Carbohydrates, Lipids and Proteins

Question 1

Carbohydrates are polymers, what is a polymer?

Answer 1

Large complex molecules made of long chains of joined monomers.

Question 2

Name the elements carbohydrate contains.

Answer 2

Carbon, Hydrogen, Oxygen.

Question 3

What kind of monomers are carbohydrates made from?

Answer 3

Monosaccharides.

Question 4

List the monosaccharides.

Answer 4

Glucose, Fructose, Galactose.

Question 5

Glucose is a hexose sugar, what does this mean?

Answer 5

It is a monosaccharide with 6C in each molecule.

Question 6

What is the difference between alpha and beta glucose?

Answer 6

Alpha - H at top, OH at bottom.

Beta - OH at top, H at bottom.

Question 7

How are monosaccharides joined, and what bond holds them together?

Answer 7

Joined in condensation reactions. Joined by glycosidic bonds.

Question 8

What is a disaccharide?

Answer 8

Two joined monosaccharides.

Question 9

Name the disaccharides.

Answer 9

Sucrose (glucose and fructose)

Lactose (glucose and galactose)

Question 10

How are polymers broken down?

Answer 10

In hydrolysis reactions, water breaks the bonds between monomers.

Question 11

What does the Benedict’s Test test for?

Answer 11

Reducing or non-reducing sugars.

Question 12

How do you test for reducing sugars?

Answer 12

Add Benedict’s reagent to sample and heat it in a water bath that has been brought to the boil. If positive it will form a coloured precipitate: green, yellow, orange, red.

Question 13

How do you test for non-reducing sugar?

Answer 13

Take test solution, add dilute hydrochloric acid and heat in wage bath. Neutralise it with sodium hydrocarbonate and carry the test out as usual (add Benedict’s and heat). If positive for non-reducing a coloured precipitate will be formed.

Question 14

What is starch made up of?

Answer 14

Amylose - long unbranched chain of alpha glucose.

Amylopectin - long branched chain of alpha glucose.

Question 15

Structure of amylose and amylopectin related to function.

Answer 15

Amylose - coiled making it compact and good for storage.

Amylopectin - branches make glycosidic bonds easily accessible to enzymes, meaning quick release of energy.

Question 16

Why is starch good for storage?

Answer 16

Insolvable in water so doesn’t affect water potential, so no osmosis or swelling.

Question 17

How would you test for starch?

Answer 17

Add iodine dissolved in potassium iodide solution to sample. It will turn black/brown if starch is present.

Question 18

How do animals store excess glucose?

Answer 18

As glycogen - polysaccharide of alpha glucose.

Question 19

Structure of glycogen.

Answer 19

Similar to amylopectin but more branched for fast energy release and compact so good for storage.

Question 20

Describe cellulose.

Answer 20

Long unbranched chains of beta glucose, chains held by hydrogen bonds to form microfibrils - strong structural support.

Question 21

Triglycerides are a type of lipid, what are they made of?

Answer 21

Glycerol molecule and three fatty acids.

Question 22

Describe a fatty acid structure.

Answer 22

Hydrocarbon tail that is hydrophobic (making them insoluable) and a hydrophilic head.

Question 23

How is a triglyceride created?

Answer 23

A fatty acid joins a glycerol molecule in a condensation reaction forming an ester bond. Three fatty acids must join to create a triglyceride.

Question 24

How can you tell if a fatty acid is saturated?

Answer 24

By their hydrocarbon tails(R group), no double bonds between carbons means saturated.

Question 25

Which lipids are found in cell membranes?

Answer 25

Phospholipids.

Question 26

Structure of a phospholipid.

Answer 26

Phosphate group, glycerol and two fatty acids.

Question 27

Why are triglycerides good as energy storing molecules?

Answer 27

Long hydrocarbon tails contain lots of energy, insoluble so don’t affect water potential or osmosis.

Question 28

Why are phospholipid good as a bilateral in the cell membrane?

Answer 28

Hydrophobic in centre of layer so water soluble molecules can’t easily pass through, hydrophilic heads face out will hydrophobic tails inwards creating a double layer.

Question 29

How do you test for lipid?

Answer 29

Shake test solution with ethanol until dissolved, pour into water, if lipid present a milky emulsion will be present.

Question 30

What are proteins made up of?

Answer 30

Polypeptide chains of amino acids.

Question 31

Structure of amino acids.

Answer 31

Carboxyl group (-COOH), amino group (-NH2) and an R group which changes.

Question 32

How are polypeptides formed?

Answer 32

Condensation reactions which form peptide bonds between amino acids.

Question 33

Primary protein structure.

Answer 33

Polypeptide chain of amino acids.

Question 34

Secondary protein structure.

Answer 34

Hydrogen bonds form between amino acids creating coiled alpha helix or a folded beta pleated sheet.

Question 35

Tertiary protein structure.

Answer 35

Coiled or folded further which hydrogen and ionic bonds, disulphides bridges are also created making a complex 3D structure.

Question 36

Quaternary protein structure.

Answer 36

Several different polypeptide chains held together by bonds.

Question 37

How would you test for proteins?

Answer 37

Biuret test.
Add sodium hydroxide to make the test solution alkaline then add copper(II) sulfate solution. Blue if no protein, purple if protein.