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IUCHEM > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Describe the general structure of carbohydrates, including the empirical formula.

A

Carbohydrates are aldehyde or ketone derivatives of polyhydroxy-alcohols or compounds that yield these derivatives on hydrolysis

Empirical formula: (CH2O)n

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2
Q

Differentiate monosaccharide, disaccharides, and polysaccharides.

A

Monosaccharide: a simple sugar that consists of a single polyhydroxy aldehyde or ketone unit and is unable to be hydrolyzed to a simpler form

Disaccharide: two (2) monosaccharide linked together

Polysaccharide: The linkage of multiple monosaccharide units

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3
Q

State the specific composition of the following carbohydrates:
a. Lactose
b. Maltose
c. Sucrose
d. Glycogen
e. Starch

A

a. Lactose: Glucose + Galactose
b. Maltose: Glucose + Glucose
c. Sucrose: Glucose + Fructose
d. Glycogen: composed of multiple glucose chains
e. Starch: composed of amylase and amylopectins (grains and starch vegetables)

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4
Q

Explain the term “reducing sugars,” according to the reagent used for their detection and the clinical significance of a positive test for reducing sugars.

A

Glucose and galactose have a free oxygen on the alpha carbon, therefore, they have the ability to “reduce”

Benedict’s solution, which contains copper, in the presence of glucose or galactose, are capable of reducing cupric ions to cuprous ions, causing a color change

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5
Q

List two analytically important reducing sugars, according to the lecturer.

A

Glucose and Galactose

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6
Q

Describe the following aspects of carbohydrate digestion and absorption:

a. Site at which starch digestion begins and the enzyme responsible

b. Intestinal digestion and four enzymes responsible

A

a. Begins in the mouth by salivary amylase

b. Pancreatic amylase, lactase, maltase, and sucrase

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7
Q

Discuss the following intermediary metabolic pathways of carbohydrates, including in what organ in the body they occur AND the specific starting and ending products:

a. Glycolysis (aerobic and anaerobic)
b. Krebs (tricarboxylic) cycle
c. Glycogenesis
d. Glycogenolysis
e. Gluconeogenesis

A

a. Glycolysis (aerobic and anaerobic) – breakdown of glucose, forming pyruvate or lactate – start: glucose, end: pyruvate or
lactate
b. Krebs (tricarboxylic) cycle: a series of chemical reactions to release stored energy – start: acetyl CoA, end: ATP
c. Glycogenesis: making glycogen from glucose – start: glucose, end: glycogen
d. Glycogenolysis: breaking down glycogen to glucose – start: glycogen, end: glucose
e. Gluconeogenesis: making glucose from non-CHO sources – start: AAs, glycerol, fatty acids, lactate, end: glucose

*All metabolic pathways take place in LIVER

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8
Q

Discuss the following aspects of insulin:
a. Specific site of production
b. Functions of proinsulin and C-peptide
c. General effect on blood glucose concentration
d. Action on cell membranes and resultant effect on blood sugar levels
e. Major factor that regulates its release

A

a. Beta cells of islets of Langerhans of the pancreas

b. Proinsulin: precursor of insulin – in its storage phase

   C-peptide: a portion of the proinsulin, that when it’s activated into insulin, it gets cleaved – necessary to ensure the correct folded structure of insulin

c. Lowers blood glucose

d. Increases cell membrane permeability to glucose and other substances (i.e. potassium) – causing a decrease in blood sugar levels

e. Blood glucose concentration

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9
Q

List the specific site of production and general effect on blood glucose concentration (increase or decrease) for the following hormones:
a. Glucagon:
b. Growth hormone:
c. Epinephrine:
d. Cortisol:
e. Thyroid hormone:
f. Somatostatin:
g. Somatomedins:

A

a. alpha cells of pancreatic islets of Langerhans – increases glucose concentration
b. anterior pituitary gland – increases glucose concentration
c. adrenal medulla – increases glucose concentration
d. adrenal cortex – increases glucose concentration
e. thyroid – increases glucose concentration
f. delta cells of pancreatic islets of Langerhans – decreases glucose concentration
g. hormones produced in liver in response to GH – decreases glucose concentration

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10
Q

Define the following pathophysiological terms:
a. Hyperglycemia, including the specific blood sugar value associated with it

b. Hypoglycemia in adults, including the specific blood sugar value associated with it

A

a. Increased glucose concentration in the blood – >100 mg/dL

b. Decreased glucose concentration in the blood – <50 mg/dL adults, <30 mg/dL infants,
<20 mg/dL premature infants

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11
Q

Recognize nine complications of diabetes, according to the lecturer.

A
  1. Nephropathy*
  2. Neuropathy
  3. Heart disease and stroke
  4. Hypertension
  5. Blindness or retinopathy*
  6. Amputations*
  7. Dental disease
  8. Complications of pregnancy*
  9. Life-threatening events*: diabetic ketoacidosis, etc.
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12
Q

Discuss the following aspects of the diagnosis of diabetes mellitus:

	a.	Three specific diagnostic criteria, including specific laboratory values associated with the criteria
	b.	Four clinical symptoms used for its diagnosis
A

Three specific diagnostic criteria, including specific laboratory values associated with the criteria

a.             Fasting blood glucose >/= 126 mg/dL OR 
		Clinical symptoms plus random glucose >/= 200 OR
		2-hour post-prandial glucose >/= 200 mg/dL during OGTT

b.		Polyuria (urinating frequently)
		Polyphagia (eating frequently)
		Polydipsia (drinking frequently)
		Unexplained weight loss
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13
Q

Discuss Type 1 diabetes mellitus in detail, according to:

	a.	One specific general cause of the disease, according to the lecturer
	b.	Causes of beta cell injury
	c.	Relative insulin concentrations
	d.	Three general metabolic changes in disease
            e.     Treatment
A

a. Beta-cell destruction

b. Genetic factors, environmental factors, viral causes, chemical causes, autoimmune disease

c. Very decreased to absent

d.
1. Inhibition of glycolysis
2. Increased glycogenolysis, gluconeogenesis, lipolysis
3. Increased levels of Acetyl CoA (in excess, is converted to ketone bodies)

e. Administration of exogenous insulin

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14
Q

Discuss Type 2 diabetes mellitus in detail, according to:

	a.	Two specific general causes of the disease, according to the lecturer
	b.	Two factors that may predispose a patient to develop the disease
	c.	Relative insulin concentrations
	d.	Treatment
A

a.
1. Insulin resistance
2. Beta-cell failure

b.
1. Genetic factors
2. Environmental factors

c. Variable (increased, decreased, or normal depending on the cause and severity of disease)

d.
1. Weight loss
2. Dietary changes
3. Oral hypoglycemic agents

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15
Q

Briefly discuss gestational diabetes mellitus (GDM) according to:

	a.	Definition
	b.	Possible long-term sequelae
	c.	Screening test
A

a. A form of glucose intolerance in some women during pregnancy

b. Immediately after pregnancy, some women are found to have Type 2 diabetes – in general, women who have had
gestational diabetes are at a greater risk of developing diabetes within the next 10-20 years

c. O’Sullivan Test

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16
Q

Briefly discuss maturity-onset diabetes of youth (MODY) according to:

	a.	Cause
	b.	Affected age group
A

a. Single gene defect that causes faulty insulin secretion

b. Before 25 y.o.

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17
Q

Recognize four conditions that may cause secondary diabetes.

A
  1. Pancreatic disease
  2. Cystic fibrosis
  3. Corticosteroid
  4. Other hormonal disorders
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18
Q

List fasting and two-hour postprandial blood sugar levels associated with prediabetes/impaired glucose tolerance (IGT).

A

FBS > 100 mg/dL < 126 mg/dL
OGTT: 140-199 mg/DL

19
Q

Discuss the correlation between hemoglobin A1c levels and estimated fasting blood sugar levels in the diagnosis of prediabetes.

A

The higher a patient’s FBS is the higher the A1C level – A1C measures the average amount of sugar residues (glycation) that are present on the Hgb in the RBCs

20
Q

Briefly discuss adolescent diabetes mellitus according to:

	a.	Recognition of symptoms unique to this disorder

	b.	Definition of double diabetes

	c.	How patients develop double diabetes

	d.	The most important factor in the development of this disease
A

a. Blurred vision
Frequent infections
Acanthosis nigricans (skin around neck, armpits appears very dark)

b. Patient has elements of both Type 1 and Type 2 DM

c. Type 1 becomes overweight, and then becomes insulin resistant or Type 2 develops antibodies to beta cells

d. Weight gain

21
Q

Recognize typical blood glucose levels and clinical findings in hypoglycemia

A

FBS: < 50 mg/dL

Weakness
Shakiness
Lightheadedness

22
Q

Briefly differentiate four types of hypoglycemia according to cause and typical blood glucose concentrations.

A

Severe hypoglycemia: < 20-30 mg/dL – malnutrition, taking too much insulin, advance liver disease, etc.

Hypoglycemia in neonates & infants: mean glucose range reference range is ~35 mg/dL due to low glycogen stores at birth

Fasting hypoglycemia in adults: < 45 mg/dL – cause by certain drugs (most common), etc.

Reactive hypoglycemia: < 45 - 50 mg/dL after eating – caused by the uptake of too much glucose

23
Q

Discuss the following aspects of galactosemia:

a. Specific enzyme defect
b. Clinical symptoms and long-term effects
c. Three laboratory means of diagnosis

A

a. Galactose-1-phosphateuridylyltransferase (GALT)

b. Failure to thrive on cow’s milk — vomiting, diarrhea – later, liver disease, cataracts, mental retardation

c.
1. Benedict’s test (Clinitest)
2. ID of the sugar by paper chromatography
3. Direct assay of enzyme activity

24
Q

List the specific enzyme deficiency and clinical symptoms of lactose intolerance.

A

Lactase deficiency – abdominal pain, diarrhea, lactose in urine

25
Q

Discuss the following aspects of glycogen storage diseases:

	a.	Specific cause

	b.	Four general clinical and biochemical features of the liver forms

	c.	One general clinical feature of the muscle forms
A

a. Enzyme deficiency in glycogen metabolism

b.
1. Hepatomegaly
2. Hypoglycemia
3. Decreased insulin
4. Increased glucagon

c. Strenous exercise

26
Q

Discuss the following aspects of von Gierke’s disease (Type I glycogen storage disease) and Pompe’s disease (Type II glycogen storage disease):

a. Specific enzyme deficiency in each disease

b. Whether each disease is a liver or muscle form

A

a.
• von Gierke’s disease: deficiency of glucose-6-phosphatase
• Pompe’s disease: deficiency of a-1,4-glucosidase

b.
• von Gierke’s disease: liver form
• Pompe’s disease: muscle form (predominately the heart and skeletal muscle)

27
Q

Discuss the following aspects of glucose testing, specimen collection, and storage:

a. Reference range for fasting glucose in adults, premature and term neonates, and children

b. The reason why separation from the cells or testing must be performed within a half hour of venipuncture

c. The specific reason why oxalate-sodium fluoride is the preferred anticoagulant

A

a. Adults & children: 70-100 mg/dL
Preemies: 25-80 mg/dL
Term: 60-95 mg/dL

b. Glucose decreases up to 7% per hour or more when serum is left in contact with the cells

c. Inhibits enolase, a enzyme in the glycolytic pathway – cells will not be able to use the glucose available

28
Q

Specifically differentiate how glucose values may differ among:

	a.	Whole blood

	b.	Plasma

	c.	Oxygenated, deoxygenated, and capillary blood
A

a. 12-15% less than plasma

b. 12-15% more than blood

c. Oxygenated and capillary blood glucose levels ~ 2-5 mg/dL higher than deoxygenated samples

29
Q

Discuss the following aspects of CSF glucose:

	a.	Reason for prompt analysis

	b.	The relationship normally observed between plasma glucose and CSF glucose
A

a. Possible cellular utilization (i.e. bacterial infection would have the bacteria and the WBCs consuming the glucose providing a falsely lower concentration)

b. CSF is 60-70% concomitant plasma levels (i.e. if the plasma glucose is 100 mg/dL, the CSF glucose should be 60-70 mg/dL)

30
Q

Discuss the clinical significance and specific renal threshold range for urine glucose.

A

160-180 mg/dL – assuming good kidney function, they should be able to reabsorb all glucose that gets filter up to the renal threshold

31
Q

Briefly describe Benedict’s copper reduction test (Clinitest) for the measurement of glucose and other
reducing sugars, according to:

a. Principle of the measurement

b. Clinical significance of a positive test

c. Specific carbohydrates detected

A

a. Glucose and Galactose are reducing sugars that in the presence of Copper can reduce cupric ions to cuprous ions, causing a
color change

b. Presence of glucose and/or galactose in urine

c. Glucose and/or galactose

32
Q

Recognize three indications for performing an intravenous glucose tolerance test.

A
  1. Malabsorption
  2. Celiac disease
  3. GI surgery
33
Q

Briefly describe the principle of the hexokinase method for glucose, including the reagents used and products formed in both reactions in the coupled enzymatic method.

A

In hexokinase, the reaction uses glucose-6-phosphate dehydrogenase

34
Q

Recognize the principle of the glucose oxidase (“Trinder”) method for glucose in serum and urine, including the reagents used.

A

This method combines the use of the enzyme glucose oxidase and peroxidase

35
Q

Recognize patient preparation instructions for an oral glucose tolerance test (OGTT).

A
  1. Minimum of 150 grams of CHO for 3 days prior to test
  2. Fasting for 10-16 hours (water only)
  3. Discontinue medications that alter glucose levels
  4. Normal amount of activity before and during test
36
Q

State the procedure for and use of postprandial testing and the O’Sullivan test.

A

Postprandial testing: Give a 75g oral glucose load or have a patient eat a meal – if glucose is >/= 126 mg/dL, patient may be diabetic – used for a preliminary diagnosis of DM

O’Sullivan test: Give 50g oral glucose load to fasting patient, draw sample at 1 hour, if >/= 140 mg/dL, perform OGTT – used to diagnose gestational diabetes

37
Q

Discuss the following aspects of ketone bodies in detail:

a. Origin:

b. The name of the metabolic pathway that leads to their formation

c. The specific starting products

d. Names of the three ketone bodies and their specific relative proportions in the blood

A

a. Beta-oxidation of free fatty acids

b. Krebs Cycle

c. Non-CHO sources — fatty acids, amino acids, pyruvate, lactate

d.
1. Beta-hydroxybutric acid (78%)
2. Acetoacetic acid (20%)
3. Acetone (2%)

38
Q

Briefly discuss diabetic ketoacidosis (DKA) according to why the patient develops ketosis, acidosis, and hyperlipidemia.

A

The body is “tricked” into producing more glucose because the cells are not receiving an uptake – this continually initiates gluconeogenesis to make glucose, via acetyl CoA, at the expense of producing ketones as a by-product

When in ketosis, certain acids (i.e. acetoacetic acid) can be converted into acetone – leading to acidosis

Liver sends excess fatty acids leading to hyperlipidemia

39
Q

Recognize five other conditions of decreased carbohydrate availability that can lead to ketosis.

A
  1. Starvation
  2. Frequent vomiting
  3. Glycogen storage disease
  4. Alkalosis
  5. Alcoholism
40
Q

Describe the colorimetric method (Acetest or Ketostix) for the measurement of ketones, according to:

a. Specific reagent used

b. Specific relative reactivity with each of the three ketone bodies

c. Specimen storage requirements

A

a. Sodium nitroprusside

b. Reacts ONLY with acetone and acetoacetate – five times more sensitive to acetoacetate – DOES not react with beta-hydroxybutyrate

c. 1. Keep specimen container closed
2. Keep sample refrigerated

41
Q

Briefly describe the pathogenesis of hyperosmolar hyperglycemic nonketotic coma (HHNC).

A

An increase in blood glucose levels cause an increase in osmolality as water shifts from outside the bloodstream to inside the bloodstream leading to intracellular dehydration

42
Q

Briefly discuss the following aspects of lactate (lactic acid):

a. Three causes of Type A lactic acidosis

b. Five causes of Type B lactic acidosis

c. Five causes of increased CSF lactate

d. Patient preparation, specimen collection, and sample analysis requirements

A

a.
Decreased tissue oxygenation
1. Shock
2. Hypovolemia
3. Cardiac failure

b.
Metabolic causes:
1. DM
2. Neoplasia
3. Liver disease
4. Drugs/Toxins

c.
1. CVA
2. Intracranial hemorrhage
3. Bacterial meningitis
4. Epilepsy
5. Other CNS disorders

d. Patient preparation, specimen collection, and sample analysis requirements
• No tourniquet
• No exercising of arm
• MUST be placed on ice IMMEDIATELY
• Separate from cells within 15 minutes of draw

43
Q

Discuss glycated hemoglobin in detail according to:

a. A brief description of the process of glycation

b. Specifically why its measurement can be used to assess diabetic blood sugar control over a three to four month time span

c. A listing of two general categories of measurement methods

A

a. An addition of a sugar residue to amino groups of proteins

b. Because the glycated hemoglobin formation is irreversible and normal RBCs lifespan is 120 days – unaffected by day-to-day
fluctuation, exercise, etc.

c.
1. Based on charge differences
2. Based on structural differences

44
Q

State the specific clinical application of the measuring the following analytes:

	a.     Insulin
	b.	Proinsulin  
	c.	C-peptide
	d.	Urine glucose by dipstick
	e.	Urinary microalbumin
A

a. Insulin: evaluates fasting hypoglycemia (i.e. releasing insulin at an inappropriate time?)
b. Proinsulin: evaluates benign or malignant beta-cell tumors of pancreas
c. C-peptide: evaluates fasting hypoglycemia
d. Urine glucose: uses glucose oxidase to produce color change – specific for glucose ONLY
e. Urinary microalbumin: evaluates for microvascular disease – early detection of renal disease due to hypertension

IUCHEM (20 decks)

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