Revision Questions - week 6

Question 1

What is the difference between essential and non-essential amino acids?

Answer 1

Essential AA must be provided by the diet as body is unable to meet this
Non-essential can be produced by the body via transmination of dietary AA at required rate

Question 2

How are amino acids categorised?

Answer 2

• Non-essential can be produced by the body via transmination of dietary AA at required rate
• Essential AA must be provided by the diet as body is unable to meet this

Question 3

3 factors that determine amino acid essentiality

Answer 3

• cells cannot make the carbon skeleton of essential amino acids
• cells lack the enzyme to attach the amine group to the carbon skeleton to form the essential amino acids
• cells cannot achieve the manufacture of essential amino acids at a fast enough pace to meet requirements

4th - few can become essential under certain conditions e.g. PKU

Question 4

Four structures of protein

Answer 4

primary
secondary
tertiary
quaternary

Question 5

primary structure of protein

Answer 5

single sequence of amino acids in a chain

- straight line

Question 6

secondary structure of protein

Answer 6

shape of protein molecule caused by weak H+ bonding between C=O and N-H groups within chain

• looks like twisted ribbon

Question 7

tertiary structure of protein

Answer 7

3D foiling from interactions between R groups (determines overall structure/shape and function of protein)
- looks a bit tied up

Question 8

quaternary structure of protein

Answer 8

interactions between more than one chain (resulting in a fibrous, globular or conjugated protein)
- multiple chains tied up

Question 9

fate of AA once absorebed

Answer 9

added to cellular AA pool

Question 10

AA pool required for

Answer 10

• Protein synthesis
• Energy production (after deaminiation)
• Gluconeogenesis (after deaminitation)

Question 11

Why is the regular supply of essential amino acids so important?

Answer 11

required continuously from the diet is that they cannot be made by the body, yet are required continuously for gene expression. If they are not provided by the diet, the body breaks down its muscle mass (muscle wasting) to provide these EAA for gene expression to continue adequatly

Question 12

How is the quality of dietary protein assessed?

Answer 12

• Biological Value (BV)
• Protein efficiency ratio (PER)
• Chemical score (CS)
• Protein digestibility corrected amino acid score (PDCAAS)
  The quality of a protein is assessed according to the most limitinh/least containing essential (indispensable) amino acid

Question 13

What is a high quality protein? how measured? and what are food sources, including some plant sources?

Answer 13

High quality protein are

• foods that provide amino acids in amounts consistent with body’s needs (e.g. similar AA profile).
• measured by the biological value (nitrogen retained/nitrogen absorbed) – higher the better
• Egg white is highest followed by whey protein than meats then soy and casein

Question 14

‘limiting’ amino acid

Answer 14

Smallest supply of Essential amino acid (lowest conc. of protein)

Question 15

Key steps of protein ingestion and absorption and metabolism

Answer 15

• Mechanical digestion – teeth
• Stomach – protein partially digested by pepsin and HCL
• Si – final digestions to amino acids
• Liver – AA absorbed into portal vein and then rest of body

food -gastrin produced -> singals HCL production and pepsinogen secretion – HCL denatures proteins and activates pepsinogen to pepsin (which cleaves peptides into shorter fragments) - moves into SI->secretin and CKK secretions ->stimulares pancreas to release trypsinogen, chymotrypsin and carboxypeptidase (into duodenum) - > activiated enzymes breakdown polypeptides into dipeptides and AA (for absorption)-> in enterocytes dipeptides further digested by peptidase into AA ->to AA pool

Question 16

What would happen for DNA expression to continue when low quality protein, or too little protein is consumed in the long term?

Answer 16

?

Question 17

What is the difference between food allergies and food intolerances? Provide two examples of each.


Answer 17

Food allergy is an acute immune response (e.g. hivens, anaphylaxis) whereas food intolerance is dose-dependent and moreso nerve stimulation (diarrohea and bloating)

Question 18

Protein in fluid balance

Answer 18

– Blood pressure pushes fluid out of capillary bed at the arterial end into interstitial space
– Plasma albumin and globulins attracts water from the interstitial space back into the capillary for venous return
– If plasma albumin is insufficient, fluid remains in interstitial space resulting in edema

Question 19

What is gluten

Answer 19

Gluten is glutelin and prolamines (gliadin in wheat)

Question 20

Is gluten bad and should it be avoided?

Answer 20

? if celiac must avoid it ?

Question 21

Kwashiorkor

causes, the characteristic signs, and the health consequences long-term

Answer 21

• Severe protein deficit (with moderate energy) – often accompanied by infection or other diseases
• Characteristics include: edema, weight loss, growth impairment, fatty liver

Question 22

Marasmus

causes, the characteristic signs, and the health consequences long-term

Answer 22

• Severe energy and protein deficit

- Characteristics include: severe weight loss, wasting of muscle and body fat, severe growth impairment

Question 23

How was the rDI for protein determined

Answer 23

RDI same as EAR -
The biomarker of protein deficiency for the EAR is “an out of balance” nitrogen balance. Protein intake is adequate whenthe nitrogen balance is in equilibrium

Question 24

What are important factors to consider when discussing protein requirements for optimal nutrition?

Answer 24

• Protein sources
• Cooking methods
• The rest of the diet
• Health goals
• sustainability

Question 25

What is considered a high protein diet

Answer 25

Over the 15-25%

Question 26

why would high protein intake be a concern for kidney health?

Answer 26

Kidney – high protein – lots of AA – possible lots of deaminiation therefore removal of amine group from AA which is converted to ammonia which is then converted to urea which is filtered by kidney therefore overload of AA can over burdens kidney

Question 27

why would high protein intake be a concern for bone health?


Answer 27

Bone – as protein increases the acid load in body which may cause calcium to leak out of the bone to neutralize acid – not much proven research however

Question 28

Why are high protein diets quite popular in the context of weight loss?

Answer 28

Due to heat dissipation and appetite control

Question 29

What are protein related diseases that require nutritional and medical advice?

Answer 29

Rickets disease – vitamin D deficiency
Celiac disease – gluten allergy
Kidney disease

Question 30

protein turn-over

Answer 30

The balance of protein synthesis and breakdown in accordance to changes in requirements due to body repair and renewal

Question 31

What is nitrogen balance

Answer 31

the ratio between nitrogen intake (e.g
protein) and nitrogen excretion. Ideal state is equilibrium
between both

Question 32

What is negative nitrogen balance

Answer 32

A negative nitrogen balance is the state where more nitrogen is excreted than is taken in. Body protein is breaking down (e.g. due to sickness), or utilising body protein for energy, all resulting in deamination and nitrogen excretion. Intake does not meet demand

Question 33

How is BV calculated

Answer 33

Nitrogen retained (g) / Nitrogen absorbed (g) x
100 (retained means that the whole amino acid is used by the body)

*considers the whole protein ( all AA) on the basis that protein is the
major source of nitrogen in the diet.

Question 34

high bv proteins

Answer 34

Foods that
provide amino acids in
amounts consistent with
body’s needs (e.g. similar AA
profile). The body will retain
much of the absorbed
nitrogen, when consumption
does not exceed requirement
e.g. egg white, whey protein

Question 35

low bv proteins

Answer 35

Foods that
provide amino acids in
amounts not consistent with
body’s needs (e.g. different
AA profile). The body will not
retain all of the nitrogen
absorbed
e.g. corn, wheat

Question 36

What are other methods to determine the quality of protein? What do
they “add” to the assessment by BV?

Answer 36

Chemical Score, the PDCAAS or the new
DIAAS also consider the quantity of each EAA in the test protein to
determine the limiting AA (when compared to a reference protein. They
also consider the digestibility of the protein, which is important because if a
protein is not digested, there is no absorption and the body cannot use the
amino acids

Question 37

What is BV?

Answer 37

How efficiently the dietary protein is converted to body tissue protein. If all 8 (9) AA (EAA) are present, the body can use the dietary protein more efficiently. The measure takes into account % of urinary
and fecal nitrogen excretion:

Question 38

Chemical score

Answer 38

milligram (mg) of each essential amino acid (EAA)
per gram of the test food OVER the amount in mg of each EAA per
gram of the reference food. The lowest ratio measured for an EAA (e.g.
the “limiting” amino acid) of the test protein is the chemical score for
that tested protein (0 - 1.0)

pretty much is the limiting AA

Question 39

PDCAAS

Answer 39

= Chemical score * digestibility
Protein digestibility = amount of amino acids absorbed. This is the amino
acid profile able to support growth and maintenance
Highest score is 1: milk proteins, egg and soy

Question 40

___ amino acids cannot be synthesised endogenously, only ______ amino acids can

Answer 40

Indispensable; dispensable ( non-essential )

Question 41

why wouldnt phenylalanine be converted to tyrosine an d what is the result? - PKU

Answer 41

would be due to a lack of functioning phenylalanine hydroxylase

As a result

• tyrosine becomes an EAA (will need to eat a lot and havev strict diet),
• can cause a phenylalanine build up (can cause mental retardation and brain damage). Patients must reduce the amount of animal sources of protein and artificial sweeteners as a life-long diet.

Question 42

Endogenous amino acid recycling refers to

Answer 42

the absorption of amino acids from GIT cells being renewed (old cells are renewed very frequently). As old cells are disposed of, the amino acids of organelles are recycled.