Ch 6 Protein
Transcription
(nucleus) DNA TO RNA
Absorptive competition of amino acids
-If too much of one basic amino acid is present in the lumen it will outcompete the others for the basic AA transporter AKA it will reduce absorption of others -Di and Tripeptides are absorbed more efficiently than individual AA's
The proteolytic enzymes secreted by the pancreas and their roles
-Trypsin - converts zymogens into active enzymes (chymotrypsin, carboxypeptidases A and B, elastase) -Proteolytic enzymes break polypeptides into peptides, and eventually into amino acids
RDA for adults for protein
.8g/kg body weight
a. Amino acid catabolism b. Amino acid anabolism
a. Amino acid catabolism- degradation of AA's b. Amino acid anabolism- making of AA's
Someone has advanced liver disease—what happens to the blood level of ammonia?
It will go up • So will AST and ALT • Presence of Ketones in blood will go down or be non-existent
The organ associated with the urea cycle, gluconeogenesis, and ketogenesis in the human body.
LIVER
The type of enzyme for deamination.
lysases, dehydrases, dehydrogenases
ureagenesis
making of urea
What do we call amino acids that can be made by body if enough of essential amino acid is needed?
Conditionally essential
The entire digestive process of proteins
1. Gastrin released by stomach>acts on parietal cells to release HCl, chief cells to release pepsinogen 2. HCl (pH=3) denatures proteins and converts pepsinogen to pepsin 3. Pepsin is enteropeptidase>large polypeptides and oligopeptides 4. Chyme moves to small intestine 5. Secretin and Cholescystokinin release>pancreas releases bicarbonate and mixture of protein digestion zymogens 6. Enterocytes secrete enteropeptidate>converts trypsinogen to trypsin . 7. Trypsin converts zymogens to chymotrypsin, carboxypeptidases A and B, elastase 8. Chymotrypsin (Zn dependent)>endopeptidase; carboxypeptidases>exopeptidases 9. Elastase digests elastin 10. Enterocytes release intestinal peptidases>aminopeptidases (produce aa's), dipeptidyl aminopeptidases (Mg dependent) (hydrolyze dipeptides), tripeptidases (yield dipeptides and aa's) 11. All ultimately yields: aa's, dipeps, tripeps
The number of amino acids required for human protein synthesis
20
Tertiary
3D folding due to side chain interactions
If you have kidney disease and the urea level is building up high in the blood, what can be given to you to lower the protein intake?
A-keto acid supplementation
Protein digestive end products that you can absorb?
Amino acids, Dipeptides, Tripeptides
The type of enzyme for transamination
Amino transferase
The role of B-6 in transamination
B6 coenzyme form pyridoxal phosphate is required
Membrane on end of enterocyte pointing toward capillaries?
Basolateral membrane
What amino acids are not metabolized by the liver?
Branch chain amino acids
What are the two names of what's left over after you deaminate an amino acid?
Carbon skeleton or alpha keto acid (same thing)
Which cells release pepsinogen?
Chief cells
What is the digestive hormone that promotes release of proteolytic enzymes from the stomach?
Cholecystokinin
Secondary
local folding into helixes or sheets
The fate of amino acids once they leave the enterocytes
Cross the basolateral membrane enter capillaries enter portal vein to liver hepatocytes in liver use AA for energyAA's transported to tissues around the body
Translation
Cytoplasm RER (ribosomes) Instructions on RNA being used to make protein
Conditions under which deamination occurs
DIETARY CONDITIONS—when someone is on low cal low protein diet or a very high protein diet (eating a lot of amino acids so you delaminate the ones in excess)
Replication
DNA reproduction
What does the term "replication" mean?
DNA reproduction
Which are absorbed more efficiently/ effectively? Di and tri peptides or amino acids?
Di- and tri- peptides
The comparative ability of amino acids, dipeptides, and tripeptides to be absorbed
Di- and tripeptides more easily absorbed due to PEPT1 (very efficient transport proteins). AA's compete for absorption at brush border. Better to supplement with di- and tripeptides not AA's.
Proteolytic enzyme that digests polypeptides from the MIDDLE to the END
ENDOPEPTIDASES
The definition of endopeptidases
Endo - INSIDE OUT. proteolytic peptidases that break peptide bonds of nonterminal amino acids (i.e. within the molecule)
The definition of exopeptidases
Exo - OUTSIDE IN. break peptide bonds from end-pieces of terminal amino acids
Proteolytic enzyme that digests polypeptides from the END to the MIDDLE
Exopeptidases
GI hormone released by stomach to promote insulin and HCL?
Gastrin
What in the stomachs environment promotes the conversion of pepsinogen to pepsin?
HCL in the stomach
The role of the liver in amino acid metabolism
Hepatocytes use AA for energy
Basolateral (serosal) membrane
INTO THE BLOOD FROM THE ENTEROCYTE. Once thru the basolateral membrane, amino acids enter the blood thru capillaries of the villi for transport into the portal vein leading to the liver. The carriers found in the enterocyte's basolateral membrane are generally SODIUM INDEPENDENT.
Brush border membrane
INTO THE ENTEROCYTE. uses PEPT1 (PEPT1 is associated with the comovement of protons H+ and thus depolarization of the brush border membrane). An area of low pH lying adjacent to the brush border surface of the enterocyte provides the driving force of the H+ gradient
What happens to urea synthesis (increase or decrease) when someone consumes a low protein diet?
Increases
Does the urea cycle occur exclusively in the cytoplasm?
NO - part of it occurs in the mitochondrial matrix
Can a ketogenic amino acid be made into glucose?
No only glucogenic amino acids can be made into glucose
Chickpea chili with onions and tomatoes COMPLEMENTATION?
No- missing methionine
The transport protein for di- and tripeptides
PEPT1
Cells that release HCL?
Parietal cells
Dietary practice vegans must follow to make sure to get all amino acids required for protein synthesis.
Protein complementation
Quaternary
Protein consisting of more than one amino acid chain
What vitamin coenzyme is needed for the action of a transferase?
Pyridoxal phosphate (B6)
Deamination
Removal of an amino group yielding a carbon skeleton
Where does protein synthesis occur in the cell?
Ribosomes on the rough ER
The part of an amino acid's chemical structure that makes it unique compared to carbohydrates and lipids
Side chain (R group) Also has: a. Central Carbon b. At least one amino group NH2 c. At least one carboxy (acid) group COOH
Where does glycosylation of proteins occur?
Smooth ER
Where do amino acids go once they enter the blood?
The liver through the portal vein
The products of digestion of protein that can be absorbed
Tripeptides, dipeptides, and amino acids.
Enzyme key for converting all proteolytic enzymes that are zymogens into their active form?
Trypsin
The biochemical reasons why we must eat protein
We need exogenous sources (dietary sources) to provide the 9 essential/indispensable amino acids
Lentil stew with rice?
YES- complimentary
Can some carbon skeletons be used to make fatty acids?
Yes because that's how we get fat from eating too much protein
What is the one mineral required as a co factor for the functioning of chymotrypsin?
ZINC
Another word for carbon skeletons?
a- keto acids
The roles of insulin, leucine, glucagon, cortisol, and epinephrine in protein and amino acid metabolism
a. Anabolism/ uptake: Insulin INCREASES Leucine INCREASES Glucagon DECREASE Cortisol DECREASE Epinephrine DECREASE b. Catabolism/ release is the opposite!
The contrast between animal and plant sources of protein
a. Animal protein promotes faster/ greater protein synthesis than plant b. Animal protein sources complete c. Plant protein sources incomplete
Most active site in the body for protein metabolism.
a. Breakdown and synthesis: SKELETAL MUSCLE b. Trans/deamination/ureagenesis: Liver
Dietary factors that affect protein synthesis
a. Consistent intake over 24 hours b. Reaching the RDA c. Consuming Protein sources with glucose
Endogenous sources of amino acids
a. Desquamated mucosal cells b. Digestive enzymes and glycoproteins c. 70 g/d of protein
Hormonal regulation of protein metabolism
a. During catabolic state synthesis of gluconeogenesis and ureagenesis enzymes b. AA uptake: i. Insulin INCREASES ii. Leucine INCREASES iii. Glucagon DECREASE iv. Cortisol DECREASE v. Epinephrine DECREASE
1. Human body protein activity in the fed and unfed states.
a. Fed: -catabolic and anabolic processes are active - proteins are synthesized from dietary amino acids b. Unfed: - catabolic and anabolic prossess are active - protein are synthesized from endogenous sources
Protein efficiency ratio
a. Gain in body weight/ grams of protein
Digestive hormones involved in protein digestion
a. Gastrin, secretin, cholecystokinin
Significance of ALT and AST.
a. If someone has advanced liver disease, AST and ALT level go up b. High levels in the blood indicate liver damage
The role of skeletal muscle in protein metabolism
a. Most active site for breakdown and synthesis b. Prefers branch chain amino acids that are not preferred by the liver
The source of the different protein digestive enzymes
a. Parietal cells in stomach release HCL b. Chief cells in the stomach release Pepsinogen (becomes pepsin with help of HCL) c. Pancreas releases bicarbonate and a mixture of protein digestion zymogens
The processing and roles of pepsin and trypsin
a. Pepsin targets polypeptides and breaks them down into di and tripeptides b. Trypsin converts zymogens to chymotrypsin, carboxypeptidases A and B, and elastase (small intestine)
Sources of ammonia
a. Processed meats and cheeses (they are nitrogenated and have excess nitrogen) b. Deamination c. Bacterial lysis of urea d. When you remove amino groups from side chains of glutamine and asparagine
PROTEIN SYNTHESIS
a. Replication i. DNA reproduction b. Transcription i. (nucleus) ii. DNARNA c. Translation i. Cytoplasm ii. RER (ribosomes) iii. All AA's required iv. T-RNA's loaded with AA's v. mRNA protein d. Protein modification i. SER ii. Folding iii. Glycosylation
The overall absorptive process for amino acids including the fact of specialized transport proteins for different categories of amino acids
a. Specific integral protein carriers are required to transport amino acids and short peptides (di- and tri-) - Across the brush border membrane specific carriers for different types of amino acids and different carrier for short peptides (PEPT1) Ex: separate transporters for neutral, basic, and acidic aa's Some sodium dependent and others not Most aa's absorbed as di- and tripeptides - Within the enterocytes peptidases degrade di- and tripeptides to aa's - Across basolateral membrane to blood specific carriers as well b. At brush border there is competition for absorption of aa's - For instance: if too much of one basic amino acid is present in the lumen it will outcompete the others for the basic amino acid transporter reducing absorption of others - Di-and tripeptides absorbed more efficiently and effectively than individual aa's Why in elemental tube feeding formulas use di-and tripeptides rather than amino acids to supply aa's Free aa supplements not absorbed as efficiently and effectively as those with whole proteins or di- and tripeptides
The role of the urea cycle in eliminating ammonia.
a. The liver performs the urea cycle to detoxify ammonia b. Carbamoyl phosphate synthetase carbamoyl phosphate
High BV=
high nitrogen content
Nonessential/ dispensable AA
i. Body CAN synthesize ii. 11
Essential/ indispensable AA
i. Body cannot synthesize/ must be supplied by the diet ii. 9 iii. Supplied by diet
Protein Modification
i. SER ii. Folding iii. Glycosylation
Conditionally indispensable
i. Synthesized from other amino acids ii. Rate limitations to synthesis or improper organ function 5 phenylketoneuria
Transamination
i. When you take an amine group from an amino acid to an a-keto acid making a different amino acid
Primary structure
sequence of a chain of amino acids
Carbon skeleton
structure left after removal of amino groups from AA
Conditions under which transamination occurs
α-ketoacids used in nutrition therapy Ex: Kidney disease urea accumulates in blood Can reduce protein intake and give formula of α-ketoacids of essential aa's and nitrogen from urea can be transferred to these to form essential amino acids. Reduces nitrogen load in blood
1. The fate of carbon skeletons- Uses:
• Energy (pyruvate or Acetyl CoA) • Glucose o Glucogenic aa's o Gluconeogenesis • Ketones o Ketogenic aa's o Ketogenesis • Cholesterol o Ketogenic aa's • Fatty acids o Excess aa's
