PROTeenies

Question 1

3 primary functions of dietary proteins

Answer 1

• functional proteins in the body (enzymes, actin and myosin, collagen, fibrin, transport proteins, some hormones, antibodies, etc)
• essential amino acids for protein synthesis
• energy (10-15% of ATP)

Question 2

RDA for dietary protein

Answer 2

0. 8g/kg body weight/day
   - increases during growth periods: infants, kids, teens, pregnancy, lactation, athletes. also for people suffering wasting from old age or end-stage cancer

Question 3

protein AMDR

Answer 3

10-35% daily energy intake

Question 4

how many proteinogenic amino acids are there in humans (the important ones)?

Answer 4

20

Question 5

what is the chemical structure of an amino acid? (3 parts) which parts make up the carbon skeleton?

Answer 5

• an amino group (NH2)
• an acid group (COOH)
• a unique side chain

carbon skeleton: the acid group and side chain

Question 6

how is protein quality determined?

Answer 6

determined by whether a given dietary protein provides all the essential amino acids in adequate amounts

Question 7

how many essential amino acids are there?

Answer 7

9

Question 8

what is a complete protein?

Answer 8

a protein that provides all 9 essential amino acids (can be combos of foods like rice and beans)

Question 9

what are examples of complete plant proteins?

Answer 9

soy, quinoa, hemp seeds, buckwheat, chia seeds

Question 10

what are incomplete proteins?

Answer 10

foods that lack one or more EAA (most plant proteins are incomplete)

Question 11

what is primary protein structure?

Answer 11

amino acid chain

Question 12

what is secondary protein structure?

Answer 12

folding of polypeptide chain into helices or sheets

Question 13

what is tertiary protein structure?

Answer 13

three dimensional folding of the chain with side-chain interactions

Question 14

what is quaternary protein structure?

Answer 14

protein consisting of more than one amino acid chain (functional protein)

Question 15

what are the links between amino acids called?

Answer 15

peptide bonds

Question 16

two amino acids linked together

Answer 16

dipeptide

Question 17

three amino acids linked together

Answer 17

tripeptide

Question 18

4 or more amino acids linked together (up to several thousand)

Answer 18

polypeptide

Question 19

what happens to proteins in the mouth?

Answer 19

not much: just chewing them and moistening them

Question 20

what happens to proteins in the stomach?

Answer 20

HCl denatures proteins (unravels them). HCl also activates the inactive proenzyme pepsinogen, to make pepsin. pepsin breaks up denatured proteins into smaller polypeptides and some amino acids. it also inhibits further pepsinogen synthesis.

Question 21

what happens to proteins in the small intestine?

Answer 21

When polypeptides enter the small intestine, small intestine enterocytes release the hormone cholecystokinin (CKK). CKK in turn stimulates the release of inactive pancreatic proteases trypsinogen and chymotrypsinogen from the pancreas into the small intestine. then enterocytes release enteropeptidase in order to activate the proteases into trypsin and chymotrypsin. these proteases then break up polypeptides even more: into tripeptides, dipeptides and amino acids. these three kinds of peptides can then be absorbed into the enterocytes.

Question 22

pepsinogen

Answer 22

the inactive form of pepsin. needs HCl in the stomach to be activated.

Question 23

pepsin

Answer 23

the active form of pepsinogen. breaks down denatured proteins in the stomach into smaller polypeptides.

Question 24

cholecystokinin

Answer 24

(CKK). a hormone released by small intestine enterocytes when proteins enter the small intestine.
-stimulates the release of pancreatic proteases (trypsinogen and chymotrypsinogen: inactive forms) into the small intestine

Question 25

trypsinogen and chymotrypsinogen

Answer 25

• inactive proteases released into the small intestine by the pancreas. this release is stimulated by the presence of CKK, a hormone released by SI enterocytes in the presence of dietary polypeptides.
• the proenzyme enteropeptidase (“enterocyte peptide enzyme”) needs to be released from the enterocytes in order to convert them into their active forms, trypsin and chymotrypsin

Question 26

trypsin and chymotrypsin

Answer 26

• active forms of pancreatic proteases trypsinogen and chymotrypsinogen
• need enteropeptidase, release by the enterocytes, to be activated
• inactive forms initially released by the pancreas in response to enterocyte hormone cholecystokinin (CKK)

Question 27

enteropeptidase

Answer 27

(“enterocyte peptide enzyme”): the proenzyme released by the small intestine enterocytes that activate trypsinogen and chymotrypsinogen into their active forms, trypsin and chymotrypsin, so that they can break down polypeptides into tripeptides, dipeptides and amino acids to be absorbed into the enterocytes.

Question 28

what happens to amino acids once they enter the enterocytes?

Answer 28

they leave the enterocytes and enter the bloodstream. they travel via the portal vein to the liver (just like carbs!).

Question 29

what is the primary contributor of amino acids to the amino acid pool?

Answer 29

breakdown and turnover of old proteins in the body

Question 30

amino acid pool

Answer 30

place in the liver where all amino acids go (dietary and old) to be turned into new proteins

Question 31

what percentage of amino acids are released into the bloodstream by the liver?

Answer 31

only 30%

Question 32

what does the liver do with amino acids? (4 options)

Answer 32

• synthesis of proteins or amino acid-derived compounds (ie carnitine)
• synthesis of non essential amino acids
• oxidized (used for immediate energy)
• converted to glucose or fatty acids

Question 33

amination

Answer 33

using an ammonium ion (NH4+) to form an amino group, and attaching that to a carbon skeleton (side chain and acid group)

Question 34

transamination

Answer 34

transferring an amino group from one amino acid to a different carbon skeleton to make a different amino acid

Question 35

what happens when an amino acid is converted to glucose or triglycerides/what is it called?

Answer 35

gluconeogenesis and lipogenesis: amino acid group is removed (deamination) to get the carbon skeleton. the nitrogen is disposed of in urea. carbon skeleton is turned into pyruvate, and the pyruvate is turned into either glucose or TG.

Question 36

deamination

Answer 36

removal of amino (nitrogen) group to get carbon skeleton for gluconeogenesis or lipogenesis. N is excreted.

Question 37

urea cycle

Answer 37

takes place in the liver. used to excrete urea from N via urine or feces. increases with the increase of dietary protein.

Question 38

cancer cachexia

Answer 38

complex metabolic syndrome characterized by involuntary muscle loss or “wasting”

• affects majority of end stage cancer patients
• leads to decreased survival rates and negatively affects cancer therapy (treatment is harder to tolerate)

Question 39

treatment of cancer cachexia

Answer 39

increase protein RDA from 0.8g/kg/day to 1-1.5g

Question 40

sarcopenia

Answer 40

characterized by progressive and generalized loss of skeletal muscle mass and strength (like cancer cachexia but not cancer related and slower).
-happens normally with age but sometimes unusually with bedrest or other conditions (punctuated decline)

Question 41

treatment for sarcopenia

Answer 41

• physical exercise if possible–especially resistance
• diet and dietary supplements
• nutritional intervention (often the main one because old people have a hard time exercising)
• protein quality and adequate leucine specifically important

Question 42

how to build muscle

Answer 42

• 1.6g/kg/day protein
• exercise and resistance training
• pace protein intake to every 3 hrs to avoid normal protein breakdown
• high branched chain amino acids like leucine (high in whey protein specifically)