Protein Flashcards
According to NNR 2012 how much protein should an adult consume?
10-20 E%
corresponds to 0.8-1.5g protein/kg of bodyweight
According to WHO/FAO/UNU how much protein should an you consume?
0.66 g protein/kg of bodyweight –> 0.83 g protein/kg as
recommendation (based on nitrogen balance studies)
How many amino acids are there?
How many essential and non-essential
20 total
- 9 essential
- 11 non-essential
How many amino acid is a peptide and when does it become a protein?
<50 AA = peptide
>50 AA = protein
Which amino acids are essential (EAA)?
Fenylalanin isoleucine* leucine * Valine* Methionine Treonine Tryptophan Lysine Histidine (*BCAA)
Which amino acids are non-essential
Alanine Arginine Asparagine Aspartic acid Cysteine Glutamine Glutamic acid Glycine Proline Serine Tyrosine
What kind of reaction occurs in a peptide bond formation?
Condensation reaction
or dehydration reaction
because of the release of a water molecule
What needs to be done in order for the proteins to be absorbed in the small intestine?
They need to be broken down to AA or alternatively dipeptides and oligopeptides
Digestion:
What happens in the stomach?
HCl denature protein because of the low pH
Pepsin starts degrading the protein into peptides (about 10-15% is degraded by pepsin)
Which digestive enzymes are produced by the pancreas?
Trypsin
Chymotrypsin
Elastase
Carboxypeptidase
What are brush border enzymes?
The microvilli that constitute the brush border have enzymes for the final part of digestion anchored into their apical plasma membrane as integral membrane proteins. These enzymes are found near to the transporters that will then allow absorption of the digested nutrients.
Brush border enzymes in digestion of proteins?
aminopeptidase
dipeptidase
What does trypsin do in protein digestion?
Trypsinogen is produced in pancrease - goes to the small intestine or duodenum and get’s activated into trypsin
starts cleaving polypeptides into peptides
The role of chymotrypsin in protein digestion?
is a digestive enzyme component of pancreatic juice acting in the duodenum, where it performs proteolysis, the breakdown of proteins and polypeptides. Chymotrypsin preferentially cleaves peptide amide bonds where the side chain of the amino acid C-terminal to the scissile amide bond (the P1 position) is a large hydrophobic amino acid (tyrosine, tryptophan, and phenylalanine). These amino acids contain an aromatic ring in their side chain that fits into a hydrophobic pocket (the S1 position) of the enzyme. It is activated in the presence of trypsin.
Role of elastase in protein digestion?
Produced pancreas. elastase is an enzyme from the class of proteases (peptidases) that break down proteins. In particular, it is a serine protease.
Role or Carboxypeptidase in protein digestion?
Produced pancreas
is a protease enzyme that hydrolyzes (cleaves) a peptide bond at the carboxy-terminal (C-terminal) end of a protein or peptide.
What is important to be able to absorb proteins?
Need to break down proteins to AA to be absorbed
Can dipeptide and tripeptides be absorbed?
Yes dipeptides and tripeptides can also be absorbed – but in the enterocyte they are converted into AA and then transported into the blood. (maybe some will be absorbed as they are)
How are AA, tripeptides and dipeptides absorbed?
Through Enterocyte to blood
How much energy is 1g of protein?
4 kcal
Proteins in excess are used for…?
It is used to supply energy or build reserves of glucose, glycogen, or lipids.
Why is nitrogen metabolism important?
Proteins make up the structural tissue for muscles and tendons, transport oxygen or hemoglobin, catalyze all biochemical reactions as enzymes, and regulate reactions as hormones. Our bodies must be able to synthesize the many proteins, amino acids, and other non-protein nitrogen containing compounds needed for growth, replacement, and repair.
What is the “amino acid pool” what is the function and why do we need it?
The “nitrogen or amino acid pool” is a grand mixture of amino acids available in the cell derived from dietary sources or the degradation of protein. Since proteins and amino acids are not stored in the body, there is a constant turnover of protein. Some protein is constantly being synthesized while other protein is being degraded. For example, liver and plasma proteins have a half-life of 180 days or more, while enzymes and hormones may be recycled in a matter of minutes or hours.
How many grams of protein are turned over/day?
300 grams
–> 3% turnover rate
