Proteins Flashcards
What are the recommendations for protein?
increase variety, lower fat animal sources, legumes(dried beans,lentils,peas)
Name the 3 functions of proteins
- Maintenance and regulation of body functions(enzymes,hormones,accumulation of lean tissue,immune system)
- Growth
- Energy
How can protein be used as energy?
- Converted to glucose, and other amino acids
- Converted to fat and stored (as fat from glucose)
- Burned as fuel(carbon skeleton in TCA cycle)
Can protein be fattening?
Yes
How do we store macromolecules?
We store carbohydrates as glucose in glycogen, fatty acids as fat in adipose cells, we do not store protein
What are the functions of amino acids?
- Precursors of neurotransmitters (dopamine,serotonin), nucleotides, melanin, thyroid hormone, histamine (from histidine, when we have an allergy or a very bad cold)
- Peptides
- Proteins
How much protein do we make in a day?
300 g of protein/day
What % of proteins circulate in blood?
25%
Name the 3 types of proteins in blood.
- Plasma proteins(albumin,pH buffering, fibronogen)
- Red blood cells (hemoglobin)
- White blood cells
Name the 4 roles of plasma proteins.
- Nutrient transport(albumin,transferrin)
- Acute phase proteins (protection, blood clotting)
- pH buffering ( fibronogen)
- Regulation of fluid balance
What do red blood cells do?
Transport oxygen, packed with hemoglobin
What do white blood cells do?
Antibodies and immune effectors
How much does the production of immune system increase to an inflammation?
By 30 %
What is the lifespan of hemoglobin?
120 days
Which cells in blood have DNA?
White blood cells
Name the 2 types of proteins.
Tissue Proteins
Secretory Proteins
Give examples of tissue proteins.
enzymes, structural proteins, membrane receptors, carriers
Give examples of secretory proteins.
digestive enzymes, human milk proteins, hormones and grow factors
How many amino acids have a tRNA?
20
How many amino acids are essential?
9
Name the essential amino acids.
Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
Which amino acids are conditionally indispensable?
Arginine, cysteine, glycine, glutamine, proline, and tyrosine.
What does the concept conditionally indispensable mean?
Needed in the diet under certain conditions. (premature babies, liver disease)
What aa is needed with rapid growth?
Arginine
Which protein has disulfide bonds?
Insulin
Describe the formation of insulin molecule
Posttranslational modification, in which disulfide bonds are made and the c part is chopped. Looks like there are two peptides, indeed it is one.
How can we assess the work of pancreas?
By measuring C chains from insulin in the urea
What are the methods to denature proteins?
Heating, pH, organic solvents, detergents
Which enzyme cleaves proteins in the stomach?
Pepsin (pepsinogen-precursor)
Is heme an amino acid?
No, it is a special product from amino acids, but the amino acid
Which enzyme cleaves proteins in the small intestine?
Trypsin and many more
Where are the enzymes from the small intestine from?
Pancreas
What macromolecules start to be digested in the mouth?
Starch and Fat, but not the protein
What happens to the proteins in the stomach?
With the HCl the protein is danatured, making its more available for pepsin. It cleaves strands int polypeptides, tripeptides, dipeptides and a few amino acids
What happens to the proteins in the small intestine?
Pancreotic proteases split the peptide chains into tripeptides,dipeptides and amino acids
Where are amino acids absorbed?
Intestinal cells absorb(AAs transporters) and transfer amino acids to the bloodstream
Where is the last stage of protein digestion?
The brush border(dipeptidases)
How do amino acids get to the bloodstream?
AA go to portal vein, then bloodstream transports AA to the body
Differentiate allergies and intolerances.
Allergies: immune response to a specific protein Intolerances: not immune, could be a digestion problem for example
Define transcription.
1st step: segment of DNA copied into RNA (mRNA) by the enzyme RNA polymerase
Define translation.
Messenger RNA (mRNA) produced by transcription is decoded by a ribosome to produce amino acid chain or polypeptide.
How does sickle cell anemia occur?
change in DNA : glutamate -> valine
What happens if you’re missing an amino acid in the body?
translation stopped -> no protein
Name 3 single gene disorders.
cystic fibrosis, pku(phenylketonuria), sickle cell anemia
How does biotechnology help food industry and medicine?
production of proteins ex: cheese (rennet) insulin (humulin)
Define nutritional genomics.
Interaction between genes, diet, and nutrients
Define nutrigenetics.
genes affecting nutrient metabolism (ex: lactose intolerance)
Define nutrigenomics.
Compounds in food affect genome (ex: dietary cholesterol, sat fat on cholesterol synthesis)
Phenylketonuria. Describe the cause and effect
The cause: lack of phenylalanine hydroxyalse( the enzyme that converts PHE to Tyr), because of damaged DNA
The effect: no production of Tyr, alternative digestion of Phe. It is converted to phenylketoses. When the concentration of Phe and phenylketoses is very high ->toxic , irreversible damage
Treatment of PKU
Minimize the intake of Phe, so medical diets and medications
What is done in the first day of child’s birth
They are tested to gene diseases, like PKU, because infant’s brain is vulnerable
What % is absorbed during protein turnover?
90%
What % is excreted in feces during protein turnover?
10%
Which intermediate will produce glucose during protein turnover?
Pyruvate or in storage
Which intermediate will produce fat during protein turnover?
AcetylCoA or in storage
How can amino acids from digestion can be used?
It can enter the aa pool if we need it or it can catabolised
Does the increase in protein intake increase protein synthesize?
No, it will just increase catabolism rate
How aa are catabolised?
Ammonia group will be transaminated from one amino acid to another and delivered to the liver, where it will be transfered into urea.
OR
Depednsing on the carbon skeleton, fat or glucose are generated
The protein has 5.65 kcal per gram, explain why we count 4 kcal per gram
90% of the protein is absorbed in our body, so we het 5.25 kcal/g, but we also take energy in order to produce urea( 25%), and thus we have 4 kcal/g
Nitrogen balance is
Balance = N intake - Fecal N - Urinary N
Does consuming more protein increase protein synthesis? What does?
No
Weight training
What % of N is in protein?
16%
What does positive nitrogen balance mean?
Intake > output growing kids, pregnancy, training phase,requiring from the injury( in case you eat enough protein)
What does negative nitrogen balance mean?
Intake < output low protein diet, injury
-Muscle wasting
What enzyme transfers amino group from one amino acid to another?
Aminotransferases
What coenzyme does aminotransferases have?
B6-pyrodoxine
What aa are the major transporters for amino group?
Alanine,glutamine and others
where does the primer filtration of blood in the kidney happens?
Glomerulus
How urea ends up in the bladder?
As urea is a waste product , there is no transporters for it in the tubule and it gets to the bladder
Can we measure nitrogen balance in real life
Very hard to accurately measure intake and output
Name the 3 components of protein adequacy.
- Energy intake
- Protein Quantity
- Protein Quality
What happens if energy isn’t met?
AA catabolized to provide E->negative nitrogen balance-> muscle wasting and other abnormalities
Why is it important to keep protein high when going on a diet?
To avoid negative nitrogen balance->muscle wasting instead of adipose tissue
What is the current RDA for protein?
0.8 g/kg/d
What is the AI for protein for infants? What is is based on?
1.5 g/kg/d based on breastfeeding
Why there is no AI for infants?
Because we take milk as the reference, and it seems about right. It seems right is AI. There is no sense of adding to more SD to a milk, from which children get enough protein
What happens to protein requirement as we grow up?
We need less protein
Does clinical nutrition should consider inadequate protein intake?
No, because people consume enough protein with their meal( 1.5X more)
How much protein should power athletes have? Endurance athletes?
Power: 1.6g/kg/d Endurance: 1.2g-1.6g/kg/d
Should athletes have more protein than RDA? Normal diet?
RDA: yes Normal diet: no
What is the average intake of proteins for males? Females?
Males: 96g Females: 65g
Is excess protein a huge issue?
No, since it’ll just be catabolized
What N excreted as urea is a problem for who?
Infants, especially premature, elderly( elderly do not consume enough protein and waste their lean tissue)
Can we gain weight because of the protein extra intake?
No, if it is within our caloric requirement
Yes, if is exceed our caloric requirement, will become fat
What do we need for protein synthesis?
ALL amino acids
Why supplements are not the greatest idea?
Because they can cause major imbalance, some amino acids are toxic
High aa index
Make parallel to high GI index
we want slow absorption, to avoid peaks, to avoid aa catabolic reactions
Define limiting amino acid.
The AA present in the lowest amount relative to the body’s need for it.
What happens if an amino acid is limiting to other amino acids?
All other AA are present in excess and must be degraded
What happens if an amino acid is limiting to protein synthesis?
Severely limit protein synthesis
What happens if an amino acid is limiting to urea production and N balance?
High urea production and negative N balance
What can we do to improve limiting proteins?
Improve protein quantity or quality( better solution)
What is the standard protein AA content?
Egg white (adult) Breast milk (babies)
What is the equation to determine amino acid score?
(Test protein AA / Standard protein AA) x 100%
What is the protein score?
AA with the lowest score
How do we assess protein quality?
- Amino acid score - correct for digestibility( for example corn 85%,milk 90%)
What are complementary proteins?
combining sources (beans and rice)
What are legumes low in?
methionine, tryptophan
What are grains low in?
Isoleucine, Lysine
What is the name for the test for assessing protein quality?
Digestible Indispensable Amino Acid Score (DIAAS)
