Carbs

Question 1

What are carbohydrates

Answer 1

aldehydes or ketone derivatives of polyhydroxy alcohols or compounds which give rise to these on hydrolysis.
Most abundant molecules on earth

Question 2

3 sources of carbs in plants ?

Answer 2

◦ Starch
◦ Cellulose/lignin (Cell wall)
◦ Inulin (sweetener for diabetics)

Question 3

3 sources of carbs in animals ?

Answer 3

In animals
◦ Plant foods
◦ Glycogen
◦ Others (fat, protein)

Question 4

What are 4 classifications of carbs

Answer 4

Monosaccharides – Simple sugars
Disaccharides – 2 monosaccharides
Oligosaccharides – 3 – 10 monosaccharides
Polysaccharides – More than 10 joined together by glycosidic bond

Question 5

What are Glycocongugates

Answer 5

Sugar chain attached to other biomolecules,
◦Proteins – Glycoproteins
◦Lipids – Glycolipids

Question 6

Explain isomer formation

Answer 6

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)

Question 7

What are stereoisomers

Answer 7

Compounds which are identical in composition but differ in their spatial configuration

Question 8

5 classifications of stereoisomers

Answer 8

1. Aldose and ketose
2. D and L isomers
3. α and β anomers
4. Epimers
   5- Pyranose and furanose

Question 9

What are aldoses and ketoses

Answer 9

Aldose - monosaccharide containing one aldehyde group per molecule [chemical formula - Cn(H2O)n].
Ketose - sugar containing one ketone group per molecule.

Question 10

D and L isomers

Answer 10

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

Question 11

A and B anomers

Answer 11

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

Question 12

Epimers

Answer 12

Two sugars which differ from one another by only one carbon atom except the anomeric carbon atom
Ex: glu/Man (2)

Question 13

What is epimerization

Answer 13

Epimerization – the conversion of one epimer to another Ex; Galactose to Glucose in the liver

Question 14

Pyranose vs furanose

Answer 14

Pyranose is 6 member ring (hemiacetal Haworth structure)
Furanose is 5 member ring (hemiketal, Haworth structure )

Question 15

3 monosaccharide hexoses

Answer 15

D - glucose (dextrose)
D-fructose
D-galactose

Question 16

What is D-glucose ?

Answer 16

◦ Hydrolysis of starch (polysaccharides), maltose, lactose (disaccharides) yield glucose.
◦ All tissues utilize glucose for energy
◦ Stored as glycogen in liver

Question 17

12 Consequence of too much sugar

Answer 17

Dizziness
Allergies
Cholesterol
Hypertension
Colon and and pancreatic cancer
Type 2 diabetes
ADD/ADHD
Obesity.
Metabolic syndrome
Cardiovascular disease

Question 18

What is fructose

Answer 18

◦ 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)

Question 19

What is galactose ?

Answer 19

◦ Constituent of milk sugar (lactose) and glycolipids and glycoproteins
◦ Synthesized in the mammary gland

Question 20

What are derivatives of monosaccharides and 4 examples .

Answer 20

OH groups of sugars can be replaced by some other groups.
1. Deoxy sugars
2. Amino sugars
3. Sugar alcohols
4. Sugar acids

Question 21

How are deoxy sugars formed and function

Answer 21

◦ Hydrogen atom replaces -OH group on C-2
◦ Constituent of nucleic acids

Question 22

How are amino sugars formed and 2 examples

Answer 22

◦ Sugars containing an amino group are called amino sugars [Amino group (NH-) substituted for OH group]
1. Glucosamines
2.galactosamines

Question 23

Biomedical importance of amino sugars ( glucosamines, galactosamines, antibiotics )

Answer 23

1. Glucosamines
   ◦ Constituents of certain mucopolysaccharides /glycosaminoglycans
   ◦ Constituents of cell walls of fungi and lobster
2. Galactosamines
   ◦ Constituents of sulphated mucopolysaccharides
3. Antibiotics (erythromycin, carbomycin) contain amino sugars

Question 24

What are sugar alcohols and 3 examples

Answer 24

Sugars reduced to their corresponding alcohols
1. Glucose to sorbitol
2. Mannose to mannitol
3. Galactose to galactitol

Question 25

What is cataract and what causes it ?

Answer 25

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

Question 26

What are sugar acids ?

Answer 26

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

Question 27

What are glycosides and 2 examples

Answer 27

Compounds containing a carbohydrate and a non- carbohydrate residue Glucose is glucoside Galactose is galactoside

Question 28

4 importances of glycoside

Answer 28

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)

Question 29

What is glycosidic bond

Answer 29

Two monosaccharides joined by a covalent bond is called a glycosidic linkage.

Question 30

What is disaccharide ? 3 examples

Answer 30

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

Question 31

What is lactose ?

Answer 31

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

Question 32

What is sucrose

Answer 32

Present in cane sugar, fruits and some vegetables Sucrose is Glucose + Fructose

Question 33

What are 2 types of polysaccharides and their examples

Answer 33

1. Homoploysaccharides – Starch, Cellulose, Glycogen 2. Heteropolysaccharides – Glycosaminoglycans

Question 34

What is starch and where found

Answer 34

Storage form of carbohydrate in plants. Present in cereals (rice, wheat, rye), potatoes, legumes Mixture of amylose and amylopectin

Question 35

What is amylose

Answer 35

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

Question 36

What is amylopectin

Answer 36

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

Question 37

What is cellulose?

Answer 37

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

Question 38

5 benefits of fibre

Answer 38

1, acheivment of healthy weight 2l lower blood troll levels 3. Cancer prevention 4. Lpwer risk of heart disease 5.Regulate blood sugar

Question 39

What is glycogen and structure

Answer 39

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.

Question 40

What is reducing sugar and 3 example

Answer 40

Some monosaccharides and disaccharides have ◦ A reactive carbonyl group or ◦ Anomeric carbon that can be oxidized. Ex. Glucose, maltose, lactose / Benedicts test

Question 41

What is non reducing sugar and 1 example

Answer 41

Non reducing sugars have both anomeric carbons in a glycosidic bond ( ex . Sucrose)

Question 42

What is heteroglycan

Answer 42

Different types of sugars are joined by glycosidic linkages

Question 43

What are GAG

Answer 43

Repeating disaccharide units. Disaccharide units contain either of two amino sugars, N-acetylgalactosamine (GalNAc) or N- acetylglucosamine (GlcNAc), and a sugar acid (uronic acid)

Question 44

Name 7 GAG

Answer 44

1. Chondroitin sulphate 2. Dermatan sulphate 3. Keratan sulphate (type I) 4. Keratan sulphate (type II) 5. Hyaluronate 6. Heparin 7. Heparan sulphate

Question 45

What is Chondroitin sulphate (structure and location)

Answer 45

Most abundant GAG Mainly present in adult bone, cartilages and cornea. It consists of N-acetylgalactosamine, D-glucuronic acid and is sulphated.

Question 46

What is heparin (function and formation )

Answer 46

Anticoagulant present in liver produced mainly by the mast cells of liver. Prevents blood clotting by inhibiting the conversion of fibrinogen to fibrin

Question 47

What’s a glycoprotein

Answer 47

Proteins with short oligosaccharide chains which are highly branched and generally do not have a repeating sequence.

Question 48

What is carb content of glycoprotein

Answer 48

1% - 85% by weight.

Question 49

3 functions of carbohydrate chain in glycoprotein

Answer 49

◦ May stabilize against denaturation (modifying the structure of proteins) ◦ Protect from proteolytic degradation ◦ Enhance solubility

Question 50

5 functions of glycoproteins and examples where possible

Answer 50

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.

Question 51

What are proteoglycans

Answer 51

Proteoglycans are proteins with long, linear, unbranched oligosaccharides with a repeating disaccharide unit. Disaccharide unit is a glycosaminoglycan

Question 52

What is mucopolysaccharidoses

Answer 52

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.

Question 53

Significance of type AB

Answer 53

Universal recipient

Question 54

Significance of type O

Answer 54

Universal donor

Question 55

What are 4 blood group antigens

Answer 55

Type A Type B Type AB (Universal recipient) or Type O (Universal donor)

Question 56

What are blood group antigens

Answer 56

ABO substances are complex oligosaccharides Carbohydrate antigens are present on RBC Oligosaccharide portion gives the antigenic property

Question 57

What are H substance

Answer 57

◦ 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.

Question 58

Structure and function of H substance

Answer 58

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).

Question 59

Order of structure of H antigen R to L?

Answer 59

Ceramide chain, glucose , galactose , N-acetylglucosamine , galactose

Question 60

How vis A substance formed

Answer 60

A allele encodes a glycosyltransferase; GalNAc transferase. Enzyme bonds N-acetylgalactosamine to D- galactose end of H antigen

Question 61

How is B substance formed

Answer 61

B allele encodes a glycosyltransferase; Gal transferase Above enzyme joins α-D-galactose to D-galactose end of H antigen.

Question 62

How us AB type formed

Answer 62

Individuals of AB type possess both enzymes (GalNAc transferase, Gal transferase). Have both oligosaccharide chains.

Question 63

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

Answer 63

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)