Rapid Review- Biochemistry

Front 1

What is the rate limiting step in the metabolism of NH3 that is produced during protein degradation? Describe what happens to the NH3 concentrations in the blood and the BUN when the urea cycle is not functioning.

Back 1

The rat limiting step is the synthesis of Carbamoyl phosphate from NH3 and CO2, which is catalyzed by Carbamoyl Phosphate Synthetase I. Because the urea cycle is dysfunctional, blood NH3 levels increase and BUN decreases.

Front 2

Which enzyme is responsible for the conversion of Glucose to Sorbitol?

Back 2

Aldose Reductase.

Front 3

The osmotic effects of Sorbitol is responsible for the development of what eye condition seen in diabetic patients?

Back 3

Cataracts.

Front 4

Does insulin activate or inactive Capillary Lipoprotein Lipase and Hormone Sensitive Lipase?

Back 4

Insulin activates Capillary Lipoprotein Lipase (fat storage) to deal with nutrients from meals just ingested, and it inactivates Hormone-sensitive lipase (fat mobilization), which is located in adipose tissue. It inactivates Hormone-sensitive lipase by activating phosphorylase which dephosphorylates the enzyme.

Front 5

Defects in the oxidation of branched chain amino acids such as valine, leucine, and isoleucine lead to the formation of what type of molecules?

Back 5

Defects in oxidation of branched chain amino acids leads to the formation of alpha-keto acids.

Front 6

What types of amino acids accumulate in the blood in a patient who suffers from chronic liver disease and contribute to hepatic encephalopathy?

Back 6

The Aromatic Amino acids phenylalanine, tyrosine, and tryptophan.

Front 7

Defects in metabolization of what type of amino acids are likely to lead to Homocystinuria? What enzyme is likely to be deficient in these conditions? Describe some of the symptoms that would be associated.

Back 7

Metabolism of Sulfur-containing amino acids is more likely associated with Homocystinuria, which is caused by a deficiency of Cystathione Synthetrase. Homocystinuria is characterized by mental retardation, osteoporosis, and lens dislocation.

Front 8

What types of states are found to have negative nitrogen balances? Which are found to have positive nitrogen balances?

Back 8

Negative nitrogen balance in common following surgery, during advanced stages of cancer, or in individuals with starvation syndromes (e.g. kwashiorkor). Positive nitrogen balances occur in anabolic states such as "growth spurts".

Front 9

Causing a right shift in the O2 dissociation is called what "effect".

Back 9

The Bohr Effect.

Front 10

What Growth Factor Receptor is associated with Breast Cancer?

Back 10

erb-B2 is a mutated growth factor receptor that is active in the absence of the its growth factor that may result in breast cancer.

Front 11

What type of protein is the mutated Ras protein?

Back 11

Mutated Ras is a G-protein that has lost its "off" switch, an so is a constiuitvely activated GTPase.

Front 12

PDGF is found to be associated with what CNS malignancy?

Back 12

Astrocytoma.

Front 13

sis Oncogene is associated withe what type of sarcoma?

Back 13

Osteogenic Sarcoma.

Front 14

myc Oncogenes are associated with what two types of cancer?

Back 14

Neuroblastomas (n-myc), and Burkitt's lymphoma (c-myc).

Front 15

Which two amino acids are primarily used for gluconeogenesis? Where do they enter the metabolic cycles on their way yo becoming glucose?

Back 15

Alanine and Aspartate are both used as substrates for gluconeogenesis. Via transamination Aspartate is converted into Oxaloacetate and Alanine is converted to Pyruvate.

Front 16

Which tissues in the body store glycogen, and which can release that glycogen into the blood stream? Why are they able to do that?

Back 16

Muscle, and liver store glycogen, but only the liver and kidneys are able to release glucose into the circulation. This is because only they possess the gluconeogenic enzyme Glucose-6-Phosphatase which allows the conversion of Glucose-6-phosphate to Glucose.

Front 17

Alkaptonuria is caused by a deficiency of what enzyme? What is the function of this enzyme? Describe a key clinical finding associated with this disease?

Back 17

Deficiency of Homogentisate oxidase causes Alkaptonuria. This enzyme is normally involved in the metabolism of Tyrosine. The urine of these patients turns very dark when left out exposed to free air, as a result of oxidation of Homogentisic acid.

Front 18

Explain the connection between Chronic Renal Failure, hypocalcemia, and Secondary Hyperparathyroidism.

Back 18

In Chronic Renal Failure there is underproduction of Vitamin D, and often times a Vitamin D deficiency that causes hypocalcemia. Hypocalcemia is the normal stimulus for increased synthesis of PTH. So a Secondary Hyperparathyroidism is created of because of the effort of the parathyroid gland to increased serum calcium.

Front 19

A person deficient in Sphingomyelinase has what disease? What are the clinical findings associated with this disease? How early in life do the effects of this disease begin affecting the patient?

Back 19

A deficiency of Sphingomyelinase causes Niemann-Pick disease. This results in accumulation of Sphingomyelin in the lysosomes. Signs of the disorder include an enlarged liver and spleen and mental retardation of rapid onset, usually within the first 6 months of life.

Front 20

A Secondary form of PKU results from an inability regenerate what key cofactor? Which enzyme deficiency creates this inability? What are the amino acid reactions that this cofactor is responsible for helping drive forward?

Back 20

The Secondary form of PKU results from an inability to regenerate Tetrahyrobiopterin. Deficiency of dihydrobiopterin reductase is associated with this Secondary form of PKU. This lack of Tetrahydrobiopterin affects not only the conversion of Phenylalanine to Tyrosine, but also the hydroxylation of Tyrosine to Tryptophan leading to deficiencies of NTs and additional CNS effects.

Front 21

Congenital Spherocytosis is caused by a defect in what protein? How is this disease inherited? What happens to the Spherocytes?

Back 21

Congentital Spherocytosis disease is caused by a defect in Spectrin, which is responsible for maintaining the structural integrity of the RBC membrane. This AUTOSOMAL DOMINANT disorder is associated with the destruction of the spherocytes by macrophages in the spleen.

Front 22

Prolactin increases the synthesis of what molecule in the growing fetal lung?

Back 22

Surfactant.

Front 23

Cyanide and Carbon Monoxide share what common intracellular target?

Back 23

Cytochrome oxidase.

Front 24

How does Hydroxyurea help to treat Sickle Cell anemia?

Back 24

It helps increase the production of HbF.

Front 25

Deficiency of what vitamin causes the Wet and Dry forms of Beriberi? Describe the symptoms associated.

Back 25

Thiamine (Vitamin B1) is deficiency is what causes the Wet and Dry forms of Beriberi. Wet beriberi involves both a left sided heart failure (resulting in pulmonary edema) & right sided heart failure (pitting edema and neck vein distention). Dry Beriberi involves peripheral neuropathy (foot drop caused by deep peroneal nerve palsy).

Front 26

What type of patient/immigrant might come in presenting with symptoms of Wet/Dry Beriberi. What key enzymes malfunction as a result of the vitamin deficiency associated with this condition?

Back 26

Immigrants that have a hulled rice diet (such as asian immigrants) or others with malnutrition would be most likely to present with these conditions. Transketolase (Ribulose-5-P from PPP to Fructose-6-P in the glycolytic pathway), PDH, and AKG-DH, all use Thiamine in their reactions as a cofactor and would malfunction without it.

Front 27

Most Carboxylases require what vitamin as a cofactor?

Back 27

Biotin.

Front 28

Elevated urinary levels of ALA (delta-aminolevulinic acid) occur as a result of poison with what heavy metal? Explain the mechanism for the increase of ALA and the pathway that is disrupted. What blood disorder is going to be present with this increased level of ALA?

Back 28

Elevation of ALA is usually a clue that lead poisoning is present because lead denatures ALA dehydratase, which converts ALA to porphobilinogen. Lead poisoning often results in a microcytic anemia, with characteristic coarse basophilic stippling.

Front 29

Describe the pathophysiology of lead poisoning. Malfunction of what enzyme leads to elevated ALA levels? What mechanisms lead to demylination and cerebral edema? What type of anemia does lead poisoning cause? Explain the etiology of the basophilic stippling of RBC's.

Back 29

Because lead denatures ALA Hydratase, which converts ALA to porphobilinogen there is a increase in ALA excretion in the urine. Increased levels of ALA, along with lead, produce demyelination in the brain and increased vessel permeability leading to cerebral edema. Lead poisoning results in microcytic anemia, with basophilic stippling of RBC's because of denaturation of Ribonuclease, the enzyme that degrades ribosomes.

Front 30

Ringed sideroblasts associated with lead poisoning represent what intracellular organelle with collection of what metal? What happens when these sideroblasts die in marrow?

Back 30

Ringed sideroblasts are mitochondria with aggregation of iron trapped inside, which surround the nucleus. When the sideroblasts die in bone marrow, the iron is stored in macrophages, leading to an increase in iron stores in the marrow as well as iron in the blood.

Front 31

What are the two main enzymes associated with hemoglobin synthesis that are denatured in lead poisoning?

Back 31

ALA Dehydratase and Ferrochelatase.

Front 32

Is the microcytic anemia associated with Lead Poisoning observed with increased or decreased serum Ferritin? Increased or decreased zinc RBC protoporphyrin?

Back 32

Increased serum Ferritin and increase zinc RBC serum protoporphyrin.

Front 33

Why is hydroxyurea used to increased the amount of HbF in patients with Sickle cell? What is the therapeutic advantage?

Back 33

HbF does not have the same Glu --> Val mutation that HbA does in patients with sickle cell anemia. Therefore, it will not aggregate with sticky ends and cause occlusive crises.

Front 34

Thick skin, follicular hyperkeratosis, and dry eyes are all signs of what vitamin deficiency?

Back 34

Vitamin A deficiency.

Front 35

What enzyme is responsible for the rate limiting step in Ketogenesis?

Back 35

HMG-CoA synthase, which takes the CoA from acetoacetyl-CoA and acetyl-CoA to leave the remains for ketone body formation.

Front 36

Where is Glucokinase found in the body? Even though they perform the same function, describe the difference between Glucokinase and Hexokinase in terms of enzyme regulation.

Back 36

Glucokinase is located in liver and pancreatic cells. Glucokinase is increased in concentration and activity by Insulin, whereas Hexokinase is unaffected by insulin.

Front 37

List the Hyperlipoproteinemia diseases I-IV, their associated causes, and their resulting clinical findings.

Back 37

Type I: Deficiency of capillary lipoprotein lipase or apolipoprotein C-II in VLDL. Leads to accumulation of Chylomicrons (the least dense and and the best floating of all lipoproteins)
Type IIa: Deficiency of LDL receptors results in increased plasma LDL
Type IIb: Unknown cause, but increased LDL is present like in Type IIa, and also increased TAGs
Type III: Deficiency of apolipoprotein E, which leads to accumulation of intermediate-density lipoprotein and chylomicron remnants. Patients typically form Xanthomas.
Type IV: Associated with overproduction or reduced clearance of VLDL in the liver in individuals with Glucose intolerance.

Front 38

Lesh-Nyhan syndrome is due to a deficiency of what enzyme? What is the role of this enzyme? What are the symptoms associated?

Back 38

Lesh-Nyhan syndrome is due to a deficiency of HGPRT (hypoxanthine-guanine phosphoribosyl transferase) (H-ow G-ross P-eople 'R' T-o eat at themselves?!?). HGPRT is responsible for Purine salvage of hypoxanthine and guanine. Destruction of free hypoxanthine and guanine results, along with increased uric acid levels (gout), mental retardation, and self-mutilation.

Front 39

What type of condition does deficiency of Adenosine Deaminase lead to?

Back 39

Deficiency in "AIDS-denosine deaminase" inhibits the conversion of adenosine to inosine in the degradation of adenosine. A deficiency of this enzyme leads to a severe form of combined immunodeficiency disease.

Front 40

Acyclovir inhibits the viral version of what enzyme used in the salvage pathway for pyrimidines?

Back 40

Acyclovir inhibits Thymidine kinase, an enzyme that is used to convert thymidine to TMP.

Front 41

Which test is the most sensitive test for all iron-related disorders?

Back 41

The Serum Ferritin Test. This is because a fraction of the circulating ferritin closely correlates with the amount of iron stored in the macrophages in the bone marrow; more closely and consistently

Front 42

What disease is due to a deficiency of Alpha-L-Iduronidase? What molecules accumulate as a result of this enzyme deficiency? What type of cells are evaluated to confirm this enzyme deficiency?

Back 42

Alpha-L-Iduronidase (Hurler's disease) is a lysosomal storage disease, which is classified as a mucopolysaccharidosis. This enzyme deficiency leads to an accumulation of dermatan and heparan sulfate. Analysis of fibroblast cultures provides evidence for the presence or absence of many enzymes.

Front 43

Describe some of the classic features and symptoms associated with Hurler's disease (deficiency of Alpha-L-Iduronidase).

Back 43

Hurler's disease presents with coarse facial features and mental retardation (like a Burley Hurler), corneal clouding (like the ice used in Hurling), and hepatomegaly (like the 'H' in Hurlers)

Front 44

What enzyme deficiency is involved in Gaucher's disease? What type of disease classification is this? Describe the most prominent features and clinical findings.

Back 44

Gaucher's disease is a deficiency of B-Glucosidase, which leads to an accumulation of glucocerebroside in reticuloendothelial cells (Gaucher cells). This disorder is the most frequent form of Sphingolipidoses and is characterized by Splenomegaly, increased skin pigmentation, and bone lesions.

Front 45

Hexosaminidase A deficiency is responsible for what disease? What molecule is accumulated as a result? What are two key features of this disease?

Back 45

Deficiency of Hexosaminidase A is seen in patients with both Tay-Sach's and Sandhoff's disease. Here there is an accumulation of GM2 Ganglioside, which causes the two key features of mental retardation and blindness.

Front 46

Describe some of the key features of someone affected with I-cell disease. What is the enzyme deficiency associated?

Back 46

I-cell disease involves the loss of phosphotransferase that tags enzymes with mannose-6-phosphate and localizes them for compartmentation in the lysosome. Affected individuals have mental deterioration, skeletal deformities, and elevated lysosomal enzymes in the plasma.

Front 47

Does Carnitine Acetyltransferase bring fatty acids into or out of the mitochondria?

Back 47

It brings them into the mitochondria.

Front 48

Describe some of the symptoms associated with Pernicious Anemia. What is the main cause of Pernicious Anemia?

Back 48

Progressive loss of energy, numbness, tingling/peripheral neuropathy in extremities, loss of balance, and sore tongue. Pernicious Anemia is caused by a lack of intrinsic factor.

Front 49

Methyl-FH4 is used in the conversion of what molecule for what reaction?

Back 49

Methyl-FH4 is used in the conversion of Homocystine --> Methionine.

Front 50

What significance do C-peptide blood levels have?

Back 50

C-peptide levels are an indicator of endogenous insulin release by the B-islet cells.

Front 51

What lipid disorder is classically seen in conjunction with Diabetic Ketoacidosis? What are some of the symptoms and signs associated?

Back 51

Hyperchylomicronemia syndrome, is classically seen in DKA. The excess TG causes eruptive xanthomas. Epigastric pain results from acute pancreatitis, and retinal findings are indicative of lipemia retinalis.

Front 52

Explain the pathophysiology of why a deficiency in Adenosine (AIDS-denosine) Deaminase leads to Severe Combined Immunodeficiency.

Back 52

Adenosine deaminase is responsible for the conversion of adenosine to inosine in the degradation pathway of adenosine. Accumulation of adenosine is toxic to lymphocytes and dATP inhibits ribonucleotide reductase. Inhibition of ribonucleotide reductase results in a decreased supply of deoxynucleotides for DNA synthesis and decreased production of both B and T cells.

Front 53

Does Pertussis toxin stimulate Gs protein or inhibit Gi protein in order to raise intracellular levels of cAMP?

Back 53

It inhibits Gi.

Front 54

A ketone urine dipstick only reacts to what molecule?

Back 54

Acetoacetate.

Front 55

Under what conditions are nitrites found in the urine?

Back 55

Nitrites are usually present in urine only with urinary tract infections cause by bacteria capable of reducing nitrate to nitrite (e.g. E.coli).

Front 56

Describe the most common cause of Pyrioxidine deficiency and what the associated symptoms would be.

Back 56

The most common cause of Pyroxidine deficiency is due to the medication Isoniazide that is used to treat Tuberculosis. B6 deficiency is associated with defects in heme synthesis (sideroblastic anemia), peripheral neuropathy, and convulsions.

Front 57

What are four key metabolic reactions that require that require Thiamine as a cofactor?

Back 57

Thiamine is involved in transketolase reaction and oxidative decarboxylation reactions involving PDH, AKG-DH, and alpha-keto-acid-DH reactions.

Front 58

What tissue is the glycosaminoglycan Dermatan Sulfate found in?

Back 58

Valvular heart tissue. (A tanned-Derm is the way to some people's heart).

Front 59

What tissue is the glycosaminoglycan Chondroitin Sulfate found in? What other GAG is it associated with there?

Back 59

This is found primarily in Cartilage and is also associated with Keratan Sulfate.

Front 60

What tissue is the main location of the glycosaminoglycan Heparan Sulfate? What is its key job in this tissue?

Back 60

Heparan Sulfate is mainly found in the glomerular basement membrane of the kidney where its strong negative charge serves to repel albumin from filtration.

Front 61

What tissue and location is Hyaluronic Acid found in? Describe its main function.

Back 61

Hyaluronic Acid is the major component of synovial fluid, where it serves as a joint lubricant.

Front 62

What tissue is the glycosaminoglycan Keratan Sulfate found in? What other GAG is it associated with there?

Back 62

This is found primarily in Cartilage and is also associated with Chondroitin Sulfate.

Front 63

What type of stain would you use to detect the sulfate-containing ceramide granules in the lysosomes of a patient with Metachromatic Leukodystrophy? What class of disease is this? Describe some of the symptoms associated.

Back 63

To detect sulfate-containing ceramide granules you would use PAS and Alcian blue stain. Metachromatic Leukodystrophy results from a deficiency in Arylsulfatase A and is a lysosomal storage disorder that causes demyelination of nerve cells leading to mental retardation and motor abnormalities.

Front 64

Where does Ketogenesis occur primarily in the body?

Back 64

Ketogenesis occurs primarily in the liver and requires the acetyl-CoA derived from the B-oxidation of fatty acids in the mitochondrial matrix.

Front 65

Where does the primary catabolism of branched chain amino acids (e.g. Valine, Leucine, and Isoleucine) occur in the in the body?

Back 65

Muscle tissue is the primary tissue where the catabolism of branched chain amino acids occurs.

Front 66

What is the mechanism of action of Oligomycin? It disrupts the production of ATP, but how? What is its unique method?

Back 66

Oligomycin closes the proton channel in the stalk of ATP synthase. Prevention of the flow of protons through the ATP synthase prevents the production of ATP.

Front 67

Which glycosaminoglycan is responsible for the pretibial myxedema seen in hyperthyroidism?

Back 67

Dermatan sulfate, which is found in skin and valvular heart tissue.

Front 68

What type of mineral deficiency is common in people with chronic inflammation?

Back 68

Zinc deficiency commonly occurs in patients with chronic inflammation.

Front 69

What are the key signs and symptoms associated with Zinc deficiency? What type of enzymes is it a cofactor for?

Back 69

Poor wound healing, inability to taste (dysgeusia), and inability to smell (anosmia), PERIORAL RASH, hypogonadism, and growth retardation. Zinc is a cofactor in many metalloenzymes including superoxide dismutase, collagenase, and alkaline phosphatase.

Front 70

What is a key role of Chromium in the body? Describe some of the signs and symptoms of Chromium deficiency.

Back 70

Chromium is a component of glucose tolerance factor, which helps maintain a normal glucose level in the blood, and is also a cofactor in insulin. Associated signs of Chromium deficiency are glucose intolerance and peripheral neuropathy.

Front 71

What types of enzymes is Copper a cofactor for? Describe some of the key signs and symptoms associated with Copper deficiency.

Back 71

Copper, like Zinc, is a cofactor in metalloenzymes, including ferrooxidase, lysyl oxidase, and tyrosinase. Signs and symptoms of copper deficiency include poor wound healing, as well as iron deficiency and aortic dissection.

Front 72

What role does Vitamin E play in maintaining the health and integrity of cells?

Back 72

Vitamin E is an antioxidant that protects polyunsaturated fats and fatty acids in cell membranes from lipid peroxidation. Signs and symptoms of Vitamin E deficiency include hemolytic anemia, peripheral neuropathy, posterior column degeneration and myopathy.

Front 73

How does phototherapy of physiological jaundice of the newborn treat the hyperbilirubinemia that is occuring?

Back 73

The phototherapy with blue light causes bilirubin to undergo photooxidation, which produces a water-soluble form of bilirubin.

Front 74

What compensatory mechanism exists in order to lessen the degree of anemia associated with Pyruvate Kinase deficiency?

Back 74

Because Pyruvate Kinase is subsequent to 1,3-bisphosphoglycerate (1,3-BPG) in the glycolytic pathway, there is an increased conversion of 1,3-BPG to 2,3-BPG, which shifts the oxygen binding curve to the right and lessens the effect and severity of anemia.

Front 75

Which lipid formations is the Apolipoprotein B family of proteins a part of?

Back 75

ApoB is necessary for the formation of Chylomicrons (apoB-48), VLDL (apoB-100), and LDL (apoB-100).

Front 76

Describe the clinical findings associated with Abetalipoproteinemia (deficiency of apoliporotein B). What is the mechanism of their manifestation?

Back 76

The clinical findings in the patient with Abetalipoproteinemia result from Vitamin E deficiency. This fat-soluble vitamin is normally reabsorbed with fat. In Abetalipo. TG and fat soluble vitamins cannot be packaged into chylomicrons in the small intestine. TG accumulates in the lamina propria of the villi and prevents the reabsorption of fat and fat-soluble vitamins, which leads to steatohrrea. Vitamin E deficiency is associated with spinocerebellar degeneration and hemolytic anemia.

Front 77

Which lipid packaging molecule is Apoliprotein-A unique to?

Back 77

HDL. Deficiency of apoA is a rare disease associated with the absence of HDL and a predisposition for premature coronary artery disease.

Front 78

Which lipid packaging molecules is apoE found in? What happens when there is a mutant form of the protein produced?

Back 78

Apo E is present in chylomicrons, VLDL, and IDLs. A mutant form of apoE characterizes familial dysbetalipoproteinemia (Type III hyperlipoproteinemia). The apoB and apoE receptors in the liver cannnot remove chylomicton remnants and IDLs that have the mutant form of ApoE, so these remnants accumulate in the blood an increase TG and cholesterol levels.

Front 79

What is the most common cause of Gout: underexcretion or overproduction of uric acid? Explain the mechanism behind the cause. What type of chronic patient of develops Gout because of this?

Back 79

Underexcretion of Uric acid is the most common form of Gout. Underexcretion in the kidneys results from competition for excretion of acids (e.g. lactic acid and ketoacids) with Uric acid for excretion in the proximal tubules. Alcoholics commonly have both lactic acid and B-hydroxybutyric acid ketoacidosis, the former due to conversion of pyruvate to lactate by excess production of NADH in alcohol metabolism and the latter due to increased ketogenesis related to excess acetyl-CoA from alcohol metabolism

Front 80

When should you suspect Galactosemia in an infant? What types of symptoms will be present? What is the enzyme deficiency associated with this disease?

Back 80

Galactosemia should be suspected in infants with growth failure, cataracts, liver disease, jaundice, aminoaciduria, mental retardation, vomiting, and diahrrea. Its an autosomal recessive disease caused by a deficiency of Galactose-1-Phosphate Uridyltransferase

Front 81

Describe the etiology behind Hemorrhagic disease of the newborn. What is the special reaction that isn't taking place with and with which clotting factors?

Back 81

Hemorrhagic disease of the newborn is due to Vitamin K deficiency, which is due to the lack of Vitamin K-producing bacteria in the gut. Vitamin K is normally responsible for Gamma-carboxylation of Glutamate residues on Clotting Factors II, VII, IX, X, and Proteins C & S.