Molecules of Life

Question 1

Bonds

Answer 1

Covalent
Other types
- Ionic
- Hydrogen
- Van der Waals interactions

Question 2

Covalent Bonds

Answer 2

A covalent bond is the sharing of a pair of valence electrons by two atoms

Question 3

Van der Waals Interactions

Answer 3

Dipole-dipole
Dipole-induced-dipole
Dispersion

Question 4

Water

Answer 4

The solvent of life
Cohesive (the molecules stick to one another due to hydrogen bonds), allowing to have surface tension
Moderates temperature changes (high specific heat capacity; evaporative cooling)
Ice is less dense than its liquid form (due to having 4 H-bonds, which require a certain distance between the molecules, instead of 2); however, cold liquid water is denser than when it is warm
Hydrophilic
2 molecules dissociate to form Hydronium and Hydroxide (2H_2O ⇌ H_3O^+ + OH^−)

Question 5

Carbon

Answer 5

Often forms bonds to itself
Forms four covalent bonds
Can form double bonds
Is versatile

Question 6

Isomers

Answer 6

Have the same number and type of atoms
Structural isomers (same formula, different structure)
Geometric isomers (different arrangement of atoms around a double bond)
Enantiomers (mirror images of each other)

Question 7

Polymers

Answer 7

Grouping of multiple monomers
Can be created through a dehydration reaction
Can be broken through hydrolysis

Question 8

Macromolecules of Life

Answer 8

Carbohydrates (sugars)
Proteins (amino acids)
Lipids (fatty acids)
Nucleic acids (nucleotides)

Question 9

Carbohydrates

Answer 9

Role
- Fuel
- Structure
Monosaccharides, disaccharides, polysaccharides
C_n(H_2O)n → C_nH_2nO_n
Different types

Question 10

Glucose

Answer 10

C_6H_(12)O_6
A hexose
Most of it in our body is in ring formation

Question 11

Glycosidic Bonds / Glycosidic Link

Answer 11

Formed from a dehydration reaction (an H_2O escapes)

An oxygen atom forms a bond between the two molecules

Question 12

Maltose

Answer 12

α-glucose + α-glucose forming a 1-4 glycosidic link

Question 13

Sucrose

Answer 13

α-Glucose + β-Fructose forming a 1-2 glycosidic link

Question 14

Lactose

Answer 14

β-galactose and α-glucose forming a 1-4 glycosidic link

Question 15

Glycogen

Answer 15

Animal storage of sugar
Linked and branched glucose
α1-4 and α1-6 glycosidic links

Question 16

Starch

Answer 16

Plant storage of glucose

Amylopectin and Amylose

Question 17

Amylopectin

Answer 17

Branched glucose
Makes up 70% of starch
α1-4 and α1-6 glycosidic links

Question 18

Amylose

Answer 18

Unbranched glucose
Denser than Amylopectin
α1-4 glycosidic links

Question 19

Cellulose

Answer 19

Structural

Straight (not helical) due to β1-4 linkages between glucose

Question 20

Nucleic Acids

Answer 20

Transmit and store genetic information
DNA (complementary bases in double helix) and RNA
Monomers are called “nucleotides”

Question 21

Nucleotide

Answer 21

Made up of a phosphate group, a sugar (pentose) and a nitrogenous base, the latter two forming the nucleoside
The sugars are either Deoxyribose (in DNA) or Ribose (in RNA)
The nitrogenous bases are either pyrimidines or purines

Question 22

Pyrimidines

Answer 22

Cytosine (C)
Thymine (T, in DNA)
Uracil (U, in RNA)

Question 23

Purines

Answer 23

Adenine (A)

Guanine (G)

Question 24

Phosphodiester Bond

Answer 24

Bond between two nucleotides, with the phosphate group involved

Question 25

Proteins

Answer 25

Effectors of most cell functions
Widely diverse
Can be delicious

Question 26

Amino Acid

Answer 26

Contains a central carbon atom attached to a hydrogen atom, to a carbonyl group, to an amino group and to a variable side chain
Amphipathic
The side chain can be non-polar (hydrophobic), such as glycine (Gly, G) and proline (Pro, P), or it can be electrically charge (either positively - basic - or negatively - acidic - charged) or polar (the latter two being hydrophilic)

Question 27

Zwitterions

Answer 27

Dipolar ions

Change depending on pH

Question 28

Peptide Bond

Answer 28

Caused by a condensation reaction in which an H_2O escapes to link the C and N atoms of two amino acids

Question 29

Polypeptide Chain

Answer 29

Protein

Many amino acids linked with peptide bonds

Question 30

Protein Functions

Answer 30

Catalysts (in our body, enzymes)
Amino acid storage
Coordination of an organism’s activities (insulin, secreted by the pancreas, causes other tissues to take up glucose, thus regulating blood sugar concentration)
Movement
Protection against disease (activates antibodies)
Response of cell to chemical stimuli
Support

Question 31

Denaturation

Answer 31

Breaking side chain interactions in a protein, creating a denatured protein
Caused by pH, temperature, solvents…

Question 32

Renaturation

Answer 32

Reforming side chain interactions in a protein, usually by cells, creating a normal protein
Protein folding is a significant area of research: Fibrosis, Alzheimer’s, Parkinson’s, Creutzfeldt-Jakob disease…

Question 33

Lipids

Answer 33

No common structure (grouped by property instead)
Hydrophobic
Varying functions depending on the type of lipid
Types of lipids: fatty acids, phospholipids, steroids

Question 34

Triglycerides / Triaglycerols

Answer 34

Fatty acids
Always hydrophobic
Serve as storage
Include ester bonds
Form by releasing three H_2O molecules

Question 35

Phospholipids

Answer 35

Glycerol with two fatty acids
Varying polar head group, but always hydrophilic
Amphipathic
Create cell membranes
Unsaturated fatty acids increase fluidity
Can form bilayers

Question 36

Steroids

Answer 36

Lipids
Derived from four fused rings
Largely hydrophobic (amphipathic)
Can play many roles
Cholesterol disrupts cell membranes
Hormones, vitamin D

Question 46

Hydrogen Bonds

Answer 46

H-bonds form when the partial positive charge of hydrogen atoms are attracted to the partial negative charge of oxygen atoms