BIOLOGICAL MOLECULES- carbohydrates

Question 1

Define a monomer.
give some examples

Answer 1

smaller units that form together to form larger molecules (polymer).

-monosaccharides (glucose,fructose,galactose)
-amino acids
-nucleotides

Question 2

Define a polymer.
Give some examples

Answer 2

molecules formed when many monomers join together
-polysaccharides
-proteins
-DNA/RNA

Question 3

What happens during a condensation reaction?

Answer 3

A chemical bond is formed and a water molecule is produced.

Question 4

What happens during a hydrolysis reaction?

Answer 4

A water molecule is used to break a chemical bond between 2 molecules.

Question 5

name 3 hexose monosaccharides.

Answer 5

glucose
fructose
galactose

they all have the same molecular formula C6H12O6

Question 6

Name the type of bond formed when monosaccharides react

Answer 6

Glycosidic bonds

Question 7

draw alpha glucose.

Answer 7

diagram.

Question 8

draw beta glucose

Answer 8

diagram.

Question 9

what are the three main groups of carbohydrates called?

Answer 9

monosaccharides, disaccharides, polysaccharides

Question 10

what are monosaccharides? general formula?

Answer 10

simple sugars, (CH20)n
alpha glucose,beta glucose,fructose,galactose

Question 11

what are disaccharides and how are they formed?

Answer 11

they are double sugars, formed by the condensation reaction of 2 monosaccharides.
-maltose
-sucrose
-lactose

Question 12

what are polysaccharides?

Answer 12

large molecules formed from many sugars. ie.many monosaccharides
they are created by condensation reactions between many glucose monomers.

Question 13

what is starch made up of?

Answer 13

made up of 2 polysaccharides of a-glucose - amylose + amylopectin

Question 14

description of amylose?

Answer 14

• has 1-4 glycosidic bonds.
  -unbranched helix with a coiled structure.
• helix can compact to fit in a lot of glucose in a small space.

Question 15

description of amylopectin?

Answer 15

• has 1-4 and 1-6 glycosidic bonds.
• long branched molecules
  -branched structure increases the surface area for rapid hydrolysis back to glucose.

Question 16

Is starch soluble or insoluble?

Answer 16

starch is insoluble in water and doesn’t affect water potential. Doesnt cause water to enter the cell by osmosis.

Question 17

where is starch found?

Answer 17

Starch is found in plant cells Store of glucose ,form of chemical energy.

Question 18

Where is cellulose found?

Answer 18

plant cell wall

Question 19

What is the function of cellulose?

Answer 19

It’s provide structural strength in the cell wall.

Question 20

what is cellulose made up of?

Answer 20

• made up of unbranched chains of beta glucose
• 1-4 glycosidic bonds
• cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils.
• many hydrogen bonds provide collective strength.

Question 21

Is cellulose soluble or insoluble?

Answer 21

it is insoluble- wont affect water potential.

Question 22

Where is glycogen found?

Answer 22

It is found in the animals – mainly in muscle and liver cells. It is a store of glucose which can be released quickly.

Question 23

What is glycogen made up of?

Answer 23

-made up of alpha glucose
- 1-4 and 1-6 glycosidic bonds.
- highly branched molecule.
-large structure increases surface area for rapid hydrolysis back to glucose.

Question 24

Is glycogen soluble or insoluble?

Answer 24

Insoluble – won’t affect water potential.

Question 25

what is a reducing sugar?

Answer 25

all monosaccharides (eg glucose)
and some disaccharides (eg maltose and lactose)

• they gain electrons

Question 26

Describe the Benedict’s test for reducing sugars?

Answer 26

1.add equal volume of Benedict reagent to a sample .
2.heat the mixture in a water bath between 75-95 degrees
3.positive results: colour change from blue to orange/brick red precipitate forms.

Question 27

what is a non-reducing sugar?

Answer 27

most disaccharides and
some polysaccharides

you need to break them down into monosaccharides when testing non-reducing sugars.

Question 28

Describe the Benedict’s test for non-reducing sugars?

Answer 28

1.negative results: Benedict’s reagent remains blue
2. hydrolyse the non reducing suagr. eg sucrose into their monomers (glucose and fructose) by adding 1cm^3 of HCl. heat in a boiling water bath for 5 mins.
3. neutralise with sodium hydrogen carbonate
4. proceed with Benedict’s test as usual/

Question 29

Describe the test for starch

Answer 29

1. add iodine solution
   2.positive result: colour change from orange to blue-black