Unit 6 - Carb structure and measurement Flashcards
What is the basic composition of all carbohydrates
Cn(H2O)n
What are carbohydrates made up of
Carbon and Water
(C,H,O)
Composition of Glucose
6 Carbons
6 Waters (H2O)
What is the molecular weight of 1 Carbon
12 g/mol
What is the molecular weight of 1 Water (H2O)
18 g/mol
Monosaccharide
One sugar
Disaccharide
Two sugars linked together
Polysaccharide
Multiple sugars linked together
What determines if a sugar is a reducing sugar
If it can form an aldehyde group
Reducing sugars are capable of what action?
Reducing cupric ions into cuprous ions
What sugars are monosaccharides?
Fructose
Glucose
Galactose
What sugars are disaccharides?
Sucrose
Maltose
Lactose
What sugars are NOT reducing sugars?
Sucrose
What sugars are reducing sugars
Glucose
Galactose
Maltose
Fructose
Lactose
What is maltose composed of?
Two glucose linked together
What is galactose made up of
6 Carbons
6 H2O
What is different between glucose and galactose?
OH-H flipped
What is lactose made up of
1 galactose
1 glucose
What is different about fructose
Location of C=O on the second carbon makes the structure look different
What is sucrose made up of
Glucose and fructose
Storage form of carbs in animals
Glycogen
What is glycogen made up of
Glucose polysaccharide
What is the storage carb in plants
Starch
What is starch made up of
Glucose polysaccharide
How is glucose broken down for energy production?
Broken down into CO2 and H2O
Clinitest reacts with reducing sugars such as
Fructose
Glucose
Galactose
What energy processes is glucose used in?
Anaerobic glycolysis
Aerobic Krebs cycle
Aerobic oxidative phosphorylation
Where is glucose stored in
Liver - Glycogen
Adipose tissue/Fat - Triglycerides
What can glucose be converted into? (noncarbohydrates)
Ketoacids
Amino acids
Protein
What is the carbohydrate nutrition process?
Food
Salivary amylase breaks disaccharides and polysaccharides
Pancreatic amylase continues breakdown in small intestine
Monosaccharides absorbed by small intestines
Monosaccharides transported to liver via hepatic portal vein
Liver converts non glucose monosaccharides into glucose
What structure transports monosaccharides to the liver
Hepatic portal vein
What is glucogenesis
When the liver converts non-glucose monosaccharides into glucose
What is the only monosaccharide that can be used for ATP production?
Glucose
Glycogenesis
Liver converting glucose into glycogen for storage
Glycogenolysis
Breakdown of glycogen into glucose for energy
If oxygen is low in the tissues and glucose is used, what happens?
Glucose used anaerobically, lactic acid builds up
Gluconeogenesis
Glucose made from non-carbohydrate sources
What does your body do if there is not enough glucose?
Gluconeogenesis
Where does your body grab from to produce glucose?
Lipids
Amino acids
Glycerol
Lactate
Why is the conversion of non-carbohydrate sources not preferred?
Byproducts like ketoacids are produced, can be dangerous
Lipogenesis
Production of fat with excess glucose
Where is insulin produced
Beta islets of langerhans in pancreas
What does insulin want to do?
Lower blood glucose
How does insulin lower blood glucose
Increase tissue cell uptake
Glycogenesis
Prevent breakdown of glycogen
Lipogenesis
Suppress glucagon release
Promote formation of proteins
What is insulin formed from?
Proinsulin
What does proinsulin do
Break down into insulin and C-peptide
Where is glucagon produced
Alpha islets of langerhans
What does glucagon want to do
Increase blood glucose
How does glucagon increase blood glucose
Glycogenolysis
Lipgenolysis
Gluconeogenesis
Where does Cortisol come from
Adrenal glands, adrenal cortex
What does cortisol do
Stimulate gluconeogenesis
What does cortisol want to do
Increase blood glucose
Cushings Syndrome
Increased cortisol
Hyperglycemia
Addisons Disease
Low cortisol
Hypoglycemia
Where is epinephrine produced
Adrenal medulla
When is epinephrine produced
Stress or fright
What does epinephrine want to do
Increase blood glucose
How does epinephrine increase blood glucose
Inhibit insulin
Produce glucagon
Stimulate glycogenolysis
What do thyroid hormones do
Regulate body metabolism
Increase blood glucose
How do thyroid hormones increase blood glucose
Increase glucose absorption in GI
Stimulate glycogenolysis
Break down insulin
Where is growth hormone produced
Anterior pituitary
What does growth hormone do
Growth
Increase blood glucose
How does growth hormone increase glucose
Inhibiting glycolysis
Antagonizing insulin
What does an overproduction of GH cause
pituitary gigantism
Acromegaly
What hormones raise blood glucose
Glucagon
Cortisol
Epinephrine
Thyroid Hormones
Growth Hormone
Glycolysis
Glucose oxydation
Krebs cycle
Citric acid cycle
ATP
Oxidative phosphorylation
Glucose metabolism forms..?
ATP
Carbon Dioxide
Water
What anticoags are used for glucose analysis
NaF
Lithium heparin
When using CSF to measure glucose, what needs to be done?
Centrifuge and assay supernatant only
When should CSF be analyzed for glucose levels?
Immediately
What can signify there’s something wrong when analyzing CSF glucose levels?
False decrease - WBC and Bacteria consume glucose
Preferred blood glucose measurement method?
Fasting
Fasting
Specimen collected after 8 hours no food, drink besides water
Normal fasting glucose levels
74-99 mg/dL
What can emotional disturbances do to blood glucose levels?
Falsely elevate because of cortisol and epinepherine
How long do you have to wait for a postprandial glucose test?
Two hours
Taken after a high carb meal
Time limit for removal of glucose from cells
2 hours, ideally ASAP
What tube is ideal for glucose testing only?
NaF because it inhibits other analytes
How long does NaF preserve blood for glucose testing at RT?
24 hours
How long does NaF preserve blood glucose for testing in the refrigerator?
48 hours
How much do glucose levels go down per hr if NOT separated?
5-7% per hour
How long are separated specimens stable at RT for?
8 hours
How long are separated specimens stable for in the refrigerator?
3 days
What can affect glucose drop/usage?
High hematocrit in storage
Neonate blood has high hct
What percent of glucose is in CSF
60% of plasma glucose
What can happen if testing on CSF is delayed?
WBC and Bacteria cause extremely low decrease
How do children and infant levels of glucose differ from adults?
Lower than adults
Arterial & Capillary vs Venous glucose levels
Arterial about 2-5 mg/dL higher than venous but 20-70 mg/dL higher in non fasting people
WB glucose levels vs venous
~10-15% lower in WB than plasma or serum
Bcz of dilution effect
High hematocrit results in _ glucose values
Lower
Low hct results in _ glucose levels
Higher
A whole blood glucometer is being used to evaluate a critically ill patients glucose. Is this okay?
No, abnormal hct, pH, and maltose can alter glucose readings
IFCC recommends standardizing adjustment levels for WB to Plasma by what %?
11%
Formula for WB glucose value to serum or plasma glucose value
WB glucose x 1.11 = Serum/Plasma glucose
Formula for serum/plasma glucose value to WB value
Serum/Plasma glucose x 0.9 = WB glucose
or
Serum/Plasma glucose/1.11 = WB glucose
What is the renal threshold for glucose
160-180 mg/dL in blood
What is renal glycosuria
Low renal threshold because PCT isn’t as efficient
A person eats a meal and then urine is tested for glucose levels. What should that look like?
Little to no glucose should be present in the urine
What is the downfall of clinitest or copper reductase?
Not specific for glucose
Many interferences
Current enzymatic glucose measurement methods
Hexokinase
Glucose Oxidase
Hexokinase reaction
Glucose + ATP < Hexokinase + Mg > Glucose-6-PO4 + ADP
Glucose-6-PO4 + NADP <G6PD> 6phosphogluconate + NADPH + H</G6PD>
What are the two detection methods for glucose using Hexokinase?
Absorbance of NADPH measured at 340 nm
or
NADPH detected using tetrazolium
Glucose oxidase reaction
Glucose + 2 H2O + O2 <Glucose> Gluconic acid + 2 H2O2</Glucose>
Two detection methods using glucose oxidase
Chromogen to detect peroxide production
or
Consumption of oxygen using oxygen electrode or production of peroxide using electrode
What enzyme is required for glucose oxidase method?
Mutarotase to convert alpha-D glucose to beta-D glucose
What form of glucose is required for glucose oxidase?
Beta - D glucose
Copper reduction method formula
Cu + Glucose –> Cu2O (red) + CuOH (yellow)
Cupric
Cu2+
Cuprous
Cu+
What color is cuprous ion
Red
What reducing sugars are detected by clinitest
Glucose
Galactose
Lactose
Fructose
What reducing agent interferes with clinitest/copper reductase
ascorbic acid or vitamin C
Newborn screening for inborn errors of metabolism of glucose
Copper reductase for Galactose
Replaced by HPLC Tandem MS
Glycated hemoglobin
Glucose rects with a.a. of proteins
What does glycation do to tissues?
Damage
How does glucose bind to amino group?
In its aldehyde form
Is the attachment of glucose to an a.a. enzymatic or non enzymatic?
Non-enzymatic
Is the attachment of glucose to an a.a. reversible or irreversible?
Irreversible
What factors dictate glycated hgb levels?
Plasma glucose
Lifespan of RBC
What specimen is used for Glycated hgb?
EDTA with no fasting
How long is specimen for glycated hgb stable for?
4C for 1 week
HbA1c reflects average blood glucose over how long?
8-12 weeks
Normal adult glycated hgb
A1
Normal adult nonglycated Hgb
A0
Where does hgbA1c attach on hb?
Amino terminus of the beta chain of hgb
Most abundant glycated hgb?
A1c
85%
What % of all hgb is A1c?
4-6%
Different methods of detecting A1c
Bond between glucose and amino group (done w/ ab, chemical affinity)
Charge difference (Ion exchange chromatography, HPLC)
Enzymatically split glycated portion off and measure it
If A1c is <4% or >15%, what should you suspect?
Variant hgb
Populations with higher prevalence of hgbopathies have a higher prevalence of…?
Diabetes
Short RBC life span or young cells result in ___ Ghgb
False decrease
How does iron deficiency anemia affect glycation?
Enhanced glycation from metabolic alteration or smaller cells
Iron deficiency anemia causes a false ___ in Hgb A1c levels
Increase
When can you use A1c measurements in iron deficiency anemia?
Not until anemia is gone
How do transfusion affect A1c levels in high A1c levels?
False decrease
how do transfusions affect A1c in low A1c?
False increase, because have been sitting in glucose
How does renal insufficiency affect Ghgb?
False decrease because high urea attaches to hgb, EPO produces young cells
What can cause true hypoglycemia?
Overuse of diabetes medicaiton
Extreme diet
Liver failure
What causes a false hypoglycemia?
Renal insufficiency
