Biological molecules

Question 1

What is cellulose made of (1)

Answer 1

beta glucose

Question 2

What is starch made of (1)

Answer 2

alpha glucose

Question 3

Explain how the structures of starch and cellulose are related to thier functions as storage and structural molecules respectively (4)

Answer 3

• starch is made of amylose and amylopectin joined by alpha 1-4 glycosidic bonds
• molecules coil in amylose and in amylopectin branch
• easy to remove glucose molecules
• cellulose alternate unites rotate by 180 degrees in a straight chain
• hydrogen bonds froming cross links which gives strength and stability

Question 4

What is the bond between a glycerol molecule and a fatty acid (1)

Answer 4

ester

Question 5

Describe the type of reaction involved in the breakdown of a monoglyceride (1)

Answer 5

hydrolysis

Question 6

Explain why triglycerides are not considered to be polymers (1)

Answer 6

glycerol and fatty acids are different structures

Question 7

State two functions of triglycerides in a mammal except for energy storage (2)

Answer 7

• portection of internal organs against impact
• thermal insulation
• buoynacy
• waterproofing
• source of metabolic water

Question 8

Describe a biochemical test for the presence of glucose in a solution (2)

Answer 8

• add benedicts test and heat
• colour would change from blue to brick red
• blue precipitate - neutral

Question 9

Explain why a positive test would be seen with glucose but not sucrose for benedicts test (1)

Answer 9

• glucose is a reducing sugar
• reduces copper II sulphate to copper I oxide
• sucrose is a non reducing sugar

Question 10

Describe the function of magnesium ions (1)

Answer 10

component of chlorophyll

Question 11

Describe the function of iron ions (1)

Answer 11

component of haemoglobin

Question 12

Describe the function of phosphate ions (1)

Answer 12

component of nucleic acids

Question 13

Describe the function of calicum ions (1)

Answer 13

hardens bones / teeth / synaptic transmissions

Question 14

Name the bond crosslinking cellulose molecule (1)

Answer 14

hydrogen

Question 15

Explain the importance of hydrogen bonds in the role of celluloe in plant cell walls (2)

Answer 15

• holds celluloe chains together to form microfibrils
• strengthens the cell wall giving structural tability
• can resist tugor / prevenet cell wall from bursting

Question 16

Name the chemical reaction by which monomers join together

Answer 16

• condensation
• polymerisation

Question 17

What is the additional compound in chitin replacing one of the OH groups (1)

Answer 17

• has amino acid

Question 18

State the structural role of chitin in insects and why it is suitable for the role (1)

Answer 18

• exoskeleton
• strong
• waterproof
• light
• tough

Question 19

Name the storage polysaccharide in animal cells (1)

Answer 19

glycogen

Question 20

Name the storage polysaccharide in plant cells (1)

Answer 20

starch

Question 21

name the product formed when a triglyceride molecule is broken down (2)

Answer 21

• one glycerol molecule
• three fatty acid molecules

Question 22

Name the type of bond broken in a triglyceride and the process (2)

Answer 22

• ester
• hydrolysis
• chemical insertion of water

Question 23

Describe two functions of lipids in plants (2)

Answer 23

• energy sstroae
• respiratory substrate
• source of energy
• waxy cuticle
• leaf waterproofing
• membrane structure

Question 24

State how the structure of a saturated fatty acid differs from the unsaturate fatty acid (2)

Answer 24

• saturates has no double bonds
• fewer hydrogen atoms in an unsaturated

Question 25

Many amino acids can join in a long chain name the process the molecules join together and the bond formed (2)

Answer 25

* peptide bond * condensation

Question 26

Name a sutiable test to show the prescence of amino acids (2)

Answer 26

* add bieurt to test solution * blue change to purple is a positive result

Question 27

Suggest a problem that could arise if there were very low concentrations of amino acid present in the solution when performing the biuret test (1)

Answer 27

* little colour change purple colour may be masked

Question 28

Describe the inorganic iron present in the haem group (1)

Answer 28

iron

Question 29

Why is haemoglobin have a quantenary structure (2)

Answer 29

* four polypeptide chains in tertiary form are combined

Question 30

Name two types of bonds that would be present to maintain polypeptide chain in it teritary structure (2)

Answer 30

* disulphide bridges * ionic bonds * hydrogen bonds * hydrophobic interactions

Question 31

How does the structure of phospholipids differ to triglycerides (2)

Answer 31

* phospholipids have two fatty acids whereas triglycerides have three fatty acids * phospholipids have a phosphate head whereas triglucerides do not contain a phosphate head * phospholipids have a polar head and non polar tailes whereass triglycerides are non polar

Question 32

Explain the arrangement of phospholipids when near water (2)

Answer 32

* hydrophophillic phosphate heads are attracted to water * fatty acids tails are hydrophobic and are repelled by water

Question 33

name the bond broken in a lactose molecule (1)

Answer 33

glycosidic

Question 34

name the molecules produced when lactose is broken down (1)

Answer 34

* glucose and galactose