Module 2- Carbohydrates Flashcards
What are the 3 classifications of carbohydrates?
Monosaccharides, oligosaccharides, polysaccharides
Most common isomer in the human body
B-D-glucose
What are polysaccharides?
High molecular weight
Glycogen
Starch
Are broken down by specific enzymes secreted by pancreas or intestinal wall
What is anaerobic glycolysis?
Not oxygen dependent
Splitting of glucose into 2 pyruvates to produce small amounts of ATP
What is aerobic glycolysis?
Oxidation of pyruvate in the mitochondria via the Kreb’s cycle and electron transfer chain to produce large amounts of ATP
Is anaerobic glycolysis reversible?
All steps are reversible EXCEPT conversion to G-6-P by hexokinase (liver cells can reverse this step)
What is glycogenesis vs. glycogenolysis?
Glycogenesis - excess glucose converted into glycogen
Glycogenolysis - breakdown of glycogen back to G-6-P
What is gluconeogenesis?
Synthesis of new glucose from non-carbohydrate sources
Not efficient
What occurs in glucose regulation?
Low blood glucose - release of glucagon acts to increase blood glucose levels
High blood glucose - release of insulin acts to decrease blood glucose levels
Other hormones that raise blood glucose levels
Cortisol
Epinephrine
Growth hormone
What is the renal threshold?
Maximum concentration in the blood that can be completely reabsorbed
All glucose is normally filtered and reabsorbed by kidneys
Blood levels above 10 mmol/L are unable to reabsorb all the glucose
Analysis of glucose specimens
Serum or plasma
Whole blood values are about 10% LOWER
Must separate cells within 1-2 hours
Fasting must be 10-12 hourly
Urine - glucose levels in diabetes
CSF - identifying bacterial meningitis
Glucose oxidase method
Reacts with B-D-glucose
Converts glucose to gluconic acid and hydrogen peroxide
What are 2 ways glucose oxidase can be measured?
Amperometry - uses an oxygen electrode to measure consumption of oxygen
Colormetric - Trinder’s Reaction, add a peroxidase and a chromagen to form an oxidized colored product (subject to interference)
Hexokinase method for measuring glucose
Formation of NADPH measured photometrically at 340nm
Glucose dehydrogenase method for measuring glucose
NADH formation measured at 340nm
What are the collection protocols for glucose?
Fasting glucose - at least an 8hr fast
Random glucose - any time
2 hrs glucose tolerance - 2 hours postcibal
Gestational diabetes screen - glucose tolerance test for gestational diabetes mellitus
What is the process for the 2 hour PP (glucose tolerance) test?
2 hours post pranidal
- Standard glucose load administered 75g in 300mL
- Measure blood glucose levels after 2 hours (should be less than 6.7mmol/L)
What is the process of the gestational diabetes screen?
- 50g carbohydrate load
2. Blood collected at 1 hour (result should be >11.0 mmol/L)
What are the reference ranges for glucose?
Fasting: 3.3-6.0 mmol/L
Random: 3.3-11.0 mmol/L
Critical Low: = 25.0 mmol/L
What are the reference intervals for arterial and CSF samples?
Arterial samples HIGHER by 15%
CSF about 60% of plasma levels
What are the criteria for diagnosis of diabetes mellitus (DM)?
Must have at least TWO of the following:
Fasting glucose > 7.0 mmol/L
2 hour PP > 11.1 mmol/L
Random glucose > 11.1 mmol/L with symptoms
HbA1C >= 6.5%
What is diabetes mellitus?
Disorders of HYPERGLYCEMIA Caused by: 1. Insufficient insulin secretion 2. Defective insulin action 3. Target tissue has insulin resistance
Lab findings in diabetes mellitus:
Hyperglycemia Glycosuria Increased serum and urine osmolality Ketonemia and ketonuria Wight loss Confusion
Complications in diabetes mellitus
Hyperlipidemia - increased circulating fatty acids
Damage due to glycation of proteins - vascular, kidneys, retinas, nervous tissue
What is Type 1 Diabetes Mellitus?
Insulin deficiency due to decreased secretion
10% of cases and insulin dependent
What is Type 2 Diabetes Mellitus?
Insulin resistance - target tissues not affected or secreted insulin not as effective
90% of cases and not insulin dependent - can be controlled through diet and exercise
What is gestational diabetes?
Glucose intolerance induced by pregnancy
High blood glucose levels in mother can transfer to fetus
How is diabetes mellitus monitored?
Glycated hemoglobin
- reference range 4.0-6.0%
- can be used to predict average blood glucose levels over time and
Glycated albumin
Urine microalbumin
C-peptide
What are ketones and ketosis?
Glucose cannot enter cells due to low levels
Lipolysis increases for energy - can cause lipemia
Fatty acids convert to acetyl-CoA, and cannot be converted back into glucose so they are converted to cholesterol and ketones instead
What are ketones?
Acetone (can show up in breath)
Acetoacetic acid
Increased acid levels in blood leads to acidosis
- hypoxia due to affect on hemoglobin binding affinity for oxygen
What is ketoacidosis?
Acids are excreted as dissociated anions - don’t take hydrogen so it’s left in the blood to decrease pH
Cations and water follow the excreted anions resulting in dehydration and electrolyte imbalance
What is diabetes insipidus?
NOT related to glucose levels
Caused by decreased levels of ADH - unable to concentrate urine and lose a lot of water
Large quantities of dilute urine causing excessive thirst and urination
What is hypoglycemia?
Most commonly associated with insulin overdose
High levels of insulin
What are carbohydrates?
Organic molecules
Primarily carbon, hydrogen, and oxygen
Contain either an Aldose or ketoses
