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Lecture: Chemical Pathology > Amino Acids & Proteins > Flashcards

Amino Acids & Proteins Flashcards

1
Q

basic structure of amino acid

A

at least one amino group (NH2) and one carboxyl functional group (COOH) bonded to an alpha-carbon

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2
Q

amphoteric

A

molecule that is both an acid and a base

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3
Q

peptide bond

A

a covalent bond formed between the amino group of one amino acid and the carboxyl group of another amino acid

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4
Q

how are amino acids amphoteric?

A
  • amino group can accept a proton to form NH3+ (basic)
  • carboxyl group can donate a proton to form COO- (acidic)
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5
Q

polypeptide

A

a chain of amino acids linked together by peptide bonds

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6
Q

how does the body obtain amino acids?

A
  • half of amino acids cannot be produced in vivo at a rapid enough rate to support growth
  • essential amino acids supplied by diet in form of proteins
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7
Q

metabolism of amino acids

A
  • stomach: gastrin stimulates secretion of HCl and proteolytic enzymes to promote denaturation of proteins and to catalyze hydrolysis into polypeptides
  • small intestine: HCl is neutralized by sodium bicarbonate secreted from the pancreas because of secretin to protect the intestinal lining
  • secretin and cholecystokinin stimulate the release of proteolytic enzymes which continue the process of digestion by hydrolyzing polypeptides into constituent amino acids
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8
Q

essential amino acids

A

histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

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9
Q

difference between essential and nonessential amino acids

A
  • essential: cannot be synthesized in vivo at a fast enough rate and must be acquired through dietary intake
  • nonessential: body can synthesize adequate amounts and additional dietary intake is unnecessary
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10
Q

nonessential amino acids

A

alanine, asparagine, aspartic acid, glutamic acid, selenocysteine, serine

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11
Q

aminoacidopathies

A
  • inborn errors of metabolism that inhibit the body’s ability to metabolize specific amino acids
  • can cause severe medical complications (brain damage) due to accumulation of toxic amino acids or their by-products in the tissue
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12
Q

maple syrup urine disease

A
  • deficiency in branched chain keto acid decarboxylase
  • leads to excess branched chain amino acids which causes metabolic acidosis
  • maple syrup scented urine
  • amino acids involved: valine, leucine, isoleucine
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13
Q

phenylketonuria

A
  • phenylalanine hydroxylase is reduce or absent which impedes abnormal cerebral development
  • leads to loss of interest, mental retardation, restlessness, irritability
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14
Q

cystinuria

A
  • defect in renal tubule transport protein affecting dibasic amino acids
  • causes cystine kidney stones and crystalluria
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15
Q

alkaptonuria

A
  • black urine disease
  • defect in homogentisic acid
  • causes black cartilage and arthritis
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16
Q

primary protein structure

A

number, type, sequence of amino acids in polypeptide chain

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17
Q

secondary protein structure

A

commonly formed arrangements stabilized by hydrogen bonds between nearby amino acids within a protein; alpha-helix and beta-pleated sheets

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18
Q

tertiary protein structure

A

overall shape or conformation of protein molecule; fold

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19
Q

quaternary protein structure

A

shape or structure that results from interaction of more than one protein molecule that functions as a single unit

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20
Q

what does the basic structure of protein include?

A

carbon, oxygen, hydrogen, nitrogen, sulfur

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21
Q

where are plasma proteins predominantly synthesized?

A

synthesized in liver and secreted into circulation
**immunoglobulins are synthesized by b lymphocytes

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22
Q

what are the main physiologic functions of plasma proteins?

A

energy source, maintaining water distribution through compartments of body, role in maintaining acid-base balance by serving as buffers to maintain pH, involved in hemostasis by participating in formation and dissolution of blood clots; catabolism, nitrogen balance, hormone regulation

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23
Q

what are the chemical properties of proteins?

A
  • amino acid chain changes properties
  • can be positively or negatively charged due to n- or c- terminal ends
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24
Q

isoelectric point

A

pH at which an amino acid or protein has no net charge
- pH > isoelectric point = net negative charge
- pH < isoelectric point = net positive charge

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25
Q

protein synthesis

A
  • amino acid sequence determined by corresponding sequence of nitrogenous bases in DNA
  • genetic code is a set of three-nucleotide combination (codon) standing for a specific amino acid
  • double-stranded DNA unfolds in nucleus, one strand is used as a template for the formation of a complementary strand
  • DNA to mRNA to tRNA to CODON to PROTEIN
  • transcription, translation, initiation, elongation, termination
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26
Q

isoelectric point

A

pH at which a substance has a net neutral charge
- pH > isoelectric point = net negative charge
- pH < isoelectric point = net positive charge

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27
Q

transcription

A

process where double-stranded DNA unfolds in nucleus and one strand is used as template for the formation of a complementary strand of mRNA; occurs in cell nucleus

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28
Q

translation

A

mRNA is translocated across nuclear membrane into cytoplasm; occurs in cytoplasm

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29
Q

why do proteins have no designated storage?

A

because are repetitively synthesized (anabolism) and degraded (catabolism) so amino acids are always recycled

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30
Q

protein catabolism

A

nitrogen balance is maintained by equal intake and excretion of amino acids

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31
Q

what conditions are associated with when more nitrogen is excreted than incorporated?

A

excessive tissue destruction, burns, starvation

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32
Q

what can be done when nitrogen is in excess?

A

amino acids can be converted to urea for kidney excretion and into glucose or ketones for energy

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33
Q

how are proteins classified?

A

based on structure, composition, function

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34
Q

simple proteins

A

peptide chains composed of only amino acids and may be globular or fibrous in shape

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35
Q

complex/conjugated proteins

A

protein that consists of amino acids and a nonprotein prosthetic group; prosthetic group is what defines characteristics of proteins
- ie. enzymes, hormones, immunoglobulins

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36
Q

what plasma proteins are commonly analyzed?

A

albumin or globulin

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37
Q

what does a routine analysis of blood specimens typically include?

A

measurement of total protein and albumin, and calculation of albumin-to-globulin ratio

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38
Q

prealbumin

A
  • migrates before albumin in classic serum protein electrophoresis
  • transport protein for thyroid hormones, thyroxine and triiodothyronine
  • forms a complex with retinol-binding protein to transport retinol (vitamin a) and is rich in amino acid tryptophan
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39
Q

why could prealbumin have decreased serum or plasma concentrations?

A

hepatic damage due to decreased protein synthesis, during an inflammatory response, result of tissue necrosis, poor nutritional status

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40
Q

why could prealbumin have an increased serum or plasma concentration?

A

steroid therapy, alcohol abuse, chronic renal failure

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41
Q

negative acute-phase reactant

A

substance that decreases in the presence of an acute disease state

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42
Q

what are decreased blood concentrations of albumin commonly associated with?

A

acute inflammatory response, liver/kidney disease, damage to hepatocytes, malnutrition, malabsorption

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43
Q

albumin

A
  • negative acute-phase reactant
  • most abundant plasma protein and found in significant amounts in extravascular space
  • responsible for nearly 80% of colloid osmotic pressure; involved in maintaining fluid balance
  • maintains a homeostatic pH by serving as buffer in circulation
  • binds and transports large variety of substances throughout the body
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44
Q

what are increased blood concentrations of albumin commonly associated with?

A

dehydration

45
Q

positive acute-phase reactant

A

substance that increases markedly in presence of an acute onset of a disease state

46
Q

what are the alpha-1 globulins?

A

antitrypsin, fetoprotein, acid glycoprotein

47
Q

antitrypsin

A
  • glycoprotein synthesized predominantly in the liver
  • function: to inhibit neutrophil elastase, a protease released from neutrophils and macrophages during an infection
  • positive acute-phase reactant
48
Q

when is antitrypsin increased?

A

inflammation, infections, injuries, pregnancy, contraceptive use

49
Q

when is antitrypsin decreased?

A

lung damage, emphysema

50
Q

fetoprotein

A
  • synthesized in utero by developing embryo and then by fetal liver and gastrointestinal tract
  • positive acute-phase reactant
51
Q

when are increases of fetoprotein seen?

A

inflammatory conditions, increased likelihood of spina bifida, neural tube defects, abdominal wall defects, anencephaly, general fetal distress, presence of multiple gestation

52
Q

when are decreases of fetoprotein seen?

A

increased risk for Down Syndrome, Edwards Syndrome

53
Q

acid glycoprotein

A
  • produced primarily by liver
  • physiological functions include maintaining barrier function of capillaries, regulating immunity, meditating sphingomyelin metabolism, acting as a transport protein
  • positive acute-phase reactant
54
Q

when is acid glycoprotein elevated?

A

stress, inflammation, tissue damage, acute myocardial infarction, trauma, pregnancy, cancer, pneumonia, rheumatoid arthritis, surgery

55
Q

what are the alpha-2 globulins?

A

haptoglobin, ceruloplasmin, macroglobulin

56
Q

haptoglobin

A
  • synthesized in the liver as a tetrameter consisting of two alpha and two beta chains
  • primary function is to bind free hemoglobin to prevent loss of iron into urine
  • positive acute-phase reactant
57
Q

when does haptoglobin increase?

A

inflammation, ulcerative colitis, acute rheumatic disease, acute myocardial infarction, severe infection

58
Q

when does haptoglobin decrease?

A

hemolytic anemia, decreased liver synthesis

59
Q

ceruloplasmin

A
  • copper-containing glycoprotein synthesized in liver
  • primary function is to serve as transport protein for copper
  • primarily measured along with blood and urine copper concentrations to aid in diagnosis of Wilson’s
  • Kayser Fleischer Rings
  • positive acute-phase reactant
60
Q

when can ceruloplasmin be increased?

A

inflammation, severe infection, tissue damage, some cancer, pregnancy, patients taking estrogen, oral contraceptives, medications

61
Q

when can ceruloplasmin be decreased?

A

Wilson’s, malnutrition, malabsorption, severe liver disease, nephrotic

62
Q

macroglobulin

A
  • tetramer of four identical subunits synthesized by liver
  • protease inhibitor, reducing accessibility of protease functional sites but does not fully inactivate them
  • regulation of growth factors and cytokines as well as chaperoning misfolded proteins
63
Q

when do macroglobulins appear increased?

A
  • nephrotic syndrome, pregnancy, using hormoned-based contraceptives, patients with renal disease secondary to diabetes mellitus or hepatorenal syndromes
64
Q

when do macroglobulins appear decreased?

A

pancreatitis, liver disease

65
Q

what are the beta globulins?

A

transferrin, microglobulin, fibrinogen, c-reactive protein

66
Q

transferrin

A
  • synthesized by liver
  • major component of beta globulin fraction in protein electrophoresis
  • primary function: bind and transport iron to and from storage sites and to prevent iron from being inappropriately deposited in other tissues
  • negative acute-phase reactant
67
Q

when could transferrin be decreased?

A

liver disease, malnutrition, nephrotic syndrome, infection, inflammation, malignancy

68
Q

what is associated with an increase in transferrin?

A

iron deficiency anemia

69
Q

microglobulin

A
  • light chain component of major histocompatibility complex of human leukocyte antigen
  • found on surface of most nucleated cells and is present in high concentrations on lymphocytes
  • filtered by the renal glomeruli but is almost completely reabsorbed and catabolized in proximal tubules
70
Q

what does an elevated plasma concentration of microglobulin reflect?

A

impaired renal clearance, rheumatoid arthritis, systemic lupus erythematosus

71
Q

fibrinogen

A
  • largest proteins in blood plasma
  • synthesized in the liver and classified as a glycoprotein because of its considerable carbohydrate content
  • function: form a fibrin clot when activated by thrombin, meaning all fibrinogen should be removed in clotting process and leaving none present in serum specimens
  • increases significantly during an inflammatory response
  • positive acute-phase reactant
72
Q

when do fibrinogen levels rise?

A

pregnancy, oral contraceptive

73
Q

when do fibrinogen levels decrease?

A

extensive coagulation

74
Q

complement c3

A
  • synthesized in the liver as single polypeptide chains and circulate in blood as non-functional precursors
  • most abundant complement protein in human plasma
75
Q

what are increased levels of complement c3 linked to?

A

acute inflammatory disease, tissue inflammation

76
Q

what are decreased levels of complement c3 linked to?

A

autoimmune disease, neonatal respiratory distress syndrome, bacteremia, tissue injury, chronic hepatitis

77
Q

c-reactive protein

A
  • synthesized in the liver
  • first acute phase reactant to increase
  • non-specific inflammation indicator
78
Q

when does c-reactive protein rise?

A

tissue inflammation, active coagulation or complement, rheumatic fever, bacterial infection, gout

79
Q

what are the gamma globulins?

A

immunoglobulins including IgG, IgA, IgM, IgD, IgE

80
Q

immunoglobulins

A
  • glycoproteins composed predominantly with a small percentage of carbohydrate
  • produced by b lymphocytes that confer humoral immunity
  • consists of two identical heavy chains and two identical light chains linked by two disulfide bonds
81
Q

IgG

A
  • most abundant class of antibodies found in blood plasma and lymph
  • act on bacteria, fungi, viruses, and foreign particles by agglutination, opsonization, and complement activation by neutralizing toxins
  • can cross the placenta
82
Q

what is increased IgG associated with?

A

liver disease, infections, IgG myeloma, parasitic disease, rheumatic diseases

83
Q

what is decreased IgG associated with?

A

acquired immunodeficiency, increased susceptibility to infection

84
Q

IgA

A
  • found in mucus secretions
  • secretory IgA is resistant to enzyme degradation and remains active in digestive and respiratory tracts to provide antibody protection in body secretions
85
Q

when do you see increases in IgA?

A

liver disease, infections, autoimmune diseases nutritional hepatic cirrhosis

86
Q

when do you see decreases in IgA?

A

impaired protein synthesis, immunodeficiency

87
Q

IgM

A
  • first antibody to respond to antigenic stimulation
  • cannot cross the placenta
  • only immunoglobulin synthesized by neonate
88
Q

what conditions present an increased IgM concentration?

A

bacterial infections, toxoplasmosis, primary biliary cirrhosis, cytomegalovirus, rubella, herpes, fungal diseases, Waldenstrom’s

89
Q

what conditions present a decreased IgM concentration?

A

protein-losing conditions, hereditary immunodeficiencies

90
Q

IgD

A
  • present on surface of most b lymphocytes
  • very little is released into circulation
  • helps regulate b lymphocyte function
91
Q

when is IgD concentration typically increased?

A

infections, liver disease, connective tissue disorders

92
Q

IgE

A
  • associated with allergic and anaphylactic reactions, autoimmune processes, parasitic infections
  • concentration in circulation is very low
  • elevated concentration observed in many inflammatory and infectious diseases
93
Q

troponin

A
  • specific to cardiac muscle
  • considered the gold standard for diagnosis of acute coronary syndrome, in which blood supply to heart muscle is impeded
94
Q

b-type natriuretic peptide

A
  • produced initially as prohormone which is cleaved by enzymes corin and furin
  • found in greatest concentration in left ventricular myocardium
  • neurohormones that affect body fluid homeostasis
95
Q

what are elevated concentrations of b-type natriuretic peptides associated with?

A

congestive heart failure, acute coronary syndrome

96
Q

hypoproteinemia

A

conditions in which serum or plasma total protein concentration is below the reference range

97
Q

what are the general causes of hypoproteinemia?

A

excessive loss, decreased synthesis, increased protein catabolism

98
Q

hyperproteinemia

A

increase in total plasma proteins

99
Q

what are the general causes of hyperproteinemia?

A

dehydration caused by vomiting, diarrhea, excessive sweating, diabetic acidosis, hypoaldosteronism, excessive production of proteins

100
Q

biuret method

A
  • used to determine total protein concentrations in serum or plasma
  • an alkaline medium and the presence of at least two peptide bonds, cupric ions (Cu2+) will complex with groups involved in peptide bond to form violet-colored chelate
  • color and absorbance are proportional to number of peptide bonds present and reflect total protein concentration of specimen
101
Q

turbidimetry and nephelometry

A
  • used to measure concentration of solution with particles
  • measuring amount of light transmitted through particulate solution or light scattered by particles
102
Q

dye binding

A
  • based on ability of most proteins to bind dyes, causing a spectral shift in absorbance maximum
103
Q

ultraviolet absorption

A
  • concentration of protein can be estimated by ultraviolet absorption at 280 nm
  • used to estimate protein concentration in a solution
  • utilization of ultraviolet absorption to measure peptide bonds is limited to peptide fragments
104
Q

hemoglobin

A
  • transport protein
  • role: transport oxygen from lungs to tissues and transport carbon dioxide back to lungs
  • measured in peripheral blood as part of complete blood count
  • decreased hemoglobin is indicative of anemia
105
Q

hemoglobinopathies

A

qualitative defects caused by mutations in DNA of globin chain that produce a structurally different form leading to a decrease in red blood cell survival

106
Q

thalassemias

A

quantitative defects due to mutations that reduce the synthesis of normal hemoglobin

107
Q

myoglobin

A
  • primary oxygen-carrying protein found in striated skeletal and cardiac muscle
  • can reversibly bind oxygen and requires a very low oxygen tension to release bound oxygen
  • transports oxygen from muscle cell membrane to mitochondria
  • serves as extra reserve of oxygen to help exercising muscle maintain activity longer
108
Q
A

Lecture: Chemical Pathology (9 decks)

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