Proteins Flashcards
Protein Digestion and Absorption
- In the mouth, chewing begins the mechanical breakdown of protein
- In the stomach, hydrochloric acid and the enzyme pepsin begin the chemical digestion of protein
- In the small intestine, protein-digesting enzymes secreted from the pancreas, along with those in the microvilli, break down polypeptides into amino acids, dipeptides, and tripeptides.
- A variety of transport proteins move the products of protein digestion into the mucosal cell. Some amino acids share the same transport system.
- Dipeptides and tripeptides can enter the mucosal cell. Once inside, they are broken down into single amino acids.
- Amino acids pass from the mucosal cell into the blood and travel to the liver, which regulates the distribution of amino acids to the rest of the body.
- Little protein is lost in feces.
Primary Protein Structure
The polypeptide chain is the primary structure of the protein
Secondary Protein Structure
Hydrogen bonds between side chains in the polypeptide help form alpha-helices and beta pleated sheets which form its secondary structure
Tertiary Protein Structure
Disulphide, hydrogen bonds etc. between side chains form the tertiary structure
Quaternary Protein Structure
is the binding of 2+ polypeptide chains together
The primary structure of an amino acid is the result of _______ bonds
peptide
Denaturation
Denaturation refers to the alteration of a protein’s 3D structure
–
Heat, acid, agitation can denature a protein
•
Ex. Cooking an egg
•
When a protein loses its 3D structure, it loses its original function
Complete proteins
have all 9 essential aa’s (animal products)
Have B vitamins, iron, zinc, calcium
Tend to be low in fiber
Incomplete proteins
lack 1+ essential aa’s (plant products)
Contain some B vitamins, iron, zinc, calcium
–
but they are less available in the body
These sources tend to be high in fibre, unsat fats and phytochemicals
Amino acids, unlike sugars/fatty acids_____
have nitrogen
Amino acids are linked together by ____
peptide bonds to form polypeptides.
aa’s are then absorbed into the SI by ____
active transport
Protein Synthesis:
Our ____ contains the ‘recipe’ for making all our body proteins
DNA
Genes turned on/off to drive/halt protein synthesis
Protein Synthesis:
Our body will pick and choose from the _____ in order to make up specific body proteins as needed.
amino acid pool
Protein Synthesis:
If we lack one of the 11 non-essential aa’s required to make a protein, we can synthesize that aa from a similar one
–
Through the process of ___
transamination
Protein Synthesis:
If we lack one of the 9 essential aa’s that is needed to form a specific protein, that protein cannot be synthesized!
That missing aa =
limiting amino acid!
Protein Functions:
*Movement
*Protection from disease
______ are proteins
Skin is mostly protein
*Fluid Balance
___ may result with low blood
protein levels
*Producing ATP from amino acids
Antibodies
Edema
Protein as a source of energy
Proteins provide 4kcal/gram
BUT: minor source of energy overall!
When carbs, fats are insufficient to fuel cellular needs, will break down body proteins to form ATP
Recall that proteins must first be _____ in order to extract energy from them
When the diet is excessive in calories, aa’s can be converted into FA’s and stored in adipose tissue
deaminated
Kwashiorkor
protein deficiency leading to fluid accumulation in the abdomen, fat accumulation in the liver
Marasmus
protein and energy deficiency leading to depletion of fat stores and wasting of muscle
Protein Recommendations
AMDR = \_\_\_ of Calories • RDA = \_\_ g/kg body weight • Pregnant women RDA \_\_ g/d • Protein needs increase during infections, fevers, burns, surgery • Endurance/strength athletes may benefit from \_\_ g/kg body weight – Most athletes get enough as is
10-35%
0.8
+25
1.2-1.4
Choosing Protein Wisely
•
_______- measure of how well a food provides all the essential aa’s
–
Assessed using the _____
Takes into account digestibility of the protein
Animal proteins have a higher PDCAAS, and are more likely to be ___ proteins, having all 9 essential aa’s
•
Plant proteins have lower PDCAAS and are more likely to be ___ proteins
Protein quality
protein digestibility corrected amino acid score (PDCAAS)
complete
incomplete
5 Risks of Vegetarian Diets
Vitamin and mineral deficiencies are more common
•
Vegans require vitamin B12 supplements
•
Calcium, vitamin D deficiencies may occur if milk products are not consumed
•
Iron, zinc are poorly absorbed from plants
•
Omega-3 may be low in vegan diets
