protein and amino acids

Question 1

what is protein a major component of

Answer 1

plant and animal tissue

Question 2

amino acids are needed in every what

Answer 2

living cell

Question 3

why do we need a constant supply of protein

Answer 3

as Our bodies constantly make, break down and use proteins so we need protein to replace what we use.

We don’t store amino acids. As although stored in protein the protein always has a function to carry out so isn’t stored

Question 4

what is excess protein converted into

Answer 4

energy or fat

protein is important in energy gen

Question 5

if theres not enough protein or in form of glucose in body them what happens to muscles

Answer 5

broken down causing wasting - PEM. This helps to provide our bodys the fuel they need.

Wasting weakens muscles including the heart

Question 6

insulin is a protein needed as what

Answer 6

a hormone for homeostasis

Question 7

what is excess protein converted into and used for

Answer 7

proteins converted to glucose to be used as energy. Or to create fatty acids, so is incorporated into our fat store

Question 8

what is the structure of protein

Answer 8

Made of strings of amino acids linked with peptide bonds.

there are 20 amino acids

R group determines the identity and unique chemical properties of the amino acid

alpha carbon is the central one
Amine group is a nitrogenous group
Proline is only amino acid that rings around the central carbon

Question 9

what are essential amino acids and how many are there

Answer 9

9
Essential as were unable to synthesis that amino acid so it must come from diet
All 20 amino acids are needed

Question 10

what are non essential amino acids and how many are there

Answer 10

Non essential – don’t have to get them from the diet as we can biochemically synthesis them

there are 3

Question 11

explain semi-essential amino acids an dhow many there are

Answer 11

8

Semi essential amino acids we can synthesis but we need something else from the diet, Often another Animo acid to synthesis them

Cystine can only be synthesised if we have methionine (an essential amino acid)

We can only synthesis tyrosine if there’s adequate amount of phenylalanine in diet, (an essential amino acid )

Question 12

what is Phenylketonuria (PKU)

Answer 12

Autosomal recessive disorder.

Cannot metabolise Phe due to (virtually) absent phenylalanine hydroxylase.

Excess Phe builds up in blood affecting brain development.

Heel-prick blood test in UK

Treatment is a low protein diet (Phe-restricted)

Question 13

how do peptide bonds form

Answer 13

between CO and NH of 2 amino acids
it produces the product of water

often known as dehydration synthesis of polypeptides

Question 14

what is the breaking of polypeptide bonds called

Answer 14

hydrolysis
as adds water across the bond

Question 15

what is an ex of the structure of insulin

Answer 15

Sulphydryl (-SH) groups of 2 cysteine molecules may be oxidised to form a disulphide bridge.

Question 16

what are the functions of proteins

Answer 16

Enzymes (e.g. amylase) (Anything ending is ase is an enzyme)

Energy source

Transport (e.g. haemoglobin) (eg na/k, channels, etc are all proteins)

Hormones (e.g insulin - released into blood by pancreas) (not all hormones are proteins but lots are)

Movement (e.g. actin & myosin - allow for shape changes in muscles allowing contraction)

Structure (e.g. collagen)

Storage (e.g. ferritin - stores iron in body)

Immunity (e.g. antibodies- for immune response)

Growth, differentiation and gene expression

Question 17

explain hormones in terms of protein function

Answer 17

Chemical messengers made in one part of the body which act on cells elsewhere, e.g. insulin

hormones can travel slow taking minuets to hours for response

Question 18

explain immune function in term of protein function

Answer 18

Antibodies are blood proteins which attack and inactivate bacteria.

Antibodies circulate in fluids, destroying targets

We have immune cells which manufacture proteins

Nervous system acts fast in seconds,

Question 19

explain structural functions of protein

Answer 19

Fibrin in blood (can turn to a solid to clot blood when needed)

Collagen gives skin and bone their elastic strength

Keratin gives hair and nails their strength

Question 20

nitrogen in protein foods is measured using what method, explain the method

Answer 20

Kjeldahl method.

Developed in 1883 by Johan Kjeldahl

Method used for UK food tables
Digestion
Neutralisation
Titration

Question 21

name some non amino nitrogen’s

Answer 21

cyanide, nitrate, nitrite, nitrogen gas, azo compounds

Question 22

what some of the amino nitrogen’s

Answer 22

• Amino acids
  most have nutritional value
  some excreted (no value)
• Peptides, e.g. carnosine
• Nucleic acids
  purines, pyrimidines (may be subtracted)
  (Some biological amines are derived from nucleic acids )

Question 23

why do children need more protein

Answer 23

as are growing

Question 24

explain plant protein compared to animal protein nutrition in the diet

Answer 24

Plant protein has less value then animal protein . As its easier to get all amino acids with eating animal protein. But you can achieve all amino acids with plant diet but need lots more plant material eaten

Question 25

If a child needs 1 g/kg/day milk/egg protein, they need how much of mixed animal and plant protein, and how much of just plant protein

Answer 25

1.5 g/kg/day mixed animal and plant protein OR 2.0 g/kg/day plant protein per day

Question 26

what are the UK DRV requirements for protein based on

Answer 26

on recommendations of FAO/WHO/UNU expert consultation in 1985. Values based on estimates of amount of high quality egg or milk protein required for N equilibrium. egg and milk protein are of highest quality

Question 27

whats the requirement of protein during pregnancy and lactation

Answer 27

Pregnancy: +6 g/day Lactation: +11 g/day for 0-6 months +8 g/day for 6+ months

Question 28

whats the requirements of protein in g per kg/day

Answer 28

0.75g protein per kg/day

Question 29

whats the upper limit on protein in g per kg/day

Answer 29

1.5g

Question 30

whats protein quality determined by

Answer 30

the profile of amino acids, in that food substance

Question 31

whats high quality protein

Answer 31

supplies all essential aa in the proportions needed by the body.

Question 32

what is lower quality protein

Answer 32

lacks adequate amounts of one or more essential aa.

Question 33

what is limiting amino acid protein quality

Answer 33

the essential aa present in the lowest amount relative to the reference protein.

Question 34

whys the quality of protein in mixed diets not so important

Answer 34

because of ‘complementation’ of different proteins Mixing protein sources increases the nutritional value of the mixture.

Question 35

how can we express quality of protein

Answer 35

by comparing amino acid scores The AA score doesn’t tell us what amino acid is missing tho

Question 36

what is biological value (BV)of protein

Answer 36

The proportion of absorbed protein retained in the body

Question 37

how can biological value of protein be calculated

Answer 37

N retained X 100 ------------------- N absorbed N is nitrogen

Question 38

examples of Biological values of protein in egg, meat, and wheat products

Answer 38

Egg, human milk 90 – 100 % Meat, fish 70 – 80 % Wheat protein 50 %

Question 39

what is net protein utilisation (NPU), and what does it take into account

Answer 39

The proportion of dietary protein retained in the body Takes into account digestibility of the protein

Question 40

how do we calculate Net protein Utilisation (npu)

Answer 40

BV = N retained X 100 ---------------- N intake NPU = BV x digestibility

Question 41

explain the indictor of protein quality: Protein Efficiency Ratio (PER)

Answer 41

The gain in weight of growing animals per gram of protein eaten.

Question 42

explain the indicator of protein quality: Relative Protein Value (RPV)

Answer 42

The ability of a test protein, fed at various levels of intake, to support nitrogen balance, compared with a standard protein.

Question 43

what is the chemical score

Answer 43

Based on chemical analysis of the protein. The amount of the limiting amino acid compared with the amount of the same amino acid in egg protein(egg white) reference protein in calc will be egg protein

Question 44

how do we calculate chemical store

Answer 44

mg of aa in 1g test protein -------------------------------------------------------- mg of aa in 1g reference protein (mg/g)

Question 45

what are DIAAS scores and how do we calculate them

Answer 45

Digestible Indispensable Amino Acid score. Recommended to replace Protein Digestibility Corrected AA score (PDCAAS) Reference protein = human milk DIASS (%) = 100 X (mg of digestible dietary IAA in 1g of dietary protein) in wheat for ex --------------------------------------------------------------------- (mg of the same dietary IAA in 1g of reference protein) IAA = indispensable amino acids DIAAS score will come across more often than other scores

Question 46

give ex of protein sources of high quality

Answer 46

wholemeal bread tortilla(maize) peanuts peas roast chicken baked cod meat Peanuts are high quality but not completely high quantity protein as limit an AA Plant protein generally has lower levels of total protein than animal sources

Question 47

where do protein sources in Scottish diet come from

Answer 47

Meat & meat products 38% Cereals & cereal products 23% Milk & milk products 13% Fish & fish dishes 8% Vegetables & potatoes 8% Vegetables & potatoes 8% Other(nuts and seeds) 7% So most of protein source is from high quality meat products Issue with red meat as protein is its levels of saturated fat and its sustainability, eg co2 emissions with growing that meat, etc

Question 48

the processing of some plant material can chanage the profile of what

Answer 48

limiting amino acids such as boiling rice can prevent lysine from being limited

Question 49

ae red meats higher or lower in protein than white meats

Answer 49

little higher

Question 50

explain how portion size should be taken into consideration when looking at protein content

Answer 50

Peanuts and meat / fish may have similar protein levels but portion size eat will be different, so will influence the protein levels. So take this into consideration

Question 51

processing of wheat does what to protein content

Answer 51

reduces the content

Question 52

how does toasting bread impact protein content

Answer 52

Toasting changes structure of bread which increases protein content, but isn’t always a healthier increase in protein

Question 53

do softer or hander cheese have more protein

Answer 53

harder the cheese the more protein content

Question 54

explain body composition between males and females

Answer 54

Women have more body fat than males to protect vital organs around pelvic area and for pregnancy males have more protein in body than females males hold more water in body than females males have less essential fat in body than females

Question 55

when do we lose bone mineralisation

Answer 55

We lose bone mineralisation as we age, starts in mid / early 20s in males and females In menopause females lose bone minerals much faster So why elderly females are at high risk of osteoporosis at old age

Question 56

when does muscle protein decline

Answer 56

Our peak lean tissue is at age 30, after that age our muscle protein content starts to decline as we age, once were 50 rate of decline dramatically increases, so is why we lose muscle at old age but increase body fat. This leads to sarcopenia. If we lose too much protein then simple activities become difficult The more muscles used at young age the longer it takes for muscle to reduce Diet and physical activity prevent this

Question 57

why do adults require protein

Answer 57

Adults require protein for repair processes And cos protein is constantly broken down and needing renewed Need calcium to replace calcium usage as the skeleton isn’t static, and to help repair bone

Question 58

our dietary protein intake must replace what

Answer 58

what's being excreted

Question 59

explain the overview of protein metabolism

Answer 59

10kg protein in body. Protein is constantly degraded and resynthesized. 70g endogenous protein of the 80g from dietary protein is secreted into intestinal lumen, these are then digested and absorbed, the amino acids and dipeptides then go back into this amino acid pool, which is then in equilibrium with the proteins being synthesised and metabolised. Small faecal loss of 10g a day. This is faecal nitrogen from undigested dietary protein and also from intestinal bacteria, and shed mucosal cells, and protective mucus Some amino acids are oxidised with carbon skeletons used for glucogenesis or used as fuel. And nitrogen is excreted as urea

Question 60

how can protein status be assessed

Answer 60

by measuring dietary intake of N compounds and output of N compounds. Measuring the intake could be done by food dairies

Question 61

nitrogen output sources

Answer 61

Urine Faeces Sweat Shed skin cells Hair & nail growth Blood & tissue loss Urine and feaces have greatest nitrogenous output

Question 62

what are urinary nitrogen metabolites, and name and explain some urinary nitrogen metabolites

Answer 62

urinary N metabolites = things in urine that nitrogen is lost via Urea: main N containing substance. Uric acid: product of breakdown of purine nucleotides. High blood concentrations lead to gout. Which blocks blood vessels (Uric acids associated with diabetes's and kidney stones and high sugar intake) Creatinine: breakdown product of creatine phosphate in muscle. (Amount of creatinine excreted depends upon muscle mass (so why more excreted in men than women)) Creatine: N containing organic acid – helps supply E to cells –mainly the muscle (originates from meat) Muscle loss increases when ill so you produce more creatinine and creatine

Question 63

what is nitrogen balance or equilibrium

Answer 63

Intake = excretion (N balance or equilibrium) So no change in total body content of protein, normal state in adults

Question 64

whats a positive nitrogen balance

Answer 64

Intake > excretion (positive N balance) Increase in body protein. Normal in pregnancy and growth

Question 65

whats a negative nitrogen balance

Answer 65

Intake < excretion (negative N balance) Gives net loss of nitrogen in body and loss in body protein

Question 66

when would pos and neg balances of nitrogen occur

Answer 66

Pos nitrogen balance required in childhood as there growing etc Neg nitrogen balance means ur losing lean tissue mass, so losing protein for muscle and is associated with illness, infection, trauma or inadequate intake When losing weight we don’t want to lose weight as well as muscle protein

Question 67

how can protein turnover be measured, and explain this

Answer 67

as half lives Half life is the teim taken for labelling to fall to half of its original peak. 1 half life = loss from 100 to 50 %, 2 half lives = 50% to 25% etc theres variation within protein half life

Question 68

explain dynamic equilibrium in terms of protein turnover

Answer 68

If an isotopically labelled amin acid is given then the process of turnover can be followed, The labelled amino acids are rapidly incorporated into the newly synthesised proteins and are gradually lost as proteins are broken down. The rate at which the label is lost from an individual protein depend son the rate at which the protein is broken down and replaced

Question 69

more on why do adults need protein

Answer 69

Continual catabolism of tissue proteins creates the requirement for dietary protein. Also, protein lost in mucus, enzymes and other proteins secreted into the GI tract. Requirements based on amount needed to maintain N balance. Intakes above requirements do not result in positive N balance, except after protein loss

Question 70

why do children need protein

Answer 70

Growing children should be in +ve N balance. Requirement for growth smaller than for protein turnover. Protein deficient child: grow slower so stunting of growth.

Question 71

protein requirements when Recovering from trauma (tissue loss, or surgery) or infection

Answer 71

Patients will be in +ve N balance. Do NOT require a diet richer in protein than usual. Semi-essential amino acids (e.g. proline & glutamine) may become more essential in diet

Question 72

why might people lose protein when ill

Answer 72

change and reduction in protein is due to the prolonged bedrest. So if someone unwell theyre confined to bed and protein loss can be due to wasting or atrophy of muscles that aren’t being used. So muscle protein s changed and reduced as normal but without the stimulus of exercise, less is being replaced so more lost Protein loss mediated by: Cortisol Cytokines