Biochemistry Chapter 11 Flashcards
What are the simplest carbohydrates?
Monosaccharides
What are monosaccharides?
- monosacchardies are aldehydes or ketones that contain two or more hydroxyl groups
- Monosaccharides can be linked together to form a large variety of oligosaccharide structures
- exist in many isomeric forms
- simple sugars that cannot be hydrolyzed to simpler compounds
what are the smallest monosaccharides composed of?
Three carbons!!
-dihydroxyacetone (ketone)
-D glyceraldehyde (aldose)
-L glyceraldehyde (aldose)
What are common Monosaccharides?
- D-Ribose
- D-Deoxyribose
- D-Glucose
- D-mannose
- D-Galactose
- D-Fructose
Which is a constitutional isomer?
Dihydroxyacetone and glyceraldehyde
which is a stereoisomer?
D-glyceraldehyde and L- glyceraldehyde
Hemiacetal
Aldehyde and alcohol
Hemiketal
Ketone and alcohol
In the case of glucose, the hemiacetal, a …… carbon ring, is called a ….
six
pyranose
In the case of Ketose fructose, the hemiketal a … carbon ring is called a …..
five
furanose
An additional asymmetric center is created when a cyclic hemiacetal is formed, generating yet another diastereoisomeric form of sugars called
anomer
the a form means that the hydroxyl at C-1 is…..
below the plane of the ring
the B form means that the hydroxyl at C-1 is…
above the plane of the ring
Fructose forms borth the ….. and ……. form
-pyranose
-furanose
what two conformations can pyranose form
baot and chair
chair form has two orientations
axial and equatorial
why does B-D glucopyranose adopt the chair form?
B-D glucopyranose adopts the chair conformation because the axial positions are occupied by hydrogens, reducing steric hindrance
glucose is a reducing sugar
- A solution of glucose contains one third a anomer, two thirds B anomer, and about 1% open chain
reducing agent
Sugars that react with oxidizing agents are called reducing sugars, whereas those that do not are non reducing sugars
open chain glucose can react with …., reducing the …. while itself becoming oxidized
-Cu2+
-copper
less than 6% of hemoglobin is glycosylated
nondiabetic people
almost 10% of hemoglobin is glycosylated
uncontrolled diabetes
As a reducing sugar, glucose can react with amino groups, often …… residues in proteins
lys or arg
glucose can react with hemoglobin, forming …
glycosylated hemoglobin (Hemoglobin A1c), which is fully functional
Advanced glycation end products (AGEs)
Following the primary modification, cross-linking may occur between the site of the first modification and elsewhere in the protein, further compromising function. These modifications, known as advanced glycation end products (AGEs), have been implicated in aging, arteriosclerosis, and diabetes, as well as other pathological conditions.
Monosaccharides are joined to alcohols and amines through glycosidic bonds
A bond formed between the anomeric carbon atom and oxygen atom of an alcohol is called an O-glycosidic bond
What is a bond formed between the anomeric carbon atom and an amine is called an
N-glycosidic bond
Phosphorylated sugars
Phosphorylated sugars are key intermediates in energy generation and Biosynthesis
phosphorylation
- Phosphorylation is a common modifications of carbohydrates
- Phosphorylation makes the sugar anionic and prevents them from leaving the cell
- Phosphorylation also facilitates the metabolism of sugars
monosaccharides are linked to form complex carbohydrates
ogliosaccharides containing two or more monosaccharides are linked by O-glycosidic bonds
sucrose, lactose and maltose are the common disaccharides
sucrose
Sucrose is obtained from sugar cane and sugar beets and is composed of a glucose linked to a fructose. The linkage is A for glucose and B for fructose. Sucrose is cleaved by sucrase (also called invertase)
lactose
Lactose is the disaccharide of milk that consists of a galactose linked to a glucose by a B-1,4 linkage. Lactase cleaves lactose.
maltose
Maltose, a degradation product of large oligosaccharides, is composed of two glucose molecules linked by an a-1,4 linkage. Maltose is hydrolyzed by maltase.
what are the storage forms of glucose
glycogen and starch
what is the glucose storage form in animals
polysaccharide glycogen
most glucose units in glycogen are linked by …….. with branches formed by ……… about every …. glucose untis
- a-1-4 glycosidic bonds
- a-1-6 glycosidic bonds
- 12
in plants, glucose is stored as …. of which there are two forms
starch
amylose
Amylose is a linear polymer of glucose units linked by a-1,4 glycosidic bonds
amylopectin
Amylopectin is a branched polymer, with an a-1,6- glycosidic bond for every 30 a-1,4-glycosidic bonds
cellulose
- cellulose is a structural component of plants and is made of chains of glucose
- homopolymer linked by B-1,4-glycosidic bond
- the b linkage yields a straight chain capable of interacting with other cellulose molecules via H bonds to form strong fibris
- the a-linkages of starch and glycogen form compact hollow cylinders suitable for accessible storage
insoluble and soluble fiber are an important part of the diet
- mammals cannot digest cellulose, but it is still useful in the diet increasing the rate at which digestion products pass through the large intestine
- soluble fibers such as polygalacturonic (pectin) also aid in the digestion, faciltating absorption of nutrients from the diet
human milk oligosaccharides protect newborns from infection
- more than 150 different oligosaccharieds have been identified in human milk, with the composotion and amount varying in women
- these are NOT digested by the infants but play a protective role against bacterial infection
- milk oligosacchardies appear to prevent the growth of certain streptococcus bacteria, which may otherwise be transferred from the mothers vaginal epithelium and caue pneumonia, blood positing or meningtisis in the infant
what are the three main classes of glycoproteins?
- Glycoproteins
- proteoglycans
- mucins or mucoprotiens
glycoproteins
- protein by weight
- membrane proteins
- cell adhesions
- binding of sperm and egg
proteoglycans
- carbohydrates by weight
- play structural role or act as lubricants
- attached to glycosaminoglycan
