SAS #10: Protein Metabolism Flashcards
It’s in the mouth and has no effect on digestion
Saliva
In the stomach which denatures protein
HCl
In the stomach, which hydrolyzes peptide bonds
Pepsin
Pepsin makes _____
Large polypeptides
Amino acids that is in the small intestine, which hydrolyze peptide bonds
Trypsin
Chymotrypsin
Carboxypeptidase
Aminopeptidase
The intestinal lining uses _____ transport
Active
Dietary protein entering the stomach effects the release of the hormone ________ by stomach mucosa cells.
gastrin
its antiseptic properties kill most bacteria
Hydrochloric acid
its denaturing action “unwinds” globular proteins, making peptide bonds more accessible to digestive enzymes
Hydrochloric acid
its acidity leads to the activation of pepsinogen, which is the inactive form of the digestive enzyme pepsin
Hydrochloric acid
Gastrin’s presence causes both
hydrochloric acid and pepsinogen secretion
is the repetitive process in which proteins are degraded and resynthesized within the human body.
protein turnover
in the liver (nonessential amino acids only)
biosynthesis of amino acids
is the state that results when the amount of nitrogen taken into the human body as protein equals the amount of nitrogen excreted from the body in waste materials.
Nitrogen balance
TWO TYPES OF NITROGEN BALANCE:
protein degradation exceeds protein synthesis, the amount of nitrogen in the urine exceeds the amount of nitrogen ingested (dietary protein).
negative nitrogen balance
TWO TYPES OF NITROGEN BALANCE:
accompanies a state of “tissue wasting,” because more tissue proteins are being catabolized than are being replaced by protein synthesis.
negative nitrogen balance
TWO TYPES OF NITROGEN BALANCE:
Protein-poor diets, starvation, and wasting illnesses produce a negative nitrogen balance.
negative nitrogen balance
TWO TYPES OF NITROGEN BALANCE:
nitrogen intake exceeds nitrogen output, indicates that the rate of protein anabolism (synthesis) exceeds that of protein catabolism.
positive nitrogen balance
TWO TYPES OF NITROGEN BALANCE:
state indicates that large amounts of tissue are being synthesized, such as during growth, pregnancy, and convalescence from an emaciating illness.
positive nitrogen balance
FOUR WAYS to use the amino acids from the body’s amino acid pool:
75% of the free amino acids in a healthy, well-nourished adult go into ____________. Proteins are continually needed to replace old tissue (protein turnover) and also to build new tissue (growth).
protein synthesis
FOUR WAYS to use the amino acids from the body’s amino acid pool:
Amino acids are regularly withdrawn from the amino acid pool for the synthesis of nonprotein nitrogen-containing compounds. Such molecules include the purines and pyrimidines of nucleic acids (A, C, G, T, and U), the heme of hemoglobin, the choline and ethanolamine of phosphoglycerides, hormones such as adrenaline, and neurotransmitters such as norepinephrine, dopamine, and serotonin. The neurotransmitter serotonin is synthesized from the amino acid tryptophan, and the neurotransmitters norepinephrine and dopamine are synthesized from the amino acid tyrosine
Synthesis of nonprotein nitrogen-containing compounds.
FOUR WAYS to use the amino acids from the body’s amino acid pool:
When required, the body draws on the amino acid pool for raw materials for the production of nonessential amino acids that are in short supply. The “roadblock” preventing the synthesis of the essential amino acids is not lack of nitrogen but lack of a correct carbon skeleton upon which enzymes can work. In general, them essential amino acids contain carbon chains or aromatic rings not present in other amino acids or the intermediates of carbohydrate or lipid metabolism.
Synthesis of nonessential amino acids.
FOUR WAYS to use the amino acids from the body’s amino acid pool:
Because excess amino acids cannot be stored for later use, the body’s response is to degrade them. The degradation process is complex because each of the 20 standard amino acids has a different degradation
pathway.
Production of energy
In all the degradation pathways, the amino nitrogen atom is removed and ultimately is excreted from the body as ______.
urea
always involve two amino acids (one as a reactant and one as a product) and two keto acids (one as a reactant and one as a product). Two keto/amino acid pairs are involved, with the members of a pair having a common carbon-chain base.
Transamination Reactions
is a biochemical reaction that involves the interchange of the amino group of an a-amino acid with the keto group of an a-keto acid.
transamination reaction
The needed enzyme for a transamination reaction is an ______________.
aminotransferase
is a biochemical reaction in which an a amino acid is converted into an a- keto acid with release of an ammonium ion.
oxidative deamination reaction
Oxidative deamination occurs primarily in ______ and ______ mitochondria.
liver and kidney
Oxidative deamination of glutamate requires the enzyme ___________.
glutamate dehydrogenase.
is a cyclic biochemical pathway in which urea is produced, for excretion, using ammonium ions and aspartate molecules as nitrogen sources.
urea cycle
Three amino acids are involved as intermediates in the operation of the urea cycle: _____________
arginine, ornithine, and
citrulline
The “fuel” for the urea cycle. This fuel is formed from ammonium ion (from oxidative deamination), carbon dioxide (from the citric acid cycle), water, and two ATP molecules.
Carbamoyl Phosphate
The removal of the amino group of an amino acid by transamination/oxidative deamination produces an _____________ that contains the carbon skeleton from the amino acid. Because each of the 20 amino acids has a different carbon skeleton, each amino acid has a different degradation pathway for its carbon skeleton.
α-keto acid
Amino acids that are degraded to citric acid cycle intermediates can serve as glucose precursors and are called ________.
glucogenic
is an amino acid that has a carbon-containing product that can be used to produce glucose via gluconeogenesis.
Glucogenic amino acid
Amino acids that are degraded to acetyl CoA or acetoacetyl CoA can contribute to the formation of fatty acids or ketone bodies and are called ___________.
ketogenic
acid is an amino acid that has a carbon-containing degradation product that can be used to produce ketone bodies.
ketogenic amino acid
Amino acids that are degraded to pyruvate can be either ____________ or _______.
glucogenic or ketogenic
Two amino acids that are purely ketogenic
Leucine and lysine
amino acid that can be converted into glucose through gluconeogenesis.
KETOGENIC (2)
L,K
KETOGENIC (2)
Amino acids that are degraded to pyruvate
BOTH KETO & GLUCO (9)
pyruvate coverted to oxaloacetate (glucogenic) or acetyl CoA (ketogenic
BOTH KETO & GLUCO (9)
Y, F, I, A,G,C,S,TW
BOTH KETO & GLUCO (9)
are converted into ketone bodies.
GLUCOGENIC (9)
V, P, M, N, Q, E, D, H, R
GLUCOGENIC (9)
The classification of amino acids as essential or nonessential for humans roughly parallels the number of steps in their ___________ and the energy required for their synthesis.
biosynthetic pathways
Three of the nonessential amino acids—__________________— are biosynthesized by transamination of the appropriate a-keto acid starting material.
alanine, aspartate, and glutamate
The nonessential amino acid ______ is obtained from the essential amino acid phenylalanine in a one-step oxidation that involves molecular O2, NADPH, and the enzyme phenylalanine hydroxylase.
tyrosine
highly specialized cells whose primary function is to deliver oxygen to, and remove carbon dioxide from, body tissues.
Red blood cells
have no nucleus or DNA. Instead, they are filled with the red pigment hemoglobin.
Mature red blood cells
The life span of a red blood cell is about ______________.
four months (120 days)
The oxygen-carrying ability of red blood cells is due to the ________________.
protein haemoglobin.
The protein portion of Hemoglobin is called
globin
the prosthetic group (nonprotein portion) of hemoglobin is called
heme
The iron atom of heme becomes part of ________, an iron-storage protein, which saves the iron for use in the biosynthesis of new hemoglobin molecules.
ferritin
Degradation of heme begins with a ring-opening reaction in which a single carbon atom is removed. The product is called _____,
biliverdin
Biliverdin is converted later to
bilirubin.
is a colored tetrapyrrole degradation product present in bile
Bile pigment
green bile
biliverdin
red bile
Bilirubin
urine bile
Urobilin
dung bile
Stercobilin
is the condition that occurs when this balance is upset such that bilirubin concentrations in the blood become higher than normal. The skin and the white of the eyes acquire a yellowish tint because of the excess bilirubin in the blood.
Jaundice
caused by a deficiency of phenylalanine hydroxylase, is the most common clinically encountered inborn error of amino acid metabolism
Phenylketonuria (PKU)
is a rare (1:185,000), autosomal recessive disorder in which there is a partial or complete deficiency in branched chain α-keto acid dehydrogenase, an enzyme complex that decarboxylates leucine, isoleucine, and valine. These amino acids and their corresponding α keto acids accumulate in the blood, causing a toxic effect that interferes with brain functions.
Maple syrup urine disease (MSUD)
The disease is characterized by feeding problems, vomiting, dehydration, severe metabolic acidosis, and a characteristic maple syrup odor to the urine. If untreated, the disease leads to mental retardation, physical disabilities, and even death.
Maple syrup urine disease (MSUD)
refers to a group of conditions in which a defect in tyrosine metabolism results in a deficiency in the production of melanin.
Albinism
These defects result in the partial or full absence of pigment from the skin, hair, and eyes.
Albinism
are a group of disorders involving defects in the metabolism of homocysteine. The diseases are inherited as autosomal recessive illnesses, characterized by high plasma and urinary levels of homocysteine and methionine and low levels of cysteine.
Homocystinuria
is a rare metabolic condition involving a deficiency in homogentisic acid oxidase, resulting in the accumulation of homogentisic acid.
Alkaptonuria
The condition has three characteristic symptoms: homogentisic aciduria (the patient’s urine contains elevated levels of homogentisic acid, which is oxidized to a dark pigment on standing, large joint arthritis, and black ochronotic pigmentation of cartilage and collagenous tissue.
Alkaptonuria
