Carbs Flashcards
What are carbohydrates
aldehydes or ketone derivatives of polyhydroxy alcohols or compounds which give rise to these on hydrolysis.
Most abundant molecules on earth
3 sources of carbs in plants ?
◦ Starch
◦ Cellulose/lignin (Cell wall)
◦ Inulin (sweetener for diabetics)
3 sources of carbs in animals ?
In animals
◦ Plant foods
◦ Glycogen
◦ Others (fat, protein)
What are 4 classifications of carbs
Monosaccharides – Simple sugars
Disaccharides – 2 monosaccharides
Oligosaccharides – 3 – 10 monosaccharides
Polysaccharides – More than 10 joined together by glycosidic bond
What are Glycocongugates
Sugar chain attached to other biomolecules,
◦Proteins – Glycoproteins
◦Lipids – Glycolipids
Explain isomer formation
Asymmetric carbon atom – (C*) carbon atom with four different groups attached.
Presence of asymmetric carbon atoms lead to formation of isomers. Isomers - 2n (n- no. of chiral centres)
What are stereoisomers
Compounds which are identical in composition but differ in their spatial configuration
5 classifications of stereoisomers
- Aldose and ketose
- D and L isomers
- α and β anomers
- Epimers
5- Pyranose and furanose
What are aldoses and ketoses
Aldose - monosaccharide containing one aldehyde group per molecule [chemical formula - Cn(H2O)n].
Ketose - sugar containing one ketone group per molecule.
D and L isomers
Called enantiomers (mirror images)
Naturally occurring monosaccharides belong to D series
When the OH group around the carbon atom adjacent to the terminal primary alcohol carbon (C- 5) is on the
Right – D series left – L series
A and B anomers
Carbon 1 - anomeric carbon atom
α – “OH” is below the plane of the ring
β - “OH” is above the plane of the ring
Anomeric carbon is the type of carbon that changes from acyclic form to cyclic form to become a stereocenter
Epimers
Two sugars which differ from one another by only one carbon atom except the anomeric carbon atom
Ex: glu/Man (2)
What is epimerization
Epimerization – the conversion of one epimer to another Ex; Galactose to Glucose in the liver
Pyranose vs furanose
Pyranose is 6 member ring (hemiacetal Haworth structure)
Furanose is 5 member ring (hemiketal, Haworth structure )
3 monosaccharide hexoses
D - glucose (dextrose)
D-fructose
D-galactose
What is D-glucose ?
◦ Hydrolysis of starch (polysaccharides), maltose, lactose (disaccharides) yield glucose.
◦ All tissues utilize glucose for energy
◦ Stored as glycogen in liver
12 Consequence of too much sugar
Dizziness
Allergies
Cholesterol
Hypertension
Colon and and pancreatic cancer
Type 2 diabetes
ADD/ADHD
Obesity.
Metabolic syndrome
Cardiovascular disease
What is fructose
◦ Found in fruits
◦ Canned, dried or preserved (jams) more than fresh
◦ Common sweeteners (honey, maple syrup) more than fresh (tbs)
◦ High consumption leads to Non communicable Diseases (NCD) (not natural sources)
What is galactose ?
◦ Constituent of milk sugar (lactose) and glycolipids and glycoproteins
◦ Synthesized in the mammary gland
What are derivatives of monosaccharides and 4 examples .
OH groups of sugars can be replaced by some other groups.
1. Deoxy sugars
2. Amino sugars
3. Sugar alcohols
4. Sugar acids
How are deoxy sugars formed and function
◦ Hydrogen atom replaces -OH group on C-2
◦ Constituent of nucleic acids
How are amino sugars formed and 2 examples
◦ Sugars containing an amino group are called amino sugars [Amino group (NH-) substituted for OH group]
1. Glucosamines
2.galactosamines
Biomedical importance of amino sugars ( glucosamines, galactosamines, antibiotics )
- Glucosamines
◦ Constituents of certain mucopolysaccharides /glycosaminoglycans
◦ Constituents of cell walls of fungi and lobster - Galactosamines
◦ Constituents of sulphated mucopolysaccharides - Antibiotics (erythromycin, carbomycin) contain amino sugars
What are sugar alcohols and 3 examples
Sugars reduced to their corresponding alcohols
1. Glucose to sorbitol
2. Mannose to mannitol
3. Galactose to galactitol
What is cataract and what causes it ?
cataract is a cloudy area in the lens of the eye that leads to a decrease in vision.
Dietary sorbitol is rapidly converted to fructose by sorbitol dehydrogenase and other carbohydrates in the liver.
Diabetes – sorbitol is produced rapidly
Intracellular accumulation of sorbitol leads to osmotic changes resulting in hydropic lens fibers that degenerate and form sugar cataracts
What are sugar acids ?
Aldoses are oxidized in a way that the aldehyde group remains unaltered but the primary alcohol group is converted to COOH group.
The sugar acid formed in this case is known as an “Uronic acid”.
Ex; D-Glucose to D-Glucuronic acid
D-Galactose to D-Galactouronic acid
What are glycosides and 2 examples
Compounds containing a carbohydrate and a non- carbohydrate residue
Glucose is glucoside
Galactose is galactoside
4 importances of glycoside
Cardiac glycosides –used to increase the cardiac output and important in cardiac insufficiency
Oubain – Inhibits Na+-K+ ATPase in cardiac muscle (Inhibitor of Na pump)
Found in certain drugs, spices etc.
Antibiotics (streptomycin)
What is glycosidic bond
Two monosaccharides joined by a covalent bond is called a glycosidic linkage.
What is disaccharide ? 3 examples
Bond is created between the C-1 of one sugar and the OH of another carbon
1. Maltose
2. Lactose
3. Sucrose
Intermediate product formed during the breakdown of starch by amylase enzyme
What is lactose ?
Present in milk (milk sugar) and produced in the lactating mammary gland
Breast milk – main source of energy for the new born
Lactose is Glucose + galactose
What is sucrose
Present in cane sugar, fruits and some vegetables
Sucrose is Glucose + Fructose
What are 2 types of polysaccharides and their examples
- Homoploysaccharides – Starch, Cellulose, Glycogen
- Heteropolysaccharides – Glycosaminoglycans
What is starch and where found
Storage form of carbohydrate in plants.
Present in cereals (rice, wheat, rye), potatoes, legumes
Mixture of amylose and amylopectin
What is amylose
15-20% of starch
Glucose joined by α-1,4 glycosidic linkages
Unbranched chain
Forms a helical structure
There are 6 glucopyranose units per turn
What is amylopectin
80-85% of starch
Highly branched structure
Main chain has α-1,4 glycosidic linkages
Each branch point has a α-1,6 glycosidic linkages
What is cellulose?
Straight chain homoglycan of glucose with β-1,4 linkages with alternating glucose molecules.
Humans cannot hydrolyze cellulose.
Dietary fibre (Insoluble dietary fibre)
Dietary fiber is the edible parts of plants that are resistant to digestion and absorption in the human small intestine, with complete or partial fermentation in the large intesti
5 benefits of fibre
1, acheivment of healthy weight
2l lower blood troll levels
3. Cancer prevention
4. Lpwer risk of heart disease
5.Regulate blood sugar
What is glycogen and structure
Carbohydrate storage form in animals
After a meal glucose will be converted to glycogen (Glycogenesis)
During starvation/fasting glycogen will be broken down to glucose to provide energy (Glycogenolysis)
Main chain has α-1,4 glycosidic linkages and each branch point has a α-1,6 glycosidic linkages.
What is reducing sugar and 3 example
Some monosaccharides and disaccharides have
◦ A reactive carbonyl group or
◦ Anomeric carbon that can be oxidized.
Ex. Glucose, maltose, lactose / Benedicts test
What is non reducing sugar and 1 example
Non reducing sugars have both anomeric carbons in a glycosidic bond ( ex . Sucrose)
What is heteroglycan
Different types of sugars are joined by glycosidic linkages
What are GAG
Repeating disaccharide units.
Disaccharide units contain either of two amino sugars,
N-acetylgalactosamine (GalNAc) or N- acetylglucosamine (GlcNAc), and a
sugar acid (uronic acid)
Name 7 GAG
- Chondroitin sulphate
- Dermatan sulphate
- Keratan sulphate (type I)
- Keratan sulphate (type II)
- Hyaluronate
- Heparin
- Heparan sulphate
What is Chondroitin sulphate (structure and location)
Most abundant GAG
Mainly present in adult bone, cartilages and cornea.
It consists of N-acetylgalactosamine, D-glucuronic acid and is sulphated.
What is heparin (function and formation )
Anticoagulant present in liver produced mainly by the mast cells of liver.
Prevents blood clotting by inhibiting the conversion of fibrinogen to fibrin
What’s a glycoprotein
Proteins with short oligosaccharide chains which are highly branched and generally do not have a repeating sequence.
What is carb content of glycoprotein
1% - 85% by weight.
3 functions of carbohydrate chain in glycoprotein
◦ May stabilize against denaturation (modifying the structure of proteins)
◦ Protect from proteolytic degradation
◦ Enhance solubility
5 functions of glycoproteins and examples where possible
Integral components of cell membrane
Function as receptors for hormones/molecules in the circulation
Transport molecules of vitamins, minerals – Transferrin, Caeruloplasmin
Immunogenic molecules – Immunoglobulins
Facilitate cell- cell recognition sites – Interaction of sperm with ovulated eggs.
What are proteoglycans
Proteoglycans are proteins with long, linear, unbranched oligosaccharides with a repeating disaccharide unit.
Disaccharide unit is a glycosaminoglycan
What is mucopolysaccharidoses
Genetic disorder
Some lysososmal enzymes that degrade GAGs are inactive Unable to break down proteoglycans
Leads to the accumulation of proteoglycans within cells.
Leads to a variety of disease symptoms, depending on the type of proteoglycan not degraded.
Significance of type AB
Universal recipient
Significance of type O
Universal donor
What are 4 blood group antigens
Type A
Type B
Type AB (Universal recipient) or
Type O (Universal donor)
What are blood group antigens
ABO substances are complex oligosaccharides
Carbohydrate antigens are present on RBC
Oligosaccharide portion gives the antigenic property
What are H substance
◦ Blood group substance in type O individuals.
◦ Precursor of both A and B substances
formed by addition of the terminal fucose in α,1- 2 linkage onto the terminal Galactose residue.
Structure and function of H substance
Encodes a fucosyltransferase that produces the H antigen on RBCs.
Consists of a chain of 2 β-D-galactose, β-D-N- acetylglucosamine, and α-L-fucose,
Chain is attached to a protein or ceramide (Type of a lipid molecule).
Order of structure of H antigen R to L?
Ceramide chain, glucose , galactose , N-acetylglucosamine , galactose
How vis A substance formed
A allele encodes a glycosyltransferase; GalNAc transferase.
Enzyme bonds N-acetylgalactosamine to D- galactose end of H antigen
How is B substance formed
B allele encodes a glycosyltransferase; Gal transferase
Above enzyme joins α-D-galactose to D-galactose end of H antigen.
How us AB type formed
Individuals of AB type possess both enzymes (GalNAc transferase, Gal transferase).
Have both oligosaccharide chains.
Regarding carbohydrates
(A) Starch is storage form
(B) RNA contain a derivative of a monosaccharide
(C) Cellulose is digested in the gastrointestinal tract
(D) Heparin is a mucopolysaccharide
(E) Individuals with O blood group type have Gal transferase enzyme
Regarding carbohydrates
(A) Starch is storage form in plants (T)
(B) RNA contain a derivative of a monosaccharide (F)
(C) Cellulose is digested in the gastrointestinal tract (F)
(D) Heparin is a mucopolysaccharide (T)
(E) Individuals with O blood group type have Gal transferase enzyme (F)
