Chapter 9 Carbs Flashcards
Exam 2
What are carbohydrates?
Carbon based molecules that have several hydroxyl groups (C-OH)
What are the functions of carbohydrates?
Energy source and storage
Lubricants in joints
Structural component of cell walls and exoskeletons
Cell cell signaling, DNA, RNA info
How can carbohydrates be linked to proteins and lipids?
Covaletly
What are the three groups of carbohydrates?
Simple sugars (mono,di,oligosaccharides) Polysaccharides (glucose homopolymers and disaccharide heteropolymers) Glycoconjugates (Glycoproteins, Proteoglycans, Glycolipids)
What are simple sugars used for
Energy source (broken down for energy)
What are polysaccharides used for?
Energy storage (built up to store energy) Structural components (plants, shellfish, insects)
What are glycoconjugates used for?
Cellular communication (immune response and recognition)
Protection
Protein diversification
What is the building block of all carbs?
Monosaccharide
How are monosaccharides named?
Number of carbons and -ose
What is the simplest monosaccharide?
Triose - contains the minimum 3 carbon atoms
What is an aldose?
A carb with aldehyde functionality
What is a ketose?
A carb with ketone functionality
What are constitutional isomers?
Have identical molecular formulas but differ in the order of attachment
What are stereoisomers?
Isomers that differ in spatial arrangement
What are enantiomers?
Stereoisomers that are non superimposable mirror images
Are most hexoses in living organisms D or L isomers?
D (right) stereoisomers
What are diastereomers?
Stereoisomers that are not mirror images
How would you find the total amount of possible stereoisomers?
2^n where n is the number of asymmetric carbon atoms
True/False: Diastereomers have different physical properties
True
What are epimers?
Diastereoisomers that differ at 1 asymmetric center
What type of monosaccharide is shown here?
ketotriose (three carbon carb with a ketone as a functional group)
What type of isomers are shown?
Constitutional isomers
Same molecular formula but different arrangement of attachment
What kind of isomers are shown here?
Enantiomer (stereoisomer that is not a superimposable mirror image)
What kind of isomer is shown?
Diastereoisomers
not mirror images - you cannot flip them and them be the same
What kind of isomer is shown here?
Epimer (diastereoisomer that differ at 1 asymmetric center aka at 1 chiral carbon)
What are the most commonly seen sugars in biochemical processes?
6 carbon aldoses (glucose, mannose, galactose, fructose)
What is a ribose?
A standard 5 carbon sugar
What is a glucose?
Standard 6 carbon sugar
What is galactose to glucose?
An epimer (differs at one chiral carbon)
What is fructose to a glucose?
Ketose form of glucose
has 1 less asymmetric carbon with the same number of carbons
What form of monosaccharides predominate in a solution?
Cyclic forms
What is a pyranose?
A six carbon ring
What is a 5 membered ring called?
Furanose
What carbons link to form a six membered ring?
pyranoses are created by linking the hydroxyl group on C5 with the ketone on C1
What formation cyclizes monosaccharides?
Hemiacetal formation
What does it mean when a cyclic sugar is in the alpha formation?
The hydroxyl group at C1 is below the plane of the ring
beta is above
Is this sugar in the alpha or beta form?
Alpha since the OH on C1 is below the plane of the rings
What are reducing sugars and what form must they be in to function as a reducing sugar?
Reducing sugars are sugars that react with oxidizing agents and they are in the open chain form
What can glucose form when reacting to hemoglobin?
Glycosylated hemoglobin (HbA1c- how we measure diabetes risk)
True/False: Glycosylation of Hemoglobin decreases the ability of oxygen binding to Hb?
False
Glycosylation of Hb has NO effect on the oxygen binding ability of Hb
How long does glycosylation of Hb last?
For the lifespan of the RBCs (90-120 days)
What are monosaccharides?
Compounds that contain a single carbonyl group and two or more hydroxyl groups
They CANNOT be hydrolyzed to simpler carbs
What are disaccharides?
2 sugars linked together by O glycosidic bonds (O bonds are when OH is used to create a glycosidic linkage)
What are oligosaccharides?
2 or more sugars linked by O-glycosidic bonds
cell cell interactions and immune recognition
When are polysaccharides formed?
When many monosaccharides are bonded together
What kind of glycosidic bond is seen here?
Alpa 1-4 Glycosidic bond
What kind of glycosidic bond makes up maltose?
Alpa 1-4 linkage
What hydrolyzes maltose?
Maltase
What molecules make up maltose?
two glucose molecules
What molecules make up sucrose (table sugar)?
Glucose linked to fructose
What hydrolyzes sucrose into glucose and fructose?
Sucrase
What kind of glycosidic linkage is used in sucrose formation?
alpha 1- Beta-2 linkage
remember fructose’s anomeric carbon is on C2
Where are enzymes that cleave disaccharides found?
on surface of epithelial cells lining the small intestine
What is lactose made up of?
Galactose linked to glucose by a Beta-1-4 glycosidic bond
What enzyme cleaves lactose into glucose and galactose?
Lactase
What are homopolysaccharides?
Polysaccharides (many monosaccharides linked together by glycosidic bonds) that are repeating unites of the same monomer units
What are heteropolysaccharides?
Polysaccharides that are made up of many multiple monomer unites (more than just the same monomer)
What creates branched polysaccharides?
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 (amylose and amylopectin)
Is amylopectin linear or branched?
Branched
Are glycogen and starch soluble?
No they have high molecular weight and usually form granules in the cell
What hydrolyzes glycogen and is secreted by salivary glands and the pancreas?
Alpha amylase (use this to break down starch in the mouth during mastication)
What 2 enzymes breakdown glycogen?
Glycogen phosphorylase
Debranching enzymes
(degrade the alpha 1-6 linkages)
What is cellulose and what type of glycosidic bond is seen?
Homopolymer of glucose that is linked by beta-1-4 glycosidic bonds
What makes cellulose difficult to break down?
Fibrous structure (fiber in the body) Water insolubility
Why do most animals not have the ability to break down cellulose into fuel?
Because they lack the enzyme to hydrolyze BETA-1-4 linkages (we can only break down alpha-1-4 linkages)
What kind of bond is made when amines are joined to glucose?
N-glycosidic bonds
What kind of linkage joins carbs to phosphates?
Ester linkages
What does phosphorylation of a sugar do?
Adds a phosphate to the carbohydrate and makes it anionic (negatively charged) so that it cannot be recognized by transporters so it is stuck in the cell to be made into fuel
What are glycoproteins?
Proteins with carbs attached
What are the three main classes of glycoproteins?
Glycoproteins
Proteoglycans
Mucins or mucoproteins
What do glycoproteins do?
Play a variety of roles including as a membrane protein
What is found in proteoglycans?
A protein that is attache to a particular type of polysaccharide called a glycosaminoglycan
What do proteoglycans do?
Play structural roles or act as lubricants in the joints
What are mucins?
Mainly carbohydrates by weight are are O-linked glycoproteins
Protein attached to carbohydrate by N-acetylgalactosamine
Where on a protein are glycosidic linkages happening?
on the Ser or Thr residues in the protein
Where are carbohydrates linked to on proteins and what linkage does this?
to the aminde N of Asn residue through a N-glycosidic linkage
What must a proteoglycan have?
one of the sugars must be an amino sugar
at least one sugar has a negative charge due to the presence of sulfate or carboxyl group
What are glycolipids?
Lipids with covalently bound oligosaccharide
Where can you find glycolipids in a cell?
In gram negative bacteria and parts of membrane
