1.Carbohydrates and lipids

Question 1

Monomer

Answer 1

small identical or similar molecules which can be condensed (joined/linked together) to make larger molecules called polymers.

Question 2

Polymer

Answer 2

large molecules made from joining many (3 or more) identical or similar monomers together

Question 3

Condensation reactions

Answer 3

joins two monomer units together with the removal of one water molecule which forms a bond.

Question 4

Hydrolysis

Answer 4

A hydrolysis reaction involves the addition of one molecule of water to break the bond between two monomers.

Question 5

Disaccharides

Answer 5

Formed by a condensation of two monosaccharides

Question 6

How is maltose made

Answer 6

Two glucose molecules

Question 7

How is sucrose made

Answer 7

Glucose and fructose

Question 8

How is lactose made

Answer 8

Glucose and galactose

Question 9

The structure of cellulose is related to its role in plant cell walls. Explain how.

Answer 9

Long straight unbranched chains of Beta glucose
Joined by many weak hydrogen bonds
Which form microfibrils to
Provide rigidity and strength

Question 10

Hydrogen bonds are important in cellulose molecules. Explain why.

Answer 10

1. Hydrogen bonds holds cellulose molecules together forming microfibrils
2. Providing strength/rigidity
3. Weak Hydrogen bonds provides strength in large numbers

Question 11

What are the three different tests for carbohydrates:

Answer 11

1. Benedict’s test for reducing sugar (glucose, galactose, lactose, maltose, fructose)
2. Benedict’s test for non-reducing sugar (sucrose)
3. Iodine test for starch

Question 12

Benedict’s test for reducing sugars

Answer 12

1. Add equal volumes of Benedict’s solution;
2. Heat to 95 ⁰C;
3. Red/orange/yellow/green precipitate (shows reducing sugar present);

Question 13

Test for non reducing sugar

Answer 13

1. Complete Benedicts test and observe a negative result/stays blue
2. Add acid (HCl) to sugar solution AND Heat to 95 ⁰C;
3. Then neutralise with alkali (sodium hydrogen carbonate (NaHCO₃);
4. Add equal volumes of Benedict’s solution to the sugar solution;
5. Heat again to 95 ⁰C;
6. Red/orange/yellow/green precipitate;

Question 14

Standardising the method when using calorimeter

Answer 14

• Samples should always be shaken before testing
• Zero the colorimeter before use (with a control)
• Use the same (absorbance/transmission) filter throughout
• Use same volume for each reading

Question 15

Describe how you would produce a calibration curve for a reducing sugar of unknown concentration and use it to obtain results

Answer 15

1. Make up several known concentrations of maltose / glucose / lactose / galactose / fructose;
2. Carry out the Benedict’s test on each sample;
3. Use a colorimeter to measure the colour intensity of each solution and plot a calibration curve;
4. Known Conc. on X axis and absorbance / transmission on Y.
5. Find the concentration of the unknown sample using the calibration curve;