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Clinical Chemistry > Carbs > Flashcards

Carbs Flashcards

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1
Q

What’s the general description of carbs?

A
  • C=O (carbonyl) and -OH (hydroxyl/alcohol) functional groups
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2
Q

Carb classification

A
  • Size of base carbon chain
  • C=O location
  • Number of sugars
  • Stereochemistry
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3
Q

Galactase converts galactose to ____

A

Glucose

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4
Q

Which sugar can be directly used for energy? What happens to the ones that can’t?

A

Glucose

Others such as fructose, galactose, and lactose get converted to glucose first

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5
Q

Name two main polysaccharides and their sources

A
  • Starch: plant
  • Glycogen: animal
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6
Q

Most common non-reducing substance

A

Sucrose (table sugar)

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7
Q

Which body system can’t store/concentrate carbs?

A

Nervous system
But glucose is its main source of energy so must maintain constant supply in tissues

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8
Q

Purpose of villi

A

Increase surface area, which increases absorbed energy from food

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9
Q

Types of glucose pathways and explanations

A

:)

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10
Q

Describe glucose storage

A

Glucose -> Liver -> glycogen -> fat

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11
Q

Describe insulin production pathway (fed state)

A
  • preproinsulin -> proinsulin (A, B, and C peptides) -> insulin + C-peptide
  • Anabolic process
  • Promotes cellular uptake of glucose
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12
Q

In which conditions is insulin increased?

A
  • Lipogenesis (fat creation)
  • Protein synthesis
  • Glycogenesis
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13
Q

In which conditions is insulin decreased?

A
  • Lipolysis (breakdown of fat)
  • Ketone formation
  • Gluconeogenesis (new glucose made from aa)
  • Glycogenolysis
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14
Q

Describe “fasting” state

A
  • Glucagon released from pancreatic alpha cells during stress and fasting states
  • Goal: increase glucose levels (hyperglycemic agent)
  • Catabolic
  • Liver: glycogen -> glucose -> blood
  • Muscle: glycogen -> G6-P
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15
Q

Function/source of epinephrine in fight or flight?

A
  • Secreted from adrenal medulla
  • Similar to glucagon
  • Increases plasma glucose by increasing glycogenolysis/lipolysis, and inhibiting insulin secretion
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16
Q

List disorders that involve hyperglycemia

A
  • Diabetes mellitus
  • Endocrine disorders (acromegaly, Cushing’s syndrome, thyrotoxicosis, pheochromocytoma)
  • Drugs (anesthetics, steroids)
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17
Q

Acromegaly

A

Increased growth hormone

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18
Q

Cushing’s syndrome

A

Increased cortisol

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19
Q

Thyrotoxicosis

A

Increased T4

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20
Q

Pheochromocytoma

A

Increased epinephrine

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21
Q

List 3 symptoms of diabetes mellitus

A
  • Polyuria (too much urine made)
  • Polydipsia (too much thirst)
  • Unexplained weight loss
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22
Q

Diagnostic criteria for diabetes mellitus

A
  1. HbA1C >= 6.5%
  2. Fasting plasma glucose >= 126 mg/dL
  3. 2hr plasma glucose >= 200 mg/dL
  4. Random plasma glucose >= 200 mg/dL
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23
Q

Describe Type 1a diabetes

A
  • Beta cell destruction due to autoimmunity -> absolute insulin deficiency
  • Patients must take insulin to survive
  • Usually young, with acute onset (days-wks)
  • Islet-cell Ab
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24
Q

Describe Type1b diabetes

A

Idiopathic

25
Q

Describe Type 2 diabetes

A
  • Insulin resistance in peripheral tissue + insulin secretory defect of beta cells
  • Variable insulin levels
  • Highly associated with family history, age > 40, obesity, lack of exercise
  • Smoking, high blood pressure, overweight, high fat/cholesterol lvls
26
Q

Describe “other types” of hyperglycemia

A
  • Pancreatic, hormonal disease
    • pancreatitis, cystic fibrosis
    • acromegaly, Cushing’s syndrome
  • Drug/chem toxicity
  • Insulin receptor abnormalities
  • No renal/retinal complications
27
Q

Lab findings in hyperglycemia

A
  • Decreased/absent insulin
  • Increased glucose in plasma/urine (greater than 180 mg/dL)
  • Increased urine-specific gravity
  • Increased serum/urine osmolality
  • Ketones in serum/urine (ketonemia/ketonuria)
  • Decreased blood/urine pH (acidosis)
  • Electrolyte imbalance
28
Q

Normal fasting glucose mg/dL

A

70-99 mg/dL

29
Q

Provisional diabetes diagnosis mg/dL

A

FPG (fasting plasma glucose) >= 126 mg/dL

30
Q

Generally describe gestational diabetes mellitus

A
  • Pregnancy
  • Frequent but temporary glucose intolerance
  • Greater risk of perinatal complications
  • Human placental lactogen
31
Q

Describe glucose screening results for diagnosis of gestational diabetes mellitus

A
  • glucose > 140 mg/dL 1 hr after 50g glucose load screening
    2-step approach:
  • FPG >= 95 mg/dL
  • FPG >= 180 mg/dL 1hr
  • FPG >= 155 mg/dL 2hrs
  • FPG >= 140 mg/dL 3 hrs
32
Q

Patient prep for glucose tolerance test (to diagnose gestational diabetes)

A
  • Normal diet 3 days before test
  • No food after regular evening meal on day before test
  • Take fasting blood and urine specimen
  • Drink 100 g glucose load within 5 min
  • Allow water, but NO food, chewing gum, smoking, or exercise during test
  • Specimens taken 1, 2, and 3 hrs after ingestion
33
Q

Normal glucose tolerance after 2hrs
PG = plasma glucose

A

2 hr PG <= 140 mg/dL

34
Q

Provisional diabetes diagnosis

A

2 hr PG >= 200 mg/dL

35
Q

List disorders associated with hypoglycemia

A
  • Insulin overdose
  • Drugs (sulfonylureas, antihistamines)
  • Long-term alcoholism
  • Insulinoma (pancreatic tumor)
  • Galactosemia (missing enzyme that breaks down galactose)
  • Glycogen storage diseases
36
Q

Level 1 hypoglycemia criteria + description

A
  • Glucose < 70 mg/dL
  • Treat with fast-acting carb and ???dose adjustment of glucose lowering therapy???
37
Q

Level 2 clinically significant hypoglycemia criteria + description

A
  • Glucose < 54 mg/dL
  • Sufficiently low to indicate serious/clinical importance
38
Q

Level 3 severe hypoglycemia criteria + description

A
  • NO specific glucose threshold
  • Associated with severe cognitive impairment requiring external assistance for recovery
39
Q

Serum/plasma glucose collection/processing criteria

A

Spin within 2-4 hrs to remove serum/plasma otherwise cells will continue to use up glucose -> false decrease

40
Q

Renal threshold in proximal convoluted tubule

A
  • Reabsorbs ALL glucose if <180 mg/dL
  • Glycosuria if blood glucose > 180 mg/dL
  • Diabetic nephropathy blows out glomerulus
41
Q

Describe whole blood specimen requirements for glucose measurment

A
  • Used with home glucose monitoring units
  • Cellular use of glucose gives 7% decrease/hr
  • NaF preserves glucose 24 hr, RT but can’t use specimen for enzyme assays, esp. urease
  • Lithium iodoacetate preserves glucose and does NOT interfere w urease
  • Capillary blood = fasting venous level + 5 mg/dL
42
Q

Describe plasma/serum specimen requirements for glucose measurement
RR = reportable range

A
  • 10-15% higher level than whole blood glucose
  • RR: 70-105 mg/dL
43
Q

CSF specimen reference ranges for glucose measurement

A
  • RR: 60-70% of plasma glucose
  • CSF glucose = 40-70 mg/dL
44
Q

Urine specimen reference ranges for glucose measurement

A
  • RR: <30 mg/dL
  • Random < 500 mg/day
45
Q

List 3 methods of glucose measurement

A
  1. Glucose oxidase
  2. Hexokinase
  3. Clinitest (uses copper reduction)
46
Q

T/F: Redox rxns are highly specific for glucose

A

False: Least specific for glucose

47
Q

Why don’t we use glucose to monitor diabetes? What do we use instead

A

Because its levels change fast. Instead, use glycated hemoglobin (HbA1C)

48
Q

Describe glycated hemoglobin

A
  • Making it is an irreversible rx occuring throughout the 120-day RBC lifespan
  • Reflects timed average [glucose] over previous 4-8 wks
  • HbA1C = 80% of total glyco-Hgb
  • Ref range = 3-6% total Hgb
49
Q

Considerations when measuring HbA1C

A
  • Abnormal Hgb can also be glycated
  • Variability in levels of “labile fraction” aka intermediates
50
Q

For every ____ decrease in HbA1C, risk of _____ complications is reduced by _____

A
  • 1%
  • Microvascular
  • 35%
51
Q

List manual methods for managing diabetes

A
  • Ion-exchange chromatography (HbA1C fast fraction elutes first
  • Affinity chromatography (HbA1C elutes last)
52
Q

Roche diagnostics method for managing diabetes

A
  • Doesn’t have same risk of interference with Hgb variants
  • Automated
  • Based on turbidimetric inhibition immunoassay (TINIA) for hemolyzed whole blood
53
Q

Glycated serum protein “other testing”

A
  • Albumin (fructosamine) colored product
  • Turnover 2-3 wks
  • Rapid method using tetrazolium dye reduction
54
Q

Describe glycogen storage diseases

A
  • Lack of enzymes in glycogen metabolism
  • Increased tissue glycogen
  • Results in severely limited lifespan
  • von Gierke’s disease (liver cells lack glucose-6-phosphatase, which prevents blood glucose from increasing
55
Q

Lactose intolerance

A
  • Deficiency in intestinal mucosal lactase
  • GTT done as baseline
  • 2nd day, give lactose instead of glucose
  • normal: GTT curve
  • abnormal: flat curve + pain
56
Q

Ketones

A
  • Complication of uncontrolled diabetes
  • Acid-base imbalance
  • Can be life-threatening
  • Acetone, acetoacetate, beta-hydroxybutryate -> can act drunk without actually being drunk
57
Q

Ref range serum or plasma fasting glucose

A

70-99 mg/dL

58
Q

Ref range HbA1C

A

4.0-5.6%

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