1.1 Carbohydrates

Question 1

What is an organic compound?

Answer 1

• Compound, carbon linked by covalent bonds to each other + hydrogen molecules.
• Large, exist as chains or rings.

Question 2

What elements do carbon atoms covalently bond with in organic compounds?

Answer 2

• Hydrogen, oxygen, nitrogen + sulfur.

Question 3

What are the elements included in carbohydrates?

Answer 3

• Carbon, hydrogen + oxygen.

Question 4

What is the general formula for carbohydrates?

Answer 4

• CnH2nOn.
• Cx(H2O)y.

Question 5

What are the three types of monosaccharides?

Answer 5

• Trioses (C3H6O3).
• Pentoses (C5H10O5).
• Hexoses (C6H12O6).

Question 6

What two examples of pentoses (monosaccharides)?

Answer 6

• Ribose + deoxyribose.

Question 7

What are three examples of disaccharides?

Answer 7

• Sucrose.
• Lactose.
• Maltose.

Question 8

What is sucrose made from?

Answer 8

• Glucose + fructose.

Question 9

What is lactose made from?

Answer 9

• Glucose + galactose.

Question 10

What is maltose made from?

Answer 10

• Glucose + glucose.

Question 11

What are three examples of polysaccharides and what are their functions?

Answer 11

• Starch (fuel store in plants).
• Glycogen (fuel store in animals).
• Cellulose (major component of plant cell walls).

Question 12

Why is glucose an important monosaccharide?

Answer 12

• All green leaves manufacture glucose using light.
• Cells use it in respiration (it is a respiratory substrate).

Question 13

What is the molecular formula of glucose?

Answer 13

• C6H12O6 (hexose).

Question 14

What is a isomer?

Answer 14

• 2 or more different structural formulae of the same molecular formula.

Question 15

What are the 2 isomers of glucose?

Answer 15

• Alpha glucose.
• Beta glucose.

Question 16

What is the structural formula of alpha glucose?

Answer 16

CH2OH
|
H C — O H
\ / \ /
C OH H C
/ \ / \ / \
OH C — C OH
/ \
H OH

Question 17

What is the structural formula of beta glucose?

Answer 17

CH2OH
|
H C — O OH
\ / \ /
C OH H C
/ \ / \ / \
OH C — C H
/ \
H OH

Question 18

What is the structural formula of pentose ribose?

Answer 18

. O
CH2OH / \ OH
| / \ |
C H H C
| \ | | / |
H C — C H
| |
OH OH

Question 19

What is a condensation reaction?

Answer 19

• Reaction where two molecules are chemically linked w elimination of a water molecule.
• Catalysed by an enzyme.

Question 20

What is the bond between monosaccharide residues after the condensation reaction to form a disaccharide?

Answer 20

• Glycosidic bond.
• Strong, covalent bond.

Question 21

What is a hydrolysis reaction?

Answer 21

• Reaction in which a molecule of water is used in breaking a chemical bond.
• Reverse of condensation.
• uses enzyme asw, but diff enzyme.

Question 22

How is maltose formed?

Answer 22

• Condensation reaction of 2 glucose molecules.

Question 23

How is lactose formed?

Answer 23

• Condensation reaction of galactose + glucose.

Question 24

How is sucrose formed?

Answer 24

• Condensation reaction of glucose + fructose.

Question 25

How is a polymer defined?

Answer 25

- Large molecule comprising repeated, identical smaller molecules (**monomers**) linked together by chemical bonds.

Question 26

Which polysaccharides function as fuel stores?

Answer 26

- Glycogen + starch.

Question 27

Which polysaccharide has a structural function and how does its structure affect it?

Answer 27

- Cellulose. - Has huge molecules - not easily hydrolysed by enzyme action.

Question 28

What two polysaccharides is starch a mixture of?

Answer 28

- Amylose - unbranched chain of α-glucose residues. - Amylopectin - branched chain of α-glucose residues.

Question 29

How does the shape of starch form?

Answer 29

- Helix - glycosidic bonds between α-glucose residues. - Stabilised by lots of hydrogen bonds between parts of the component glucose residues.

Question 30

What is a residue?

Answer 30

- When monomers are linked into polymer - no longer called molecules, now called residues.

Question 31

Where is starch used and how is it used?

Answer 31

- Storage carb in plants. - Laid down as compact grains.

Question 32

Why is the structure of starch useful?

Answer 32

- Molecules are compact + insoluble. - ready hydrolysed to form sugar when required (enzymes are involved).

Question 33

How do we test for the presence of starch?

Answer 33

- Adding solution of iodine in potassium iodide. - Iodine molecules fit neatly into centre of starch helix, creating blue-black colour.

Question 34

What is glycogen a polymer of?

Answer 34

- α-glucose. - Similar to amylopectin but larger and more branched.

Question 35

Where can glycogen be found?

Answer 35

- Granules seen in liver cells and muscle fibres under e- microscope. - Can be seen throughout whole body apart from brain.

Question 36

When do we draw our glycogen reserves?

Answer 36

- During prolonged and vigorous exercise. - Once these are exhausted, body starts to metabolise fat.

Question 37

What is a cellulose polymer made up of?

Answer 37

- 2000 to 3000 units of beta-glucose.

Question 38

How do beta-glucose molecules join together?

Answer 38

- The way glycosidic bonds form causes adjacent β to be upside down w respect to each other. - referred to as 1-4 glycosidic bonds.

Question 39

How does the bond of β-glucose affect the structure of cellulose?

Answer 39

- Arrangement leads to cellulose molecules being long, straight chains. - 200 of these chains naturally become packed into fibres, held together by hydrogen bonds.

Question 40

How is the strength of plant cell walls created?

Answer 40

Combined effect of: - Bonds between β-glucose monomers, - Hydrogen bonds between + within β-glucose chains, - Way in which fibres are arranged in different directions.