Proteins

Question 1

Protein Digestion and Absorption

Answer 1

1. In the mouth, chewing begins the mechanical breakdown of protein
2. In the stomach, hydrochloric acid and the enzyme pepsin begin the chemical digestion of protein
3. 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.
4. A variety of transport proteins move the products of protein digestion into the mucosal cell. Some amino acids share the same transport system.
5. Dipeptides and tripeptides can enter the mucosal cell. Once inside, they are broken down into single amino acids.
6. 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.
7. Little protein is lost in feces.

Question 2

Primary Protein Structure

Answer 2

The polypeptide chain is the primary structure of the protein

Question 3

Secondary Protein Structure

Answer 3

Hydrogen bonds between side chains in the polypeptide help form alpha-helices and beta pleated sheets which form its secondary structure

Question 4

Tertiary Protein Structure

Answer 4

Disulphide, hydrogen bonds etc. between side chains form the tertiary structure

Question 5

Quaternary Protein Structure

Answer 5

is the binding of 2+ polypeptide chains together

Question 6

The primary structure of an amino acid is the result of _______ bonds

Answer 6

peptide

Question 7

Denaturation

Answer 7

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

Question 8

Complete proteins

Answer 8

have all 9 essential aa’s (animal products)

Have B vitamins, iron, zinc, calcium

Tend to be low in fiber

Question 9

Incomplete proteins

Answer 9

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

Question 10

Amino acids, unlike sugars/fatty acids_____

Answer 10

have nitrogen

Question 11

Amino acids are linked together by ____

Answer 11

peptide bonds to form polypeptides.

Question 12

aa’s are then absorbed into the SI by ____

Answer 12

active transport

Question 13

Protein Synthesis:

Our ____ contains the ‘recipe’ for making all our body proteins

Answer 13

DNA

Genes turned on/off to drive/halt protein synthesis

Question 14

Protein Synthesis:

Our body will pick and choose from the _____ in order to make up specific body proteins as needed.

Answer 14

amino acid pool

Question 15

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 ___

Answer 15

transamination

Question 16

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 =

Answer 16

limiting amino acid!

Question 17

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

Answer 17

Antibodies

Edema

Question 18

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

Answer 18

deaminated

Question 19

Kwashiorkor

Answer 19

protein deficiency leading to fluid accumulation in the abdomen, fat accumulation in the liver

Question 20

Marasmus

Answer 20

protein and energy deficiency leading to depletion of fat stores and wasting of muscle

Question 21

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

Answer 21

10-35%

0.8

+25

1.2-1.4

Question 22

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

Answer 22

Protein quality

protein digestibility corrected amino acid score (PDCAAS)

complete

incomplete

Question 23

5 Risks of Vegetarian Diets

Answer 23

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