carbs 3 Flashcards
sugars which yield two molecules of the same or
d i ff e r e n t m o l e c u l e s o f m o n o s a c c h a r i d e o n
hydrolysis.
> also called double sugar, any substance that is
composed of two molecules of simple sugars
(monosaccharide) linked to each other.
• are crystalline water-soluble
compounds.
disaccharide
Glycosidic bonds are cleaved by
enzymes known as ____________
The three major disaccharides are
sucrose, lactose, and maltose.
glycosidases
malt sugar”
- Intermediary in acid hydrolysis of
starch and can be obtained by
enzyme hydrolysis of starch.
• alpha 1-4 bond
- anomeric carbon of one glucose is
free, it can form alpha and B-forms
and exhibit mutarotation
maltose
In the body, dietary starch digestion by _____________ in gut yields maltose, which requires a specific enzyme ________ to form glucose.
- amylase
- maltase
sweet; soluble in water; has one aldehyde free or potentially free it has reducing properties, and
forms characteristic osazone which has
characteristic “sunflower” appearance
maltose
milk sugar
• not very soluble and is not so sweet; dextrorotatory; enzyme which hydrolyzes is “lactase” present in intestinal juice; yield one molecule of D-glucose and
one molecule of D-galactose upon hydrolysis.
lactose
yields “mucic acid”
w h e n treated with conc. nitric acid after
hydrolysis
• one of the aldehyde is free or potentially free, it
has reducing properties.
• Exhibit M u t a r o t a t i o n
lactose
• “table sugar” or “cane sugar”
• from sugar cane, sugar beet, pineapple, carrots
• very soluble and sweet;
enzyme that hydrolyzes is sucrase
present in the intestinal juice
• as both aldehyde and ketone groups are linked together
(alpha 1-2), it does not have reducing properties and cannot form osazones
• both anomeric carbons are involved in “linkage”, it does not exhibit mutarotation
sucrose
is a disaccharide consisting of two
glucose units in beta (1-4) glycosidic linkage.
Obtained from the partial hydrolysis of cellulose.
Cellobiose
commonly used as an indicator
carbohydrate for intestinal permeability in Crohn’s disease and malabsorption syndrome.
cellobiose
is a disaccharide composed of two
units of D-glucose joined with a P(1->6) linkage.
Gentiobiose
It is a white crystalline solid that is soluble in water or hot methanol. it is incorporated
into the chemical structure of crocin, the chemical
compound that gives saffron its color.
- It is a product of the caramelization of glucose.
Gentiobiose
integral membrane proteins contain covalently attached
carbohydrate units oligosaccharides, o n their
extracellular face
oligosaccharides
Starch granules are insoluble in cold water, but when their suspension is heated, water is taken up and
swelling occurs at first to a slight degree but later to several hundred times to their original volume, viscosity
increases, and starch “gels” or “pastes” are formed
Composition: consists of two polymeric units of glucose called?
amylose and amylopectin
is the major glucose storage molecule in animals.
- The structure is similar to amylopectin in which the main
chain is link by alpha (1-4) glycosidic bond and its
numerous alpha(1-6) glycosidic bond.
CH-OH
glycogen
_________ have more and shorter branches, is stored in the liver and skeletal muscle.
synthesis and degradation in the liver are carefully regulated.
glycogen
polysaccharide that
serves as a structural
element in plant cell
walls a n d a n i m a l
e x o s k e l e t o n s
structural polysaccharides
structural component of plant
cell w a l l s
> “woody” portions of plants -
stems, stalks, and trunks have
high concentrations o f this
fibrous, w a t e r- i n s o l u b l e
s u b s t a n c e
cellulose
like amylose, it is an unbranched glucose polymer;
difference is that glucose residues in cellulose have
beta-configuration, whereas in amylose its in alpha
configuration; glycosidic linkages is beta (1-4).
cellulose
_______ have spiral-like structures
whereas cellulose have linear
(straight-chain) structures which
when aligned side by side become
water-insoluble fibers because of
inter-chain hydrogen bonding
cellulose contains about 5000
glucose units; cotton is p u r e
cellulose (95%) and wood is (50%)
amylose
cellulose is hydrolyzed by an enzyme ____________, which cleaves all of the B-glycosidic
bonds forming glucose.
• It’s an important component of a balanced diet ; it
serves as dietary fiber which provides the digestive
tract with “bulk” and facilitates the excretion of
solid wastes.
• humans do not possess this enzyme, and therefore
cannot digest cellulose.
B-glycosidase
> similar to cellulose in both function and
s t r u c t u r e
its f u n c t i o n is t o give rigidity to the exoskeletons of crabs, lobsters, shrimp, insects,and other arthropods; also occurs in the cell walls of fungi
chitin
polysaccharide with a disaccharide repeating unit in which one of the disaccharide components is an amino
sugar and one or both disaccharide components has a
negative charge due to a sulfate group or a carboxyl group;
they are heteropolysaccharides, where two different monosaccharides are present in an alternating pattern
serve as
lubricants in the fluid o f joints and they are associated with the jelly-like consistency of the vitreous humor of the eye.
hyaluronic acid
monosaccharide present in the
disaccharide repeating unit for
heparin are D-glucuronate-2-
s u l f a t e and N - s u l f o - D -
glucosamine-6-sulfate, both of
which contain two negatively
charged acidic groups
> 15-90 disaccharide residues
per chain
• anticoagulant, it helps prevent blood clots; binds strongly to a protein involved in
terminating the process of blood clotting, thus inhibiting blood clotting
heparin
the process of breaking down food by mechanical
and enzymatic action in the alimentary canal
into substances that can be used by the body.
digestion
Which part of Digestive - oesophagus
System is the main site for
absorption?
small intestine
(duodenum and ileum)
convert polysaccharides t o disaccharides
amylase
2 Types of enzymes are important for the digestion of
carbohydrates
amylase and disaccharide
Digestion of Carbohydrate
starts in the mouth, upon
contact with saliva during
mastication or chewing.
Saliva c o n t a i n s a
carbohydrate spliting
enzyme called salivary
amylase, also known as
___________.
ptyalin
Ptyalin action stops in the
stomach when the pH falls to
________
• T h e e z y m e h y d r o l y s e s a - 1 - 4
g l y c o s i d i c m o l e c u l e s
3.0
T h e r e is no enzyme to break
the glycosidic bonds in
gastric juice.
However, HCl present in the
stomach causes hydrolysis of
sucrose to fructose and
glucose.
Digestion is completed by
____________ b e c a u s e
food stays for a longer time in
t h e i n t e s t i n e .
pancreatic amylase
They are present in the brush
border epithelium of intestinal
mucosal cells where the resultant monosaccharides a n d
othe arising from the diet a r e
a b s o r b e d .
disaccharides
• The process by which molecules spontaneously
diffuse from a region of higher solute
concentration to a region of lower solute
c o n c e n t r a t i o n
• Non-energy requiring
• It is the slowest absorption process.
passive diffusion
2 types of CARRIER-MEDIATED
T R A N S P O RT
A.ACTIVE T R A N S P O RT
B.FACILITATED DIFFUSION
Movement of substance from Iow-high concentration
against a concentration gradient
• “pushing rock uphill”
• Energy requiring (ATP)
• Faster rate of transport
active transport
• Movement of substance from high-low concentration
along a concentration gradient
• “downhill movement”
• Non-energy requiring
• Fast rate of transport
FACILITATED DIFFUSION
T H E F O L L O W I N G A R E S O M E O F T H E T E S T S
PERFORMED BY MEDICAL TECHNOLOGISTS
INVOLVING CARBOHYDRATES:
• Blood Glucose (sugar ) Tests
• L a c t o s e T o l e r a n c e T e s t s
• D-Xylose Absorption
is the inability to digest lactose due to the deficiency of Lactase enzyme.
Lactose intolerance
There is complete absence or deficiency of lactase enzyme.
• The child develops intolerance to lactose immediately after birth.
• It is diagnosed in early infancy.
• Milk feed precipitates symptoms.
congenital lactose intolerance
develops over time
• There is no congenital absence of lactase but the deficiency is precipitated during adulthood.
• The gene for lactose is normally expressed upto
RNA level but it is not translated to form enzyme.
• It is very common in Asian population.
primary lactose intolerance
may develop in a person with a
Intestinal parasite health small intestine during episodes of acute illness.
• This occurs because of mucosal damage or from medications resulting from certain gastrointestinal diseases, including exposure to intestinal parasites such as Giardia lamblia.
• In such case the production of lactase may be permanent disrupted.
• A very common cause of temporary lactose intolerance is gastroenteritis, particularly when the gastroenteritis is caused by rotavirus.
Secondary Lactase Deficiency
Undigested lactose in
intestinal l u m e n is acted u p o n
by bacteria a n d is converted to
COz, H2, 2 carbon compounds
and 3 Carbon compounds or it
may remain undigested
biomedical basis
Diagnosis o f Lactose Intolerance:
• Hydrogen Breath test
• Stool Acidity Test
• U r i n e T e s t
• Mucosal Biopsy test
measure the ability of your intestines to break down a type of sugar found in milk and other dairy products called
lactose. If your body cannot break down this sugar you are said to have lactose intolerance.
lactose tolerance test
the blood test is considered normal if
your glucose level rises more than _____________ within 2 hours of drinking the
lactose solution.
• A rise of 20 to 30 mg/dL is
inconclusive. Note: Normal value
ranges may vary slightly among
different laboratories.
30 mg/dL
Measures the amount of a type of sugar
(glucose) in your blood.
• Insulin is a hormone that helps your body’s cells use the glucose. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.
• Blood glucose levels that remain high over
time can damage your eyes, kidneys, nerves,
and blood vessels.
blood glucose test
- measures blood glucose after you have
not eaten for at least 8 hours. - It is often the first test done to check for
pre diabetes and diabetes.
Fasting blood sugar (FBS)
- measures blood glucose exactly 2 hours
after you start eating a meal. - This is not a test used to diagnose
diabetes. - This test is used if someone with
diabetes is taking the right amount of
insulin with meals.
2-hour postprandial blood sugar
measures blood glucose regardless of when you last ate.
- his test is also called a casual blood glucose test.
random blood sugar
- is used to diagnose prediabetes and
diabetes. - test is a series of
blood glucose measurements taken after you
drink a sweet liquid that contains glucose. - This test is commonly used to diagnose
diabetes that occurs during pregnancy .
oral glucose tolerance test
- measures how much sugar (glucose) is stuck to
red blood cells. - This test can be used to diagnose diabetes.
- It also shows how well your diabetes has been controlled in the past 2-3 months
whether your diabetes medicine n e e d s to be changed. - The result of your Aic test can be used to
estimate your average blood sugar level. This is called your estimated average glucose, or eAG
Hemoglobin A1c, or glycohemoglobin,
Fasting plasma glucose-
70-99 mg/dL
• Postprandial plasma glucose at 2 hours -
Less than 140 mg/dL
- Less than 140 mg/dL
Random plasma glucose
