CARBOHYDRATES

MONOMERS, POLYMERS, AND CARBOHYDRATES.

WHICH MONOSOSACCHARIDE HAS TWO ISOMERS AND WHAT ARE THEY?

WHAT ARE THEIR STRUCTURES? EXPLAIN WHAT THE DIFFERENCE IS BETWEEN THEIR STRUCTURES?

DEFINE THIS MONOSACCHARIDE.

GLUCOSE:

1. ALPHA

2. BETA

DIFFERENCE IN STRUCTURE: IN BETA GLUCOSE, ON THE CARBON-1, THE HYDROXYL GROUP POINTS UPWARDS, WHILE IN ALPHA GLUCOSE IT POINTS DOWNWARDS.

GLUCOSE: THE PRODUCT OF PHOTOSYNTHETIS AND A MAJOR SUBSTRATE OF RESPIRATION.

WHICH MONOSACCHARIDES FORM MALTOSE, SUCROSE, AND LACTOSE?

M: ALPHA

S: FRUCTOSE

L: GALACTOSE

CARBOHYDRATES

CARBS ARE KEY BIO MOLECULES THAT STORE GLUCOSE AND CAN PROVIDE STRUCTURAL SUPPORT TO PLANT CELLS.

MONOSACCHARIDES QUALITIES + FORMULA

WHAT IS THE BOND IN MALTOSE?

• THEY ARE SOLUBLE AND SWEET.

• C6H1206

MALTOSE FORMED FROM TWO GLUCOSE MOLECULES JOINED BY AN ALPHA 1-4 GLYCOCICYDIC BOND.

STARCH

1. WHAT IS IT MADE FROM? (WHICH MONOS AND WHICH POLYS)

2. JOB?

3. STRUCTURE?

4. TYPES OF BONDS PRESENT?

5. SOLUBILITY IN WATER?

1. MADE FROM:

   1. MONOS: ALPHA GLUCOSE.

   2. POLYS: AMYLOSE AND AMYLOPECTIN.

2. STARCH GRAINS ARE USED FOR GLUCOSE STORAGE IN PLANTS.

3. STRUCTURE:

   • AMYLOSE FORMS A HELICAL CHAIN (MAKING IT COMPACT) TO STORE LARGE NUMBERS OF GLUCOSE MOLECULES IN A SMALL SPACE.

   • AMYLOPECTIN IS BRANCHED, PROVIDING A LARGE SURFACE AREA FOR ENZYMES TO ATTATCH. THIS MEANS THAT STARCH IS READYILY HYDROLISED BACK INTO GLUCOSE WHEN PLANT CELLS ARE RUNNING LOW ON GLUCOSE FOR RESP.

   • ALPHA 1-6 BOND CAUSES BRANCHING

4. GLYCOSIDIC.

5. INSOLUBLE.

GLYCOGEN

1. WHAT IS IT MADE FROM?

2. JOB?

3. STRUCTURE?

4. TYPES OF BONDS PRESENT?

5. SOLUBILITY IN WATER?

6. WHERE IS IT FOUND?

1. ALPHA

2. ENERGY STORAGE MOLECULE IN ANIMALS AND FUNGI.

3. (SIMILAR TO AMYLOPECTIN) HELICAN CHAIN WITH EXTENSIVE BRANCHING.

   • ALLOWS IT TO BE HYDROLISED BECAUSE THERES MORE ENDS.

   • NEEDED BECAUSE ANIMALS RESPIRE MORE THAN PLANTS.

   • POLYMER OF GLUCOSE: SO ITS EASILY HYDROLISED AND PROVIDES RESPIRITORY SUBSTRATE FOR ENERGY RELEASE.

4. GLYCOSIDIC.

5. INSOLUBLE.

6. LIVER AND MUSCLE CELLS.

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

1. THEY ARE COMPACT AND SO STORE LOTS OF GLUCOSE IN A SMALL SPACE.

2. THEY ARE LARGE AND INSOLUBLE AND HAVE NO OSMOTIC EFFECTS.

3. THEY ARE RELETIVELY INERT AND SO DO NOT BECOME INVOLVED IN CHEMICAL REACTIONS IN THE CELL.

4. GLYCOGEN (AND AMYLOPECTIN) ARE QUICKLY HYDROLISED TO SOLUBLE GLUCOSE BECAUSE THEY HAVE MANY ENDS FROM AMYLASE ENZYMES 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.

CELLULOSE

1. WHAT IS IT MADE FROM?

2. JOB?

3. WHY IS IT SUITED TO ITS JOB?

4. TYPES OF BONDS PRESENT?

1. POLYMER FORMED BY THE CONDENSATION OF MANY (UP TO 10,000) BETA GLUCOSE MOLECULES.

2. MAJOR COMPONENT OF PLANT CELL WALLS.]

3. SUITED BECAUSE:

   • IT IS MADE UP ON CHAINS OF BETA GLUCOSE WHICH FORM STRAIGHT UNBRANCHED CHAINS (LINEAR POLYMER).

   • THE CHAINS RUN PARALLEL TO EACHOTHER AND HYDRGOEN BONDS FORM CROSS-LINKAGES BETWEEN CHAINS. MANY HYDROGEN BONDS ARE COLLECTIVELY STRONG AND SO PROVIDE A HIGH TENSILE STRENGTH. THIS MAKES THE WALLS RIGID AND PREVENTS OSMOTIC LYSIS.

   • CELLULOSE MOLECULES ARE GROUPED TO FORM MICROFIBRILS WHICH IN TURN ARE GROUPED TO FORM FIBRES, WHICH PROVIDES YET MORE STRENGTH.

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. 1. Heat with acid and neutralise; Accept boil/water bath for heat Accept named alkali for neutralise Accept named examples, eg HCl, NaHCO3.

2. Heat with Benedict's (solution).

3. Red precipitate/colour; Accept other colours eg orange/ brown/green.

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 IS USED TO DETERMINE THE RESULT, SO WE CANNOT OBTAIN A VALUE FOR THE CONC OF REDUCING SUGAR. HOWEVER, THE COLOUR CHANGE DEPENDS UPON THE AMOUNT OF REDUCING SUGAR PRESENT, SO THE TEST CAN BE DESC AS SEMI-QUALIATIVE, ALLOWING AN EST OF HOW MUCH REDUCING SUGAR IS PRESENT:

   • BLUE - NONE

   • G - VLOW

   • Y - LOW

   • B/O - MEDIUM

   • R - HIGH

3. SUBJECTIVE. A COLOUROMETER CAN BE USE TO QUANTIFY RESULTS.

HOW CAN YOU FIX THE ISSES WITH THE BENEDICTS TEST?

1. A SERIAL DILLUTION OF A GLUCOSE SOLUTION CAN BE CARRIED OUT, PRODUCTING A SET OF SULTIONS OF KNOWN CONCENTRATIONS.

2. THE BENDICT’S TEST CAN BE PERFORMED ON EACH OF THESE AND THE COLOUR INTENSITY MEASURED USING A COLOUROMITER.

3. A CALIBRATION CURVE CAN BE PRODUCED FROM THE RESULTS, WHICH CAN THNE BE USED TO READ OFF THE CONCENTRATION OF GLUCOSE IN AN UNKNOWN SOLUTION.

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.

A quantitative Benedict’s test produces a colour whose intensity depends on the concentration of reducing sugar in a solution. A colorimeter can be used to measure the intensity of this colour. The scientist used quantitative Benedict’s tests to produce a calibration curve of colorimeter reading against concentration of maltose. Describe how the scientist would have produced the calibration curve and used it to obtain the results in the graph. Do not include details of how to perform a Benedict’s test in your answer.