Lecture 14

Question 1

8x roles of Proteins

Answer 1

1. Building material
2. Hormones
3. Enzymes- digestive
4. Immune Function (Immunoglobulins)
5. Fluid Balance (spaces- interstitials., inter/extra cellular spaces, maintin correct fluid volume-maintained by levels of proteins and electrolytes)
6. Transporters - nutrients to sites required
7. Antibodies
8. Sources of Energy (2nd call after glucose/glycogen stores/carbs, convert aa amino acids–> glucose)

Question 2

Amino acids

Answer 2

Amino group + C + Acid group
-+ side group varies (influential factor giving unique properties)
Non essential amino acids
Essential amino acids

Question 3

Phenylalanine side chain

Answer 3

CH2 - Benzoate ring

Question 4

Glycine side chain

Answer 4

H

Question 5

Alanine side chain

Answer 5

CH3

Question 6

Aspartic acid side chain

Answer 6

CH2 - COOH

Question 7

9x essential aa Amino acids

Answer 7

essential = cannot be produced in body- have to be sourced in diet

1. histidine (his)^1
2. isoleucine (ile)
3. Leucine (leu)
4. lysine (lys)
5. methionine (met)^3
6. Phenylalanine (phe)^4
7. Threonine (thr)
8. Tryptophan (trp)
9. valine (val)

Question 8

8x non-essential aa Amino acids

Answer 8

Can be produced in body from essential amino acids/derived from metabolic products

1. alanine (ala)
2. asparagine (asn)
3. aspartic acid (asp)
4. glutamine (gin)
5. Glutamic acid (glu)
6. Glycine (gly)
7. Proline (pro)
8. Serine (ser)

Question 9

Conditionally essential amino acids

Answer 9

=Non-essential amino acids sitting in essential side of aa amino acid table
Tyrosine - in people with phenylketinuria (they have to avoid dietary phenylalanine- cannot make tyrosine)
Arginine - in young infants (part. premature infants). no capacity to manufacture that aa arginine
Rare inborn metabolic errors sometimes make non-essential aa –> essential

Question 10

Protein formation

Answer 10

Amino acids joined together to form water and Dipeptide
Peptide bond
Di-peptide
Tri-peptide
Polypeptides/proteins
-sequence of aa gives protein’s its function (dictated by DNA and RNA)
e.g. Hb Hemoglobin - polypeptide bound on its self with sulphur bonds, forming protein which attracts Iron and carries O2 around body

Question 11

Incorrect protein sequences

Answer 11

When amino acid sequence is incorrect in a polypeptide/protein, protein cannot function in normal form

Question 12

Haemoglobin

Answer 12

Illustration of Polypeptide/protein structure
-one of the four highly folded polypeptide chains that forms the globular hemoglobin protein
-Traps Iron
Heme-the non-protein portion of the hemoglobin- holds iron
The amino acid sequence determines the shape of the polypeptide

Question 13

Sickle cell anaemia

Answer 13

Protein a/acids sequence in structure incorrect, stopping it from functioning normally
Genetic mutation that stops them from producing correct sequencing to make Hb
-crescent shaped
-reduced capacity to carry O2

Question 14

Recommended intakes of Protein

Answer 14

RDI: Adults (not children or adlescent)
Males: O.84g/kg/day
Females: 0.75g/kg

Recommmended Percentage: 12-25% of energy intake (4kcal per gram)

(1.6-8 g/kg) - for more active people, protein utilisation/synthesis/turn over increased

Question 15

Derivation of RDI

Answer 15

• arbitary or established
• balance studies : during WWII where people were starved of specific nutrients in concentration camps, until became deficient, then refeed. once deficiency reversed would call that is the nutrient requirement for that individual

Question 16

Consuming extra protein supplements for gym

Answer 16

(1. 6-8 g/kg) - for more active people, protein utilisation/synthesis/turn over increased
- can easily increase protein intake
- majority of NZ’s consume 120% more protein than required
- whey protein- from milk products. just use skim milk powder
- build muscle by working fibres and do resistant activity to increase muscle mass (not by consuming more protein)
- But when your physical activity has increased = increased protein turnover = do need to eat more protein (but dont know the impact of eating excessive amount of protein)
- large popn studies done, people eating high amounts of protein, esp. from animal sources/meat have higher risk of CDV and cancer
- also if dont consume enough fluid with them- can result in kidney problems
- some renal stones

Question 17

Protein quality

Answer 17

High quality proteins - food which supplies the Essential a/acids (varying sources e.g. for vegans)
Digestibility
-Animal (easier digestion and absorption)vs. plant
Amino acid composition
-according to limiting amino acid
“some legumes, nuts, seeds, fish and other seafood, eggs, poultry (e.g. chicken) and/or red meat with the fat removed
-guideline emphasises getting more protein from non-animal sources. and making sure protein makes up a proportionate amount of diet
-recommended to have 1-2 servings of protein daily (not all from meat/mixed sources)

Question 18

Protein quality sources

Answer 18

Reference protein
Complementary protein
Legumes: Ile Lys
Grains:Met Trp
Together: Ile Lys Met Trp
-combine different plant based sources and carb sources, to make up all essential aminoacids (dont need to eat animal products to get all essential a/acids)
-beans and rice

Question 19

Protein absorption in mouth

Answer 19

Mouth and salivary glands
Chewing and crushing moisten protein-rich foods and mixing them with saliva to be swallowed
-breaking down fibres assoc with protein (e.g. in meat structure)
-dont produce digestive enzymes in mouth

Question 20

Protein absorption in stomach

Answer 20

HCl uncoils protein strands and activates stomach enzymes
(pepsinogen –> pepsin)
-protein enzymes secreted into gut in precursor state, otherwise would digest yourself
Protein –Pepsin + HCl –> smaller polypeptides + a/acids(cleaved of pp chain)
-not a huge amount of digestion occurs in stomach, but just enough to be in smaller chain lengths before SI
-mixing of chyme and release signals pancreatic enzymes and intestinal enzymes

Question 21

Protein absorption in small intestine

Answer 21

Pancreatic enzymes and small intestinal enzymes spit polypeptides further
(Pancreatic Endopeptidases- Trypsin, Chymotripsin and Elastase)
Polypeptides –pancreatic and intestinal proteases –> tripeptides, dipeptides and a/acids
Then enzymes of the surface of the small intestinal cells hydrolyse these peptides and the cell absorb them
(intestinal enzymes specific for chopping up smaller chain lengths of peptides (Tripeptidases, Dipeptidases and aminopeptidases)
Peptides –intestinal tripeptides and dipeptidases –> aminoacid (absorbed)
-cascading event: one enzyme system has to cut up longer chain lengths, have to wait until small chain lengths can start cleaving of a/acids.
-some specific to certain a/acids, only cleave of points of peptide where certain a/acid sits)

Question 22

HCl and the Digestive enzymes in the Stomach

Answer 22

HCl
-denatures protein structure
-activates pepsinogen to pepsin
Pepsin
-cleaves protein to smaller polypeptides and some free a/acids
-inhibits pepsinogen synthesis

Question 23

List of intestinal digestive enzymes

Answer 23

Enteropeptidases
Trypsin
Chymotrypsin
Carboypeptidases
Elastase and collagenase
Intestinal tripeptidases
Intestinal Tripeptidases
Intestinal Aminopeptidases

Question 24

Enteropeptidases in small intestine

Answer 24

-enterokinase

Converts pancreatic trypsinogen to typsin

Question 25

Trypsin in small intestine

Answer 25

Inhibits trypsinogen synthesis Cleaves peptide bonds next to the a/acid lysine and arginine Converts pancreatic procarboxypeptidases to carboxypeptidases Converts pancreatic chymotrypsinogen to chymotrypsin

Question 26

Chymotrypsin in small intestine

Answer 26

Cleaves peptide bonds next to the amino acid phenylalanine, tyrosine, tryptophan, methionine, asparagine and histidine

Question 27

Carboypeptidases in small intestine

Answer 27

Cleave a/acids from the acid (carboxyl) ends of polypeptides

Question 28

Elastases and collagenase in small intestine

Answer 28

Cleave polypeptides into smaller polypeptides and tripeptides

Question 29

Intestinal tripeptidases in small intestine

Answer 29

cleaves tripeptides to dipeptides and aminoacids

Question 30

Intestinal dipeptidases in small intestine

Answer 30

cleaves dipeptides to a/acids

Question 31

Intestinal aminopeptidases

Answer 31

cleave a/acids from the amino ends of small polypeptides (oligopeptides)

Question 32

pancreas negative feedback loop

Answer 32

once trypsin is produced - it stops the production of trypinsogen - trypsin reaches a certain level, feeds back to pancreas

Question 33

Disease of pancreas re protein digstion

Answer 33

inability or reduction of pancreatic enzyme secretion -decrease of digestion and absorption of protein (no trypsin activation to initiate protein digestion - enzyme cascade)

Question 34

Protein absorption

Answer 34

Proteins --> Peptides --> (most absorption facilitates by sodium of H (active cotransported) ) a) Di and Tripeptides cotransport with H+ (active) b) Amino acid cotransport with Na+ (acitve) -ecoport on basalateral mebrane, which swaps sodium with potassium, allows active gradient to occur which allows a/acids and peptides into cell -some breakdown of di- and tri-peptides by peptidases in the enterocyte itself --> converting them into a/acids c) Small peptides are carried intact across the cell by transcytosis -engulfed by membrane and diffuse into enterocyte All enter venule --> villi --> portal vein --> liver --> changes a/acids structure depending on body requirement

Question 35

Nitrogen Balance

Answer 35

Nitrogen intake = Rate of Nitrogen expenditure -majority of people are in balance Nitrogen balance N in = N out -measure nitrogen rather than protein, as nitrogen is the products which are measured in uring gN x 6.25 = g protein

Question 36

Factors causing negative nitrogen balance

Answer 36

1. Decreased protein intake (over the short term) (trying to lose weight, unwell and no appetite) 2. Starvation or reduced GI function(decreased protein absorption) 3. Injury, trauma or surgical operation 4. Illness or infection or burns (up to 70g/d) (esp severe/high percentage of body burns- sometimes the negative nitrogen balance which will kill them. Unable to synthesise enough protein to repair burn damage) -even if youre desperately to give them nitrogen/proteint through NG tube or vein often cant get enough in to synthesize enough protein to repair burns) 5. Some post operative conditions 6. Many cancers -Catabolism of cancer= Cakexia (not starvation. caused inflammatory factor produced by the cancer cells, pushing people into hypercatabolic state, cuasing neg nitrogen balance. sometimes hard to correct, even through given medication to try slow down process/high protein diet. so debilitating that kills them) 7. Lactation - whenbreast feeding. but temporary and not risky re mortality Degradation > Synthesis

Question 37

Factors which cause Positive nitrogen balance

Answer 37

1. Increased protein intake (over short term) -only for a temporary time, as body will always try to return to equilibrium -temporary +ve n balance, utilise for energy and then will adapt and will start to excrete more nitrogen containing products i.e. urea 2. Growth -growth spurts during first 6months of life, prepubertal growth spurt 3. Pregnancy 4. Recovery from illness or trauma -after being in -ve nitrogen balance. will metabolically start to convert to try increase synthesis synthesis or protein and reduce degradation -"Ebbing phase": metabolism changes into positive nitrgoen state to try and get body to equilibriate its nitrogen balance Synthesis> Degradation

Question 38

What does nitrogen balance mean

Answer 38

stage of nutrition | whether need to intervene or not

Question 39

Urinary nitrogen losses to asses protein losses

Answer 39

Record mmol/day Calculate mg/d 24hr urine urea 24hr urine creatine 24hr urine uric acid Insert into formula and figure out nitrogen balance -now labs do the calculations -used in clinical practice esp for patients who are severely traumatised

Question 40

Protein Energy malnutrition

Answer 40

Infections- Dysentery Rehabilitation -not really seen in NZ -is seen in Aus

Question 41

The toll of malnutrition

Answer 41

Global deaths of children under 5 years by cause 2008, % of total -greatest age group effected by malnutrition 8.8 million total deaths per year -35% of which are due to malnutrition (particularily protein-energy malnutrition) 34% Other 18% Pneumonia 15% Diarrhoea 12% Prematurity 9% Malaria 9% Birth asphyxia 3% HIV/AIDS/Measles -stats havent changed much even with millenium goals

Question 42

Malnutrition Infection Cycle

Answer 42

If not much food around becomes malnourished susceptible to infection once got infection and not much food around = makes infection worse even when try to rehabilitate/feed them, almost missed the boat -really difficult to eat enough and regain appropriate nutritional status to have appropriate immunity to fend off further nutrition -this Malnutrition Infection cycle eventually kills them

Question 43

Marasmus

Answer 43

Severe deprivation, or impaired absorption of protein, energy, vitamins and minerals Develops slowly(over long periods of time); chronic PEM -countries experiencing chronic famine due to war/inability to transport food to those who need it. -diets are poor overall, not just energy Severe weight loss (chronic) Severe muscle wasting, with no body fat Growth:

Question 44

Kwashiorkor

Answer 44

More acute: occurs where acute shortage of food (esp protein) Older infants and young children (1 to 3 years) (more than adults) Inadequate protein intake or, more commonly, infections Rapid onset acute PEM Some weight loss (not as much as marasmus) Some muscle wasting, with retention of some body fat Growth: 60-80% weight for age (effects children's growth) Edema Enlarged fatty liver (collection of water particularily around liver) - characteristic Apathy, misery, irritability, sadness Loss of appetite Hair is dry and brittle; easily pulled out; changes colour; becomes straight -assoc wih other micronutrient deficiencies (zinc, iron, B vit) - effecting hair and skin Skin develops lesions (and infections)

Question 45

Summary

Answer 45

Proteins are made up of AA, 9 of which are essential Cell Synthesise proteins according to DNA -sequencing of a/acids important Protein has many roles in the body Proteins are constantly synthesised and broken down This can be tracked by measuring nitrogen balance Dietary protein adequacy is characterised by AA and protein digestibility of food