Carbohydrates Flashcards
____________ are the most abundant biomolecule on earth.
Carbohydrates
Which biomolecule is often abbreviated to ‘CHO’?
Carbohydrate
Name two carbohydrates that are staples of the human diet.
Sugar and starch
___________ of carbohydrates is the central energy-yielding pathway in most non-photosynthetic cells.
Oxidation
Which type of carbohydrates are found in the cell coats of animals?
Insoluble
Name two classes of simple sugars.
Aldehyde sugars (aldoses) and ketone sugars (ketoses)
How many R-groups does an aldose have?
One
How many R-groups does a ketose have?
Two
Define ‘stereoisomers’.
Molecules that are non-superimposable, mirror images of each other
Glyceraldehyde has a single _______ carbon atom.
Asymmetric
Name the stereoisomers of glyceraldehyde.
D- and L-glyceraldehyde
What do ‘D and L’ refer to, in the context of stereoisomers?
D and L refer to the configuration of the asymmetric carbon atom, furthest from the aldehyde or ketone group
L-sugars rotate polarised light to the _____.
Left
D-sugars rotate polarised light to the _____.
Right
True or false: most hexose sugars are found naturally in the D-sugar form.
True
Name a sugar that naturally occurs in the L-sugar form.
L-arabinose
What is an epimer?
A D-sugar that differs in configuration at only a single asymmetric carbon atom
What are the two crystalline forms of D-glucose?
Downward-pointing alpha-D-glucose and upward-pointing beta-D-glucose
Glucose undergoes a reversible reaction between -OH group of C5, and the anomeric carbon (C1) forms a _______ _______ structure
Pyranose ring
Fructose undergoes a common reaction between the -OH group of ___ and the anomeric carbon (C2), forming a furanose ring structure.
C5
Six-membered sugar rings are called ________.
Pyranoses
Five-membered sugar rings are called ________.
Furanoses
What type of sugar will the following reaction for maltose yield?
A condensation reaction takes place. A bond is formed that is termed ‘glycosidic linkage’. Maltose involves the linking of two glucose molecules, 1-4 glycosidic linkage between the C1 and C4 positions of two D-glucose molecules.
The D-glucose containing C1 atom is in its alpha form, therefore the bond is termed an alpha (1-4) glycosidic bond.
Disaccharide
A ______ glycosidic bond is seen in the glycosidic linkage of sucrose
1 - 2
True or false: Multiple reactions in a sugar create smaller polysaccharides.
False
Carbohydrates may be _________ or branched.
Linear
Name two functions of carbohydrates.
Storage and structure
Excess glucose is stored as ________.
Glycogen
Plants store excess glucose as _______.
Starch
What is the exoskeleton of some animals called?
Chitin
Cellulose is a plant storage __________.
Polysaccharide
Bacteria and yeasts store excess glucose as _______.
Dextran
What is amylose?
Unbranched polymers of glucose units, joined by α1-4 glycosidic bonds
What is amylopectin?
Similar to amylose, but additional α1-6 bonds occur every 25-30 units, creating branchpoints
_________ consists entirely of glucose units, mostly linked by α1-4 bonds
Glycogen
Every ___ sugar units, glycogen’s chains are branched by the formation of an α1-6 bond
10
Where is glycogen primarily made and stored?
The liver and the muscles
Cellulose strands are held together by which type of bond?
Hydrogen
Name two animals that are capable of degrading cellulose in their gut.
Cow and horse
Cellulose is made up of unbranched ___________ of glucose units, linked by β1-4 glycosidic bonds
Polysaccharides
α and β forms exist for all cyclic _______________.
Monosaccharides
