Biological Molecules: Carbohydrates: In Depth

Question 1

What are some of the IMPORTANT USES for CAROHYDRATES?

Answer 1

-RESPIRATORY SUBSTRATES which provides ENERGY FOR CELLS
-STRUCTURE IN CELL MEMBRANES and CELL WALLS in PLANTS

Question 2

Which GROUP of MONOSACCHARDIES react with each other to form DISACCHARIDES?

Answer 2

HYDROXYL GROUPS

Question 3

Describe the POLYMER STARCH

Answer 3

-POLYMER of α-GLUCOSE, joined by 1-6 GLYCOSIDIC BONDS via CONDENSATION
-COMPACT, COILED, BRANCHED and INSOLUBLE MOLECULES
>So it DOESN’T EFFECT OSMOSIS, making them IDEAL STORAGE MOLECULES
*USED IN PLANTS
-HYDROLYSIS releases GLUCOSE for RESPIRATION
-Made up of AMYLOSE and AMYLOPECTIN

Question 4

Describe the molecule GLYCOGEN

Answer 4

-STORAGE of CARBOHYDRATES in ANIMALS, joined by α 1-4 GLYCOSIDIC BONDS
*BUT, CHAINS of GLYOGEN MOLECULES are joined by 1-6 GLYCOSIDIC BONDS
>Leading to a MORE BRANCHED MOLECULE (MORE BRANCHED than STARCH), allows for QUICKER ENERGY RELEASE as it’s easier to HYROLYSE and also MORE STORE
-Also not TOTALLY SOLUBLE
-HYDROLYSIS releases GLUCOSE for RESPIRATION

Question 5

Describe the molecule CELLULOSE

Answer 5

-POLYMERS of β-GLUCOSE 1-4 GLYCOSIDIC BONDS (EVERY 2ND GLUCOSE IS INVERTED) that form STRAIGHT CHAINS
>100s of these chains are held together by H BONDS to form CELLULAR MICROFIBRILS
–>STRONG and RIGID giving STRENGTH to PLANT CELLS

Question 6

Why CAN’T CELLULOSE be BROKEN DOWN by HUMAN BODIES?

Answer 6

-β-GLYCOSIDIC BONDS cannot be broken down my AMALAYSE, but instead CELLULASE
-CELLULASE is only produced by HERBIVOROUS ANIMALS as they have MUTUALISTIC BACTERIA in their GUT
-HUMANS CANNOT DIGEST CELLULOSE, and is referred to as FIBRE

Question 7

Why are DIFFERENT ENZYME required to digest STARCH AND CELLULOSE?

Answer 7

-β-GLUCOSE has a DIFFERENT SUBSTRATE to STARCH
-So they have DIFFERENT ACTIVE SITES
–>Meaning it requires DIFFERENT ENZYMES to digest

Question 8

Describe how you would carry out a TEST to DETECT REDUCING SUGARS

Answer 8

-Mix SAMPLE SOLUTION with BENEDICTS SOLUTION in a TEST TUBE
-HEAT the MIXTURE in a WATER BATH at ~50oC for 10 MINUTES
-OBSERVE the COLOUR CHANGE and any formation of a PRECIPITATE
-If there is a REDUCING SUGAR present, the COLOUR of the MIXTURE will change from BLUE-BRICK RED

Question 9

Describe how you would carry out a TEST to DETECT NON-REDUCING SUGARS

Answer 9

-Add DILUTE HCL to the SAMPLE and HEAT in a WATER BATH at BOILING TEMP
-NEUTRALISE the SOLUTION with SODIUM HYDROGENCARBONATE
-Add BENEDICTS SOLUTION to SAMPLE and HEAT in a WATER BATH at BOILING TEMP
-If a COLOUR CHANGE occurs (ORANGE-RED PRECIPITATE) a NON-REDUCING SUGAR is PRESENT