Chapter 5: The Structure and Function of Large Biological Molecules

Question 1

What are carbohydrates ? Describe its function and name examples.

Answer 1

Carbohydrates serve as fuel and building material. Examples are glucose and fructose which are monosaccharides and lactose and sucrose which are disaccharides.

Question 2

What are lipids? Describe its function and name example(s).

Answer 2

Lipids serve as an important energy source. Some examples are triglycerides, phospholipids and steroids.

Question 3

What are proteins? Describe its function and name example(s).

Answer 3

A protein is a biologically functional molecule made up of one or more polypeptides, each folded and coiled into a specific three- dimensional structure. Proteins have many functions, some of are that include catalyzing chemical reactions, protecting against disease, transport substances, and storing amino acids. Some examples are enzymes, defensive proteins, and hormones

Question 4

What are nucleic acids? Describe its function and name example(s).

Answer 4

Nucleic acids store, transmit, and help express hereditary information. Some examples are DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid)

Question 5

What is a a polymer?

Answer 5

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

Question 6

What is a monomer?

Answer 6

The repeating units that serve as the building blocks of a polymer are smaller molecules is a monomer.

Question 7

What is dehydration reaction?

Answer 7

A reaction in which two molecules are covalently bonded to each other with the loss of a small molecule. If a water molecule is lost, it is known as a dehydration reaction.

Question 8

What is hydrolysis?

Answer 8

A process that is essentially the reverse of the dehydration reaction. Hydrolysis means water breakage (from the Greek hydro, water, and lysis, break).

Question 9

What is a monosaccharide? What groups does it contain?

Answer 9

Monosaccharides (from the Greek monos, single, and sacchar, sugar) generally have molecular formulas that are some multiple of the unit CH2O. Glucose (C6H12O6), the most common monosaccharide, is of central importance in the chemistry of life.

The molecule has a carbonyl group and multiple hydroxyl groups.

Question 10

What is the function of monosaccharides?

Answer 10

They function as the raw material for the synthesis of other monomers, such as amino acids and fatty acids.

Question 11

What is a disaccharide?

Answer 11

A disaccharide consists of two monosaccharides joined by a glycosidic linkage.

Question 12

What is a glycosidic linkage?

Answer 12

A covalent bond formed between two monosaccharides by a dehydration reaction (glyco
refers to carbohydrate).

Question 13

What is a polysaccharide? What is its function?

Answer 13

Polysaccharides are macromolecules, polymers with a few hundred to a few thousand monosaccharides joined by glyco- sidic linkages. It serves for storage and are hydrolyzed as sugars are needed.

Question 14

What is starch?

Answer 14

A polymer of glucose monomers, as granules within cellular structures known as plastids. The simplest form of starch is amylose which forms an unbranched helix.

Question 15

What is glycogen?

Answer 15

A polymer of glucose that is like amylopectin but more extensively branched. Animals store glucose in glycogen.

Question 16

What is amylopectin?

Answer 16

A more complex starch, is a branched polymer with 1–6 linkages at the branch points.

Question 17

What is cellulose?

Answer 17

A major component of the tough walls that enclose plant cells.

Question 18

What is chitin?

Answer 18

The carbohydrate used by arthropods (insects, spiders, crusta- ceans, and related animals) to build their exoskeletons—hard cases that surround the soft parts of an animal

Question 19

What are lipids?

Answer 19

Lipids are the one class of large biological molecules that does not include true polymers, and they are generally not big enough to be considered macromolecules. The compounds called lipids are grouped with each other because they share one important trait: They are hydrophobic: They mix poorly, if at all, with water. This behavior of lipids is based on their molecular structure.

Question 20

What is a fat?

Answer 20

A fat consists of a glycerol molecule joined to three fatty acids. Glycerol is an alcohol; each of its three carbons bears a hydroxyl group.

Question 21

What is a fatty acid?

Answer 21

A fatty acid has a long carbon skeleton, usually 16 or 18 carbon atoms in length. The carbon at one end of the skeleton is part of a carboxyl group, the functional group that gives these molecules the name fatty acid.

Question 22

What is a glycerol?

Answer 22

A three carbon alcohol with a hydroxyl group attached to each carbon.

Question 23

What is a saturated fatty acid?i

Answer 23

If the fatty acid has no carbon carbon double bonds, then the molecule is a saturated fatty acid.

Question 24

What is an unsaturated fatty acid?

Answer 24

If the fatty acid has one or more carbon carbon double bonds formed by the removal of hydrogen atoms from the carbon skeleton, then the molecule is an unsaturated fatty acid.

Question 25

What is the major function of fats?

Answer 25

The major function of fats is energy storage.

Question 26

What is the function of adipose tissue?

Answer 26

It serves to cushion vital organs such as the kidneys.

Question 27

What is a phospholipid?

Answer 27

They are the major components of cell membranes. They have two fatty acids attached to glycerol and a phosphate group at the third position. A phospholipid has a hydrophilic (polar) head and two hydrophobic (nonpolar) tails.

Question 28

What is a steroid?

Answer 28

They are lipids characterized by a carbon skeleton consisting of four fused rings. Different steroids are distinguished by the particular chemical groups attached to this ensemble of rings.

Question 29

What is cholesterol?

Answer 29

Cholesterol, a type of steroid, is a crucial molecule in animals. It is a common component of ani- mal cell membranes and is also the precursor from which other steroids, such as the vertebrate sex hormones, are synthesized. In vertebrates, cholesterol is synthesized in the liver and is also obtained from the diet. A high level of cholesterol in the blood may contribute to atherosclerosis, although some researchers are questioning the roles of cholesterol and saturated fats in the development of this condition.

Question 30

What is a peptide bond?

Answer 30

The bond between amino acids.

Question 31

What are catalysts?

Answer 31

Chemical agents that selectively speed up chemical reactions without being consumed in the reac- tion.

Question 32

What is an amino acid?

Answer 32

An amino acid is an
organic molecule with both an amino
group and a carboxyl group.

Question 33

What is at the center of an amino acid?

Answer 33

At the center of an amino acid is an asymmetric carbon atom called the alpha carbon.

Question 34

What is attached to the alpha carbon?

Answer 34

Four components are attached to the alpha carbon; a hydrogen atom, a carbonyl group, an amino group, and a variable R group.

Question 35

What are the four levels of protein structure?

Answer 35

Primary structure, secondary structure, tertiary structure, and quaternary structure.

Question 36

What is a primary structure?

Answer 36

The primary structure of a protein is its sequence of amino acids.

Question 37

What is a secondary structure?

Answer 37

These coils and folds, collectively referred to as secondary structure, are the result of hydrogen bonds between the repeating constituents of the polypeptide backbone (not the amino acid side chains).

Question 38

What is a helix?

Answer 38

A delicate coil held together by hydrogen bonding between every fourth amino acid

Question 39

What is a pleated sheet?

Answer 39

two or more segments of the polypeptide chain lying side by side (called d strands) are connected by hydrogen bonds between parts of the two parallel segments. d pleated sheets make up the core of many globular proteins, as is the case for transthyretin (see Tertiary Structure), and dominate some fibrous proteins, including the silk protein of a spider’s web.

Question 40

What is a tertiary structure?

Answer 40

the overall shape of
a polypeptide resulting from interactions between the side chains
(R groups) of the various amino acids.

Question 41

What are disulfide bridges?

Answer 41

Strong covalent bonds that form between the sulfhydryl groups of two cysteine monomers.

Question 42

What causes a hydrophobic interaction?

Answer 42

It is caused by the exclusion of nonpolar substances by water molecules.

Question 43

What is a quaternary structure?

Answer 43

The overall protein structure that results from the aggregation of these polypeptide subunits.

Question 44

What is hemoglobin?

Answer 44

The oxygen-binding protein of red blood cells, is another example of a globular protein with quaternary structure

Question 45

What is collagen?

Answer 45

Collagen is a fibrous protein of three polypeptides that are super coiled like a rope.

Question 46

What is sickle cell disease?

Answer 46

An inherited blood disorder, is caused by the sub- stitution of one amino acid (valine) for the normal one (glutamic acid) at the position of the sixth amino acid in the primary structure of hemoglobin, the protein that carries oxy- gen in red blood cells. Normal red blood cells are disk-shaped, but in sickle-cell disease, the abnormal hemoglobin molecules tend to aggregate into chains, deforming some of the cells into a sickle shape

Question 47

What is denaturation?

Answer 47

Disruption of hydrogen bonds, ionic bonds, and disulfide bridges that maintain the protein’s shape.

Question 48

What is X-ray crystallography?

Answer 48

A technique that determines protein conformation.

Question 49

What is a gene?

Answer 49

Gene consist of DNA and are a discrete unit of inheritance.

Question 50

What is DNA?

Answer 50

DNA or Deoxyribonucleic acid, is a type of amino acid that stores genetic information. It also directs RNA synthesis and through that controls protein synthesis.

Question 51

What is RNA?

Answer 51

RNA or Ribonucleic acid, is considered the messenger and interacts with the cells protein synthesizing machinery to direct the ordering of amino acids in a polypeptide.

Question 52

Where does protein synthesis occur?

Answer 52

Protein synthesis occurs on cellular structure called ribosomes.

Question 53

What is a polynucleotide?

Answer 53

Nucleic acids that exist as polymers are called polynucleotides

Question 54

What is a nucleotide composed of?

Answer 54

It is composed of three parts: a five-carbon sugar (a pentose), a nitrogen-containing (nitrogenous) base, and one to three phosphate groups.

Question 55

What are purines?

Answer 55

There are two types of purines; Adenine (A) and Guanine (G). Purines have a six membered ring joined to a five membered ring.

Question 56

What are pyrimidines?

Answer 56

There are three different pyrimidines; cytosine (C), thymine (T), and uracil (U). They have a six membered ring.

Question 57

What is the sugar in DNA called?

Answer 57

It is called deoxyribose.

Question 58

What is the sugar in RNA called?

Answer 58

The sugar is called ribose.

Question 59

What is a double helix?

Answer 59

A DNA molecule has two polynucleotides, or “strands,” that wind around an imaginary axis, forming a double helix

Question 60

What is a antiparallel?

Answer 60

The two sugar backbones that run from 5 to 3 directions from each other.