Nutrition Chapter 6: Proteins

Front 1

Amino Acids

Back 1

-building blocks of proteins
-each amino acid contains amine group (NH2) and acid (COOH)
-the side chains are what differentiates the 20 different amino acids
-amino acids connect to each other by peptide bonds

Front 2

Specificity of proteins

Back 2

-proteins are often composed of 500 or more amino acids
-the sequence of the amino acids determines a proteins shape and thus its function

Front 3

Composition of insulin

Back 3

-composed of 2 chains of 51 amino acids, connected by sulfur

Front 4

Protein as an energy source:

Back 4

-generally the body uses carbohydrates and fat for energy
-if the body is not supplied with enough energy, protein can be utilized
-like carbs, it gives 4 calories per gram
-the body can use amino acids to form glucose but can't do the reverse
-the use of protein as an energy source compromises its other functions
-excess dietary protein can be stored as fat

Front 5

Uses of protein:

Back 5

-makes and repairs tissues (muscles, blood, internal organs, skin, hair, nails, and bones)
-essential for growth
-important to maintain body fluid balance (and electrolyte balance)
-acid-base balance
-

Front 6

Some examples of proteins:

Back 6

-enzymes
-antibodies
-transport vehicles
-hormones
-tendons
-muscles
-ligaments
-core of bones and teeth
-filaments of hair
-the material of nails

Front 7

effect of alkalosis or acidosis on proteins

Back 7

-if pH balance is not maintained, individual may develop acidosis or alkalosis and denature proteins in the body, rendering them unable to function

Front 8

Inborn errors of metabolism:

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-the sequence of amino acids needed to form specific proteins is encoded in the DNA in the cell nucleus
-some genetic diseases result in an error in protein production (cystic fibrosis, sickle-cell anemia)
-an incorrect order of amino acids can lead to an altered shape of a protein, changing its function

Front 9

Sickle-cell anemia

Back 9

-In the disease sickle cell anemia, the hemoglobin molecule that carries oxygen or carbon dioxide throughout the body is altered. 

-Due to a single amino acid error of valine replacing glutamic acid in the polypeptide sequence of hemoglobin, the red blood cell has a sickle shape instead of the normal disc shape. 

-This altered shape hinders oxygen transport

Front 10

Protein denaturation:

Back 10

-can be denatured by:
1. heat (think of cooking eggs)
2. Acids and Bases
3. Toxins (such as heavy metals mercury or silver)

-we use denaturation for protein digestion (stomach hydrochloric acid). the proteins are unfolded so enzymes can get to the peptide bonds to break them down

-no bonds are broken in protein denaturation (amino acid content is unchanged)

Front 11

Protein breakdown and re-synthesis:

Back 11

-Proteins in food are broken down into amino acids during digestion, which are then absorbed and used to make new proteins in the body. 

-Once the amino acids are absorbed into the bloodstream, they can be used directly to resynthesize proteins

-To use dietary proteins for protein synthesis, we must consume adequate energy. If we do not consume enough energy, our body will break down dietary protein for energy 

-Proteins in the body are being constantly broken down and resynthesized. (The process of re-synthesizing your body’s proteins is not 100% efficient and so we require daily protein to replace the amount of protein that was not completely re-synthesized.)

Front 12

Nitrogen balance:

Back 12

-amount of nitrogen we excrete can let us know how much protein we are using
-ex. after surgery, body is under stress and uses a lot of protein and we will lose a lot of nitrogen to indicate this use (negative nitrogen balance).

-the nitrogen balance should be zero
-if you are trying to build muscle, if you are growing as a child, or if you are pregnant; you need a positive nitrogen balance

Front 13

Recommended protein intake:

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-10-35% of daily calories
-RDA = 0.8g of protein per kg body weight
-The RNI takes into account that our diets are generally a mix of poorer quality vegetable proteins (2/3) and higher quality animal proteins (1/3).

Front 14

Protein Quality:

Back 14

measured by:
-amino acids
-how well it supports growth
-digestibility

*animal proteins are of a higher protein quality than vegetable proteins

Front 15

Essential amino acids:

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-there are 9 a.a. that our body cannot produce (must obtain them from diet)

Front 16

High- Intermediate- and Low-quality proteins

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-high: egg, milk, beef, fish
-intermediate: soy, flour, sunflower seed, rice, oats
-low quality: peas, cornmeal, cassava gelatin

Front 17

limiting amino acid

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the amino acid in shortest supply (most plant proteins are lacking or short in supply of at least one amino acid, this is a limiting amino acid)

Front 18

Protein Efficiency Ratio:

Back 18

-PER= gain in body weight divided by weight of protein consumed
-used to judge the quality of protein in infant formulas and baby food

Examples:
-whey: 3.6
-milk protein: 3.1
-casein: 2.9
-soy: 2.1

*any protein that has PER of 2.7 or higher is considered an excellent quality of protein

Front 19

athletes require more..

Back 19

-sulfur amino-acids (methionine and cysteine) not for re-synthesis of hair, but for growing quality muscle fiber after an energy expenditure

Front 20

Protein Digestibility Corrected Amino Acid Score:

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-reflects the digestibility of a protein as well as the proportions of amino acids that it provides

-Protein PDCAAS:
-whey: 1.00
-egg white: 1.00
-soy: 0.94
-beef: 0.92
-pea flour: 0.67
-rice: 0.47
-wheat flour: 0.40
-wheat gluten: 0.25
*pea flour + wheat gluten = 0.82

Front 21

only plant source to offer complete protein?

Back 21

-soy
-other plant proteins can be combined to get complete proteins (they are incomplete proteins by themselves)

Front 22

Effect of physical activity:

Back 22

-decreased protein synthesis
-increased protein degradation
-increased AA (alanine and glutamine) released from muscle
-5-15% of energy expenditure depending on total energy supply and PA intensity
-mainly in endurance exercise

Front 23

Use of protein as an energy source during exercise

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-branched chain amino acids (isoleucine, leucine, and valine)
-provide energy directly to muscle
-provide energy via carbohydrate produced in liver
*endurance training increases the capacity of muscle to derive energy from the body's protein

Front 24

Effects after physical activity:

Back 24

-increase in protein synthesis leading to positive protein balance
-further increase after resistance exercise
-the anabolic effect of intense training is observed after a specific intensity threshold (70% of 1RM)

Front 25

Whey protein vs. Casein protein supplements:

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-whey can be digested and absorbed faster
-casein is absorbed slower, so absorption is over a longer period of time

Front 26

When is it most beneficial to drink a protein shake?

Back 26

-prior to workout (prevents protein deficit that occurs during training)
-after workout it is good to eat carbs to replenish glycogen stores.

Front 27

Amino acid supplements

Back 27

-controversial, studies are contradictory and generally show no effect on performance
-Margin of Safety for Large Amino Acid and Protein Doses are not established

-can cause amino acid imbalance and toxicity

Front 28

Creatine Supplements

Back 28

-Nitrogen Containing Compound Known As an Amine, not AA
-found in meats
-formed in liver from glycine and arginine
-we would have to eat about 5kg of beef to get as much as we do from supplements
-we eat about 1g/day and body produces about 2g/day
-blood level is at about 50-100 micro moles per liter
-with supplemetn spikes to 500-1000 micro moles per liter
-brings water with it, so gives muscles "water weight"
-effects more seen in the last reps or last set
-May Enhance Performance in Repetitive, Short-term, High Intensity Tasks in Which the Body Does Not Move From Point to Point Such As Resistance Exercise
-Can help when doing the final “sprint" during endurance exercise
-Does Not Improve Performance Where the Body Has Moved Such As Swimming and Running
-if you are a big meat eater you might not see the effects of creatine supplements

Front 29

Protein requirements for PA

Back 29

-endurance athletes: 1.2-1.4 g per kg body weight
-strength athletes: 1.6-1.8 g per kg body weight

Front 30

Excessive intake of protein

Back 30

DRI: no UL excessive protein intake
-extra protein may be converted to glucose or fat or excreted in the urine
-can lead to calcium losses that compromise bone health
-foods that are high in protein are also high in fats (CVD risk)
-risk of kidney disease
-may exceed liver's ability to convert excess nitrogen to urea

1. 200-400g
2. 5g/kg body weight
3. >35% of total energy

Front 31

High protein/low carb diets?

Back 31

-forces body to obtain glucose from other sources
-results in a build up of ketone bodies
-disrupts acid-base balance
-disrupts fluid/electrolyte balance
-normal breakdown of fat to energy is blocked
-the body responds by breaking down protein which is supposed to be used for other duties
-often rapid weight loss due to excessive water loss

Front 32

Positive aspects of vegetarian diets:

Back 32

-promotes leaner body composition and lower blood pressure
-less sat. fat
-provides more: vegetable protein, fiber, antioxidant nutrients, phytochemicals

Front 33

Negative aspects of vegetarian diets:

Back 33

-have difficulty getting enough protein
-lack of omega-3 fatty acids in diet
-risks of stunted growth
-vitamin D, B12, calcium, iron, and zinc deficiencies

Front 34

Marasmus

Back 34

-protein-energy deficient
-develops slowly in children under 2 years of age
-severe weight loss, severe muscle wasting, hair loss, thin dry skin

Front 35

Kwashiorkor

Back 35

-protein-deficient
-develops quickly in children 1-3 years of age
-weight loss, muscle wasting, decreased growth rate, big swollen bellies

Front 36

Food allergies

Back 36

-antibody IgE
-1-2 Percent of Adults and 3 Percent of Children Have Food Allergies
-about 90% caused by: milk, egg, wheat, peanut, soy, tree nuts, fish, and shellfish

Front 37

Food intolerance

Back 37

-An Adverse Effect of a Food or Food Additive Usually Not Involving the Immune System
-Ex. celiac disease, food poisoning

Front 38

Celiac Disease

Back 38

Certain Peptides From Wheat Proteins (Gluten) Are Toxic to the Gut When They Are Not Broken Down During Digestion

Front 39

Food Poisoning

Back 39

caused by microorganisms in the food, not the food itself