Biological Molecules

Question 1

Define a monomer and polymer

Answer 1

A monomer is the basic building block for polymers- a relatively simple molecule which can undergo chemical reactions, joining with other monomers to form polymers.

A polymer is a large molecule formed from similar repeating subunits.

Question 2

Give the four main types of biological monomers and their respective macromolecules

Answer 2

• monosaccharides- polysaccharides
• nucleotides [organic bases and monosaccharides]- nucleic acids
• amino acids- proteins
• fatty acids and glycerol- lipids

Question 3

Differentiate between a condensation reaction and hydrolysis.

Answer 3

Condensation reactions involve the removal of a water molecule to join monomers together by covalent bonds. Hydrolysis involves the addition of a water molecule to break down a polymer into its monomers by breaking the covalent bonds.

Question 4

Identify two monosaccharides, disaccharides and polysaccharides.

Answer 4

• glucose and fructose
• sucrose and maltose
• starch and glycogen

Question 5

Identify the monomers that make up sucrose and maltose

Answer 5

2 alpha-glucose; beta-fructose and alpha-glucose

Question 6

Mention two hexoses and two pentoses

Answer 6

glucose & galactose; ribose & deoxyribose

Question 7

Draw the structure of an alpha and beta glucose molecule

ring structure

refer to txtbook

Answer 7

• 5 OH groups
• OH on carbon 5 is above the plane for beta glucose
• 1 oxygen atom
• one OH branched out of plane

Question 8

What is the energy storage molecule for plants and animals, composed of glucose?

Answer 8

plants- starch, animals- glycogen

Question 9

Why does glucose have to be stored in other forms in plants and animals?

Answer 9

• Glucose is reactive and would interfere with cellular reactions
• It is a large molecule and cells would have to accomodate it somehow
• It is soluble and would thus affect the osmotic properties of the cell

Question 10

What is a glycosidic bond?

Answer 10

The bond formed between two sugar molecules by a condensation reaction; C-O-C link which is a covalent bond
Two OH groups line up and one joins to the H of the other to form water.

Question 11

Describe the structure of starch

Answer 11

• It is a combination of amylose and amylopectin
• Amylose is made up of alpha-glucose. The molecules are in a chain of 1,4 linked glucose molecules
• The final structure is compact as the chains curve and coil up into a helical shape.
• Amylopectin is made of 1,4 glucose links and 1,6 links as well
• The chain is shorter and the 1,6 links branch out
• Amylose and amylopectin form relatively large starch grains

Question 12

Describe the structure of glycogen

Answer 12

• It is structured like amylopectin- 1,4 linkages in the glucose chain and 1,6 linkages making branch points
• Glycogen molecules clump together to form granules

Question 13

Discuss the benefit/features of the structures of starch and glycogen to plants and animals.

Answer 13

• The branched points from amylopectin in starch allow glucose to be readily available by hydrolysis during cellular respiration, and be added for storage
• The helical compact structure takes longer to digest
• Glycogen is more branched and hence more compact allowing animals to store more energy
• More free ends on the branch points allow condensation or hydrolysis reactions to take place rapidly, so the storage or release of energy can easily fit the demands of the cell