Chapter 5: Proteins Flashcards
proteins are compounds composed of _____ (4) which are arranged into amino acids linked in a chain
carbon, hydrogen, oxygen, nitrogen
have the same basic structure - a central carbon atom with a hydrogen (H) group, an amino group (NH2), and an acid group (COOH) attached to it
amino acids
a protein is made up of _____ different amino acids, each with a different side group
20
amino acid classification - essentiality
are those that the human body cannot make at all or cannot make in sufficient amount to meet its needs
ex: phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, lysine, leucine
essential amino acid
amino acid classification - essentiality
are those whose rate of synthesis in the body are inadequate to support growth and are needed by young animals
ex: arginine, histidine
semi-essential amino acids
amino acid classification - essentiality
are those that can be synthesized in the body in sufficient amounts
ex: alanine, asparagine, aspartic acid, cystine, cystine, glutamic acid, glutamine, glycine, hydroxyproline, hydroxylysine, proline, serine, and tyrosine
nonessential amino acids
amino acid classification - chemical property
have one amino and one carboxyl group
neutral amino acids
neutral amino acids - types
have straight branched chains of carbon atoms, and other substituents
ex: glycine, alanine, valine, leucine, isoleucine, serine, threonine
aliphatic amino acids
neutral amino acids - types
have aromatic rings attached
ex: phenylalanine, tyrosine, and tryptophan
aromatic amino acids
neutral amino acids - types
contain sulfur as a substituent
ex: cysteine, methionine, and cystine
sulfur-containing amino acids
neutral amino acids - types
have an additional NH2 group attached
ex: aspartic acid and glutamic acid
acidic amino acids
neutral amino acids - types
amino nitrogen that forms part of a ring structure
ex: proline and hydroxyproline
imino acid
protein - metabolism
can be catabolized/broken down to form glucose or glycogen
glucogenic amino acids
protein - metabolism
glucogenic amino acid yield _____ components or pyruvate
tricarboxylic acid cycle
protein - metabolism
alanine, serine, glycine, cysteine, aspartic acid, asparagine, glutamic acid, glutamine, arginine, histidine, valine, methionine, threonine, and proline
purely glucogenic
protein - metabolism
can be catabolized to form ketone bodies
ketogenic amino acids
ketogenic amino acids yield _____ or _____
acetyl coa or acetoacetate
protein - metabolism
leucine and lysine
purely ketogenic
protein - metabolism
isoleucine, phenylalanine, tyrosine, and tryptophan
both ketogenic and glucogenic
amino acids characteristics
ability to form mirror images called d and l forms
stereoisomerism
amino acids characteristics
nature of amino acid refers to having both the amino and carboxyl groups, which can regulate pH
amphoteric
proteins classification - acc to physicochemical properties
refers to degraded amino acids upon hydrolysis
ex: albumin, collages, elsatin, myosin
simple proteins
proteins classification - acc to physicochemical properties
pertain to simple proteins combined with a nonprotein
ex: mucoproteins, glycoproteins, lipoproteins
compound proteins
proteins classification - acc to physicochemical properties
substances resulting from decomposition of simple and conjugated proteins
ex: peptides, peptones, and proteoses
derived proteins
proteins classification - acc to shape
coiled or ellipsoidal-shaped amino acids
ex: insulin, albumin, globulin
globular proteins
proteins classification - acc to shape
helical peptide chains
ex: elastin, fibrin, collages
fibrous proteins
proteins classification - acc to amino acid content
all the essential amino acids as with the case of all animal proteins except gelatin
complete proteins
proteins classification - acc to amino acid content
contain all the essential amino acids but in limited amounts to support growth
ex: gliadin and hordein
partially complete proteins
proteins classification - acc to amino acid content
lack one or more essential amino acids; cannot maintain life nor support growth
ex: zein and gelatin
incomplete proteins
protein functions
proteins provide amino acids needed for the synthesis of specific cellular tissue proteins and other essential nitrogen-containing substances
ex: enzymes, hormones
growth and maintenance of tissues
protein functions
some amino acids can be converted to glucose via _____
gluconeogenesis
protein functions - specific physiologic roles
refers to sulfur-containing amino acid formed from methionine and is abundant in human milk
needed for retinal and visual function, brain development, and stability of central nervous activity
taurine
protein functions - specific physiologic roles
formed from methionine and lysine and converts acyl compounds (products of fat metabolism) to less toxic forms and removed them from the cell
carnitine
protein functions - specific physiologic roles
exerts oncotic pressure for water balance
albumin
protein functions - specific physiologic roles
transport lipids
lipoproteins
protein functions - specific physiologic roles
involved with immune response
globulins
protein functions - specific physiologic roles
necessary for blood clotting
fibrinogen
protein functions - specific physiologic roles
both are for muscle contraction
actin and myosin
protein - digestion
in the ____, mechanical digestion of proteins occurs when the food is chewed
mouth
protein - digestion
chemical digestion of protein begins in the _____ with the help of the enzyme pepsin
stomach
enzymes that helps chemical digestion of protein
pepsin
protein - digestion
provides the degree of acidity necessary to convert inactive pepsinogen to its active form pepsin
hydrochloric acid
protein - digestion
chon digestion proceeds with trypsin, chymotrypsin carboxypeptidase from the _____, and aminopeptidases and dipeptidase from the _____
pancreas; intestine
end product of chon digestion are the amino acids that are ready to be absorbed by the
intestinal mucosa
protein absorption
amino acid absorption occurs mostly by _____ in the proximal portion of the _____, requiring carrier, energy, pyridoxine (vitamin b6) and manganese (mn)
active transport; small intestine
chon metabolism
amino acids pass through the portal vein into the liver, which maintains normal levels of amino acid nitrogen in the blood from _____ mg/dL
4-6 mg/dL
chon metabolism - anabolism
is present in the cell nucleus and provides the genetic blueprint
deoxyribonucleic acid (dna)
chon metabolism
involves the incorporation of amino acids in the synthesis of tissue proteins
anabolism
chon metabolism
sources of amino acids in the body can either be _____ (from dietary protein) or _____ (from tissue protein breakdown in the body)
exogenous; endogenous
chon metabolism - anabolism
is carried from the dna to the site of protein synthesis in the ribosome by messenger ribonucleic acid (mRNA)
genetic code
chon metabolism - anabolism
molecules that are present in the cytoplasm then transport the amino acids based on the code in mRNA
transfer RNA
chon metabolism - anabolism
is formed through the addition of one amino acid at a time in the ribosomes
polypeptide chain
chon metabolism - anabolism
when the chain is complete, the protein is release into the _____
cytoplasm
chon metabolism
(tissue protein breakdown) involves the breakdown of amino acids into their component parts
ex: formation of glucose or ketone bodies whenever necessary
catabolism
chon metabolism - catabolism
the breakdown of amino acids result to 2 components
nitrogenous and a non-nitrogenous residue
chon metabolism - catabolism
deamination or removal of the nitrogenous portion to form ammonia that is excreted in the urine; occurs in the liver and kidneys
nitrogenous (nh2)
chon metabolism - catabolism
or the transfer of the nitrogenous group to a keto-acid residue to form another nonessential amino acid
transamination
chon metabolism - catabolism
chief nitrogenous end-product of protein metabolism
occurs through the urea cycle
formation of _____ the urea cycle, ammonia in the blood (toxic) combines with ornithine to form urea (nontoxic) that is excreted in the urine; occurs in the liver and involves the amino acid arginine
urea
urea cycle is also known as
ornithine cycle
urea cycle occurs in the
liver
chon metabolism - catabolism
the carbon skeleton can form either carbohydrates (for glucogenic amino acids) or fat (for ketogenic amino acids)
non-nitrogenous or keto-acid residue
-synthesis and repair of tissues
-source of energy
-formation of TAG or fat in the adipose tissue
-formation of ketone bodies
-source of glucose
fates of amino acids
protein - supplementary value
amino acid that is inadequate in a food item
limiting amino acid
protein - supplementary value
is the pairing with another protein, which can supply the lacking amino acid
supplementary value
is the amino acid found in short supply relative to need
limiting amino acid in protein
limiting amino acid
soybeans and rice
methionine
limiting amino acid
legumes
methionine and tryptophan
limiting amino acid
green leafy vegetables
methionine
limiting amino acid
cereal grains
lysine and threonine
nitrogen balance1 g nitrogen is equivalent to _____ g dietary protein
6.25
nitrogen balance
at nitrogen equilibrium
n intake = n output
nitrogen balance
at positive nitrogen balance
occurs in growth, pregnancy, rehabilitation from illness
n intake > n output
nitrogen balance
at negative nitrogen balance
occurs in illness, malnutrition
n output > n intake
protein - recommended intake
proteins must constitute _____ of the total energy requirement
10-15%
protein sources
include meat, fish, poultry, egg, milk, and cheese
animal sources
protein sources
include soybeans, cowpeas, lentils, and grains
plant sources
protein - health effects
-burden on liver for ammonia detoxification and kidneys for nitrogen excretion
-obesity
-depressed calcium absorption
-hypercholesterolemia
-heart diseases (meat sources are high in saturated fat)
-cancer (protein intakes from meats, carcinogens)
-weight control (protein-rich foods are also high in fat sources)
excess
protein - health effects
protein malnutrition
affects ages 1-6 y/o; severe protein deficiency
kwarshiorkor
protein - health effects
clinical manifestations
-presence of bilateral pedal edema
-muscle wasting in the gluteal region
-loss of subcutaneous fats
-prominence of bony structures particularly over the thorax
-appetite loss
-pale, thin, peeling skin
-hair sparse
-infection
deficiency
