▪️🔹1.1 Carbohydrates -chemical elements

Question 1

What type of compounds are carbohydrates?

Answer 1

Organic compounds

Question 2

What elements do carbohydrates contain?

Answer 2

Carbon, hydrogen and oxygen

Question 3

What is the basic unit of a carbohydrate?

Answer 3

A monosaccharide

Question 4

What do two monosaccharides combine to form?

Answer 4

A disaccharide

Question 5

What do many monosaccharide molecules combine to form?

Answer 5

A polysaccharide

Question 6

What are monosaccharides?

Answer 6

Small organic molecules that are the building blocks for larger carbohydrates

Question 7

What is the general formula of monosaccharides?

Answer 7

Cn(H2O)n

Question 8

Name the value (n) of carbon atoms in triose and hexose

Answer 8

Triose= 3 carbon atoms 
Hexose= 6

Question 9

Give an example of a hexose carbohydrate?

Answer 9

Glucose is a hexose sugar

Question 10

How many isomers does glucose have an what are these?

How do these differ?

Answer 10

2 isomers
a- glucose and B- glucose
They are based on the different positions of an (OH) and (H) in the structure of the molecule

Question 11

What does the different forms of glucose result in?

Answer 11

The biological differences of polymers such as starch and glucose

Question 12

Define monosaccharide

Answer 12

An individual sugar molecule

Question 13

Name 4 functions of monosaccharides

Answer 13

1) source of energy in respiration
2) building blocks for larger molecules e.g glucose makes polysaccharides starch, glycogen and cellulose
3) parts of nucleotides (D in DNA, R in RNA)
4) intermediates in reactions (triose are intermediates in reactions of respiration and photosynthesis)

Question 14

How are disaccharides formed?

Answer 14

Composed of 2 monosaccharides bonded together with the formation of a glycosidic bond and the elimination of water (condensation reaction)

Question 15

Name the monomers present in, and biological role of maltose

Answer 15

Glucose + Glucose

Needed for germinating seeds

Question 16

Name the monomers present in, and biological role of sucrose

Answer 16

Glucose + fructose

Needed for transport in the phloem of flowering plants

Question 17

Name the monomers present in, and biological role of lactose

Answer 17

Glucose + galactose

Found in mammalian milk

Question 18

Which test tests for reducing sugars?

Name the positive result

Answer 18

Benedicts test

Blue - green -orange —> brick red

Question 19

Why do non-reducing sugars not change during a normal Benedicts test?

Answer 19

Because the disaccharide is not broken down to its monosaccharides, this is done by heating with hydrochloric acid and then adding alkali, positive result should now occur

Question 20

Name an enzyme that can detect sucrose by hydrolysing it into glucose and fructose
Name a negative of this

Answer 20

Sucrase

It is specific, only hydrolyses sucrose no other non reducing sugars

Question 21

How can you get a quantitative measurement of the concentration of sugar

Answer 21

Using a biosensor, provides an accurate measurement, used in conditions such as diabetes

Question 22

Define a polymer

Answer 22

A large complex polymer formed from large values of monosaccharides linked by glycosidic bonds

Question 23

Why is starch (a polysaccharide) a better storage product in the body than glucose (reasons why we convert starch to glucose)

Answer 23

1) starch is insoluble so has no osmotic effect
2) you can’t diffuse out of a starch cell
3) starch is a compact molecule and can be stored in a small space
4) starch carries a lot of energy in its C-H and C-C bonds

Question 24

What is starch made out of?

Answer 24

A-glucose molecules bonded in two different ways forming amylose and amylopectin

Question 25

Describe amylose

Answer 25

1)linear unbranched molecule with a-1-4 glycosidic bonds between (C1) and (C4) in the next.
2)repeated, forming a chain which could into a helix
(Need to know how it’s drawn)

Question 26

Describe amylopectin

Answer 26

-chains of glucose monomers joined with a-1-4 glycosidic bonds
-these are cross linked within a-1,6-glycosidic bonds.
(Need to know how it’s drawn)

Question 27

Describe a test to identify starch

Answer 27

The iodine, potassium iodide test
Colour change = orange/brown —> blue/black
Qualitative test not quantitive

Question 28

What is glycogen used for?

Answer 28

The main storage product in animals

Question 29

Describe the structure of glycogen

Answer 29

Similar to amylopectin it has a-1,4 and a-1,6 bonds but glycogen molecules have shorter a-1,4 linked chains so are more branched than amylopectin
(Learn diagram)

Question 30

What is the purpose of cellulose

Answer 30

Structural polysaccharide found in plant cell walls

Question 31

• Describe the structure of the polysaccharide cellulose?

- What rotates the glucose molecules by 180 degrees

Answer 31

Has many long parallel chains of B-glucose
Glucose monomers are joined by B-1,4 glycosidic bonds
-the B- link rotates the adjacent molecules by 180 degrees which allow hydrogen bonds to form between the OH groups of adjacent parallel chains creating stability

Question 32

Describe the different layers inside cellulose

Answer 32

1) 60-70 cellulose molecules are tightly corsslinked to form microfibrils
2) micofibrils are held in bundles called fibres
3) cell wall has many givers that run parallel within a layer but at an angle to adjacent layers
4) laminated structure contributes to cell walls strength

Question 33

Explain how cellulose fibres are permeable

Answer 33

Because of the spaces between the fibres, this allows water and it’s solutes to penetrate through the spaces in the cell wall to access the cell membrane

Question 34

Where is chitin (structural polysaccharide) found?

Answer 34

In the exoskeleton if insects and in fungal cell walls

Question 35

Describe the structure of chitin

Answer 35

Has long chains of B-1,4 linked monomers with groups derived from amino acids added to form a hetropolysaccharide
-monomers are rotated through 180 degrees and chains are cross linked by hydrogen bonds, forming microfibrils