Ch 6: Proteins Flashcards
chem structure of amino acids
- composed of C, H, O, N
- central C, w H and unique side chain that gives it its functional properties
- amino group : NH2
- carboxylic acid group : COOH
essential and non essential amino acids
and how many of each?
9 essential
11 non essential
–non essential can sometimes become conditionally essential
dipeptide
two amino acids joined together by a condensation rxn bw amino group on one and the acid group of another
- most proteins are polypeptides = chains of 10 or more
primary structure amino acid sequencing
sequence of amino acids
tertiary structure amino acid sequencing
complex structure due to side chain properties ex hydrophillic
secondary structure amino acid sequencing
- determined by weak electrical attractions w/in chain
- results in twisting or folding of protein
quaternary structure amino acid sequencing
- interactions b/w polypeptide chains
- form subunits w/in a protein which each have diff structure and function
protein denaturation
disturbs stability
results in loss of functional ability
causes protein to uncoil and lose its shape
- accomplished by heat, acid or other conditions
ex. cooking an egg
protein digestion in the stomach
HCl uncoils proteins, exposing peptide bonds to pepsin
results in smaller peptides being left
protein digestion in small intestine
- pancreatic and intestinal proteases split polypeptides into tri- and dipeptides and amino acids
- enzymes of surface of sm intestinal cells hydrolyze the smaller peptides into amino acids that can be absorbed
protein absorption
- amino acids must be transported into intestinal cells by specific carriers
- once amino acids are in intestinal cells, they’re used for energy, synthesis of other compounds
- unused protein are sent to the liver via the bloodstream
does the digestive tract distinguish b/w proteins?
no. it treats them all the same. fair freak
protein synthesis
- info in DNA needs to be transcribed
- DNA acts as template for mRNA which copies the DNA
- mRNA leaves the nucleus, attaches to ribosomes which are the protein making machines of cells
- info on mRNA needs to be translated by tRNA
- tRNA collects amino acids from cell fluid and attaches them in sequence based on template
- protein is released
sequencing errors in protein synthesis
can result in mutations or proteins could have no function
- ex sickle cell anemia caused by protein sequencing error and results in Hb no longer being able to carry oxygen properly
name all the ROLES OF PROTEINS
- building materials (growth, maintenance, repair)
- hormones
- enzymes (catalyze reactions)
- fluid balance (attract water inside cells)
- acid/base balance (accept and release H+)
- transporters ex Hb or Na+/K+ pump
- antibody production
- provide energy and glucose
protein metabolism includes:
protein turnover
nitrogen balance
protein turnover
proteins are constantly being synthesized and degraded
- the body doesn’t store proteins like it does lipids and glucose
nitrogen balance
- equilibrium of nitrogen (N in = N out) positive nitrogen: N in > N out ex. growing negative nitrogen: N in < N out ex. injured significantly
amino acids are used to make ___?
- energy and glucose
- fat
- compounds ex neurotransmitters
deamination reactions
- removing amino groups (they contain N)
- results in NH3 being produced and the remaining carbon structure is a keto acid used for energy to make glucose or non essential amino acids
- in order for amino acids to be used they must be deaminated
converting ammonia to urea
this is how we rid our body of excess nitrogen
- NH3 is toxic, urea is less so
- liver combines ammonia w CO2 to make urea
- urea released into blood and is passed through kidneys
people who consume a lot of protein must _
must drink a lot of water to dilute and excrete urea from the body
protein quality is determine by
- digestability
- amino acid composition
digestability
depends on source of protein
animal: 90-99%
soy and legume: >90%
plant: 70-90%
amino acid composition
we do not make partial proteins
we must get all 9 essential amino acids
complementary proteins
means combining plant proteins to create full amino acids complement
PDCAAS
stands for: protein digestability-corrected amino acid score
- measures protein quality from low to high (0 -> 100)
examples of protein sources that rank high on the PDCAAS
egg white, ground beef, chicken, tuna, skim milk
Protein Energy Undernutrition (PEU)
- 1 in 4 children, poor growth
- most prevalent form of malnutrition globally
- results in infections (antibodies degraded)
- it is curable w rehydration, electrolytes, grad add protein to diet
what are the 2 forms of PEU most often found in children
Maramus: children less than 2 yo
Kwashiorkor: children 1-3 yo , results usually when weaned off of breast milk
other health effects of amino acids
- cardiovascular disease (animal protein w sat. fat & chol)
- colon cancer from processed meat
- osteoporosis (increased ca2+ excretion)
- weight control (satiety) , could result in other nutrient deficiencies
- kidney disease only if you have weak ones already
AMDR for protein
10-35% total energy intake
RDA for protein
0.8 g/ kg body weight/day
protein supplementation
powders: do not build muscle unless taken when exercising
- excess load on kidneys
single amino acid supp: no benefit, toxicity, can lead to deficiencies in other amino acids
nutritional genomics
look at how genes affect interaction bw diet and disease and how nutrients affect our genes
sarcopenia
divided into what 2 categories
- brought on by frailty
2 categories:
myopenia: loss of muscle qty (1%/yr)
dynapenia: loss of muscle strength (3%/year)
what is the optimal dose of protein?
1.62-2.2 g/kg bodyweight/day
what is the goal of protein supplementation?
to increase muscle protein syntheis
