Carbohydrates Multiple Choice

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Hey guys, so you’ve read all the blogs and watched all the videos…so now its time to test yourself and see how much you’ve learnt! i have faith in you! let’s do this!

 

  1. Sucrose is composed of what monomers?

        a) Glucose + Glucose

        b) Fructose + Glucose

        c) Cellulose + Glycogen

        d) Glucose + Sucanose

     2. What is a glycosidic bond?

          a) Carbon from carboxylic acid bonded to Nitrogen from nitrile group

          b) Disulphide Bond formed by two cysteine molecules

          c) Hydrogen bond

          d) Oxygen bridge formed by two hydroxyl groups

      3.  Another name for Lactose Intolerance is?

          a) Lactosa Intolerosa

          b) Lactate Malnutrition

          c) Lactogen Deformation

          d) Carbohydrate Malabsorption

       4.  What causes acid and gas formation of Lactose Intolerance?

          a) Intestinal Bacteria

          b) Fermentation

          c) A series of reduction reactions

          d) A series of oxidation reactions

       5. What type of linkage does Amylose have between C1 + C4?

¬† ¬† ¬† ¬† ¬† a) Beta 1 –> 6

¬† ¬† ¬† ¬† ¬† b) Alpha 1 –> 6

¬† ¬† ¬† ¬† ¬† c) Alpha 1 –> 4

¬† ¬† ¬† ¬† ¬† d) Beta 1 –> 4

¬† ¬† ¬† 6. What is a “reducing end”?

          a) anomeric C1 not involved in a glycosidic bond.

          b) opposite end where redox reaction takes place

          c) opposite end of anomeric carbon

          d) None of the above

        7. In Amylopectin, branches form after how many residues?

            a) every other residue

            b) 24 glu residues

            c) 25 glu residues

           d) branches randomly occur

       8. What is an advantage of branching?

           a) It makes the molecule more complex and hence stable

           b) provide multiple chain ends at which enzymatic cleavage can occur

           c) No advantage, branching just naturally occurs

           d) To create redox ends.

        9. What are the branches involved in Glycogen?

¬† ¬† ¬† ¬† ¬† ¬† a) Beta 1 –> 6

¬† ¬† ¬† ¬† ¬† ¬† b) Alpha 1–> 4

¬† ¬† ¬† ¬† ¬† ¬† c) Alpha 1 –> 6

¬† ¬† ¬† ¬† ¬† ¬† d) Beta 1 –> 4

¬† ¬† ¬† ¬† 10. Which dissacahride would give a negative result in Fehling’s Solution?

            a) Glucose

            b) Sucrose

            c) Fructose

            d) Galactlose

Disaccharides,Polysaccharides and Lactose intolerance

Welcome, welcome all! Let’s continue talking about carbohydrates shall we?! ..No worries, we’re almost through with it.

Today we shall discuss:

  • Glycosidic Bonds
  • Disaccarides
  • Polysaccharides
  • Lactose intolerance
  • Tests for reducing sugars

Glycosidic Bonds:

gly

1) Two hydroxyl groups next to each other

2) One combines with a Hydrogen atom from the other to lose H2O molecule (condensation)

3) An oxygen bridge is formed, this is the glycosidic bond, keeping the two molecules together forming a disaccharide.

4) Glycosidic bonds can be broken by hydrolysis (addition of water).

Disaccharides:

Glucose + Glucose= Maltose

Glucose + Galactose= Lactose

Glucose + Fructose= Sucrose

All this talk about Glucose…

glu2

Polysaccharides:

Composed of monosaccharides, joined by condensation, that may be up to several thousands of units long.

Starch. Glycogen. Cellulose.

Starch: Storage in plants.

Composed of alpha 1 –> 4 linkage between Carbon1 and Carbon4 and Amylopectin. Amylopectin composed of alpha 1 –> 4 linkage and branches at every 24 glucosyl residues formed by 1 –> 6 linkage.

Reducing end: end of polysaccharide with anomeric Carbon1 not involved in glycosidic bond.

Advantage of glucose storage in polymeric form: reduces osmotic effects.

Advantage of branching: produces a compact structure and provide multiple chain ends at which cleavage can occur.

Glycogen: storage polymer in animals.

Similar to amylopectin except more highly branched (alpha 1–>6 branch at every 10 glucosyl residues)

Advantage of being highly branched: allows rapid release of glucose from glycogen stores.

Cellulose: Plant cell walls.

Beta 1–>4 linkage with every other glucose rotated 180 degrees.

Advantage of rotation: promotes intra-chain and inter-chain Hydrogen bonds and van der Waals interactions which causes cellulose to have a high tensile strength.

Now that those are covered, last but not least, let’s talk about Lactose Intolerance…that feeling in your stomach when you had roti and slupigen for lunch:

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As persons grow older, lactase production decreases. therefore, more lactose is consumed that can be digested, that is, not enough lactase is present. Hence, lactose builds up in the stomach, and it attracts water, which accounts for bloating and diarrhea. Also, intestinal bacteria feed on undigested lactose, producing acid and gas.

Tests for reducing sugars:

tollens

Positive result of Tollens reagent:

tollens2

 

Fehling’s or Benedict’s solution on various sugars:

feh

 

On that note…i bid you goodbye until next time (:

Hope you learnt something or got a better understanding of Carbohydrates!

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References:

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phantomclf.blogspot.com

flatworldknowledge.lardbucket.org

www.rwwwr.com

Carbohydrates!

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Hello my fellow Biochemists! I’ve been attending carbohydrates lectures and tutorials for the past two weeks, and today I’d like to share what i have learnt with you.

Topics covered includes:

  • Biosignificance
  • Monosaccharides
  • Isomerism
  • Hemiacetal and Hemiketal
  • Sugar Derivatives

Let’s get started!

First and foremost, carbohydrates are made by photosynthesis and ar essentially hydrates of carbons.

Photosynthesis Eq’n: Carbon Dioxide + Water + Light = Glucose + Oxygen

Functions of Carbohydrates:

  • Energy Source
  • Storage
  • Structure
  • Precursor molecule

Energy: respiration provides energy by breaking down carbohydrates to water and carbon dioxide.

Storage: plants use starch as storage while animals use glycogen as storage. Excess glucose is converted to glycogen by insulin while excess glycogen is converted to glucose by use of glucagon.

Structure: Carbohydrate cellulose makes up plant cell walls and provides its rigid structure. Cellulose is a polymer of Beta-D-Glucose. Chitin is another carbohydrate used for structre and it makes up the exoskeleton of insects.

Precuresor Molecules: for synthesis of certain biochemicals e.g ribose form part of the skeletons of nucleic acids DNA and RNA.

I know what you’re thinking..simple stuff huh? Now let’s get into the juicy stuff!

Isomerism:

Chiral carbon are carbons with four different side or R-groups attached to it. Chiral carbons have mirror images but is not super-imposable.

D and L designations are based on the configuration about the single asymmetrical carbon, for sugars with more than one chiral centre, D or L refers to the asymmetrical carbon farthest from the aldehyde/ketone group. When the ‘OH’ is on the right hand side its refered as “D” and when its on the left hand side its refered as “L”.

Fischer and Haworth Projections:

carb

  • Epimers: Two sugars that differ only in the configuration around one carbon atom.
  • Anomers: ¬†ő≤ and¬†őĪ Configuration. If the ‘OH’ is below the plane of the anomeric carbon then it is¬†őĪ (Alpha), and if the ‘OH’ is above the plane, it is Beta.

Difference between Epimers and Anomers:

Epimers differ in chirality at only one carbon. In the straight-chain form, epimers will have H and OH-substituents switched at one backbone carbon, but not at any others.

Anomers are special epimers; in cyclic forms of one single monosaccharide, anomers differ in chirality at the anomeric carbon only. In the straight-chain format, anomers will have the same configuation.

  • Sugar Derivatives:

Sugar Alcohol: lacks an aldehyde or ketone.

Sugar Acids: Aldehyde at C1 or OH at C6 is oxidised  to a carboxylic acid.

Amino Sugar: amino group substitutes for a hydroxyl. The amino group may be acetylated.

I hope this helped!