Chapter Five

Question 1

What is a polymer?

Answer 1

It is a long molecule consisting of many similar or identical building blocks linked by covalent bonds

Question 2

What are monomers?

Answer 2

They are the repeating units that serve as the building blocks of a polymer

Question 3

What is the reaction that connects monomers?

Answer 3

It is a dehydration reaction (sped up by enzymes), a reaction in which two molecules are covered gently bonded to each other with the loss of a water molecule that one monomer provides a hydroxyl group (OH), well the other provides a hydrogen (H)

Question 4

What is the reaction that disassemble the monomers?

Answer 4

It is the hydrolysis that consists in broking monomers by the addiction of a water molecule, with the hydrogen from water attaching to one monomer and hydroxyl group attaching to the other

Question 5

What is the number of common monomers to construct molecules?

Answer 5

It is around 40 to 50 and some others that occur rarely; The key is the arrangement, it’s like creating thousands of words from only 26 letters of the alphabet

Question 6

How many monomers are needed to construct a protein?

Answer 6

20

Question 7

What is the molecular formula of monosaccharides?

Answer 7

It is usually a multiple of the unit CH2O

Question 8

Which is the most common succharide?

Answer 8

It is the glucose (C6H12O6)

Question 9

What are the two groups of a sugar?

Answer 9

They are carbonyl group (-C=O) and hydroxyl group (-OH)

Question 10

How are sugars classified?

Answer 10

•The most common classifying method is dividing them into aldoses (aldehyde sugars) and ketose (keton sugar). •Another one is splitting them by the size of the carbon skeleton, which ranged from 3 to 7 carbon long. Trioses, Pentose and hexoses are the most common one (especially the last one). • The last one is by the way their parts are arranged especially around the assymetric carbones, for example (glucose and galactose)

Question 11

What are the main functions of monosaccharides?

Answer 11

They are major nutrients for cells during the cellular respiration. Furthermore, their skeletons serve as raw material for the synthesis of amino acids and fatty acids

Question 12

What is a disaccharide?

Answer 12

It is a carbohydrate consisting of two monosaccharides joined by a glycosidic linkage, a covalent bond formed between two monosaccharides by a dehydration reaction. One example of the saccharide is Malto, which is the linking of two molecules of glucose

Question 13

Which are the most prevalent disaccharides?

Answer 13

they are •the sucrose (table sugar), two monomers of glucose and fructose.it is the one that plants transport from leaves to roots; and the •lactose, a sugar present in milk made up of glucose and galactose

Question 14

What are polysaccharides?

Answer 14

 They are macromolecules, polymers with a few hundred to few thousand monosaccharides joined by glycosidic linkages

Question 15

What are the main functions of polysaccharides?

Answer 15

They serve as storage material, they provide sugar for cells when hydrolyzed, and finally serve as building material for structures that protect the cell or the whole organism

Question 16

What is the most famous polysaccharide?

Answer 16

It is the starch, a polymer of glucose monomer, a storage sugar used by plants

Question 17

Which is the simplest starch?

Answer 17

It is the amylose

Question 18

What is the polisaccharide that vertebrates store in liver and muscle cells?

Answer 18

It is the glycogen

Question 19

What is the most important structural polysaccharide and why it is so strong?

Answer 19

It is cellulose and it is so strong due to the rings structure of the glucose. In facts when glucose forms a ring, the hydroxyl group attached to number one carbon is positioned either below or above the plane of the ring, forming Alpha and Beta rings wich give them three-dimensional strong shape

Question 20

What is an important structural polysaccharide for the arthropods (insects, spiders, crustaceans and related animals)?

Answer 20

It is chitin,  unimportant material to build their exoskeleton

Question 21

What is a fat?

Answer 21

It is a macromolecule constructed from two kinds of the smaller molecules called glycerol and fatty acids

Question 22

What is a fatty acid?

Answer 22

It is a molecule that has usually 16 or 18 carbon atoms in length. The carbon at the one end of the skeleton is part of a carboxyl group (COOH), while the rest of the skeleton consists of a hydrocarbon chain. It is a carboxyl acid, in facts the relatively nonpolar CH bonds in the hydrocarbon chains of fatty acids are the reason why fats are hydrophobic.

Question 23

How is a fatty acid made?

Answer 23

It is made by attaching tree fatty acid molecules to glycerol by an ester linkage, a bond formed by dehydration reaction between hydroxyl group and a carboxyl group. That’s why it is also called triacylglycerol

Question 24

What is the difference between saturated fatty acid and unsaturated fatty acid?

Answer 24

The saturated one has single bonds, while the other one has one or more double bonds whose almost all are cis double bonds

Question 25

What are the types of fats that people should avoid?

Answer 25

They are trans fats and saturated fats

Question 26

What is the function of fats?

Answer 26

Day serve as energy storage, protection from the cold and protection of the inner organs. They also lubricate and hydrate the skin and they are essential to the nerve transmission through mieline

Question 27

What are phospholipids?

Answer 27

It is a molecule made up of two fatty acids attached to a glycerol. This structure makes them having a hydrophilic head and hydrophobic tails

Question 28

What are steroids?

Answer 28

They are lipids characterized by a carbon skeleton consisting of four fused rings that they are distinguished by the particular chemical group attached to ensemble of rings

Question 29

What is phospholipids main function?

Answer 29

Their main function is the one of forming semi permeable barrier.

Question 30

Which is the most famous steroid?

Answer 30

It is cholesterol, a crucial molecule in animals cells membranes and in vertebrates sexual hormones. In vertebrates, cholesterol is synthesized in the liver and is also obtained from the diet.

Question 31

 What are catalysts ?

Answer 31

They are pro to chemical agents that selectively speed up chemical reactions without being consumed in the reaction

Question 32

How is it called a bond between amino acids?

Answer 32

It is called peptide bond, so a polymer of amino acids is called polypeptide

Question 33

What is a protein?

Answer 33

It is a biological functional molecule made up of one or more polypeptide, each folded and coiled into specific three-dimensional structure

Question 34

What is an amino acid?

Answer 34

It is a biological molecule with both an amino group and a carboxyl group

Question 35

What is there at the centre of an amino acid?

Answer 35

There is an asymmetric carbon atom called alpha carbon

Question 36

What is the structure of an amino acid? Draw it

Question 37

What are the non-polar amino acids of protein?

Answer 37

Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine, Tryptophan and Proline

Question 38

What are the polar amino acids of protein?

Answer 38

Serine, Threonine, Cysteine, Tyrosine, Aspargine and Glutamine

Question 39

What are the hydrophilic electrically charged amino acids of protein?

Answer 39

Aspartic acid, Glutamic acid, Lysine, Arginine and Histidine

Question 40

How does a peptide bond form?

Answer 40

When two amino acids are positioned so that the carboxyl group of one is adjacent to the amino group of the other, a dehydration reaction happens, forming the bond 

Question 41

What do protein properties and functions depend on?

Answer 41

They depend on their shape, which can be four

Question 42

Tell about the primary structure of a protein

Answer 42

It is a protein made up of a simple linear chain of amino acids

Question 43

Tell about the secondary structure of a protein

Answer 43

It is a protein within regions stabilized by hydrogen bonds between atoms of the polypeptide backbone. It can be either alpha helix, which has hydrogen bond between every fourth amino acid, or beta strand,  in which two or more segments of the polypeptide chain are connected by hydrogen bond between parts of the two parallel segments of polypeptide backbone

Question 44

Tell about the tertiary structure of a protein

Answer 44

It is a structure resulting from interactions between the side chains (R groups) of the various amino acids. One of the most important interaction is the hydrophobic interaction, caused by the exclusion of non-polar substances by water molecules. Once nonpolar amino acids are close together, van der Waals interactions intervene. Meanwhile, hydrogen bonds between polar side chains and ionic bonds between positively and negatively charge side chains also help stabilize the structure. Finally, the structure is reinforced by covalent bonds called disulfide bridges.

Question 45

How do disulfide bridges form in the tertiary structure of a protein?

Answer 45

They form where two cysteine monomers (which contain sulfydryl groups -SH) are brought close together by the folding of the protein. The sulfur of one cysteine bonds to the sulfur of the second one, forming a disulfide bridge

Question 46

Tell about the quaternary structure of a protein

Answer 46

The quaternary structure of a protein results from the aggregation of two or more polypeptide chains

Question 47

What are some examples of quaternary structure proteins?

Answer 47

They are globular transthyretin protein, collagen and hemoglobin

Question 48

What does determine which three dimensional shape a protein will have (normal cellular conditions)?

Answer 48

The amino acids sequence of each polypeptide 

Question 49

What is the Sickle-Cell disease?

Answer 49

It is an inherited blood disorder caused by the substitution of the amino acid valine with glutamic acid at the postion of the sixth amino acid in the primary structure of hemoglobin. It is so called because the abnormal hemoglobin molecules aggregate into chains, deforming some of the red blood cells into a sickle shape

Question 50

What is the denaturation of a protein?

Answer 50

It is the destruction of a protein structure due to an alteration of the pH, salt concentration, temperature or order aspects of the environment 

Question 51

What are some diseases caused by the misfolding of polypeptide in cells?

Answer 51

They are cystic fibrosis, Alzheimer's, Parkinson's and Mad cow disease

Question 52

What Is most used method to determine the 3D structure of a protein?

Answer 52

It is the X-ray crystallography, which depends on the defraction of an x-ray beam by the atoms of the crystallized molecules. This technique is always completed by the nuclear magnetic resonance , spectroscopy and bioinformatics

Question 53

What does determine the primary structure of polypeptide?

Answer 53

It is determined by gene

Question 54

What is a nucleic acid?

Answer 54

It is a polymer made of monomers called nucleotides