cc1 CARBO LAB MIDTERM WEEK2 Flashcards
- Major food and energy source of the body
- The most abundant biomolecules on earth
- Major constituents of physiologic systems
Glycans
- Are needed for specific cellular functions
- Are hydrophilic molecules
Carbohydrate
- Most carbohydrates have the general
formula of
(CH2O)
-If the carbonyl group is located at one end of the sugar
-it forms an aldehyde group and is known as an
Aldose
aldoses are reducing
compounds, and are sometimes known as
reducing sugars
If the carbonyl group is located at an
internal position, the sugar is a
ketose
Sugar based on number of carbon
● Trioses
● Tetroses
● Pentoses
● Hexoses
● Heptoses
● Nonoses
This allows for various spatial arrangements around each asymmetric carbon forming molecules
stereoisomers
Sugars are called _________- which is
derived from the greek word __________
-Saccharide
-Sakcharon
- Simple sugars, consist of a single polyhydroxy aldehyde or ketone unit
- Most have a sweet taste
- freely soluble in water but insoluble in
non-polar solvents - Composed of backbone of several carbon
atoms
Monosaccharides
- Two monosaccharides joined covalently by
an O-glycosidic bond - Serves primarily as readily available
energy stores
Disaccharides
- Sugars linked to form small chains of about 3-10 sugar units/residues
- Most are not digested by human enzymes
-can play an informational role
Oligosaccharides
-polymer of sugar units joined by glycosidic bonds
-Most carbohydrates found in nature
-Serve as storage carbohydrates or
provides structural support
Polysaccharide
Upon hydrolysis, polysaccharides
will yield more than
10 monosaccharides
- The main storage polysaccharide of animal cells - “animal starch”
- A branched polymer containing only one
type of monomer
Glycogen
Bank of surplus of energy in plants
Starch
A homopolymer of glucose forming an
alpha-glycosidic chain called
Glucosan or Glucan
2 types of Polysaccharide
● Homopolysaccharide
● Heteropolysaccharide
- fibrous, tough, water-insoluble substance found in the cell walls of plants
- also included in diet but cannot be digested
Cellulose
centered on the provision & fate of glucose
Carbohydrate metabolism
almost identical to salivary but several times powerful
alpha-amylase
The most abundant of the absorbed monosaccharides
glucose
3 major sources of carbohydrates exist in normal human diet
● Sucrose
● Lactose
● Starch
an enzymes hydrolyzes disaccharides and small glucose polymers into monosaccharides
Intestinal epithelial cell
Glucose is transported by a ______ mechanism
Sodium Cotransporter
- Sodium combines with a transporter protein
- will not transport the sodium to the interior of the cell
SGLT2
involved in controlling the blood glucose concentrations within a
narrow range
- liver
- pancreas
-endocrine glands
Control of blood glucose is under two major hormones
-Insulin
-Glucagon Control
reflects a balance between energy intake from ingested food, hepatic glucose production, and peripheral tissue glucose uptake and utilization
Glucose homeostasis
- an exocrine and endocrine gland that controls the regulation of sugar
Pancreas
what cell produces insulin
B- cell
what cells produces Glucagon
Α-cells
in what year insulin was discover
1921-1922
- the primary and only hormone responsible for the entry of glucose into the cell
- responsible for increasing glucose levels
hypoglycemic agent
Who discovered insulin
-Frederick Banting
-Charles Best
-John Macleod
- anabolic and peptide hormone with a
MW of
5800 Daltons
Insulin stimulates:
● Glucose uptake
● Formation of glycogen
● Inhibits glucose production
● Increase protein and Triglyceride production
● Promote uptake of ions
Glucose is taken up by the Beta-cells via
GLUT2
Glucose is then phosphorylated by
glucokinase
- enter the cell and activates the Ca2+-dependent proteins
Calcium ions
3 Main targets of Insulin:
-liver
-adipose tissue
-muscles
-main target in the fasting state
-insulin stimulates glycolysis and glycogenesis, and lipogenesis
-Suppresses lipolysis and gluconeogenesis
Liver
- Insulin stimulates triglyceride synthesis
from glycerol-3-phosphate
Adipose tissue
- Stimulates glucose transport, glucose metabolism, and glycogenesis
- Increases cellular uptake of amino acids and stimulates protein synthesis
Muscle
- Synthesized by Pancreatic Alpha cells
- With a short half-life of about 5 minutes
hyperglycemic agent
hormones that increases glucose:
- Cortisol
- Catecholamines
- Growth hormone
- Thyroid hormone
- Adrenocorticotropic hormone
- Somatostatin
hypoglycemic agent hormone that stimulates:
- Glucose production
- Regulator of hepatic glycogenolysis,
gluconeogenesis, Ketogenesis, Hepatic
amino acid turn over
Glucose Uptake:
-GLUT1
-GLUT2
-GLUT3
-GLUT4
-GLUT5
glucose transporter for RBCs
-GLUT1
- Major glucose transporter in B-cells of pancreatic islets and hepatocytes
- “Glucose sensing”
-GLUT2
- Glucose transporter of the brain
- With high concentrations in the hypothalamus, hippocampus, and cortex
-GLUT3
- main glucose transporter in the
cells of skeletal muscles, cardiac muscles,
adipose tissue
-GLUT4
- for absorption of fructose, found
in the small intestine
-GLUT5
-most commonly
encountered hyperglycemia
-most common set of disorders of
carbohydrate metabolism
Diabetes Mellitus
There is an increased blood glucose
Hyperglycemia
- “Juvenile-onset Diabetes”,
Insulin-dependent diabetes mellitus” - Represents 5-10% of all cases of diabetes
-Common in the young people ( 9-14 yrs old)
-Due to an Autoimmune destruction of
insulin-producing beta cells in the islets of
langerhans
Type 1 Diabetes Mellitus
DM can be due to:
● Defect in insulin secretion
● Defect in insulin action
● Increased glucose production
which kills islet cells
CD8+ cytotoxic
T-lymphocytes
which induce
destructive inflammation
CD4+ T-cells
Pancreatic islets lymphocyte infiltration is termed
Insulitis
the following markers are
found in 85-90% of individuals with fasting
hyperglycemia:
● Islet cell autoantibodies
● Insulin autoantibodies
● Glutamic acid decarboxylase
autoantibodies
● Tyrosine phosphatase IA-2 and
IA-2B autoantibodies
● Zinc transporter 8
- due to an individual’s resistance to insulin
- Most common type of diabetes (common
in elders ages 40 above) - Not an autoimmune disease
- glucose tolerance remains near-normal, despite insulin resistance
Type 2 Diabetes Mellitus
- the following are the risk factors of type 2 DM:
● Overweight or obesity
● Lifestyle factors
● First-degree relative with diabetes
● Advance age
● High risk ethnicity
● History of GDM
● Hypertension
● Vascular disease & dyslipidemia
● Prediabetes
- not an absolute deficiency
- Intensifies DM type 2
Relative Insulin Deficiency
Hyperglycemia is toxic to beta-cell function and further impairs insulin
secretion
Glucose Toxicity
Complications of diabetes can be divided into:
-Vascular
-Non-vascular
Non-vascular:
- Infections
- Skin changes
- Hearing loss
Vascular:
- Microvascular
- Retinopathy
- Neuropathy
- Nephropathy - Macrovascular
- Coronary Heart Disease
- Peripheral Arterial Disease
- Cerebrovascular Disease
The “3 Polys”
-Polyuria
-Polydipsia
-Polyphagia
- excess glucose is thrown in the kidneys. Glucose renal excretion needs
water excretion
Polyuria
- loss of water due to polyuria induces thirst
Polydipsia
- reduced glucose introduced to cells lowers energy, thus increasing
hunger
Polyphagia
- defined as glucose intolerance first
recognized during pregnancy - conveys both short and long term
risk to both mother and offspring
Gestational Diabetes
- With increased usage of sugar but low production
- Due to: Insulin overdose, increased hypoglycemic agent, liver dysfunction
Hypoglycemia
the following symptoms of hypoglycemia:
-Increased hunger -Sweating,
-Nausea
-Vomiting
-Dizziness
-nervousness
-Shaking
-Blurring of speech and sight
-mental confusion
can be used for HbA1C or
for self-monitoring of glucose
Whole blood
most commonly used specimen
Serum
used to inhibit
glycolysis
Sodium Fluoride
Chemical Methods
- Alkaline Copper Reduction Methods
-Folin Wu Method
- Nelson Somogyi Method - Alkaline Ferric Reduction Method
- Ortho-Toluidine (Dubowski Method)
Most accurate redox method and believes
to be a measure of true glucose
Nelson Somogyi Method
a method to cuprous ions
forming cuprous oxide in hot alkaline solution by glucose
Alkaline Copper Reduction Methods
Measured calorimetrically and compared with a standard
Folin Wu Method
- “Hagedorn Jensen”
- A titrimetric method
Alkaline Ferric Reduction Method
- Most specific non-enzymatic method for
glucose - condenses with the
aldehyde group of glucose in a hot acetic
acid solution
Ortho-Toluidine (Dubowski Method)
- Reference method
- Highly accurate and precise but is time
consuming
Hexokinase Method
Enzymatic Methods
- Glucose Oxidase Method
- Hexokinase Method
- Glucose Dehydrogenase Method
- Highly specific for B-d-glucose
Glucose Oxidase Method
- Involves measurement of NADH
production
Glucose Dehydrogenase Method
Testings
-Fasting Blood Sugar
-Random Blood Sugar
-2 Hours Post Prandial -Blood Sugar
-Glucose Tolerance Test
- Measures blood sugar after 8-10 hours of
fasting
Fasting Blood Sugar
- “Casual blood glucose test”
- Measured to aid in diagnosis of diabetes
Random Blood Sugar
- A variation of this test is using a standardized solution containing 75g of
glucose
2 Hours Post Prandial Blood Sugar
- One of the laboratory’s hallmark in diagnosis of type 1 and type 2 diabetes
- 3 days before OGTT, individuals should ingest at least 150g/day of
carbohydrates
-Test is performed after an overnight fasting of 8-14 hours
Glucose Tolerance Test
- Single dose method
Janney-Isaacson Method
Glucose Loads OGTT load (WHO standard)
75 grams
- Double-dose/Divided Oral dose method
Exton Rose Method
Glycosylated Hemoglobin methods:
● Ion-Exchange Chromatography
● Electrophoresis
● Isoelectric Focusing
● Affinity Chromatography
● Immunoassays
- Short term: 2-3 weeks
- For patients with RBC lifespan problems
Fructosamine Test
- Formation of a hemoglobin compound
produced when glucose reacts with the amino group of hemoglobin - glucose molecule attaches non-enzymatically
Glycosylated Hemoglobin
normal level of Glycosylated Hemoglobin
4.5%-8%
- Used to monitor the pancreas
- Method: Immunometric assay
C-peptide Test
