Bio 107 topic 2

Question 1

What is a valence shell?

Answer 1

the outermost electron shell
- when incomplete it is reactive

Question 2

What are valence electrons?

Answer 2

the electrons in the valence shell

Question 3

What is a chemical bond?

Answer 3

attraction between atoms that hold them together. This can be due to sharing or exchange of electrons.

Question 4

What are the strong bonds?

Answer 4

covalent and ionic

Question 5

What are the weak bonds?

Answer 5

hydrogen bonds

Question 6

What are covalent bonds?

Answer 6

it is formed by electrons pairs that are shared between two atoms to complete their valence shell

Question 7

What do covalent bonds form?

Answer 7

a molecule

Question 8

What are the 2 subtypes of covalent bonds?

Answer 8

polar covalent and non polar covalent

Question 9

Polar covalent

Answer 9

• electrons are not shared equally
• atoms have different electronegativity
• results in separation of charge

Question 10

Non polar covalent

Answer 10

• electrons are shared equally
• occurs between atoms of the same electronegativity

Question 11

Electronegativity (X)

Answer 11

attraction of an atom for the electrons in a covalent bond
↑ X= greater pull towards the nucleus

Question 12

symbol ←, right arrow symbol →, up arrow symbol ↑, and down arrow symbol ↓. While arrow

Question 13

Ionic bond

Answer 13

atom with high electronegativity takes the lone valence electron from an atom with low electronegativity which produces ions
- strong attraction forms between anion and cation

Question 14

Hydrogen bond

Answer 14

attraction between the δ+H atom of one polar covalent bond and the δ-H atom of the second polar covalent bond
- allows a molecule to dissolve

Question 15

What are the rules for a hydrogen bond?

Answer 15

• each atom in the H-bond is covalently bonded to something else
• an H-bond always involves a partially positive H atom
• the second atom in an H bond is always partially negative (usually O or N)
• electrons are not shared in an H-bond. It is an attraction between partial charges
• each H atom can form only one H-bond

Question 16

Water

Answer 16

• biological solvent
• interacts with all cellular components
• determines cell structure and function
• can H-bond with polar molecules

Question 17

Hydrophilic molecules

Answer 17

water loving
- have polar covalent bonds
- forms H-bonds with water
- dissolve in water
ex. sucrose

Question 18

Hydrophobic molecules

Answer 18

scared of water
- have non polar covalent bonds
- little affinity for water
- can’t form H-bonds with water
- interact with other non polar molecules and excludes water
ex. triclyceride (fat)

Question 19

How would you identify a molecule as hydrophilic or hydrophobic?

Answer 19

If the majority of the outside atoms are non-polar and there is only one or two polar bonds then it is probably hydrophobic

Question 20

Carbon

Answer 20

• forms 4 covalent bonds
• can form chains (variations in chains of carbon= different molecules)
• C+H only chains are hydrocarbons

Question 21

Geometric isomers

Answer 21

• can form in carbon chains with double bonds. Only double bonds since singles can rotate
• atoms are in the same order but different spatial arrangement
• typically the same chemical name but with the prefixes trans and cis

Question 22

Functional groups

Answer 22

• can replace an H on a carbon skeleton
• gives molecules its unique properties
• different function group placement changes the molecule

Question 23

Hydroxyl

Answer 23

• alcohol name
• polar
• R-OH

Question 24

Carbonyl

Answer 24

• aldehyde: on end c
• ketone: on middle c
• polar

Question 25

Carboxyl

Answer 25

- acid - polar acidic

Question 26

Amino

Answer 26

- amine - polar basic

Question 27

Sulfhydryl

Answer 27

- thiol - polar

Question 28

Phosphate

Answer 28

- polar acidic

Question 29

Methyl

Answer 29

- non-polar - decreases solubility