Flashcards in Carbohydrate Structure & Function_Molecules Deck (97):
What is the general formula of carbohydrates
What is monosaccharides?
Basic building block and major energy source
What is disaccharides?
2 monosaccharides units
What is oligosaccharides?
3 - 20 monosaccharides units
What is complex carbohydrates?
Glycoproteins and glycolipids
What is polysaccharides?
Tens to thousands of monosaccharide units
What are the two types of polysaccharides?
1) Storage polysaccharides - energy store
2) Structural polysaccharides
What does monosaccharides used to create?
4) Complex carbohydrates
What are carbohydrates used for?
1) Most abundant biomolecules in nature
2) Major food source for energy generation
3) Major component of nucleic acids
4) Provide structural components
5) Cells Glyocalyx composed of: glycoproteins and glycolipids
What do carbohydrates provide structural components for?
1) Extracellular matrix
2) Physiological lubricants e..g Synovial Fluid
What is monosaccharide consisted of?
They consist of a chain of carbons with a hydroxyl group at each carbon except one.
What does the "D" in D-glucose refer to?
To the orientation of substituents at the asymmetrical carbon farthest removed from the carbonyl carbon.
What is mutarotation?
A process which allows for greater than or equal to 5C monosaccharides to form cyclic structure around the anomeric carbon
When most monosaccharides spontaneously form ring structures, what bond does the aldehyde or keto group form?
Hemiacetal bond with one of the hydroxyl group
What is a furanose ring?
Ring that contains five atoms
What is a pyranose ring?
Ring that contains six atoms
What do alpha and beta glucopyranose?
Anomers and can interconvert spontaneously via linear form
What is maturation caused by
Occasional opening and reclosure of the ring
Greatly acceerated in the presence of acid or bases
What are common monosaccharides?
Why is fructose different from other common monosaccharide?
Differ from others in bonding structure - ketose
What are the bonding structure for common monosaccharides other than fructose?
How do the monosaccharides differ from one another?
Differ in how constituent groups are arranged in space - stereoisomers
Differ in biological properties and activities
How are monosaccharides same to each other?
Same physical and chemical properties
What are enantiomers?
1) When stereoisomers are mirror images
2) Differ from one another around ALL chiral carbons = D&L forms
Glyceraldehyde has 1 chiral (asymmetrical) carbon how many stereoisomers are formed?
2^1 = 2 stereoisomers
By convention what is a D form?
Form with -OH on right of the chiral carbon furthest away from the anomeric carbon
Glucose has 4 chiral carbons how many stereoisomers are formed?
2^4 = 16 stereoisomers
8 mirror image pairs = D&L forms
What is the most common in biological systems?
What are epimers?
stereoisomers that differ around 1 chiral C
How do monosaccharides combine?
By forming glycosidic bonds
Where are glycosidic bonds formed between?
Between the anomeric carbon of one saccharide and a hydroxyl group on another molecule
The formation of glycosidic bond is called what?
What configuration is the glycosidic bond formed in?
In alpha or beta configuration
What are common disaccharides?
Once the glycosidic bond is formed, is mutarotation possible?
No, the bond is locked in its confirmation
When does alpha linkages form?
When both reacting groups are on the same side of the ring structure
When does beta linkages form?
When reacting groups are different sides of the ring structures
What can act as a reducing agent?
Where the anomeric C is free to maturate it can act as a reducing agent
How do you detect reducing sugars in urine?
Used in dip-stick tests
What are all monosaccharides?
What are polysaccharides also known as?
Most sugars are present in what?
What are the two types of polysaccharides?
1) Storage Polysaccharides
2) Structural Polysaccharides
What are examples of Storage polysaccharides?
1) Homopolymers of glucose
2) Starch in plants (rice, wheat, potatoes,...)
3) Glycogen in animals
What are examples of Structural polysaccharides?
1) Cellulose in plants - also homopolymers of glucose
2) Glycoasminoglycans in animals (aka mucopolysaccharide)
What are glycosaminoglycans in animals?
Polymers of repeating disaccharide units
What are glycosaminoglycans in animals used for?
Major constituents of the extracellular matrix and physiological lubricants
What is glycogen?
Homopolymers of glucose and the storage form of glucose in animals
What is the structure of glycogen?
Branched chains of alpha 1-4 linked glucose with alpha 1 - 6 linkages at branch points.
Which is more highly branched: glycogen or amylopectin?
What does glycogen form?
How is glycogen synthesised and broken down?
One unit at a time at the non reducing ends
What does the highly branched nature of glycogen enable?
Rapid release or storage of glucose
What does glycogen constitute up to?
Up to 10% of liver mass and 1 - 2% of muscle mass
What does liver glycogen do?
Glucose reserve for maintenance of blood glucose levels
What does muscle glycogen do?
Glucose reserve for muscle activity
What are the homopolymers of glucose?
What is starch?
Homopolymer of glucose
How many forms of starch are there?
What are the two forms of starch?
What is the structure of amylose?
Linear polymer of glucose units linked in alpha 1 - 4 linkages
What is the structure of amylopectin?
Branched and made of amylose polymers linked together via alpha 1 - 6 linkages.
What can starch do?
Act as storage polysaccharides in plants - stored packed in granules
What is the structure of cellulose?
Glucose units are linked in beta 1 - 4 glycosidic bonds
What do cellulose form?
Linear fibres - major component of wood
Is cellulose digestible?
No, its indigestible - humans don't have enzymes that can break it down
What are structural polysaccharides used for?
Are the molecules that provide:
1) compressibility to cartilage
2) Viscosity to synovial fluid (shock absorption) and vitreous humour (lubrication) of the eye
3) 'slimy' texture to mucus - protection against dehydration and infection
What do glycosaminoglycans contain?
Contain modified monosaccharides
What are glycosaminoglycans?
Long linear heteropolymers
over 100 monosaccharides long in repeating disaccharide units
What do disaccharide units usually comprise of?
disaccharide unit usually comprises of a sulphated amino sugar and an acidic sugar linked in beta linkages.
Glycosaminoglycans have what charge and are under what linkage?
Negative charge and beta linkage
= an extended, linear structure
Most GAGs are covalently linked to what?
A core protein, forming proteoglycans.
How are the GAGs linked to a core proteins?
Linked via -OH group of serine or threonine
What structure does the proteoglycan have?
GAGs extend from the core protein in a "Bottle - brush" structure
What does the Bottle - brush structure of proteoglycan allow for?
- absorbs large quantities of water
What does the bottle brush structure ensure that GAGs do?
1) Are viscous in solution
2) Form gels at high concentration
What are examples of glycosaminoglycans?
1) Chondroitin sulphate - most abundant GAG
2) Keratin sulphate
What does hyaluronic acid form?
Forms very large polymers up to 10 micrometer (MW 10^5-10^7). More than 10,000 repeating units. Not covalently linked to protein. Not sulphated
How does hyaluronic acid form large aggregates?
Associates with other glycosaminoglycans
What are the properties of hyaluronic acid?
1) Highly hydrated
What are the benefits of hyaluronic acid being highly hydrated?
1) Forms viscous solutions at low concentrations
2) Forms gels at high concentrations
What are the benefits of hyaluronic acid being a lubricant?
Major component of synovial fluid, vitreous humour of the eye
Is Heparin a structural GAG?
What is heparin structure?
Disaccharide sugars are in alpha linkage, so happen does not have an extended structure
Where is heparin found in body?
Packed into granules in mast cells and released at site of injury
What does heparin do?
Act as anti-coagulant, preventing fibrin formation
What are glycoproteins?
Protein covalently linked to an oligosaccharide
What is an oligosaccharide?
1) Usually short, 2 - 10 residues
3) Terminal sugar often = sialic acid
How do glycoproteins differ from proteoglycans?
Ratio of protein to carbohydrate much greater for glycoproteins
What are glycoprotein chains?
What is the structure of glycoprotein chain?
3) Do not contain repeating disaccharide units
What are glycoproteins linked to protein via?
O - linkage to Serine, Threonine or Hydroxylysine (in collagen)
N - linkage to Asparagine
Most glycoproteins have what attached?
Have both O- and N-linked oligosaccharides attached
Over 50% of all proteins are what?
Cell membrane associated glycoproteins are important for?
1) Membrane structure
2) Cell-cell communication
3) immune recognition
All secreted proteins are what?
glycoproteins (e..g plasma proteins)