chemistry unit 2 exam

What are carbohydrates?

Complex organic compounds and a major source of food and energy for the body.

What are monosaccharides?

Simple sugars: glucose, fructose, and galactose

What are disaccharides?

Two monosaccharides joined by a glycosidic bond

What are oligosaccharides?

Chains of 2–10 sugar units

What are polysaccharides?

Many linked monosaccharide units

disaccharides: What makes up sucrose?

Glucose + fructose.

disaccharides: What makes up lactose?

Glucose + galactose

disaccharides: What makes up maltose?

Glucose + glucose

What enzymes begin carbohydrate digestion?

Salivary and pancreatic amylase

What are the intestinal brush-border enzymes?

Maltase, sucrase, and lactase

Which carbohydrate is directly used for cellular energy?

Glucose- the rest need to be converted into glucose

Where and in what form is excess glucose stored?

As glycogen in the liver and skeletal muscles

What are the three main pathways after glucose enters cells?

Embden-Meyerhof pathway (EMP, Glycolysis), hexose monophosphate shunt (HMP), and conversion to glycogen (Glycogenesis)

What is Embden-Meyerhof pathway (EMP, Glycolysis)?

Breakdown of glucose into pyruvate to produce ATP

What is the hexose monophosphate pathway?

An alternative glucose pathway producing NADPH and ribose; important in RBCs

What is conversion to glycogen (Glycogenesis)?

Glucose → glycogen for storage

only if excess of glucose, after a big meal. Stored for later use.

What is glycogenolysis?

Glycogen → glucose when glucose is needed

short glucose depletion

In between meals- liver breaks down stored glycogen to release glucose into the blood

What is gluconeogenesis?

Make new glucose

prolonged glucose depletion

During fasting- liver makes glucose from proteins and fats to keep glucose levels up/stable

Production of new glucose from noncarbohydrate sources, including amino acids, lactate, and glycerol

What is lipogenesis?

Glucose → Fat

Conversion of excess carbohydrates or energy into fat

Creation of fat

After lots of overeating carbohydrates- excess glucose converted to fat

What is lipolysis?

Fat → energy

Decomposition/Breakdown of fat into fatty acids

During prolonged exercise or fasting/starvation- body breaks down stored fat to provide energy

What happens during short glucose depletion?

Glycogenolysis releases stored glucose

What happens during prolonged glucose depletion?

Gluconeogenesis produces glucose from noncarbohydrate sources

Which hormone decreases blood glucose?

Insulin, secreted by pancreatic β-cells

which hormone increases blood glucose?

Glucagon, secreted by pancreatic A-cells

How does insulin affect cells?

Binds cell receptors and promotes glucose entry and use

What other effects does insulin have?

Promotes formation of glycogen, proteins, and fat

Which hormones increase blood glucose?

Glucagon, epinephrine, cortisol, growth hormone, and thyroxine (T4)

What does glucagon stimulate?

Glycogenolysis and gluconeogenesis

What does epinephrine do to glucose?

↑ Glucose by mobilizing glycogen and inhibiting insulin

What does cortisol do to glucose?

↑ Glucose through increased gluconeogenesis.

What does growth hormone do?

↑ Glucose by decreasing glucose entry into cells

What does thyroxine (T4) do?

↑ Glucose absorption and glycogenolysis

What are the diet requirements for serum/plasma/blood glucose fasting levels test?

No food or drink except water for 8-12 hours

What is the normal fasting serum/plasma glucose range?

70–99 mg/dL

what is impaired fasting serum/plasma glucose range?

100-125 mg/dL

“prediabetic range”

not enough to dx

what is serum/plasma glucose provisional diabetes diagnosis range?

≥126 mg/dL

still needs further tests for final conclusion

What is the normal whole-blood glucose range?

65–95 mg/dL

What is the normal CSF glucose range?

40–80 mg/dL (2/3 of venous value)

What is the most commonly used glucose method testing?

Glucose oxidase / Polarographic technique

Which glucose method is specific for β-D-glucose?

Glucose oxidase

What happens in the polarographic method (Glucose oxidase) reaction?

B-D-Glucose + oxygen → gluconic acid + hydrogen peroxide

nnnnnnnnnnn^ ^ ^

nnn(specific substrate) (consumed) (produced)

what is depleted in the glucose oxidase / polarographic technique and what is it proportional to?

Oxygen depletion is proportional to the concentration of glucose

Oxygen is consumed; ↓ oxygen is proportional to glucose concentration

More oxygen depletion = more concentration of glucose

What happens in the glucose oxidase / colorimetric technique (Trinder reaction) reaction?

nnnnnnnnnnnnnnnnnnnn(Horseradish peroxidase (HRP))

nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnv

H2O2 + reduced chromogen → Oxidized chromogen + H2O

nnnnnnnnn^ ^

(from primary reaction) (colored product)

In the glucose oxidase / colormetric/trinder reaction what is being consumed, what is the dye compound, and what is used to catalyze the side reaction?

Consumed- H2O2

dye compound- Chromagen

Catalyzer- Peroxidase (Horseradish peroxidase (HRP))

In the glucose oxidase / colormetric/trinder reaction what is glucose proportional too?

Shift in absorbance monitored spectrophotometrically and proportional to glucose

How does the colorimetric glucose oxidase method work?

Hydrogen peroxide reacts with chromogen using HRP; ↑ color intensity means ↑ glucose

What causes falsely decreased glucose oxidase results?

High bilirubin, ascorbic acid, and uric acid

What causes falsely increased glucose oxidase results?

Bleach

What is the reference method for glucose?

Hexokinase

what is the method for hexokinase?

_____ in the presence of ATP converts glucose to G6PO4 G6PO4 and its cofactor NADP+ are then converted to 6-phosphogluconate and NAHPH by glucose-6- phosphate dehydrogenase

What does hexokinase measure?

NADPH production at 340 nm

How quickly can glucose decrease in an unprocessed specimen?

Approximately 7% per hour, beginning within the first hour

What should be done with glucose specimens?

Test promptly or separate cells promptly; refrigeration

What does urine Clinitest detect?

Reducing substances; not specific for glucose

Seen when renal threshold exceeded - 160–180 mg/dl

What does a glucose oxidase urine dipstick detect?

Glucose

Seen when renal threshold exceeded - 160–180 mg/dl

Oral Glucose Tolerance Test: what does it measure?

Blood glucose levels measured at regular intervals after drinking

What carbohydrate intake is required before an OGTT?

Patient should be ambulatory and on normal-to-high carbohydrate intake (150g) for 3 days prior to test

What fasting period is listed for OGTT preparation?

10-16 hrs before test

What other OGTT preparation instructions are emphasized?

perform only during AM/Morning, water only during fasting, and no smoking

What is the adult oral glucose dose for OGTT?

75 g glucose

What is the pediatric OGTT dose?

1.75 g/kg body weight (or max 75g)

what is the OGTT procedure?

1) draw fasting blood

2) drink glucola

3) draw blood at regular intervals

what is the 2 hour OGTT procedure?

just a variation of the OGTT but measurement taken two hours later after drinking glucola, but not routine

OGTT: what factors affect it before test?

Prior carbohydrate intake, Duration of fast, Gl surgery, intercurrent illness

OGTT: what factors affect it during test?

Nausea (CANCEL TEST)

What is normal 2-hour OGTT glucose range?

<140 mg/dL

What is impaired 2-hour OGTT glucose range?

140–199 mg/dL

What is provisional diabetic 2-hour OGTT glucose?

≥200 mg/dL

What does a normal OGTT curve look like?

Glucose rises and returns toward baseline by 2 hours, may dip slightly below (less than 140)

What does an impaired OGTT curve look like?

Glucose rises and remains elevated in the impaired range at 2 hours (140-199)

What does a diabetic OGTT curve look like?

High glucose rise, remaining above the diabetic threshold at 2 hours (above 200)

What does a flat OGTT curve suggest?

Malabsorption

How do you diagnose Diabetes Mellitus?

Should be confirmed over a few days by either OGTT, Fasting Plasma Glucose, or HbA1c

What is HbA1c?

Glycosylated hemoglobin

What does HbA1c test?

Average blood glucose over the previous 2–3 months

More reliable in monitoring long-term diabetes control

what tube do we use for HbA1c?

Purple- EDTA

HbA1c: what fasting schedule do you need to be on?

Fasting not required

HbA1c: what method is it based on?

affinity Chromatography

Based on structural characteristics of glycogroups on hemoglobin

what is the range for Normal HbA1c?

< 5.7%

what is the range for Impaired HbA1c?

5.7% to 6.4%

what is the range for Provisional Diabetes Diagnosis in HbA1c?

≥6.5%

What affects HbA1c accuracy?

Altered RBC lifespan

Are point-of-care glucose tests recommended for diabetes diagnosis?

No POC testing is not recommended for diagnosis

What is diabetes mellitus?

A group of metabolic disorders characterized by hyperglycemia

what is hyperglycemia?

abnormal increase in plasma glucose

what is renal threshold of glucose?

160-180 mg/dL

which organ plays a big role in usage and storage of glucose?

Liver

What causes Type 1 diabetes mellitus?

Cell-mediated autoimmune destruction of pancreatic β-cells.

What is the insulin status in Type 1 DM?

Absolute insulin deficiency; insulin dependence from diagnosis

What are common Type 1 DM characteristics?

Often childhood/adolescent onset, abrupt symptoms, autoantibodies, and diabetic ketoacidosis

What major emergency is Type 1 DM prone to?

Diabetic ketoacidosis (DKA)

what is Diabetic ketoacidosis (DKA)?

liver rapidly breaks down fat when not enough insulin, makes blood really acidic and causes severe dehydration.

what lifestyle is DM1 associated with?

Not associated with obesity or age

What causes Type 2 diabetes mellitus?

Insulin resistance with relative insulin deficiency and eventual secretory defect, receptors don’t work on the cells

What are common Type 2 DM risk factors?

Obesity, abdominal fat, increasing age, inactivity, and family history

What happens to insulin production early in Type 2 DM?

Pancreas compensates by increasing insulin production

What happens as Type 2 DM progresses?

β-cells may no longer compensate, causing further insulin deficiency, secretory insulin deficiency (NO LONGER BEING ACCEPTED INTO CELL)

What major emergency is Type 2 DM more prone to?

Hyperosmolar hyperglycemic state (HHS)

what is Hyperosmolar hyperglycemic state (HHS)?

where the cells can’t use glucose, so the glucose remains outside cell, raises serum glucose which increases plasma osmolality, which leads to glucose pulling water out (excess urination), causes severe dehydration, leads to a coma.

what cell secrets insulin?

Pancreatic B cells