chem exam 2

The mother of a very fussy and colicky one-year-old notices that her child’s black T-shirt is crusted over with dried salt after being outside on an extremely warm day. What (inborn) disorder could this be a sign of? What labs to order?

Cystic fibrosis
Sweat Chloride testing – Cystic fibrosis mutations

A 27 year old trainer in a local gym experiences acute and worsening chest pain. His labs come back with a total creatine kinase (CK) activity that is four-fold elevated as compared with the normal upper limit of the reference range. What additional labs would be informative in this setting?

- CK-MM (muscles)
- CK-MB (heart)
- CK-BB (brain)
- Caused by strenuous exercises – CK testing of the blood

Given pCO2 and HCO3, calculate and interpret pH levels using the Henderson-Hasselbalch buffer equation

- PH calculation given pCO2 and HCO3
- PH = 6.1 + log (HCO3)/(H2CO3)
- PH = 6.1 + log (HCO3)/ (0.03 x pCO2)
- H2CO3 = 0.03 x pCO2

expected ABG results (pCO2, pO2, HCO3-, pH) and potassium values for the following: Metabolic Acidosis

Metabolic acidosis: pH

expected ABG results (pCO2, pO2, HCO3-, pH) and potassium values for the following: Metabolic Alkalosis

Metabolic alkalosis: pH >7.45, high PCO2 (>44), high HCO3 (>27), K level low

For the following acid-base imbalances, list expected ABG results (pCO2, pO2, HCO3-, pH) and potassium values for the following: Respiratory Acidosis

Respiratory acidosis: pH < 7.35, high PCO2 (>44), high HCO3 (>27)

For the following acid-base imbalances, list expected ABG results (pCO2, pO2, HCO3-, pH) and potassium values for the following: Respiratory Alkalosis

Respiratory alkalosis: pH > 7.45, low PCO2 (

anion gap equation

Na – CL + HCO3

high anion gap?

metabolic acidosis

Explain what compensatory mechanisms arise in the context of Metabolic Acidosis

Metabolic acidosis: respiratory alkalosis increased respiratory rate to decrease PCO2; Kussmaul breathing) – associated with hyperkalemia

Explain what compensatory mechanisms arise in the context of Metabolic Alkalosis

Metabolic alkalosis: respiratory acidosis (slow breathing) (renal and respiratory) – associated with hypokalemia

Explain what compensatory mechanisms arise in the context of: Respiratory Acidosis

Respiratory acidosis: metabolic alkalosis (renal – slow bicarbonate reclamation) – COPD, overdose

Explain what compensatory mechanisms arise in the context of: Respiratory Alkalosis

Respiratory alkalosis: metabolic acidosis (dumping of bicarb) – caused by hyperventilation

List factors that shift the oxyhemoglobin dissociation curve to the right and the consequences in regard to oxygen delivery to the periphery

Low pH, decreased O2 affinity (T state), increased oxygen delivery (low pH, increased CO2, high temp, high 2,3-BPG, low O2 affinity hemoglobin variants)

List factors that shift the oxyhemoglobin dissociation curve to the left and the consequences in regard to oxygen delivery to the periphery

High PH, increased O2 affinity (R state), decreased oxygen delivery (high pH, decreased CO2, low temp, low 2,3-BPG, high O2 affinity Hemoglobin variant, fetal hemoglobin (HB F))

Identify the p50 in mmHg from inspection of an oxyhemoglobin dissociation curve

- P50 is the partial pressure of oxygen that causes hemoglobin to be 50% saturated
- 50% of Hemoglobin saturation determines the P50 partial pressure (mmHg)

Explain how HCO3 works as a volatile buffer

HCO3 takes up protons from HB and becomes carbonic acid
In the lungs carbonic acid (H2CO3) is converted to CO2 and water by carbonic anhydrase

Describe how the kidney handles acid or base excess using ammonia, carbonic anhydrase, the anion exchanger (HCO3/Cl), the H+ ATPase and the Na+/H+ and K/H+ exchanger

Proximal tubule: 70-80% of HCO3 recycling – HCO3 reabsorption – secondary active transport
Distal tubule: 20-30% of HCO3 recycling – H+ secretion
Respiratory alkalosis– low PCO2 causes high pH which causes low HCO3 reabsorption and low H + secretion – causing compensation
- Respiratory acidosis – high PCO2 causes low PH and compensate by high HCO3 reabsorbing and high H+ secretion
- Metabolic acidosis – if H+ high and HCO3 low causes kidney to compensate by increasing H+ secretion and increasing HCO3 absorption
- Metabolic alkalosis – if H+ low and HCO3 high causes kidney to compensate by decreasing H+ secretion and decreasing HCO3 reabsorption

How does an oximeter work and what does it measure?

Uses absorbance Maxima of Hb derivatives and differential equations to quantify (%): Oxyhemoglobin, Deoxyhemoglobin, carboxyhemoglobin (CO-Hb), Methemoglobin (Fe-Hb)
- spectrophotometry (Hb variants change color of blood)

Explain why lactate is the final end product of anaerobic glycolysis

So by converting pyruvate to lactate, that is a reduction that requires NADH, cytosolic NADH, and therefore liberates NAD to really participate in the glyceraldehyde-3 phosphates step. So it's a way of keeping anaerobic glycolysis going in the cytoplasm of the muscle and rbc.

monosaccharides

pentose (5 carbons – ribose), hexoses (6 carbon – glucose, fructose, galactose)

disaccharides

sucrose, lactose, maltose

glycogen

one form in which body fuel is stored; stored primarily in the liver and broken down into glucose when needed by the body

acetoacetate

B-hydroxybutyrate

lactate

Identify biological activities of insulin

-secreted by pancreatic beta cells
-Inhibits glucagon
-Induces glucokinase
-Increases transport of glucose into liver, skeletal muscle, and adipose tissue

Identify biological activities of Glucagon

-secreted by pancreatic alpha cells in islet (a response to decreasing plasma glucose)
-quickly raises blood sugar and inhibits insulin secretion. -signals carbohydrate starvation causes the liver to export glucose
-Inhibits glycolysis and uptake of glucose by liver
-Stimulates gluconeogenesis, glycogenolysis and mobilization of fatty acids from adipose cells
Medication for people with hypoglycemia

Identify biological activities of cortisol

adrenal steroid hormone – high levels promote gluconeogenesis – starvation state hormone – favored by untreated diabetes mellitus.

Identify biological activities of GLP-1 (Glucagon-like peptide-1

inhibits glucagon release from alpha cells in pancreatic islets. GLP-1 analogs used for treatment in type 2 diabetes

Identify biological activities of GIP (Gastric inhibitory peptide)

glucose-dependent insulinotropic polypeptide. GIP analogs used for type 2 diabetes

Identify biological activities of DPP-4 (dipeptidyl peptidase-4):

rapidly degrades GLP-1 and GIP. DPP-4 inhibitors use for treatment of type 2 diabetes.
- Boost insulin secretion in individuals with type 2 diabetes

Type 1 DM

immune mediated diabetes. Pancreatic beta cell destruction (immune destruction of pancreas) (B and T cell mediated). Autoantibodies against stuff in islet cells. Get insulin replacement.

Type 2 DM

insulin resistance and impairment of insulin secretion

Gestational DM

transient effect of placental hormones

MODY

rare autosomal dominant mutations in hepatic nuclear factors (HNF14, HNF4A) and glucokinase

Identify risk factors for type 2 DM and long term complications

-geographical, ethnicity, body mass index, inactivity, obesity. Nicotine (smoking) is a direct vascular toxin for coronary vascular disease which is a component of diabetes
-Long-term complications: retinopathy, nephropathy, and coronary vascular disease

long term complications of type 1

etinopathy, nephropathy, and coronary vascular disease

Hemoglobin A1c screening is performed to screen for type 2 diabetes but not for type 1. Why?

A1C reflects average blood glucose value in the last 2-3 months. Useful in diagnosing diabetes and monitoring long-term efficacy of glucose control.
- There is low sensitivity for type 1 diabetes.

Interpret HA1c % in the context of non-diabetic individuals, and those with pre-diabetes and diabetes mellitus

- Non-diabetic individuals:

Contrast HA1c and fructosamine in regard to the time period of glucose control they reflect

-HA1C: A1C reflects average blood glucose value in the last 2-3 months
-Fructose amino only over the last few weeks because of the circulating half-life of red cells and albumin

Identify HA1c measurement techniques and common interferences

- Measurement techniques: column chromatography method, electrophoresis, high pressure liquid chromatography (HPLC), immunoassay and more.
- Common interferences: hemoglobin variants like Hemoglobin S and hemoglobin C. Hemolytic anemia (short half-life or life span of RBCs – sickle cells – 14 days in HBS).

common autoantibodies included in working up individuals with type 1 diabetes

islet cell antibodies, glutamic acid decarboxylase (GAD-65), insulin autoantibodies (IAA), and IA-2A, and protein tyrosine phosphate

List ADA guidelines for the diagnosis of type1

Fasting Plasma glucose >126mg/dL (7.0mmol/L), 2-H Plasma Glucose >200 mg/dL, Plasma blood glucose recommended for acute onset of type 1 in individuals with symptoms of hyperglycemia (random plasma glucose >200 mg/dL (11.1 mmol/L)).

List ADA guidelines for the diagnosis of type 2

FPG >126 mg/dL. 2-H PG >200mg/dL, A1C >6.5%, patients with hyperglycemia – random plasma glucose >200 mg/dL

List ADA guidelines for the diagnosis of pre-diabetes

BMI, overweight – A1C >5.7 %, FPG >126 mg/dL. 2-H PG >200mg/dL

List ADA guidelines for the diagnosis of gestational DM

when oral glucose tolerance testing with plasma glucose measurement fasting (92 mg/dl), 1 hr into fasting (180 mg/dl), 2 hr into (153 mg/dL).
- If plasma glucose level 1 hr after non-fasting >130 mg/dL and more.

What are the expected values for glucose, pH, bicarbonate, sodium, potassium and pCO2 in the setting of diabetic ketoacidosis?

Glucose: hyperglycemia – high glucose
- PH: low
- Bicarbonate: low
- PCO2: low (compensation)
- Sodium: low (hyponatremia)
- Potassium: high (hyperkalemia) – cells take H+ and exchange for potassium

Define reducing sugar and the test utilized to detect them in urine

- Reducing sugar – can open glucose ring to expose free aldehyde (which carries reduction of copper) (lactose and maltose)
– non-reducing sugar is sucrose.
- Benedict’s test

Recognize immediate action values for glucose on the high and low ends

high end: >300 mg/dL
low end:

List common methodologies utilized to measure glucose in serum and urine

-Glucose is a reductant (reducing substance) – copper reduction – oldest
-Glucose oxidase technique: utilized by glucometers and urine dipstick patches
-Hexokinase technique – more specific than glucose oxidase

exothermic (exergonic) reaction

endothermic (endergonic) reaction

Identify conditions or parameters that satisfy the requirements for using Michaelis-Menten kinetics to analyze enzyme activity

- Enzymes with no extensive allosteric regulator – good candidate
- Has one substrate and one product – classical enzyme – good candidate
- Restricts kinetics to less complex allosteric enzymes.

Define the following: Km

measures substrate binding affinity for enzyme
low km (mmol) = high substrate binding, high Km = low substrate binding

Define the following: Vmax

- Substrate concentration at which ½ Vmax is achieved
-enzyme saturated with substrate and substrate concentration higher than km. Maximal velocity

Contrast competitive and non-competitive enzyme inhibition in regard to how they alter Km or Vmax.

Interpret Lineweaver-Burke plots to determine whether an enzyme inhibitor is active in a competitive or non-competitive fashion

1st order kinetics

substrate concentration much less than km
not used for clinical labs bc substrate has to be higher (it's too low)

2nd order kinetics

-used in clinical labs
-rate is only dependent on enzyme concentration and independent of substrate concentration

electron carrier

accept and donate electrons from and to various enzymes

NAD+/NADH

reduction of NAD+ and oxidation of NADH

NDP+/NADPH

-reduction of NADP+ and oxidation of NADPH
-absorbs light at 350 nm

decreasing absorbance

NAD to NADH, NADP to NADPH

increasing absorbance

NADH to NAD, NADPH to NADP

Draw a graph showing the following changes in enzyme activities (AST, LDH, CK, CKMB) and other markers of cardiomyocyte injury (Troponin T and Troponin I) over a four-week time course after symptoms of MI (ACS) occur.

Draw a graph showing the following changes in enzyme activities (Lipase, Amylase) over a 3-week period after symptoms of acute pancreatitis occur.

Lipase and amylase – markers of acute pancreatitis

Biliary tree disease markers and Hepatobiliary enzyme

Alkaline phosphatase (ALP), y-Glutamyltranspeptide (yGT)

ALP/y-GT

induction of enzymes due to stasis or obstruction of the biliary tract

ALP

cleaves phosphate group from substrates, mild increase in parenchymal liver disease, high in children and during pregnancy, a marker of bone turnover and bone disease. Increases due to increased expression of enzymes

Y-GT

plasma form derived from liver
Has highest sensitivity as a marker of biliary obstruction. Is more liver selective.
Induced by salicylates and alcohol. Used to monitor drinking.
Increased in acute pancreatitis, MI, diabetes

Hepatocellular injury

Alanine aminotransferase (ALT),
Aspartate aminotransferase (AST)

ALT

longer half-life than AST, liver disease elevates more ALT

AST/ALT

viral hepatitis causes an increase in AST and ALT (very high)
liver cell integrity and liver cell death

List LDH isoforms and where they are expressed

LDH 1 (heart muscle, RBC)
LDH 2 (WBC)
LDH 3(lung)
LDH 4 (pancreas, kidney, placenta)
LDH 5 (liver, skeletal muscle)

CK isoforms and where they are expressed

CKMM (skeletal muscle),
CKMB (heart),
CKBB (brain)

What is the most specific marker for cardiomyocyte injury?

troponins – selective cardiac markers – not selective for heart attack

What is the most specific marker for Acute pancreatitis

lipase (more pancreatic specific) and amylase

What is the most specific marker for Liver injury

ALT (more specific) and AST

What is the most specific marker for Hepatobiliary disease

y-GT (more specific) and ALP

What enzyme isoform is useful as a marker of osteoblast activity?

bone isoform – bALP (bone specific alkaline phosphatase activity)

How does PTH stimulate calcium mobilization in bone

PTH receptor 1 (PTHR1) in osteoblasts.
Increases RANKL in OB which binds to RANK on osteoclast (OC) membrane (reduces bone turnover). Increases bone resorption.
High extracellular calcium in skeleton + proteins regulated by vitamin D promote bone mineralization

How does PTH stimulate calcium mobilization in kidney tubules

increases Ca reabsorption and phosphorus excretion by decreasing insertion of Type II Na+/P cotransporters (NPT2a, NPT2c) in apical membrane of proximal tubule.

How does PTH stimulate calcium mobilization in the intestine

secondary fashion –
ca between cells in intestinal
PTH sense calcium by calcium sensing receptor (CaR)

How does PTH affect renal handling of phosphate

increases phosphorus excretion –
blocks renal phosphate reabsorption

How does the parathyroid sense calcium?

activating mutations of CaR will lower set point and Inactivity mutations will cause a high set point due to particular mutation inherited

Describe bound and free forms of calcium in plasma

Free: measured by electrodes – 48% free (biologically active in feedback loops) and parathyroid
Bound: 46% bound to albumin. Doesn’t affect the feedback loop.
- 6 % bound to small anions (citrate, phosphate, lactate)

Adjust a total calcium for a low albumin

For every 1 g/dL decrease in albumin (4.0g/dL) – total calcium is adjusted upwards by 0.8 mg/dL

Example: total calcium is 7.5 mg/dL. If an albumin concentration of 2.5 g/dL is measured, the adjusted total calcium is 8.7 mg / dL

How does FGF work to lower phosphate levels

-FGF-23 (Fibroblast Growth Factor-23) produced by osteocytes and bone lining cells.
Synthesis regulated by plasma, PTH, and calcitriol – secreted in response to hyperphosphatemia
-Has phosphate dumping effect – blocks renal phosphate reabsorption

How does FGF work to affect vitamin D activation

-Inhibits active calcitriol production by inhibiting vitamin D 1-hydroxylase and stimulating vitamin 24-hydroxylase
-Favors destruction of 125 vitamin D dihydroxy and vitamin D 25 hydroxy

Describe diseases associated with increased FGF-23 and altered set points of the CaSR

-ADHR = Autosomal dominant hypophosphatemic rickets due to resistance proteolysis of FGF-23
-TIO = tumor induced osteomalacia – due to paraneoplastic syndrome (tumor ectopically producing FGF-23) in FGF-23
- Autosomal dominant Hypocalcemia – CasR – PTH deficiency, Ca/vitamin D deficiency, vitamin D resistant, mg depletion, pseudohypoparathyroidism, high calcium set point
- Familial hypocalciuric Hypercalcemia – CasR – primary hyperparathyroidism, increased calcitriol, increased bone reabsorption (Paget’s disease), vitamin D 24 hydroxylase deficiency

Identify recommended ranges for 25-OH vitamin D (calcidiol)

Storage form - Around 30 at least (below 20 is a vitamin D deficiency)

Use that chart from the Ca/Pi PowerPoint presentation to identify individuals with: primary hyperparathyroidism, primary hypoparathyroidism and the hypercalcemia of malignancy.

High calcium, normal PTH == something wrong with the feedback loop (included in hyperparathyroidism because non-intact feedback loop is affecting parathyroid gland)

Hypoparathyroidism == lost parathyroid tissue from surgeries

Red = intact feedback loop!!!!!
Blue hollow = no feedback loop (no parathyroid)
Green = intact feedback loop
Blue solid = non-intact feedback loop

Identify enzymes that activate and degrade calcitriol

Activate = Vit D 1 hydroxylase (activated by PTH)
Degrade = Vit D 24 dehydroxylase (activated by FGF-23)

Rhabdo (compartment syndrome)

Releases myoglobin (toxic, has free iron)
Releases potassium
CKMM
Creatinine (check renal function)

C-peptide

Secreted with secretion of insulin (cleaved from insulin on secretion)
Longer half-life than insulin
Marker of quality of insulin secretion
Differentiate from CRP (inflammation marker)

What is Cinacalcet? How does it work?

Mimics activity of calcium when bound to CasR. Given to chronic kidney disease patients – acts like calcium and has inhibitory effect on secretion of PTH.
Drug to prevent tertiary hyperparathyroidism in chronic kidney disease

Primary hyperparathyroidism

High PTH, High Calcium and low phosphorus
caused by adenoma in parathyroid gland (benign tumor – not malignant)

Secondary hyperparathyroidism

chronic kidney disease
High potassium and high phosphorus
High phosphorus, low Calcium and high PTH

Tertiary hyperparathyroidism

High calcium and high PTH
parathyroid glands become autonomous (big and overactive)- consistently secreting PTH
Osteoporosis