Chapter 3 - Biological molecules - carbohydrates

Question 1

what is a monosaccharide and give examples

Answer 1

a single sugar unit - ribose, glucose, fructose

Question 2

what is a disaccharide and give examples

Answer 2

two monosaccharides bonded - lactose and sucrose

Question 3

what is the polymer and give examples

Answer 3

polysaccharide - glycogen, cellulose, starch

Question 4

what is the chemical formula for glucose

Answer 4

C6H12O6

Question 5

what is a hexose monosaccharide

Answer 5

a saccharide with 6 carbon atoms

Question 6

what is the difference between alpha and beta glucose molecules

Answer 6

in alpha the OH group on the first carbon is below the plane (down down up down up) and in beta it is above (up down up down up)

Question 7

what is the bond called and how does it form

Answer 7

glycosidic bond - the hydroxyl groups on carbon 1 and 4 interact (alpha glucose) - two hydrogen atoms and one oxygen at removed to form a water molecule in a condensation reaction

Question 8

fructose + glucose =

Answer 8

sucrose

Question 9

galactose + glucose =

Answer 9

lactose

Question 10

what do two alpha glucose molecules form

Answer 10

starch

Question 11

what are the polysaccharides called in starch

Answer 11

amylose (only 1-4) and amylopectin (with 1-6)

Question 12

what is the other bond in starch

Answer 12

1-6 glycosidic bonds

Question 13

what do 1-6 bonds form

Answer 13

a branched structure

Question 14

what is the equivalent of starch in animals and fungi

Answer 14

glycogen

Question 15

what are the advantages of glycogen

Answer 15

more compact
more branches
coiled
more free ends

Question 16

what is the reverse of a condensation reaction

Answer 16

hydrolysis reaction - requires water and breaks the bond

Question 17

why can’t beta glucose molecules form the same 1-4 bonds

Answer 17

the carboxyl groups aren’t next to each other

Question 18

how do beta glucose molecules bond

Answer 18

alternate molecules are turned upside down

Question 19

what is formed by beta glucose

Answer 19

cellulose

Question 20

cellulose chains form hydrogen bonds to form _____ which join together to form _____ which join together to form _____

Answer 20

microfibrils
macrofibrils
fibres

Question 21

what is the test for carbohydrates/reducing sugars

Answer 21

benedict’s test

Question 22

describe the benedict’s test

Answer 22

1. place the sample to be tested in a boiling tube (grind or blend with water
2. add an equal volume of benedict’s reagent
3. heat the mixture gently in a water bath

Question 23

what are the results of the benedict’s test

Answer 23

positive result (sugars present) red
negative result (none present) blue
blue - green - yellow - orange - red

Question 24

what is the test for starch

Answer 24

iodine test

Question 25

describe the iodine test

Answer 25

a few drops of iodine added to potassium iodide solution are added to the sample

Question 26

what are the results of the iodine test

Answer 26

yellow/brown - none present

purple/black - present