Carbohydrates part 1

Question 1

• what are most carbohydrates

Answer 1

most carbohydrates (as well as proteins and nucleic acids) are polymers.

Question 2

• define a polymer

Answer 2

polymers are large, complex molecules composed of long chains monomers joined together

Question 3

• what are monomers

Answer 3

monomers are small, molecular units

Question 4

• examples of monomers

Answer 4

Monosaccharides, amino acids and nucleotides

Question 5

• what are carbohydrates made from

Answer 5

carbohydrates are made from monosacchrides

Question 6

• what elements do all carbohydrates contain

Answer 6

all carbohydrates contain the elements C H and O

Question 7

• examples of monosaccharides

Answer 7

glucose, fructose and galactose

Question 8

• define glucose

Answer 8

glucose is a hexose sugar- a monosaccharide with six carbon atoms in each molecule

Question 9

• what are the two types of glucose

Answer 9

alpha and beta- theyre are isomers

Question 10

• what are isomers

Answer 10

molecules with the same molecular formula as each other, but with the atoms connected in a different way

Question 11

• draw an alpha-glucose molecule

Question 12

• what joins monosaccharides together

Answer 12

condensation reactions join monosaccharides together

Question 13

• explain a condensation reaction

Answer 13

a condensation reacction is when two molecules join together with the formation of a new chemical bond, and a water molecule is released when the bond is formed

Question 14

• what happens after the monosaccharides are joined together

Answer 14

a glycosidic bond forms between the two monosaccharide as a molecule of water is released

Question 15

• what happens when 2 monosacchrides join

Answer 15

a dissacchride is formed

Question 16

• what happens when 2 alpha-glucose molecules are joined

Answer 16

two alpha-glucose molecules are joined together by a glycosidic bond to form maltose

Question 17

• define sucrose and explain how it is formed

Answer 17

sucrose is a disaccharide

formed from a condensation reaction between an alpha glucose molecule and a fructose molecule

Question 18

• define lactose and explain how it is formed

Answer 18

lactose is another disaccharide formed from an Alpha-glucose molecule and a Beta galactose molecule

Question 19

• what breaks polymers into monomers

Answer 19

hydrolysis reactions break polymers down into monomers

Question 20

• explain a hydrolysis reaction

Answer 20

a hydrolysis reaction breaks the chemical bond between monomers using water molecule. its basically the opposite of a condensation reaction

Question 21

• what is a general term for monosaccharides and disaccharides

Answer 21

sugar

Question 22

• what can call sugars be classified as

Answer 22

reducing or non-reducing

Question 23

• what does reducing sugars include

Answer 23

reducing sugars include all monosaccharides (e.g. glucose) and some disaccharides (e.g. maltose and lactose)

Question 24

• steps to testing sugars

Answer 24

you add blue benedicts reagent to a sample and heat it in a water bath thats been brought to the boil

if the test’s positive it will form a coloured precipitate ( solid particles suspended in the solution 

the colour of the precipitate changes from: blue —) green —) yellow —) orange —) brick red 

the higher the concentration of reducing sugar, the further the colour change goes

Question 25

• how can we use the concentration of reducing sugars

Answer 25

you can use this to compare the amount of reducing sugar in different solutions.

A more accurate way of doing this is to filter the solution and weigh the precipitate

Question 26

• what does it mean if the benedicts test for sugars is negative

Answer 26

there could still be a non- reducing sugar present

Question 27

• how do you test for non-reducing sugars

Answer 27

to test for non- reducing sugars like sucrose, first you have to break them down into monosaccharides

Question 28

• how do you break non-reducing sugars into monosaccharides

Answer 28

you do this by getting a new sample of the test solution, adding dilute hydrochloric acid, and carefully heating it in a water bath that’s been brought to the boil

you then neutralize it with sodium hydrogen carbonate. then just carry out the benedicts test as you would for reducing sugar 

if the test is negative the solution will stay blue which means it doesn't contain any sugar

Question 29

• How do we make sure all the sugar reacts

Answer 29

always use an excess of benedicts solution