Final Exam

Carbohydrates are composed of
carbon, hydrogen, and oxygen, with the hydrogen and oxygen in the proportion of two to one, the same as water.
General Carbohydrate Structure
CxH2xOx
As a class of compounds Carbs include
simple sugars, starches, and cellulose
fundamental role of carbs
important source of energy
structural role of carbs
structural units in cell walls and membranes, and in cellular components responsible for function and growth
stereoisomerism
–the property of optical rotation of polarized light
simplest carbohydrates are known as
monosaccharides
monosaccharides
straight chain polyhydroxy alcohols
Usual length of monosaccharides
3 to 8 carbon atoms
How are monosaccharides classified
according to the number of carbon atoms in the chain
Carbohydrates are defined as derivatives of
polyhydroxyaldehydes or polyhydroxyketones.
aldose
Sugar containing an aldehyde group
ketose
Sugar possessing a ketone group
Trioses are derived from
polyhydroxy alcohol glycerol
oxidation on the central carbon of the triose yeilds
a ketose
pentoses
sugars whose molecules contain five carbon atoms
most pentoses contain _____asymmetric carbonds
3
How do pentoses occur in nature?
combined in polysaccharides from which monosaccharides may be obtained by hydrolysis with acids.
The Hexoses
Glucose, fructose, and galactose
by which physiological standpoint are hexoses the most important monosaccharides
nutritional and physiological standpoint
which carbs are used as food?
hexoses
Two ways haxoses can be found
free or combined in disaccharides and polysaccharides
Glucose
normal sugar of the blood and tissue fluids and is utilized by cells as a source of energy
Galactose
constituent of milk sugar and is found in brain and nervous tissue
Fructose
keto sugar whereas the others are aldoses
pyranoses
The six member ring forms of sugar
pyranoses are derivatives of
heterocyclic compound pyran.
D-glucose ring form =
?-D-glucopyranose
what reaction forms a pyranose
reaction between an aldehyde and an alcohol to form a hemiacetal.
furnaose
a derivative of furan.
The formation of furnaose rings
special case of a more general type of reaction between a ketone and an alcohol to form a hemiketal
Derived Monosaccharaides formation
reduction or oxidation of the carbonyl group
Examples of Derived Monosaccharaides
D-sorbitol or D-mannitol
reduction products of derived monosaccharides
polyols (polyalcohols)
oxidation products of derived monosaccharides
acids, ex. glucaronic acid
Sialic Acid
Important group of derived monosaccharide’s resulting from the replacement of a hydroxyl group (OH) by an amino group.
N-Acetylneuraminic Acid
This negatively charged residue is found in complex glycans, mucins and glycoproteins in the cell membrane. Also found in glycolipids, such as gangliosides, a crucial component of neuronal membranes found in the brain.
Complex Carbohydrates formation
linking two or more monosaccharides whose combination involves the splitting out of a molecule of water.
hemiacetal linkage
always made from the aldehyde group of one sugar to the hydroxyl or ketone group of the second.
simplest complex carbs
diasaccharides
Maltose
diasaccharide, composed of two glucose molecules
Lactose
diasaccharide, composed of one molecule of galactose and one molecule of glucose
Sucrose
diasaccharide, composed of one molecule of fructose and one molecule of glucose
Sucrose common name
table sugar
What is sucrose composed of?
a molecule of glucose joined to a molecule of fructose in such a way that the linkage involves the reducing groups of each sugar (carbon 1 of glucose and carbon 2 of fructose).
will sucrose reduce bendicts
no
What forms upon hydrolysis of sucrose
molecule of glucose and a molecule of fructose are formed.
What forms upon hydrolysis of Lactose
forms a molecule of glucose and a galactose
Where is lactose synthesized
mammary glands
will lacttose reduce bendicts
yes
polysaccharides
complex carbohydrates that are made up of many monosaccharide molecules and therefore possess a high molecular weight.
do polysaccharides reduce benedicts?
no
What do polysaccharides form?
colloidal dispersions instead of simple solutions
Polysaccharides can be formed
pentoses or from hexoses and there are also mixed polysaccharides.
Hexosans
important polysaccharides, two hexoses combine and a water is split off
Three most important polysaccharides
cellulose, starch and glycogen
Cellulose
consist of glucose units linked in a ?(1-4) glycosidic linkage forming long unbranched chains
Strach
consists of glucose units linked in an ? (1-4) glycosididc linkage. Scattered throughout the molecule are ? (1-6) glycosididc linkages permitting branched chains to form.
Glycogen
– Resembles amylopectin, is highly branched, and represents the primary storage form of glucose.
Two forms of starch
Amylose — straight chain
Amylopectin — and branched chain
Monosaccharides undergo dehydration in the presence of mineral acids to form
cyclic furfural derivatives
Monosaccharides and redox reactions
Can be oxidized or reduced or can serve as oxidizing or reducing agents.
Schiff base
Aldoses can react with primary amines
Glucose’s reaction with aromatic amines like o-toluidine
Used as a method for measuring glucose concentrations
Enzymatic methods represent
principle means for determination today.
Glycogen
primary storage form of glucose occurring to the greatest extent in the liver and muscle tissue
Complex carbohydrates (polysaccharides) are found in
body fluids and connective tissues – i.e., synovial fluid
Carbohydrate Metabolism
energy production by conversion to carbon dioxide and water
storage as glycogen in the liver or triglycerides in adipose tissue
conversion to keto acids, amino acids, or protein
once transported within the cell glucose is rapidly converted into
glucose-6-phosphate
Metabolic pathways available from G6P
Glycolysis
Tricarboxylic Acid Cycle
Hexose Monophosphate Shunt
Uronic Acid Pathway
Glycogenesis
glycogen synthetase
catalyzes 1-4 glycosidic linkage
What activates glycogen synthetase
insulin –> cAMP levels –> PKA
Glycogenolysis
Conversion of Glycogen to Glucose
x

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