chapter 6 Flashcards
protein consumption around the world
canada: >97% of canadians consume protein above amdr
- 62% of protein comes from animal products
- most of world relies on plant protiens
functions of protein in the body
- cell growth, repair, maintenance
- structural and mechanical functions (collagen and keratin)
- immune proteins
- enzymes
- hormones (regulate body processes, chemical messengers)
- transport (carrier molecules)
- acid base balance (buffers)
- source of energy (only if necessary, deamination)
- fluid balance (blood proteins attract fluid, intracellular or extracellular)
what are proteins
- large complex molecules made of amino acids
- primary source of nitrogen in diet
- 20 amino acids
elements in amino acids
- C H O N and sometimes S
parts of an amino acid
- carboxyl group (COOH)
- amino group (NH2)
- hydrogen
- side R group
types of amino acids
- essential: must come from diet, cant be made in the body
- nonessential: can be made in the body, made by transferring amino groups
- conditionally essential: essential under certain circumstances
transamination
- method to make nonessential amino acids
-
BCAA
- beneficial to men who perform heavy weight training
- also induced pro inflammatory gene expression in visceral adipose tissue under normal and low protein conditions
protein synthesis
- directed by cellular DNA
- draws on amino acid pool - short term storage of amino acids in cellular fluids
how are proteins made?
- transcription and translation
- combine using peptide bonds
types of peptides
- dipeptide
- tripeptide
- polypeptide
protein structure
- primary structure: sequence of amino acids
- secondary strucutre: alpha helix and beta pleated sheet
- tertiary structure: twists and turns, 3D shape
- quaternary structure: 2+ proteins interacting together,
denaturation
- heat, acid, mechanical agitation
digestion of proteins in stomach
- digestion begins in the stomach
- HCl breaks down protein structure
- HCl activates pepsinogen to pepsin
- pepsin: enzyme thatbreaks down proteins into polypeptides
- 10-20% of digestion
protein digestion in small intestines
- 90% completed before ileum
- protease = peptidase
- pancreatic proteases catalyze hydrolysis of peptides in intestine
- intestinal enzymes called peptidases complete digestion of proteins into single amino acids
absorption of amino acids
- small intestine
- plasma membrane of absorptive cells absorbs amino acids
- inside intestinal cells short peptides further split into amino acids
- amino acids abosrbed into bloodstream
limiting amino acid
imits amount of protein that can be synthesized (smallest amount of a certain amino acid available)
protein quality
- complete protein: supply all essential amino acids - animal proteins, soy proteins
- incomplete proteins: low in 1+ essential amino acids - most plant proteins
quality of protein
- high quality: complete protein bc contains all essential amino acids and is easy to digest and absorb
- low quality: incomplete protein bc lacking 1+ essential amino acid
complementary proteins
- if 2 incomplete proteins = complete protein
- if diet has no animal protein, combine grains and legumes, legumes and nuts, eat a variety of foods
complementary foods
- beans and rice
- beans and corn/wheat tortillas
- rice and lentisl
garbanzo beans a sesame paste - pasta with beans
- peanut butter on bread
protein quality determining factors
- amount of essential amino acids
- protein digestibility: animal and soy foods are highly digestible, other plant foods are less digestible
protein digestibility corrected AA score
- based on a scale of 0-100
- max value: 100 (animal foods)
- soy protein: 94
- legumes: 50-60
protein metabolism
- to enable body to use amino acid, amino group must be removed
extracting energy from protein
- HCl denatures strucutre
- enzymes split protein into peptides then amino acids
- split off amino group - converted to urea for excretion
- carbon skeleton enters breakdown pathways
- end products: ATP, H20, CO2, urea
nitrogen balance
- nitrogen intake (g) = nitrogen output (g) - eqm
- positive nitrogen balance: nitrogen intake > nitrogen output
- negative balance: nitrogen intake < nitrogen output
protein turnover
- recycling of body proteins
- 300g/d synthesized; 200g/d from recycled amino acids
adequate protein intake
- depends on: activity level, age, health status
recommended protein intake
- adult RDA = 0.8g/kg body weight
- infant RDA: 1.5g/kg body weight
athlete recommended intake
- nog veg endurance athletes: 1.2-1.4g/kg
- veg endurance: 1.3-1.5g/kg
- non veg resistance: 1.6-1.7g/kg
- veg resistance athletes: 1.7-1.8g/kg
how much protein do we wat
- 10-35% of total energy intake
- daily intake around 16% of total energy for canadians
protein energy malnutrition
- 49% of kids under 5 associated with pem
- most common in small kids
- most common areas of famine or chronically poor quality foods
- characterized by: failure to grow, increased vulnerability to medical problems
kwashiorkor
- affects toddlers
- usually develops from acute PEM
- child on marginal diet, has illness can trigger
- edema
- low body fat, high water
- no albumium to transport fat, accumulates in liver
- rounded bellies
marasmus
- chronic pem
- slow to develop
- severely inadequate diet
- wasting of muscles
- no body fat
- lethargic
- extreme stunting of growth
- inability to regulate body temp
kwashiorkor vs marasmus
- acute vs chromic
- different physiological responses to breakdown of body protein in response to food deprivation
- inherent differences in protein metabolism after recovery
PEM in canada
- poverty in inncer cities or isolated rural areas
- elderly
- homeless
- eating disorders
- drug/alchohol addiction
- aids/cancer
too much protein risks
- heart disease
- bone loss
- kidney disease
genetic conditions related to pem
- celiac disease: cant digest gluten, results in poor absorption of other nutrients
- cystic fibrosis: thick mucus prevents digestive enzymes from reaching small intestines, poor absorption of nutrients
