Week 5: Carbohydrates Flashcards
What are the general functions of carbohydrates?
- energy source
- energy storage
- lubricants
- structural component of cell walls and exoskeletons
- informational molecules in cell-cell
- signaling, DNA, RNA
What are the 3 groups of carbohydrates?
- Simple sugars
- Polysaccharides
- Glycoconjugates
What are the types of simple sugars?
- Monosaccharides
- Disaccharides
- Oligosaccharides
What are the types of polysaccharides?
- Glucose homopolymers
2. Disaccharide heteropolymers
What are the types of glycoconjugates?
- Glycoproteins
- Proteoglycans
- Glycolipids
What is the function of single sugars?
Energy storage
What is the function of polysaccharides?
- Energy storage
2. Structural components
What are the functions of glycoconjugates?
- Cellular communication
- Protection
- Protein diversification
What is the building of all carbohydrates?
Simple sugars
What is the basic nomenclature of simple sugars?
Number of carbons + -ose
What are the carbonyl classification of carbs?
- Aldose
2. Ketose
What is the simplest monosaccharides that contain 3 C atoms?
Triose
What is a constitutional isomers?
Having identical molecular formulas but differ in the order of attachment
What is a stereoisomers?
Isomers that differ in spatial arrangement
What are enantiomers?
Stereoisomers that are non superimposable mirror images
What type of hexose is most prominent in living organisms?
D-Stereoisomers
What is the term for stereoisomers that are not mirror images?
Diastereomers
What is an epimer?
Diastereoisomers that differ at 1 asymmetric center
What are example epimers of D-glucose?
D-Mannose and D-galactose
What D-mannose and D-galactose epimers to each other?
No they are diastereoisomers
What are the 6 common monosaccharides is biological process?
- D-ribose
- D-deoxyribose
- D-glucose
- D-mannose
- D-galactose
- D-fructose
Can monosaccharides be hydrolyzed to smaller molecules?
No
What form of monosaccharides be most predominate in solutions?
cyclic forms
What cyclic sugar does glucose form?
Pyranose that resembles pyran
What cyclic sugar does fructose form?
Furanose that resembles furan
What are the steps of cyclization of monosaccharides?
- The nucleophilic alcohol attacks the electrophilic carbonyl carbon, allowing formation of a hemiacetal.
- As a result, the linear carbohydrate forms a ring structure.
- At the completion of this structure, the carbonyl carbon is reduced to an alcohol 4. The orientation of the alcohol around the carbon is variable and transient.
What is the difference between a and b forms of anomers?
- a: the hydroxyl as C-1 is below the plane of the ring
2. b: the hydroxyl as C-1 is above the plane of the ring
What would a typical solution of glucose contain?
- One-third α anomer
- Two-thirds β anomer
- About 1% open chain
What is a reducing sugar?
Sugars that react with oxidizing agents
What product is created when glucose reacts with hemoglobin?
Glycosylated hemoglobin (HbA1c)
Would Glycosylation of Hb effect oxygen binding of ability of Hb
No
What are the characteristics of monosaccharides?
- Compounds that contain a single carbonyl group and two or more hydroxyl groups
- Cannot be hydrolyzed to simpler carbohydrates
What are the characteristics of disaccharides?
2 sugars linked together by O-glycosidic bonds
What are the characteristics of oligosaccharides?
- 2 or more sugars linked by O-glycosidic bonds
- Play a key role in processes that take place on the surfaces of cells, such as cell–cell interactions and immune recognition
What are the characteristics of polysaccharides?
- Formed when many monosaccharides are bonded together
2. Essential structural components of several classes of organisms
What is the hydrolyzed for of maltose?
Maltase
What are the components of maltose?
2 glucose molecules linked at a
What are the components of sucrose?
- a-glucode
2. b-fructose
Enzyme that cleaves sucrose?
sucrase
What are the components of lactose?
Galactose b-linked to glucose
Enzyme that cleaves lactose?
Lactase
Where are the enzymes that cleave disaccharides located?
The surface of epithelial cells lining the small intestine
What’s the difference between homopolysaccharides and heteropolysaccharides?
- Homo: one monomer unit
2. Hetero: multiple monomer units
What is the difference between linear and branched polysaccharides?
- Linear: bound by 1 type of glycosidic bond
2. Branched: bound by multiple types of glycosidic bonds
What is the storage form of glucose in animal cells?
Glycogen
What is the storage form of glucose in plants?
Starch
What are the 2 forms of starch?
- Amylose
2. Amylopectin
How is glycogen and starch affected when in cells?
Insoluable
Forms granules due to their high molecular weight
What enzyme hydrolyzes glycogen and secreted by the salivary gland and pancreas?
a-amylase
What enzymes assist the breakdown of glycogen by degrading a(1 -6) linkages?
- Glycogen phosphorylase
2. Debranching enzymes
How are cellose molecules linked?
B-1,4 glycosidic bond
What’s the difference between a and b linkages the regarding structure?
B: yields a straight chain capable of interacting with cellulose molecules to form strong and insoluble fibrils
a: starch and glycogen for compact hollow cylinders suitable for storage
What makes cellulose difficult to break down?
- Fibrous structure
2. Water insolubility
What enzyme is secreted by fungi and bacteria allowing them to digest cellulose?
cellulase
Why can’t animal digest cellulose?
They lack the enzyme to hydrolyze linkages
How are alcohols joined to glucose
O-glycosidic bonds
How are amines joined to glucose?
N-glycosidic bonds
How are phosphates joined to carbohydrates?
ester linkages
What is process is the most common modification of carbohydrates?
Phosphorylation
How would phosphorylation modify carbs?
Makes the sugar anionic and prevents them from leaving the cell facilitating the metabolism of sugars
What is glycoproteins?
- A component of membrane proteins
2. The largest component by weight
What is a proteoglycan?
- The protein is attached to a particular type of polysaccharide called a glycosaminoglycan
- Functions as a lubricant
What are mucins?
- Predominately carbs and O-linked glycoproteins
2. Mucus
What is the structure of glycoprotein?
A protein with small oligosaccharides attached Carbohydrate is linked through O-glycosidic linkage to the O of Ser or Thr in the protein
Carbohydrate is linked to amide N of Asn residue through a N-glycosidic linkage
Describe the structure of Glycosaminoglycans
- One of the sugars is an amino sugar
2. At least one sugar has a negative charge due to the presence of a sulfate or carboxyl group
What glycosaminoglycans produced by immune cells and is also used commercially as an anticoagulant?
Heparin
Glycosaminoglycan component of the vitreous humor of the eye and of the lubricating fluid of joints
Hyaluronic acid
Glycosaminoglycan components of connective tissue and extracellular matrix
Chondroitin sulfates and keratan sulfate
