Protein Flashcards
energy in protein
17KJ
what is protein made of
polypeptides: long chain amino acids
amino acids?
Nitrogen group + carbon skeleton (acid group, hydrogen + side chain)
what determines the properties of an amino acid
the side chain
how many amino acids are there
20
how many essential amino acids
8
Essential amino acid
body can’t manufacture, needs to come from diet
e.g. lysine, tryptophan, valine
How are non-essential amino acids produced
Via transamination of dietary amino acids at a required rate
Conditionally essential amino acids
must come from diet at certain times to meet requirements
Histidine (growth and development)
glutamine and arginine (trauma and infection)
tyrosine in PKU
Non-essential amino acids
produced by body e.g. Alanine, glycine, serine, tyrosine
3 types of essential amino acids
- cells cannot make carbon skeleton
- cells lack enzymes to attach amine group to carbon skeleton
- cells cannot manufacture EAA at a fast enough pace to match requirements
PKU
Phenylketonuria= inborn error in metabolism. Cannot convert phenylalanine to tyrosine via transamination. (lack enzyme phenylalanine hydroxylase)
What happens to amino acids
- synthesis of proteins for cell structure, immune function , enzymes, hormones and other essential functions
- E production from amino acid carbon skeleton – Urea
- glucose production (gluconeogenisis) – Urea
- synthesis of non-protein N containing products
- ketone production (fat production in exess)– Urea
Deamination
Nitrogen is stripped: used for other uses then to make proteins.
peptide bond
Covalent.
between carboxyl group of 1 amino acid and the amine group of another
O
||
C--N
|
HPrimary protein structure
simple sequence of AA
secondary structure
shape of protein caused by weak hydrogen bonding b/w C=O and N-H groups within chain
(alpha helix and beta helix)
tertiary structure
3D folding from interaction b/w R groups determining overall shape and function
Quartenary
Interactions b/w 2 or more polypeptides chains
protein= fibrous, globular or conjugated
Protein denaturation
Altering the 3D structure.
protein functions
- Enzymes from DNA
- Ridgid structure and contraction
- transport nutrients
- Hormones and neurotransmitters
- acid- base balance
- DNA product formation: DNA expression into a functional body protein
- Contributing to immune function
- Fluid balance (edema)
9 . glucose formation (gluconeogenesis) - providing E.
Edema
swollen tissue- fluid remains in tissue.
Complete protein
protein that will provide all EAA in right amount in one food.
Incomplete protein
protein that doesn’t provide all EAA
Limiting AA
those EAA that are missing from food
measure of protein quality
- Biological value
- protein efficiency ratio
- chemical score
- protein digestibility corrected Amino acid score
High quality
high amount of EAA
Biological value
How effectively protein from food is converted to body tissue
measure: Urinary % and fecal nitrogen
measure of protein quality
- Biological value
- protein efficiency ratio
- chemical score
- protein digestibility corrected Amino acid score
Biological value
How effectively protein from food is converted to body tissue
measure: Urinary % and feacal nitrogen
low biological value
high excretion= body will not retain all the nitrogen absorbed.
protein efficiency ratio
weight gain (g)/ protein consumed (reflects BV because growth and weight gain depends on uptake in body tissue)
Chemical score
mg of limiting AA in 1g of the test food mg of that AA in 1g of the reference food.
protein digestibility corrected Amino acid score
Chemical score * digestibility
Complementary proteins
foods that can be combined to supply all limiting AA’s
Gluten
general term to describe a variety of proteins found in wheat, barley, rye and oats.
2 groups: glutelins and prolamines
Kwashiorkor
protein malnutrition. minimal protein intake (moderate E deficit)
edema (large stom)
growth impairment
fatty liver
marasmus
protein and energy malnutrition. (minimal protein and Energy)
sever growth impairment, wasting muscle,
Food allergies
immune response ( non-dose dependent) stimulate white blood cells to produce antibodies- mostly immuglobin E
Food intolerance
dose dependent
- What are 3 factors that determine amino acid essentiality?
- can’t make carbon skeleton
- lack the enzymes to attach amine group onto C-skeleton
- can’t manufacture at a fast enough rate
e.g lysine, tryptophan, valine.
non-essential body can synthesise (transamination- can take amine group and transfer it to make a new essential amino acids)
e.g. alanine, glycine
conditionally- glutamine, argine , histamine.
????
What is the difference between essential and non-essential amino acids and provide two examples of each.
8- essential have to get from diet
1. can’t make carbon skeleton
2. lack the enzymes to attach amine group onto C-skeleton
3. can’t manufacture at a fast enough rate
e.g lysine, tryptophan, valine.
non-essential body can synthesise (transamination- can take amine group and transfer it to make a new essential amino acids)
e.g. alanine, glycine
conditionally- glutamine, argine , histamine.
- How was the RDI for protein determined?
Based on the biomarker of nitrogen balance.
+ve balance= take in more then what you excrete.
-ve balance= excreting more then what you take in.
Nitrogen (g) x 6.25 = protein (g) (nitrogen =16% of the weight of AA)
incomplete proteins
doesn’t have all the essential amino acids
complementary proteins
food sources that complement each other to provide all the essential amino acids
what is a limiting amino acid
the amino acid that is found in the lowest concentration. in protein.
Describe the fate of proteins from ingestion to absorption of monomers
mouth- mechanical digestion- no chemical
SI- chemical- HCL (denatures unravelling loses structure- becomes exposed) and pepsinogen (by chief cells) into pepsin by HCL breaks it up.
gastrin- signals for HCL to be released from parietal cells.
Describe the fate of proteins from ingestion to absorption of monomers
mouth- mechanical digestion- no chemical
Stom- chemical- HCL (denatures unravelling loses structure- becomes exposed) and pepsinogen (by chief cells) into pepsin by HCL breaks it up.
gastrin- signals for HCL to be released from parietal cells .
SI- main site of absorption- Chyme signals the release of secretin and CCK which stimulate pancreas to release proteases trypsin, chymotrypsin and carboxypeptidase ( in pancreatic juice) – break down into shorter peptides and amino acids
- Describe the fate of amino acids found in the amino acid
pool
- protein synthesis ( for cell structure, immune function, enzymes, hormones and other essential functions)
- E production (from amino acid carbon skeleton) `4Kcal/g
- gluconeogenesis : glucose production
- ketone production
- synthesis of non-protein containing compounds.
Describe the fate of proteins from ingestion to absorption of monomers
mouth- mechanical digestion- no chemical
Stom- chemical-pre-digested- HCL (denatures unravelling loses structure- becomes exposed) and pepsinogen (by chief cells) into pepsin by HCL breaks it up. Pepsin cleaves the peptides into shorter fragments.
gastrin- signals for HCL to be released from parietal cells .
SI- main site of absorption- Chyme signals the release of secretin and CCK which stimulate pancreas to release proteases trypsin, chymotrypsin and carboxypeptidase ( in pancreatic juice) – break down into shorter peptides and amino acids
- Compare Marasmus and Kwashiorkor. List the causes, the characteristic signs, and the health consequence long-term
Kwashiorkor: protein malnutrition, minimal protein intake but modedate E deficit.
- edema around stom
- growth impairment
- fatty liver.
Marasmus: protein and E malnutrition.
- sever growth impairment, wasting muscle, develops gradually.
- What are 5 functions of proteins in the body? Trace amino acids absorbed from the diet to each of these functions
- enzymes from DNA: catalyse metabolic processes
- rigid structure and contraction: collagen tissue bones, keratin in fingernails, muscle fibres, cilia, spindle fibres.
- transport of nutrients: membrane transport proteins, transport of vit/ minerals in blood, lipoprotein transport FA and cholesterol
- Hormone and neurotransmission
- Acid base balance- proteins act as buffers, can receive/ donate H+
- DNA product formation: DNA expression into a functional body protein.
- contributing to immune function
- fluid balance: plasma albumin and globulins attract H2O back into the capillary for venous return.
- forming glucose: gluconeogenesis.
- providing energy
once absorbed taken via portal vein to liver:
- protein synthesis
- energy production after deamination
- in gluconeogenesis after deamination
- What are high and low BV proteins? Provide two examples of each
high: foods that provide AA in amounts consistent with the bodies needs. body will retain much of the absorbed nutrients.
egg white= BV of 100%
Whey protein= 100%
low: foods that provide AA not consistent with the bodies needs, body wont retain all the absorbed= high excretion.
soy= 74%
Wheat /peas /dry beans= 55%
corn/ rice= 60%
Nitrogen retained (g) / Nitrogen absorbed (g) x 100 Measure takes into account urinary % and fecal nitrogen excretion
- Describe the four structures of proteins. What structures
determine function?
primary: simple sequence of AA
secondary: shape of protein molecules caused by weak hydrogen bonding between C=O and N-H groups within chain (alpha helix, beta sheets)
tertiary: 3D folding from interaction between R groups determining overall shape and function
quartenary: interactions between 2 or more polypeptide chains = protein= fibrous, globular or conjugated.
- What is the difference between food allergies and food
intolerances? Provide two examples of each.
Allergies: immune response
- Ceoliac: auto-immune gluten allergy disease. ( increase in production of zonalin in the presence of gluten which loosens the tight junctions between enterocytes.
- gluten Ataxia
- dermatitis herpetiformis
intolerance: dose dependent, nerve stimulating response.
1. gluten sensitivity
2. wheat allergy (respiratory/ contact)
- How is protein quality determined? (criteria and
methodology)
( high intake not nessasarily best option)
- Biological value: how effectively protein from food is converted in body tissue.: if more EAA: higher BV
- protein efficiency ratio (PER) weight gain/ protein consumed
- chemical score (amount of limiting AA)
- protein digestibility corrected AA score: chemical score * digestibility.
- Why is it important to consume high quality protein?
a high quality= a high amount of EAA.
- What happens for DNA expression when low quality protein or too little protein is consumed in the long term?
?low DNA product formation?
- What are deamination and transamination? Describe the
processes and when they occur.
deamination: removal of the Amine group. ( gives pyruvate/ intermediate of the CAC/ forms oxaloacetate) ammonia excreted via urine.
1. Removal of the amine group from an amino acid
(vitamin B6 is required)
2. Amine group converted to ammonia
3. Ammonia converted to urea in the urea cycle (in liver)
4. Urea filtered in the kidney and excreted via urine
transamination: forms no-essential amino acids. transfer of an anime group from 1 AA to a carbon skeleton ( enzymes and co-factors required).
• Enzymes and cofactors are required:
– Transaminases:
•Alanine aminotransferase (ALT)
•Aspartate aminotransferase (AST)
– Vitamin B6
- Why is it important to consume high quality protein?
a high quality= a high amount of EAA.
