Proteins, Amino Acids

Question 1

what type of isomers do protein have

Answer 1

L

Question 2

BASIC unit of pro in

Answer 2

amino acids

Question 3

does the body need pr

Answer 3

no but it needs its aa and nitrogen

Question 4

•of the Over 300 AAs found in animal tissue how many are used for ptn synthesis

Answer 4

20 used for ptn synthesis (tRNA)

– all 20 AAs are essential (some have to be in the diet)

Question 5

Common Post-Translational Amino Acids

- bone

Answer 5

OH-Lysine

• OH-Proline

Question 6

Common Post-Translational Amino Acids

- muscle

Answer 6

• 3-Methyl histidine

– released during muscle breakdown via urine

Question 7

INDISPENSABLE (ESSENTIAL) AMINO ACIDS

Answer 7

• IAA is one which cannot be made in the body or cannot be
made sufficiently to meet physiological needs, hence must
be supplied in the diet.
e.g., inability to make C-skeleton of AA de novo
• 10 AAs most commonly essential:
PHE HIS ILE LEU LYS MET TRP VAL THR (ARG ?)- not essential for human because made in the liver in the urea cycle
– Dependent on species and/or stage of growth:
GLY PRO ARG
• IAA as a misnomer: supply keto analogue (requires a
transaminase) or hydroxy analogue (requires a
dehydrogenase and a transaminase) and animal can
make the AA – used in renal failure patients
– exceptions THR, HIS and LYS

Question 8

how can we mesure muscle breakdown

Answer 8

see it in urine because it will have no where else to go

Question 9

if we eat a steak and it has 3- methyl histadine, what happens

Answer 9

cant break it down so it is seen in the urine

Question 10

what do you do to see if the aa is necessary

Answer 10

take it out a diet until see protein imbalaance - dont know about arg because take a long time because we make some of it
ex histadine with babies is more rapidly turned over - 3 month study to see negative balance

Question 11

whats wrong with aa supplements

Answer 11

have some with sulfur group, some with acid group- smell bad ex together aspertame- aspartic acid and phenylate- seperate really bad taste

Question 12

when eating high protein diet

Answer 12

broken down and produces urea- and need the urea cycle to keep going- if not enough arg made then having some in the diet makes sense

Question 13

DAA can be made in the body from

Answer 13

a) keto acid & transamination with another AA
e.g., ALA from pyruvate
b) another amino acid by conversion other than by
transamination
e.g., MET
→ CYS, PHE
→ TYR

Question 14

Conditionally Indispensable Amino Acids

Answer 14

IAA and DAA inflexible classifications - too strict?
e.g., TYR essential in PKU, TAURINE [MET] essential in TPN

Amino Acid
Tyrosine
Cysteine
Proline
Arginine
Glutamine
Precursors
Phenylalanine
Methionine, Serine
Glutamine
Glutamine or Glutamate, Aspartate
Glutamate, Ammonia

Question 15

• Function is dependent upon

Answer 15

ptn

components, shape or conformation

Question 16

• SIMPLE PROTEINS:

Answer 16

AAs only

Question 17

• CONJUGATED PROTEINS:

Answer 17

AAs
combined with other non-ptn moiety [e.g.,
lipoprotein]- glycoprotein (cell signaling)

Question 18

PRIMARY STRUCTURE

Answer 18

Sequence of strong covalently bonded
AAs as dictated by the genetic code which
determines the final form of ptn
• The side chain of one amino acid differs
from that of another amino acid making
each amino acid different; however the
polypeptide backbones do no differ
between polypeptide chains

Question 19

SECONDARY STRUCTURE:

Answer 19

Determined by attracting forces between
nearby groups (R) in the peptide chain.
Gives shape to the ptn.
α-helix
β-pleated sheet
random coil

Question 20

TERTIARY STRUCTURE:

Answer 20

The way a protein folds in a threedimensional
space
• Due to interactions occurring among R
groups that are located at considerable
distances from each other on the
polypeptide chain
e.g., cystine -S-S-
• Produces binding and looping of the ptn
molecule
e.g., enzyme pocket - site of action

Question 21

QUATERNARY STRUCTURE:

Answer 21

Aggregate of two or more polypeptide chains that form oligomers
held together by H bonds and electrostatic salt bridges (e.g.,
haemoglobin, regulatory enzymes).

Question 22

ASSESSMENT OF PROTEIN QUALITY

D) Chemical Score (AA Score)

Answer 22

• non-biological method that requires knowledge of AA
  composition of test ptn
• compares AA composition of test ptn with ref ptn
  e.g., egg, milk
  IAA test ptn (mg/g ptn) ÷ IAA ref ptn (mg/g ptn) x 100
  Criteria: IAA with lowest score = limiting AA
  +ves: easily performed
  -ves: knowledge of AA composition; no digestibility

Question 23

ASSESSMENT OF PROTEIN QUALITY

E) Amino Acid Score (FAO/WHO reference pattern)

Answer 23

relates IAA content in food to IAA requirement for
given age group
IAA in food protein (mg/g ptn) ÷
same IAA reference pattern (mg/g ptn) x 100
- pattern of requirements for amino acids in the total
dietary protein is calculated by dividing each IAA
requirement by the recommended allowance of
reference protein for the given age group

Question 24

ASSESSMENT OF PROTEIN QUALITY
F) Protein Digestibility-Corrected Amino Acid
Score (PDCAAS)

Answer 24

same as above except accounts for digestibility
- official FDA food labeling method
- except infant foods which use PER
IAA in food protein (mg/g ptn) x digestibility ÷
same IAA reference pattern (mg/g ptn) x 100

Question 25

QUANLITY OF PROTEIN

Answer 25

Dietary need affected by several factors:
1. Sufficient Energy: ptn used as energy if needs not
met by CHO & fat intake
2. Ptn Quality: with consumption poor quality
ptn requirement (IAA) not met
3. Individ. Variation: N losses vary and needs vary
Dependent on:
1. Age
2. Size
3. Growth (infant, pregnancy
)
4. Stresses (surgery, trauma,
- tissue repair (increase requirement)
5. Adaptability (controversial but we can adapt to lower pro requirements over generations, example medival ppl were stunted due to lack of protein so dont need it when theyre older)
e.g., India - ptn need less
pop’n smalle

Question 26

ai for INFANTS

Answer 26

0-6M: 1.52G/KG/D OR 9.1/DAY

Question 27

 EAR & RDA for all other age and gender groups

AVERAGE PERSON EAT 80-120G/DAY

amdr is where the rda is

Answer 27

• adults/elderly:
• EAR = 0.66 g/kg/d RDA = 0.80 (probably too low)g/kg/d (~46 – 56 g/d)
• pregnancy:
• EAR = 0.88 g/kg/d RDA = 1.1 g/kg/d (+25 g/d)
   Maintenance of nitrogen balance (plus growth factor)
   Indicates the ability to maintain body protein content at its
  current level
   General criteria used to establish requirement

Question 28

Protein

 UL

Answer 28

UL could not be established, however, this does not
mean that there is not a potential for adverse effects
from high protein intakes from food or supplements
 No separate recommendation for vegetarian (varied
diet) or athlete (“no compelling evidence”)
 AMDR = 10 – 35% of nrg for adults (wide range)
 Carbohydrate: AMDR = 45 - 65% children and adults
 Fat: AMDR = 20 - 35% adults

Question 29

nb

how much pro is required to maintain NB

Answer 29

ptn = N [g] x 6.25
nb= ni -(un +fn +mn)
urinary loss, fecal, mielaneous loss (a constant- 8mg N/kg/d example hair, skin, saliva))

n in> n out= positive n balance

n in< n out - negative balance

Question 30

High Protein Intake

Answer 30

Hunter gatherers select diets with less than 20% protein
 Protein poisoning reported by North American explorers
 rabbit starvation >40% nrg as protein (very low in fats very very lean and were dieing of fatty acid deficiency)
 Preterm neonates suffer brain damage with protein
intake >6-7.2 g/kg/d
 Hypercalciuria
 Bone loss and renal calcium oxalate stones
 Accelerates progression of renal disease
 Probably does not cause renal disease
 Not much evidence of adverse effects in adults, below
about 40% of dietary energy

Question 31

Issues for the Athlete: Protein

Answer 31

 FNB stated “In view of the lack of compelling evidence
to the contrary, no additional dietary protein is
suggested for healthy adults undertaking resistance or
endurance exercise”
 ADA, DC & ACSM (2009) concluded
 Endurance athletes 1.2 – 1.4 g/kg/d
 Strength-trained athletes 1.6 – 1.7 g/kg/d
 Research does exist suggesting different needs for
athletes
(they are not different than normal individual except more iron, water)

Question 32

Resolution: Use AMDR (10% - 35%) ?

Answer 32

• 30 y woman, wt = 60 kg, ht = 1.65m (BMI = 22)
PA sedentary – low activity
• 2000 kcal, 10% ptn or 200 kcal from ptn
50 g ptn / 60 kg = 0.83 g/kg/d
• At 15% ptn or 300 kcal from ptn
75 g ptn / 60 kg = 1.25 g/kg/d
• PA very active
• 2700 kcal, 10% ptn or 270 kcal from ptn
68 g ptn /60 kg = 1.13 g/kg/d
• At 15% ptn or 400 kcal from ptn
100 g ptn /60 kg = 1.7 g/kg/d (ACSM, ADA, DC target)
… and so on

based on your weight which i not changing

Question 33

midterm:
carbs GNG, fiber, dri for fibre and carbs, probiotics (understand concept or pre and probiotics), protein up to today, no fat, marks,

exam will emphasize on fats, less specific no fill in the blank

Answer 33

s