Friday, March 30, 2012

Biochemical Puzzles

Puzzle 1: Find seven hydrosoluble vitamins

N X S Y R F Q V W C B Y Q E R

N I L T O O H G O W I K W N Z

D K V L P S L C Y U O D N I L

E Q A A L R S Q W L T K L X V

N T V T L M A U I O I X K O G

O S T D K F N R N J N Y O D W

N A H Q S S O I F L X O H I I

F I D M K A M B R C Y M L R W

V Q A R H A M D I C K W U Y T

Q X V C L T W Y W R O X Q P Q

O A D A I T H I A M I N E T P

A F B Q Z N E Z T S V Q H Z V

P O S S N W A T Y M U U C M U

C B Q X T Z V B K X O G Q S W

P E W M X E J S F J P R H H Q

Puzzle 2: Carbohydrate Crossword

(Tip: save the crossword as a picture and print it. Then use a pencil to solve it)

Across

3. Minor disaccharide that can be obtained from starch hydrolysis

5. The main kind of carbohydrate in foods. Also the way in which glucose is stored in plants.

7. The way in which glucose is stored in animals

12. The ketotriose

14. A ketohexose

15. Milk sugar

16. Pentose forming DNA

17. A polyalcohol related to the formation of cataracts in diabetic patients

18. An amino sugar

19. A tetrose

20. A polyalcohol related to the formation of cataracts in patients with galactosemia

21. C-2 epimer of glucose

Down

1. The lineal molecule found in starch granules

2. A heteropolysaccharide with anticoagulant effects.

4. A heptose

5. Table sugar

6. An aldohexose found in lactose

8. “Blood sugar”

9. An aldotriose

10. The branched molecule forming starch granules

11. Pentose forming RNA

13. Polysaccharide with a structural rol in plants

21. Main disaccharide obtained from starch hydrolysis

Puzzle 3: Organize the tiles!

When you organize these tiles, you will find a phrase describing a feature of biological catalysts, that in fact is common to all catalysts:

Puzzle4: Solve this amino acid crossword:

ACROSS

1. amino acid positively charged at physiological pH
3. acidic amino acid
6. amino acid that can form disulfide bridges
7. aromatic amino acid
8. basic amino acid
10. polymer of amino acids
11. branched chain amino acid
12. amino acid with OH group in the lateral chain

DOWN

1. apolar amino acid
2. polar, non charged, amino acid
4. negatively charged amino acid at physiological pH
5. imino acid
9. the smallest amino acid

Puzzle 5: Find the names of ten carbohydrates:

Puzzle 6: Find the metabolites of the Krebs Cycle:

SOLUTIONS

Puzzle 1:SOLUTION TO CARBOHYDRATE PUZZLE

GLUCOSE           GLYCOGEN           MALTOSE           RIBOSE

FRUCTOSE        ERYTHROSE         SUCROSE          GLYCERALDEHYDE

GALACTOSE       LACTOSE

Puzzle2: SOLUTION TO KREBS CYCLE METABOLITES PUZZLE:

SUCCINYLCOA                        SUCCINATE                          ALFAKETOGLUTARATE
MALATE                                    CITRATE                               FUMARATE
ISOCITRATE                            OXALACETATE                    ACETYLCOAA

Puzzle 3: Solution to the Tiles problem about biological catalysts

Organizing Tiles: Q: When you organize these tiles, you will find a phrase describing a feature of biological catalysts, that in fact is common to all catalysts

Puzzle 4: ENZ/YME/S D/O N/OT /CHA/NGE/ TH/E E/QUI/LIB/RIU/M O/F T/HE / REA/CTI/ ONS

Puzzle 5: Solution to:Find seven vitamins

BIOTIN

COBALAMIN

FOLATO

NIACIN

PYRIDOXINE

RIBOFLAVIN

THIAMINE

N + + + + F + + + + B + + E +

+ I + + O + + + + + I + + N +

+ + V L + + + + + + O + + I +

+ + A A + + + + + + T + + X +

+ T + + L + + + + + I + + O +

O + + + + F + + N + N + + D +

N + + + + + O I + + + + + I +

+ I + + + + M B + + + + + R +

+ + A + + A + + I + + + + Y +

+ + + C L + + + + R + + + P +

+ + + A I T H I A M I N E + +

+ + B + + N + + + + + + + + +

+ O + + + + + + + + + + + + +

C + + + + + + + + + + + + + +

+ + + + + + + + + + + + + + +

(Over,Down,Direction)

BIOTIN(11,1,S)

COBALAMIN(1,14,NE)

FOLATO(6,1,SW)

NIACIN(1,7,SE)

PYRIDOXINE(14,10,N)

RIBOFLAVIN(10,10,NW)

THIAMINE(6,11,E)

Polysaccharides

Polysaccharides are carbohydrates formed by more than 9 monosaccharides linked by glycosidic bonds.

When they are formed by the same kind of monosaccharides, they are called homopolysaccharides, like starch, glycogen and cellulose, formed each of them by hundreds of molecules of glucose linked by glycosidic linkages.

If the polysaccharides molecules are formed by different kinds of monosaccharides, they are considered heteropolysaccharides. Hyaluronic acid, formed by thousands of alternative units of N-acetyl glucosamine and glucuronic acid, is an example of heteropolysaccharide.

HOMOPOLYSACCHARIDES:

Cellulose

Cellulose is a linear polymer of D-glucose residues bonded by b(1, 4)-O-glycosidic linkages. It is the most abundant carbohydrate in nature.

It is formed by glucose units, linked by Beta-1, 4 O-glycosidic linkages. We can say then that, if we consider the kind of linkage, the repeating unit in cellulose is cellobiose, the disaccharide formed by two molecules of glucose linked by Beta-D-O glycosidic bonds, (that is why some text books say that the monomer in cellulose is cellobiose).

The long fibers of cellulose are held together by intermolecular hydrogen bonds. Hydrogen bonding continues in the same plane with other chains as well as in planes above and below this plane to form strong, fibrous bundles. It made cellulose very appropriate for its structural function in plants

Since cellulose is formed by glucose molecules, it can be a source of energy for certain species. The lack in human beings of appropriate enzymes for digesting cellulose make this polysaccharide unsuitable for human nutrition (Have you though about how hunger in the world could disappear if we had enzymes for digesting cellulose?). Cellulose and derivatives are used as a component of laxatives for humans.

Starch:

Starch is the second most abundant carbohydrate in nature.

The biological functions include, in plants, the main way of storage of sugar, and consequently, of energetic sources; in humans, the first supply of glucose on diet (Answer to C-O7)

Starch is not really a molecule, but a grain formed by two different kinds of molecules: Amylose and Amylopectin

Amylose

Amylose is a linear molecule formed by glucose units linked by alpha-1, 4 O glycosidic linkages. Taking in account the kind of linkage we can say that the repeating unit in amylose is maltose. (It explains that some books indicate that the monomeric unit in amylose is maltose).

Amylose molecule is helicoidal

Amylopectin

Amylopectin is the second type of molecule that forms starch. It is a branched molecule, formed also by glucose. Amylopectin contains D-glucose residues bonded together by a(1, 4)-O-glycosidic linkages with branching through a(1 6)-O-glycosidic linkages.

The disaccharides that can be obtained from the digestion of amylopectin are maltose and isomaltose.

Amylopectin shows a branch each 24-30 units of glucose,

Glycogen

The structure of glycogen is very similar to amylopectin but more branched, with one branch every 8 to 12 glucose unit

Glycogen is the way in which glucose is stored in animals. Glycogen is stored mainly in liver (to release glucose to blood when necessary) and in muscle, where it is used as a reserve of energy for muscular contraction (Answer to C-o8)

HETEROPOLYSACCHARIDES

Heteropolysaccarides contain two or more different kind of monosaccharides. Usually they provide extracellular support for organisms of all kingdoms: the bacteria cell envelope, or the matrix that holds individual cells together in animal tissues, and provides protection, shape and support to cells, tissues and organs.

Heteropolysaccharides provide extracellular support to very different organisms, from bacteria to humans; together with fibrous proteins, like collagen, elastin, fibronectin, laminin and others, heteropolysaccharides are the most important components of the extracellular matrix. Hyaluronic acid, condroitin sulfates and dermatan sulfates are important heteropolysaccharides in the extracellular matrix. These heteropolysaccharides usually are formed by the repetition of a disaccharide unit of an aminosugar and an acid sugar.

A typical example

Other common constituents are sulfate groups linked to certain monosaccharides. Usually heteropolysaccharides are associated with proteins forming proteoglycans, glycosaminoglycans or mucopolysaccharides (since they are abundant in mucous secretions). As a group, they perform diverse functions: structural, water metabolism regulation (as a reservoir of water), cellular cement, biological sieve, biological lubricant, docking sites for growth factors, among other functions.

Established specific functions of some glycosaminoglycans are:

Hyaluronic Acid (Hyaluronate): It is a lubricant in the synovial fluid of joints,

give consistency to vitreous humor, contributes to tensile strength and elasticity of cartilages and tendons (Answer to C-O6)

Chondroitin Sulfates: contributes to tensile strength and elasticity of cartilages, tendons, ligaments and walls of aorta.

Dermatan sulfate (former chondroitin sulfate B) is found mainly in skin, but also is in vessels, heart, lungs. It may be related to coagulation and vascular diseases and other conditions.

Keratan sulfate: Present in cornea, cartilage bone and a variety of other structures as nails and hair.

Heparin

It is a potent natural anticoagulant produced in the Mast Cells that causes antithrombin bind to thrombin and produce inhibition of blood coagulation.

Glycosaminoglycans are synthesized in the ER and Golgi. They are degraded by lysosomal hydrolases. A deficiency of one of the hydrolases results in a mucopolysaccharidosis. These are hereditary disorders in which glycosaminoglycans accumulate in tissues, causing symptoms such as skeletal and extracellular matrix deformities, and mental retardation.

Examples of these genetic diseases are Hunter and Hurler syndromes.

These diseases, caused by different enzyme deficits, are characterized by physical deformities, mental retardation and disturbances in the degradation of heparan sulfate and dermatan sulfate.

Biochemistry Questions: Carbohydrates and Medicine

Question:

A 15-year-old black male patient complains that lately, after the ingestion of dairy products, he experiences bloating, cramps and flatulence, and sometimes diarrhea. With this information, it is reasonable to think that the patient is intolerant to:

a) cellobiose

b) lactose

c) mannose

d) sucrose

e) maltose

f) isomaltose

g) fructose

Solution:

(b) lactose

Lactose is the milk sugar.

It is formed by Beta-D galactose and D-glucose. The galactose is linked to the glucose through a beta 1,4-O-glycosidic linkage.

This linkage is hydrolyzed by a specific disaccharidase called Lactase, located in the brush border of the epithelial cells of the small intestine. The glucose and galactose are absorbed and transported through the portal system to the liver.

In spite of the common believe in developed countries, that consume great amounts of dairy products, most of the humanity are glucose intolerant. Human beings show a decrease in the synthesis of lactase after the 4 years of age. In persons with primary lactose intolerance (the “physiological” one we are talking about), this decrease is usually evident after 6 years of age, in some cases after puberty, and most of the lactose contained in the ingested food remain undigested and continue to the large intestine. where it is fermented by intestinal bacteria, producing gases, organic acids and a decrease in the pH.

It can be manifested with cramps, abdominal pain, and other gastrointestinal disorders, that begin 1 to 2 hours after the ingestion of dairy products. This condition is more frequent among Afro American than among white Americans.

Another kinds of Lactose intolerance are a congenital form, very rare, and lactose intolerance secondary to intestine diseases, including infections.

In fact, primary lactose intolerance can be hardly considered a disease, since there is a genetic programmed decrease in the synthesis of lactase (Humans were not ‘supposed” to drink milk after a few months of life!). Since around 70 % of the whole population is lactose intolerant, it has been proposed that lactose intolerance should be considered the norm, and that the minority should be considered as a lactase persistent group, that appeared as mutation of the “normal” gen.

Anyway, for those persons living in a society where milk is an important componente of diet, to be intolerant to lactose convey certain minor problems.

The “treatment” consist mainly in avoiding lactose containing products (but recall to supplement calcium and other minerals usually associated to dairy products!)

More information about this condition can be found in:

National Digestive Diseases Information Clearinghouse.

Policy of the American Academy of Pediatrics about Lactose Intolerance (2006)

Marks, J.W.: Lactose intolerance (Lactase deficiency)

Swagerty, D.L.; Walling, A.D.; Klein, R.M.: Lactose Intolerance

Guandalini, S.: Lactose Intolerance

Thursday, March 1, 2012

Biology Career booklet from Biochemistry Den

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