Tutorial - Week 7 - Carbohydrates and revision Flashcards
Key concept: Become familiar with the structure, function and nomenclature of carbohydrates (5 points)
- Ketoses vs aldoses
- L- & D monosaccharides (D-form is predominant)
- Cyclic structure of monosaccharides
- Epimers, mutarotation, anomeric forms
- Reducing sugars
Key concept: Recognise monosaccharides
Key concept: Distinguish monosaccharide isomers
Key concept: Recognise a glycosidic linkage
Key concept: Distinguish polysaccharides (energy storage vs structure)
Key concept: Functions of carbohydrate conjugates
What are the most abundant biomolecules on earth?
What percentage of human food does it represent?
Carbohydrates
50-60%
What do all carbohydrates contain and what is the empirical formula for most of them?
Carbon, Hydrogen and Oxygen and most have the empirical formula (CH 2 O)n
T/F: Some Carbohydrates also have some Nitrogen and Sulfur and Phosphorus
True
General name of carbohydrates normally ends in…? Examples?
–ose (e.g. glucose, sucrose, fructose)
Major functions of carbohydrates?
- Rapid source of energy
- Energy storage in plants as starch and in mammals as glycogen
- Structural components (e.g. ribose in nucleic acids, cellulose in plant cell walls)
- Cell surface recognition (as part of proteoglycan & glycoproteins)
Simple carbohydrates are often referred to as…? What is special about them?
sugars and are fast digesting
Complex carbohydrates refer to…? Example?
sugar that take longer to digest (e.g. starch)
What are the four major groups they are divided into?
Sugars can also be called _________
Saccharide comes from the Greek word for ______
saccharides
sugar
List all the functions of carbohydrates
What carbohydrates are in these foods?
T/F: Carbohydrates are very important for cognitive function. Why?
True
The brain needs glucose as an energy source, we need a continuous supply of glucose for our brain to work
Label these by name and group
Monosaccharides:
- Have at least how many carbons?
- What does one of the carbons contain?
- What do all the other carbons contain?
- Depending on where the _______ group is located they are divided into?
- How do you distinguish an aldose?
- How do you distinguish a ketose?
- What about a certain group is also important for the structure, properties, and naming of monosaccharides?
- Give the names for the different number of carbons from 3-7
1 Have at least 3 carbons ((e.g. (CH 2 O)3)
- One of the carbons contains a carbonyl group (C=O)
- All the other carbons contain a –OH group
- Depending where the C=O group is located they are
divided into aldoses and ketoses - Aldoses have the C=O group in the C1, it is an aldehyde
- Ketoses have the C=O group in another C, it is a ketose
- Orientation of –OH groups is also important for the
structure, properties and naming of monosaccharides
8.
Different number of carbons:
* Triose (3C)
* Tetrose (4C)
* Pentose (5C)
* Hexose (6C)
* Heptose (7C
What do the D and L in the names of carbons mean?
D (Dextro means ‘on the right side’)
L (Levo means ‘on the left side’)
Name these (mainly focus on D and L)
L-monosaccharide meaning?
-OH group is on the left side
D-monosaccharide meaning?
-OH group is on the right side
Which sugars (D or L) are more predominant in nature?
D- sugars
Define chirality
Chirality, or handedness, means that an object or molecule cannot be superimposed on its mirror image by any translations or rotations. Achiral (not chiral) objects are those objects that are identical to their mirror image
How do you spot an aldose?
- Aldoses with C=O in C1
- They have different numbers of carbons
- Different number of chiral centres
What are D-isomers in aldoses?
-OH is on the right in the chiral centre
What is the anomeric carbon in aldoses?
The anomeric carbon is the carbon with the double bond to oxygen.
In aldoses, this is the carbon that is only attached to one other carbon
What are epimers?
2 isomers that differ
in configuration of
one carbon
E.g: one carbon might have the OH on the opposite side
What are 1 & 2, and 2 & 3 examples of?
Epimers
1& 2 are two isomers that differ in the configuration of one carbon and same as 2 & 3
How do you determine if a monosaccharide is a ketose?
Ketoses with C=O in another C (not in C1)
Also have a different number of chiral centres
What is a constitutional isomer?
Aldose & ketose with
the same number of Carbons
Common monosaccharides have a _________ structure
cyclic
What is the process to this aldose becoming cyclic?
What do these create?
Formation of cyclic hemiacetal from aldoses
How does D-glucose look when it transforms into it’s cyclic form? What are the variations and final forms?
What does these result in?
Formation of cyclic hemiketal from ketoses
What does the process look like of D-Fructose turning into a cyclic structure? Name the parts and draw the final outcomes
What is this representation called?
Linear representation
What is this representation called? Label the arrows
Cyclic representation
Name the different types of projections shown
What are isomers?
Two monosaccharides with the same molecular formula
Define Constitutional isomers:
Aldose &
ketose w the same number of Carbons
Define Enantiomers (L- & D-isomers:
-OH in
the last carbon that is a chiral center
Define Epimers:
-OH in one, or several asymmetric carbons
Define Anomeric:
-OH in the anomeric
carbon (carbon 1 in the ring form)
Are monosaccharides reducing or oxidising sugars?
Monosaccharides are reducing sugars
Aldoses in the open (linear) form have a free __________ ______, which reacts with _________ ________
Aldoses in the open (linear) form have a free aldehyde group, which reacts with oxidising agents
Ketoses are also ________ sugars because the ketose group can shift to be an _________ before oxidation
reducing
aldose
Label the parts of the equation
The three most common monosaccharides in human diet are…?
Glucose, Fructose & Galactose
The common monosaccharides have _______ structures
cyclic structures
Name these three monosaccharides
Monosaccharides have the basic molecular formula ________ where monosaccharides with ____ or ____ carbons are the most common
C(H2 O)n
5 or 6
There is Large diversity in monosaccharides because of ___________
of the various hydroxyl groups (-OH), the ____________ and
whether the molecule is an __________ or __________
stereochemistry
ring structure
aldehyde or a ketone
These variations in the structure confer to monosaccharides distinct….?
physicochemical properties
Monosaccharides are __________ sugars.
reducing
How are disaccharides made?
Which groups is responsible for the joining and how?
Is there elimination of any molecules? What is the process called?
What is the reverse reaction called?
- Disaccharides are made from two monosaccharides
linked together by a glycosidic bond: - The –OH (alcohol) on one monosaccharide
condenses with a hemiacetal of another - There is elimination of one H2O (dehydration)
- The reverse reaction is a hydrolysis
What does the rest of this diagram look like and where is the glycosidic bond?
Disaccharides might have a _________ end (___________ group
can be converted into an aldehyde)
The acetal end is non-_________
reducing
hemiacetal
reducing
How do you obtain disaccharides?
Free reducing group: cyclic hemiacetal or hemiketal, or linear free aldehyde or ketone
Label if there’s a reducing end or not
Non-reducing end if anomeric carbons are attached to one another in the glycosidic bond
What are the three popular disaccharides? Explain what monosaccharides they are and how they are linked
Define Free reducing group:
Cyclic hemiacetal or hemiketal, or linear free aldehyde or ketone (i.e. the anomeric carbon
has to be free
T/F: Disaccharides have different glycosidic bonds and some are reducing and some are non-reducing
True
Label the groups based on their colours
What are polysaccharides
- Long polymerics chains of monosaccharides
- Used as energy storage and structure
- Linear or branched
What are the differences between homopolysaccharides and heteropolysaccharides
Label the categories
How are polysaccharides used for energy storage?
What is the storage system for polysaccharides of plants?
Starch
Describe starch
What are the two types of starch in plants?
Amylose: linear D-glucose polymer with a(1-4) chain
Amylose forms LH helix chain
Amylopectin: D-glucose polymer of a(1-4) chain branched with a(1-6) branch points
What is the storage polysaccharides of animals
Glycogen
Describe the 9 points of glycogen
What is the structural polysaccharide in plants?
Descibe the 6 points
Cellulose
Label the parts of how cellulose packs into plants
What are these structures and what is special about their relationship to one another?
Starch and glycogen are digested by
_____________ & __________,
enzymes in _________ & __________, which
break these into _____________.
alpha-amylases and glycosidases
saliva and intestine
glucose units
Celullose is digested by ___________, present in some ________ and _________
(which hydrolyses the ________ linkages)
cellulase
protist and bacteria
b(1-4)
Label the type of biomolecule, its linkages, and explain its monomers and any additional information
Termites have a protistan symbiont in the gut that produces…?
Which breaks down…?
b(1-4) cellulase, which breaks (b1-4 ) glycosidic bonds
Herbivores/ruminants carry symbiotic bacteria that produce…? And can use cellulose as…?
b(1-4) cellulase and can use cellulose as
source of glucose molecules
What is Chitin?
structural polysaccharide in insects, spiders and crustaceans
What are the structural components of chitin?
It is a homo__________ of which amine?
What is it’s linkage formula?
- Structural component of invertebrate exoskeletons
- homopolysaccharide of N-acetylglucosamine
- b(1-4) linked residues
What is this?
Chitin forms the exoskeleton of __________. This cicada is molting, shedding its old ____________ and
emerging in adult form
arthropods
exoskeleton
What are Glycoconjugates?
carbohydrate joined to a
protein or lipid
Polysaccharides can be information carriers. Explain
Communication between cells and
extracellular surroundings
Polysaccharides can be conjugated to _________? E.g?
They can also be conjugated to __________? E.g?
- They can be conjugated to proteins (i.e.
proteoglycans & glycoproteins) - They can be conjugated to lipids (e.g.
glycosphingolipids)
Define Proteoglycans
proteins at the cell surface, in which glycosaminoglycan chains are covalently
linked to a membrane protein
Define Glycoproteins:
proteins at the cell surface, in which one or more oligosaccharide is covalently linked to a membrane protein
Define Glycosphingolipids:
sphingolipids in which the hydrophilic headgroup are oligosaccharides
Describe 2 points of Disaccharides
- Different glycosidic bonds
- Reducing end and non reducing end
Describe Glycoconjugates (4 points)
- Carbohydrates as information carriers when conjugated
- Proteglycans
- Glycoproteins
- Glycosphingolipids
Describe Polysaccharides (7 points)
- Homopolysaccharides vs heteropolysaccharides
- Branched vs unbranched
- Energy storage: starch & glycogen
- Structure: cellulose & chitin
- Starch: amylose & amylopectin
- Rapid degradation of starch & glycogen
- Non-soluble difficult to degrade cellulose & chitin
Describe Function and nomenclature of carbohydrates (2 points)
- Rapid source of energy, energy storage, structural
components - Monosaccharides, disaccharides, polysaccharides
