Exam 1 Flashcards
(99 cards)
1
Q
What does valence refer to?
A
The number of unpaired electrons in the outer orbital shell of an atom or element.
2
Q
What is the valence of Hydrogen?
A
1
3
Q
What is the valence of Oxygen?
A
2
4
Q
What is the valence of Nitrogen?
A
3
5
Q
What is the valence of Carbon?
A
4
6
Q
What is a covalent bond?
A
It is a bond that occurs between two nonmetals that have similar electronegativities. In other words, neither atom is strong enough to attract electrons from the other. Unpaired electrons are shared.
7
Q
What can O2 form?
A
Two covalent bonds since each Oxygen has two unpaired electrons.
8
Q
Why is water important?
A
Because it is the universal biological solvent. Many cell processes occur in water.
9
Q
What does electronegativity determine?
A
Determines the distribution of electrons within a covalent bond.
10
Q
What is the EN of Oxygen?
A
3.5
11
Q
What is the EN of Nitrogen?
A
3.0
12
Q
What is the EN of Sulfur and Carbon?
A
2.5
13
Q
What is the EN of Phosphorus and Hydrogen?
A
2.1
14
Q
Electronegativity is important for the three following reasons:
A
- Determines position of electrons within covalent bonds
- Determines what bond consists of
- Determines what the consequences of that covalent bond are for cellular energetics
15
Q
What is electronegativity?
A
Electronegativity is the measure of an atom’s ability to attract shared electrons to itself.
16
Q
What is the trend of electronegativity on the periodic table?
A
Increases as you move up and to the right. This makes sense because non-metals have high electronegativities
17
Q
What is a nonpolar covalent bond?
A
A bond where the atoms have similar (or equal) electronegativities. This means that electrons are distributed equally between these atoms. This can typically mean less than or equal to 0.4 difference.
18
Q
Is a C-H bond polar or nonpolar?
A
Nonpolar because the electronegativity of Carbon is 2.5 and the electronegativity of Hydrogen is 2.1.
19
Q
What is a polar covalent bond?
A
A bond where the atoms have DISSIMILAR electronegativities, meaning that the electrons are distributed unequally between atoms.
20
Q
In a polar covalent bond, which atom will electrons be attracted to?
A
Electrons are attracted more to the atom with stronger electronegativity because it has a stronger pull.
21
Q
What are a few examples of polar covalent bonds?
A
H-O, C-O, H-N
22
Q
What is an important type of bond that involves polar covalent bonding?
A
Hydrogen bond formation
23
Q
What do the charges on atoms in polar covalent bonds allow for?
A
Allows for electrostatic type bonding. For example, in a molecule of H2O, the Oxygen has a slightly negative charge and the Hydrogens have slightly positive charges due to the difference in electronegativities. Due to these charges, electrostatic type bonding is possible.
24
Q
How do hydrogen bonds form?
A
Form between molecules that have H-O, H-N, or H-F bonds.
25
Where do we see hydrogen bonds in the body?
Hydrogen bonds can also form in protein molecules.
26
What are hydrogen bonds important for in protein molecules?
They are important for the shape. The shape of a protein molecule determines its function.
27
How does the potential energy in a nonpolar covalent bond compared to the potential energy in a polar covalent bond?
Electrons in covalent bonds between atoms of equal electronegativity have a GREATER potential energy than those between atoms with unequal electronegativity.
PE in nonpolar CB > PE in polar CB
28
What do changes in the position of electrons in covalent bonds effect?
Changes in the position of electrons in covalent bonds constitute changes in energy status. For example, metabolism.
29
What happens energetically when you break a nonpolar bond and for a polar bond?
Release energy
30
How does the potential energy between a C-H bond compare to that of an O-H or C-O bond?
Covalent C-H bonds have greater potential energy that O-H or C-O bonds because the electrons are equidistant between C and H.
31
What happens during ionic bonding?
Complete electron transfer occurs and the electron is completely donated.
32
What is an example of ionic bonding?
NaCl. In this molecule, Na loses an electron and become a cation (positive charge) and Cl gains an electron and becomes an anion (negative charge). Note that NaCl is an important biological molecule
33
Are ionic bonds strong?
YES
34
How can crystalline NaCl be dissolved?
When crystalline NaCl is placed in a beaker of water, the small electrostatic charges between O and H attract and setup with ions in NaCl. The positive Hydrogen atoms are attracted to the negative Chlorine atoms, and the negative Oxygen atoms are attracted to the positive Sodium atoms.
35
How can weak hydrogen bonds break strong ionic bonds?
Water forms hydration shells surrounding ions. The aggregated electrostatic forces within shells are strong enough to dissolve the molecule.
36
What is a hydration shell?
These shells are a large number of water molecules that are formed by electrostatic forces between the H and O atoms of water and the 'dissolved' ion.
37
What happens when hydration shells extend away from an ion?
They become less organized
38
What are hydration shells critical for in cells and tissues?
Critical for dissolving soluble proteins in the aqueous environments.
39
Can insoluble proteins be dissolved via hydration shells?
No, because they have a surface with a charge distribution that doesn't allow water molecules to be attracted to them
40
What does the pH scale tell us?
pH scale gives the relative concentrations of protons or hydroxyl ions in that solution.
41
What can be dissociated in water?
Protons or hydroxyl ions
42
Gastric juice is very...
Acidic. This environment allows enzymes to function well.
43
At what pH does a cell operate? Can different pH levels be found in a cell?
The cell operates at pH = 7, but some compartments have different pH for enzymes.
44
What is the pH of human blood?
7. If it becomes slightly acidic, you will have a lot of problems.
45
An acidic solution has a high concentration of which ions?
H+
46
A basic solution has a high concentration of which ions?
OH-
47
How are molecular shapes determined?
Based on the presence of bonded atoms and lone pairs. These determine orbitals.
48
Why is molecular shape important in biology?
Affects protein shape. Again, the shape of a protein gives it function.
49
How many covalent bonds can Carbon form?
It can form 4 covalent bonds with either itself or other atoms.
50
How can carbon skeletons vary?
1. Length
2. Branching
3. Double bond position
4. Presence of rings
51
Why can carbon chains produce complex shapes?
Because Carbon can form covalent bonds with itself
52
What are examples of carbon skeletons with a long chain of carbon?
Fatty acids, they can have 18 or 19 Cs.
| Ethane and Propane
53
What is the shape of the Butane molecule?
Linear
54
What is the shape of 2-Methylpropane (isobutane)
Branched
55
Double bond position is important because...
Two molecules with the same chemical formula can have two distinct structures which influence their function.
56
How is an isomer defined?
Each of two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.
57
What are structural isomers?
Chemical compounds that have the same formulas, but different structures.
58
What is a general example of structural isomers?
Linear vs. branched
59
What are cis-trans isomers?
A cis isomer is a double-bonded molecule that has two Xs on the same side.
A trans isomer is a double-bonded molecule that has two Xs on opposite sides.
*X refers to functional groups
60
Why do cis-trans isomers exist?
Because double bonds are rigid, thus the position is fixed.
61
What are enantiomers?
This type of isomer can only exist when the central C has four different functional groups connected.
There is an L isomer (left hand) and a D isomer (right hand). These are mirrors of one another.
62
Do both enantiomers necessarily have to be active?
No. An example of this is L-glucose and D-glucose. Enzymes can only recognize one.
63
Which is the effective enantiomer for Ibuprofen?
S-ibuprofen
64
Which is the effect enantiomer for Albuterol?
R-Albuterol
65
Why are only some enantiomers effective?
Because the body must have the proteins to recognize it.
66
What is the structure of the Hydroxyl functional group?
--OH
67
What is the name of the compound in the Hydroxyl functional group?
Alcohols (their specific names usually end in -ol.)
68
What is an example of a hydroxyl functional group?
Ethanol
69
What are the functional properties of the hydroxyl functional group?
- Is polar as a result of the electrons spending more time near the electronegative oxygen atom
- Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars
70
What is the structure of the Carbonyl functional group?
C with two single bonds and one double bond to O
71
What are the names of the compounds in the Carbonyl functional group?
Ketones if the carbonyl group is within a carbon skeleton.
| Aldehydes if the carbonyl group is at the end of the carbon skeleton.
72
When will a carbonyl group be known as a ketone?
If the carbonyl group is within a carbon skeleton
73
When will a carbonyl group be known as an aldehyde?
If the carbonyl group is at the end of the carbon skeleton
74
What are examples of the carbonyl functional group?
Acetone and Propanal
75
What are the functional properties of the Carbonyl functional group?
- The ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal
- Ketone and aldehyde groups are also found in sugars, giving rise to two major groups of sugars: ketoses (containing ketone groups) and aldoses (containing aldehyde groups)
76
What are the two major groups of sugars based on the Carbonyl group?
Ketoses and Aldoses
77
What is the structure of the Carboxyl group?
C with a single bond, a single bond to OH, and a double bond to O
78
What are the names of the compounds in the carboxyl group?
Carboxylic acids, or organic acids
79
What is an example of the carboxyl group?
Acetic acid
80
What are the functional properties of the carboxyl group?
- Acts as an acid; can donate an H+ because the covalent bond between oxygen and hydrogen is so polar
- Found in cells in the ionized form with a charge of 1- and called a carboxylate ion
81
What is the structure of the Amino group?
N with a single bond, a single bond to H, and a single bond to H
82
What is the name of the compound in the amino group?
Amines
83
What is an example of the Amino group?
Glycine
84
What are the functional properties of the Amino group?
- Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms)
- Found in cells in the ionized form with a charge of 1+
85
What is the structure of Sulfhydryl?
--SH
86
What is the name of the compound in the Sulfhydryl group?
Thiols
87
What is an example of the Sulfhydryl group?
Cysteine
88
What are the functional properties of the Sulfhydryl group?
- Two sulfhydryl groups can react, forming a covalent bond. This "cross-linking" helps stabilize protein structure
- Cross-linking of cysteines in hair proteins maintains the curliness or straightness of hair. Straight hair can be "permanently" curled by shaping it around curlers and then breaking and reforming the cross-linking bonds
89
What is the structure of the phosphate group?
P doubled bonded to O, single bonded to O-, single bonded to O-, single bonded to O
90
What is the name of the compound in the phosphate group?
Organic phosphates
91
What is an example of the phosphate group?
Glycerol phosphate
92
What are the functional properties of the phosphate group?
- Contributes negative charge to the molecule of which it is a part (2- when at the end of a molecule, as in glycerol phosphate; 1- when located internally in a chain of phosphates)
- Molecules containing phosphate groups have the potential to react with water, releasing energy
93
What is the structure of the methyl group?
C with a single bond, single bonded to H, single bond to H, single bond to H
94
What is the name of compounds in the methyl group?
Methylated compounds
95
What is an example of the methyl group?
5-Methyl cytidine
96
What are the functional properties of the methyl group?
- Addition of a methyl group to DNA, or to molecules bound to DNA, affects the expression of genes
- Arrangement of methyl groups in male and female sex hormones affects their shape and function
97
What is polymerization?
The formation of large molecules (polymers) from smaller ones (monomers)
98
What are the four types of macromolecules (polymers)?
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic Acids (RNA, DNA)
99
Write the relationship of Monomer: Polymer for the four macromolecules:
1. Sugars: Carbohydrates
2. Glycerol and Fatty acids: Lipids
3. Amino acids: Proteins
4. Sugars & nucleotide bases: Nucleic acids (RNA, DNA)
