Experiment 5 - Carbohydrates

Question 1

___ are of functional importance in living organisms as a source of metabolic energy. They also form part of a number of important molecules and structures.

Answer 1

Carbohydrates

Question 2

___ are the most abundant organic compounds in plants around the world

Answer 2

Carbohydrates

Question 3

act as store houses of chemical energy

Answer 3

glucose, starch, glycogen

Question 4

supportive structures in plants

Answer 4

cellulose

Question 5

crustacean shells

Answer 5

chitin

Question 6

connective tissues in animals

Answer 6

(acidic polysaccharides

Question 7

essential components of nucleic acid

Answer 7

D-ribose and 2-deoxy D- ribose

Question 8

____ are polyhydroxy aldehyde, polyhydroxy ketones or compounds that yield them upon hydrolysis

Answer 8

Carbohydrates

Question 9

The simpler members of the carbohydrate family are often referred to as ___ because of their sweet taste

Answer 9

saccharides

Question 10

Latin ___ which means sugar

Answer 10

saccharum

Question 11

general test for carbohydrates

Answer 11

Molisch’s test

Question 12

The 4 carbohydrates we tested

Answer 12

Glucose
Fructose
Lactose
Sucrose

Question 13

Observations during Molisch’s test

Answer 13

Glucose – A purple layer settles to the bottom of the test tube.
Fructose – A thick purple layer settles to the bottom, though it’s not as settled as observed with Glucose. Instead of being a distinct layer, it appears to be in gradients.
Lactose – It appears in a similar manner to Glucose. A clean and distinct purple layer appears at the bottom.
Sucrose – The thickest purple layer appears in this test tube.

Question 14

test for reducing sugars

Answer 14

Benedict’s Test

Question 15

Observations during Benedict’s Test

Answer 15

Glucose – 2 layers have formed, though it seems that the Carbohydrate layer has settled to the bottom while the Benedict solution has taken up most of the space.
Fructose – 3 layers appear in this one. A yellowish top layer, followed by the blue Benedict solution, and lastly, the pinkish Carbohydrate layer.
Lactose – This solution also has 3 layers, yellow, blue, and pink. However, they aren’t as vibrant as in the previous solution.
Sucrose – It appears that the Benedict Solution has overpowered the other components, leaving a blue colored liquid in the test tube.

Question 16

reduction test to determine the presence of reducing sugars.

Answer 16

Fehling’s Test

Question 17

Fehling’s test differs from Benedecit’s test because it contains ___ instead of ___

Answer 17

Rochelle’s salt or sodium potassium tartrate
sodium citrate.

Question 18

Observations during Fehling’s Test

Answer 18

Glucose – 2 layers can be observed. An orange top layer and a blue bottom layer.
Fructose – The solutions seems to have mixed, leaving a test tube full of a reddish-brown colored mixture.
Lactose – This one appears like Glucose. A brick red precipitate on top, with the rest of the blue solution below.
Sucrose – Fehling’s solution seems to overpower the solution as the test tube liquid is now entirely blue.

Question 19

distinguishes reducing monosaccharides from reducing disaccharides by controlling ph and time of heating. Also, a copper reduction test in acidic conditions.

Answer 19

Barfoed’s Test

Question 20

Observations during Barfoed’s Test

Answer 20

Glucose – We see sediments settle at the bottom of the test tube.
Fructose – We also see the orange-brick red sediments in this test tube.
Lactose – The blue reagent is seen clearly in the test tube. No sediments can be observed. This means that the reagent is not contaminated.
Sucrose – Similar to Lactose, no sediments can be observed inside the test tube. This one also means that the reagent is not contaminated.

Question 21

test that distinguishes between fructose and glucose.

Answer 21

Seliwanoff’s Test

Question 22

Observations during Seliwanoff’s Test

Answer 22

Glucose – While having a “dirty” quality to it, the solution becomes clear.
Fructose – The solution becomes opaque and the brick red color becomes prominent.
Lactose – This one looks similar to Glucose. It becomes a dirty but clear liquid in the test tube.
Sucrose – This one follows after Fructose. It also becomes opaque with a red brick color.

Question 23

is a chemical reaction that is used to test for the presence of starch or for iodine.

Answer 23

Iodine Test

Question 24

Observations during Iodine Test

Answer 24

We can observe 2 distinct layers after performing the experiment. The bottom layer is a deep blue while the top layer is still blue but much clearer.

Question 25

What reagent or test will you use if you want to test if a substance contains carbohydrate?

Answer 25

We can use Benedict’s test to see if a substance contains a carbohydrate. Benedict’s test identifies reducing sugars (monosaccharides and some disaccharides) with a free ketone or aldehyde functional groups. Benedict’s solution can be used to test for the presence of glucose in urine.

Question 26

is any chemical reaction in which a molecule of water breaks one or more chemical bonds

Answer 26

Hydrolysis

Question 27

___ is an example of a hydrolysis reaction

Answer 27

Dissolving a salt of a weak acid or base in water

Question 28

this is the transfer of electrons between species in a chemical reaction, where there is a process of gaining electrons or a decrease in the oxidation state by an element.

Answer 28

Reduction

Question 29

Reduction is known as reduction because it refers to

Answer 29

the addition of electrons, which leads to a reduction in the atom’s oxidation number.

Question 30

Which carbohydrates are monosaccharides?

Answer 30

Glucose
Fructose

Question 31

Which carbohydrates are disaccharides?

Answer 31

Lactose
Sucrose

Question 32

Which carbohydrates are reducing sugars?

Answer 32

Glucose
Fructose
Lactose

Question 33

Which carbohydrates are nonreducing sugars?

Answer 33

Sucrose

Question 34

What are the physiological functions of carbohydrates?

Answer 34

Energy Production
Energy Storage
Building Macromolecules
Sparing Protein
Lipid Metabolism