Chapter 5: Proteins Flashcards by isabelle

proteins are compounds composed of _____ (4) which are arranged into amino acids linked in a chain

carbon, hydrogen, oxygen, nitrogen

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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

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a protein is made up of _____ different amino acids, each with a different side group

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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

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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

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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

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amino acid classification - chemical property

have one amino and one carboxyl group

neutral amino acids

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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

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neutral amino acids - types

have aromatic rings attached

ex: phenylalanine, tyrosine, and tryptophan

aromatic amino acids

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neutral amino acids - types

contain sulfur as a substituent

ex: cysteine, methionine, and cystine

sulfur-containing amino acids

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neutral amino acids - types

have an additional NH2 group attached

ex: aspartic acid and glutamic acid

acidic amino acids

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neutral amino acids - types

amino nitrogen that forms part of a ring structure

ex: proline and hydroxyproline

imino acid

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protein - metabolism

can be catabolized/broken down to form glucose or glycogen

glucogenic amino acids

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protein - metabolism

glucogenic amino acid yield _____ components or pyruvate

tricarboxylic acid cycle

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protein - metabolism

alanine, serine, glycine, cysteine, aspartic acid, asparagine, glutamic acid, glutamine, arginine, histidine, valine, methionine, threonine, and proline

purely glucogenic

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protein - metabolism

can be catabolized to form ketone bodies

ketogenic amino acids

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ketogenic amino acids yield _____ or _____

acetyl coa or acetoacetate

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protein - metabolism

leucine and lysine

purely ketogenic

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protein - metabolism

isoleucine, phenylalanine, tyrosine, and tryptophan

both ketogenic and glucogenic

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amino acids characteristics

ability to form mirror images called d and l forms

stereoisomerism

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amino acids characteristics

nature of amino acid refers to having both the amino and carboxyl groups, which can regulate pH

amphoteric

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proteins classification - acc to physicochemical properties

refers to degraded amino acids upon hydrolysis

ex: albumin, collages, elsatin, myosin

simple proteins

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proteins classification - acc to physicochemical properties

pertain to simple proteins combined with a nonprotein

ex: mucoproteins, glycoproteins, lipoproteins

compound proteins

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proteins classification - acc to physicochemical properties

substances resulting from decomposition of simple and conjugated proteins

ex: peptides, peptones, and proteoses

derived proteins

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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