Final Review Flashcards
How does digestion and absorption of proteins happen in the stomach?
HCl uncoils protein strands and activates stomach enzymes: protein—-(Pepsin,HCl)—> smaller polypeptides
How does digestion and absorption of proteins happen in the small intestine and pancreas?
Cholecystokinin(hormone released in upper small intestine) triggers pancreas to secrete digestive enzymes once digestion products leave the stomach
Digestive enzymes are activated and continue to break down peptides into di-/tripeptides and free amino acids, which are taken up by intestinal cells
Ingested dietary proteins do or do not directly become body proteins(i.e. Become muscle).
Do not; Instead dietary proteins consumed supply the amino acids which are used for synthesis and numerous other function of protein in the body
The human body does or does not store protein or amino acids which means we need a continual source.
Does Not; we do need a continual source
What are some examples of multi-functionality of protein……
Enzymes, hormones, structural components
Immune function, transporters, fluid balance
Buffering, pH regulation, synthesis
Growth, energy
What are important factors dictating protein properly being used to fulfill physiological protein functions
When calorie and carbohydrate intake is sufficient then amino acids are used appropriately to meet the various function of protein
Factors that most influence the use of amino acids for body fuel or energy as contrasted to properly being used for the various protein function include: being in an energy deficit state; insufficient daily dietary carbohydrate intake
Proteins provide structure for:
cellular membranes, connective tissue(collagen), tendons, arterial walls (elastin); skin, hair, nails(keratin), transport proteins (albumin, lipoproteins), hemoglobin, immunoglobins, antibodies, hormones, enzymes
What is the average Protein turnover
synthesis and degradation of (250 g/d)
What is Net protein (or nitrogen) balance
Difference between rates of protein synthesis (PS) + breakdown(PB)
Goal during adulthood(non-pregnant or body building) is balance
What is a positive net protein(or nitrogen balance)
Protein synthesis>Protein breakdown = retaining protein
Needed for growth, pregnancy, recovery
What is negative net protein(or nitrogen balance)
Protein breakdown> protein synthesis= protein loss
In malnutrition, illness,injury, protein breakdown=increased breakdown to meet increasing energy needs
What are the different types Body proteins and where are they found?
Visceral protein: internal organs, blood cells, serum proteins; more rapid turnover compared to skeletal muscle protein
Somatice protein: skeletal muscle protein
Considerations for assessing protein status
Glycine is a precursor for…
Heme (O2 transport)
Purines (nucleic acid bases DNA/RNA)
Creatine (muscle contraction)
Tryptophan is a precursor of …..
niacin and serotonin
-nicotinic acid, NAD, NADP- coenzymes for redox reactions
-serotonin, neurotransmitter(sleep, mood, appetite)
Phenylalanine is a precursor of ..
Tyrosine, which is used in the synthesis of..
Melanin(pigments in hair,skin,eyes)
Epinephrine, Norepinephrine(neurotransmitters that stimulate CNS)
Thyroxine(thyroid hormones-metabolic rate)
Essential Vs Nonessential amino acids
Indispensable: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
Dispensible: Alanine, Aspartic Acid, Asparagine, Glutamic acid, Serine
The concept of “essential” amino acid references…
The inability of body for ‘de novo” synthesis
What is the essential amino acid pneumonic
TV TILL PM, Hi
T=threonine, V=valine, T=tyrosine, I=isoleucine, L=leucine, L=lysine, P=phenylalanine, M=methionine, Hi= histidine
What are examples of when dietary sources is required when endogenous synthesis can’t meet metabolic demand(need conditionally indispensable amino acids)
Physiological circumstances-immature organ (cysteine,proline)
Hypercatabolic conditions- infection, trauma, stress(glutamine
Disease states-CRF(serine)
How do we determine amino acid requirements?
Nitrogen balance studies
Direct amino acid oxidation (DAAO)
Indicator amino acid oxidation (IAAO)
Metabolic demand
What does FFM=BCM+ECF+ECS stand for?
Where, BCM= body cell mass(muscle, viscera, blood, brain cell matter)
Where, ECF= extracellular fluid(plasma and intersitial fluid)
Where, ECS= extracellular solids (organic/inorganic compounds(collagen; bone matrix)
Fat free mass includes…
Muscle, bone, fluid, all except for lipid
Lean body mass includes…
Essential body fat at 2-3%
-LBM=BCM(body cell mass) + ECF(extracellular fluid) +extracellular solids
What is considered essential body fat?
Brain, cell membranes, muscle, bone marrow
Tests of immunocompetence..
Can be used as functional indicators of PEM (supporting evidence only)
DCH stands for
Delayed Cutaneous hypersensitivity (DCH)
Intradermal injection of antigens
Local inflammatory response is impaired
Total Lymphocyte count can indicate
Reduced amounts of mature lymphocytes in malnutrition; TLV <1500 cells/mm3
Reference range: 200-3500 cells/mm3
What does Marasmus mean and how does it present
Means to “waste away”
Appears to be just skin and bones; wasted muscle mass and adipose tissue
Develops gradually
How does Kwashiorkor present?
Skin manifestations: rashes/pigment changes
thin , sparse hair
Presence of edema and some subcutaneous fat and muscle mass
Rapid onset
What is Protein energy malnutrition(PEM) and how does it affect the body?
Condition resulting from insufficient amounts of energy and protein
Can affect people of all ages
Most devastating in children: failure to grow, adverse LT effects on organs, brain, poor cognitive growth
What are the two things that are analyzed in nutrition focused physical exam
Malnutrition assessment
Nutrient deficiency assessment
What goes into estimating muscle mass using the CHI
Compare 24 hr urinary creatinine excretion with a standard base on height
CHI>80% normal
CHI= 60%- 80%- mild protein depletion
CHI- 40%-60%- moderate depletion
CHI<40%- severe depletion
What are the limitations of using urinary creatinine excretion
Slowly responds to changes in nutritional status
Accurate measurements require: normal kidney function and filtration, elimination or standardization of meat in diet
Collecting urine samples throughout the course of day
CHI may not always be accurate for elderly
What goes into measuring 3-methylhistidine excretion for muscle mass
Found in contractile proteins of skeletal muscle
Released during protein catabolism
Cannot be reused; excreted in urine
Excretion is an index of muscle catabolism
What are the limitations of measuring 3-methylhistidine excretion for muscle mass?
Not derived exclusively from muscle protein
Caution in states where protein oxidation is altered
What are three other ways that are indirect measures to assess protein status
Anthropometrics: mid-arm circumference +triceps skinfold thickness
Muscle weakness
Clinical signs (growth in infants and children)
What are the three majors sources of dietary protein
-Animal products
-plant products(grains, nuts/seeds, legumes and vegetables)
-exogenous proteins (EAA,NEAA and additional nitrogen)
Quality of protein:
-expression of its ability to provide the N+AA requirements for growth, maintenance and repair
Quality of protein is mainly determined by 2 factors:
-digestibility
-Amino acid composition
Define digestibility of protein:
-proportion of dietary N or amount of AA absorbed
-varies based of protein source, preparation, and other foods consumed with source
What is the major factor that affects plant protein digestibility:
-Plant proteins are often contained within cell walls that are resistant to human digestion
Define amino acid composition or profile:
-if intake of one single EAA in the diet is less than the requirement it limits the utilization of other AA and prevents normal rates of PS
-limiting AA=EAA found in the shortest supply relative to the amounts needed for protein synthesis in the body
Determines nutritional value of protein
What is a high quality/complete protein
-contains sufficient amounts of all EAA in quantities required by humans to prevent deficiency
Meat, poultry, fish, eggs, milk
Exception gelatin
What is a low quality/ incomplete protein
-low in one or more EAA to support human maintenance and growth
-plant proteins; vegetable, legumes, nuts, seeds, grains
Exception: quinoa, soy, buckwheat
How do you evaluate protein quality?
-Amino acid scoring
How do you determine amino acid score:
-amount of each EAA in 1 g of test protein/by “ideal” amount for that EAA in 1g of reference protein
EAA in the greatest deficit= limiting AA
What is the main problem with the amino acid score?
-Relies on a chemical procedure; fails to estimate digestibility of protein
What is the gold standard for assessing protein quality?
-protein digestibility corrected amino acid score
Amino acid score x true digestibility %
Accounts for AA composition and the fact that not all of the protein ingested is absorbed
What is the proposed concept for leucine as an additional indicator of protein quality?
-Dietary protein quality may refer to the ability of a protein source to support the increase in muscle protein synthesis(MPS) after ingestion
-Recent studies have suggested that leucine is the most potent AA responsible for stimulating postprandial MPS
Leucine rich protein sources such as…… are better at stimulating muscle growth than sources with less leucine such as…..
1.whey
2.soy
True or False? Plant proteins can be low in certain EAA. Thus, a vegan must consume “complimentary mixtures” of plant proteins to meet their EAA requirements.
-False
-Plant proteins are NOT missing EAA, just have lower amounts of certain EAA
-Complimenting with various sources or plant proteins just makes the diet more interesting
True or False? Different plant proteins must be consumed together in the same meal to achieve a high nutritional value(ie to be used)
-False
-Idea that all EAA must be consumed together in 1 meal or they cannot be used comes from a ridiculous abstract published in 1947
-not necessary to balance the AA profile at each meal
What is the EAR of protein?
-0.66g/kg/day
What is the RDA protein for adults?
0.8g/kg body weight
Higher protein diets-risks of overconsumption are…
-Increased risk of dehydration
-possible kidney damage
-possible bone damage (osteoporosis)
-increased CVD risk (lipid levels)
-increased cancer risk (red/processed meat)
-obesity
However evidence is insufficient to establish a UL
Higher protein diets-potential benefits include…
-increased muscle mass
-decreased CVD risk (TG levels, BP, body weight)
-better control of diabetes (PPBG and insulin response)
-weight loss/lower body weight (fat/LBM changes, increased satiety)
What are some conditions that affect protein/AA requirements
-pregnancy and lactation inc. protein needs
-severe burn injuries inc. protein needs
-infection inc. protein needs
-cancer inc. protein needs
Energy is required to sustain the body’s functions, what are some examples?
Respiration by lungs, digestion, maintenance of core body temp, beating of heat and blood circulation
-How do we sustain these body processes?
Eat, the energy in foods is released by oxidation
The heat produced is used to maintain core temperature