CARBOHYDRATES

MONOMERS, POLYMERS, AND CARBOHYDRATES.

EXPLAIN WHAT THE DIFFERENCE IS BETWEEN ALPHA AND BETA STRUCTURES?

DEFINE THIS MONOSACCHARIDE.

DIFFERENCE: Beta = Carbon-1’s hydroxyl points upwards.

GLUCOSE: Photosynthesis’s product and respiration’s substrate.

MONOSACCHARIDES QUALITIES + FORMULA

WHAT IS THE BOND IN DISACCHS?

• Sweet and Soluble.

• C₆H₁₂0₆

• ALPHA 1-4 glycosidic bond.

STARCH STRUCTURE:

• AMYLOSE: Helical chain ::: compact.

• AMYLOPECTIN: Branched ::: large SA for enzymes ::: readily hydrolised.

  • Alpha 1-6 bond = branching.

GLYCOGEN

1. JOB?

2. POLYMER OF … ? ::: ?

3. WHERE IS IT FOUND?

1. Glucose storage in animals and fungi.

2. GLUCOSE POLYMER :::

   1. Easily hydrolysed.

   2. Provides respiratory substrate for energy release.

3. Liver and muscle cells.

Highly branched.

WHY ARE STARCH AND GLYCOGEN BOTH WELL SUITED AS GLUCOSE STORAGE MOLECULES?

1. COMPACT ::: STORE LOTS OF GLUCOSE IN A SMALL SPACE.

2. LARGE AND INSOLUBLE ::: NO OSMOTIC EFFECTS.

3. INERT ::: DO NOT BECOME INVOLVED IN CHEMICAL REACTIONS IN THE CELL.

4. MANY ENDS ::: EASY TO HYDROLYSE.

SIMILARITIES BETWEEN STRUCTURE OF STARCH AND CELLULOSE:

1. Both polysaccharides; OR Both are glucose polymers OR Both are made of glucose monomers

2. Both contain glycosidic bonds (between monomers).

3. Both contain carbon, hydrogen and oxygen.

WHY IS CELLULOSE SUITED TO ITS JOB?

It comprises beta glucose chains, forming straight, unbranched chains (linear polymer).

STARCH TEST

1. SOLVENT?

2. OG COLOUR?

3. POSITIVE COLOUR?

1. IODINE

2. BROWN/ORANGE

3. BLUE-BLACK

WHAT IS A REDUCING SUGAR?

ABILITY TO DONATE ELECTRONS.

ALL MONOSACCHS AND SOME DISACCHS ARE REDUCING SUGARS.

NON-REDUCING SUGAR TEST

1. STEPS

N-RS EG: SUCROSE

1. Heat with acid and neutralise.

2. Heat with Benedict's.

3. Red precipitate/colour.

ISSUES WITH THE BENEDICTS TEST AND HOW TO FIX THEM

1. NON-SPECIFIC: A BIOSENSER E.G. GLUCOSE BIOSENSER CAN BE USED.

2. QUALIATIVE: COLOUR CHANGE DETERMINES RESULT, SO WE CANNOT OBTAIN A VALUE FOR [REDUCING SUGAR]. COLOUR CHANGE DEPENDS AMOUNT OF REDUCING SUGAR, ::: TEST IS SEMI-QUALIATIVE, ALLOWING EST OF HOW MUCH REDUCING SUGAR IS PRESENT:

   • BLUE - NONE

   • R - HIGH

3. SUBJECTIVE. COLOUROMITER CAN QUANTIFY RESULTS.

HOW DOES A COLOUROMITER IMPROVE THE REPEATABILITY OF RESULTS?

1. RESULTS ARE SUBJECTIVE.

2. THIS STANDARDISES THE METHOD.

APART FROM A COLOUROMITER, HOW ELSE CAN YOU MEASURE THE QUANITITY OF REDUCING SUGAR IN A SOLUTION?

1. FILTER AND DRY THE PRECIPITATE.

2. FIND MASS/WEIGHT.

HOW CAN A COLOUROMITER IDENTIFY WHICH SUBSTANCE (FROM A GROUP OF THEM) HAS A HIGHER SUGAR CONTENT?

IODINE SOLUTION STAINS FRESH APPLE TISSUE BLACK.

WHEN IODINE IS ADDED TO APPLES STORED FOR A WEEK, THE STAIN IS LESS BLACK.

SUGGGEST WHY THE WATER POTENTIAL OF APPLE JUICE DECREASES WHEN APPLES ARE STORED?