
d. Protein turnover and overview mechanism and control of protein catabolism
e.The major reactions involving amino acids (transamination, deamination,
decarboxylation. Mechanism and importance of amino transferases and recognize
their use in diagnosis
f. Describe precursors, cofactors, and mechanisms of non essential amino acid
biosynthesis. Normal and abnormal metabolism of phenylalanine
g. Role of amino acids as precursors of key nitrogen-containing compounds
and illustrate important metabolites derived from them
h. Energetic fates of amino acids, its cofactor requirement, and differences
between glucogenic and ketogenicones. Gluconeogenesis, and describe its
localization, substrates and energetic. Regulation of gluconeogenesis and illustrate
its coordinated control with glycolysis.
i. Glucose-lactate cycle and the alanine cycle and recognize their role in
homeostasis
j. Why fatty acids are not substrates of gluconeogenesis and explain
consequences. Short- and long-term effects of glucagon and insulin on
gluconeogenesis
Reading assignment
Garrett 768-807; 662-672, Campbell 653-671; 512-524.
Animation viewing:
http://www.wiley.com/college/fob/quiz/quiz15/15-20.swf
Homework exercises
Garrett p.811 №4, 5, 13. Campbell p.684 № 9, 10, 14, 19, 21, 23, 26, 32, 37.
In-class exercises
Choose correct answer
1. Histidine is degraded to α-ketoglutarate and is described as a
A.
B.
C.
D.
gluco amino acid
glucogenic amino acid
ketogenic amino acid
keto-gluco amino acid
2. Which of the following amino acids is considered as both ketogenic and
glucogenic?
A.
B.
C.
D.
Valine
Tryptophan
Lysine
None of these
3. A person with phenylketonuria cannot convert
A.
B.
C.
D.
phenylalanine to tyrosine
phenylalanine to isoleucine
phenol into ketones
phenylalanine to lysine
4. Oxidative deamination is the conversion of :
A.
B.
C.
D.
amino group from an amino acid to a keto acid
acid to a carboxylic acid plus ammonia
acid to a keto acid plus ammonia
amino group from an amino acid to a carboxylic acid
5. A person with phenylketonuria is advised not to consume which of the
following products?
A.
B.
C.
D.
Glycine containing foods
Fat containing food
Glucose
Aspartame
6. Which of the following compounds is responsible for coordinated regulation of
glucose and glycogen metabolism?
A.
B.
C.
D.
NAD+
Fructose 2,6 bisphosphate
Acetyl-CoA
Fructose 1,6 bisphosphate
7. The cells dependent solely on glucose as an energy source are
A.
B.
C.
D.
muscle cells
brain cells
kidney cells
liver cells
8. The main site for gluconeogenesis is
A.
C.
kidney
brain
B.
D.
liver
muscle
9. The conversion of pyruvate to oxaloacetate
A.
B.
C.
D.
requires biotin
Doesn't involves the fixation of carbon dioxide
occurs in the cytosol
all of the above
10. Which of the following can act as precursors for gluconeogenesis?
A.
B.
C.
D.
Lactate
CO2
AcCoA
All of these
11 Transaminase enzymes are present in
A.
B.
C.
D.
liver
pancreas
intestine
none of these
12. Aminoacid oxidase requires
A. NAD+/NADP+
B. Creatine
C. FMN
D. PLP
13. Which of following enzymes do not provide endopeptidase activity
A. Pepsin
B. Trypsin
C. Carboxypeptidase
D. Chymotrypsin
14. Glucose-lactate cycle is essential for which of following cells
A. RBC
B. Hepatocytes
C. Heart muscle
D. Endothelial cells
15. Name the compound that cannot be involved in gluconeogenesis
A. Oxaloacetate
B. Fructose 1,6-BP
C. Glycerol
D. Fructose 2,6-BP
16. Whish of the following enzymes is envolved in process of glucose synthesis
A. PFK-1
B. PFK-2
C. Aldolase
D. Pyruvate kinase
17. By which if the following reactions GABA is deribed from glutamine
A. Dehydrogenation
B. Decarboxylation
C. Deamination
D. Hydroxylation
18. A couple of Afroamerican gives a birth with white hairs and fair skin. Which
of the enzymes is in a deficiency in this child
A. Phenyalanine hydroxylase
B. Tyrosinase
C. Negrase
D. Colorase
19. Which of the following is the main aceptor of nitrogen by all transaminase
reactions
A. Pyruvate
B. Oxaloacetate
C. a-ketoglutarate
D. Acetoacetate
20. Histamine, a chemical mediator of allergy is synthesized from histidine by
which of the following reactions
A. Dehydrogenation
B. Decarboxylation
C. Deamination
D. Hydroxylation
21. Urea cycle takes place in
A. Cytoplasm
B. Mytochondria
C. Both mytochondria and cytoplasm
D.Nucleus
22. First line of brain defense against hyperammoniemia is
A. Synthesis of urea
B. Synthesis of glutamate
C. Synthesis of glutamine
D. Synthesis of asparagine
23. Which coenzyme is neede for oxidative deamination
A. FMN
B. Creatine
C. Pyridoxal phosphate
D. Folic acid
24. L-aminoacids are absorbed from intestine by
A. Passive diffusion
B. Active diffusion
C. Pinocytosis
D. Facilated diffusion