Carbon Chemistry pH and Buffers

Question 1

Hydrocarbons

___ of all living tissues are composed of Carbon and Hydrogen

___–> ___s and _s–> T____–> ____–>___s–> ___

Answer 1

70% of all living tissues are composed of Carbon and Hydrogen

Indiv–> Systems and Organs–> Tissues and Cells–> Organelles and Cell Structure–> Glycogen Polymers–> Sugar Monomers

Question 2

Carbon Chemistry

• Carbon is the
• Has an ___ electronegativity (Tendency to acquire electrons)
• Enables it to form bonds with electronegative and electropositive elements (large number of compounds formed)
• Forms bonds with itself resulting in carbon chains (Maximum valency is ___). Ability to form double or triple bonds between 2 carbon atoms.

Answer 2

• Carbon is the basis for life.
• Has an intermediate electronegativity (Tendency to acquire electrons)
• Enables it to form bonds with electronegative and electropositive elements (large number of compounds formed)
• Forms bonds with itself resulting in carbon chains (Maximum valency is 4). Ability to form double or triple bonds between 2 carbon atoms.

Question 3

Atomic Structure

• Atoms consists of a central positively charge nucleus (neutrons and protons), surrounded by negatively charged electrons.
• Electrons are held in a series of shells (Energy levels) surrounding the nucleus.
• Each shell/energy level is comprised of ____ ____ (s, p, d, f orbitals) Ex:- Hydrogen has a 1s1, while Carbon has a 1s22s22p2 configuration
• Elements with complete outermost shells are stable (noble gases)
• An unfilled electron shell is less stable than a filled one, atoms with incomplete outer shells have a strong tendency to interact with other atoms in a way that causes them to share or either gain/lose enough electrons to achieve a stable configuration.

Answer 3

• Atoms consists of a central positively charge nucleus (neutrons and protons), surrounded by negatively charged electrons.
• Electrons are held in a series of shells (Energy levels) surrounding the nucleus.
• Each shell/energy level is comprised of atomic orbitals (s, p, d, f orbitals) Ex:- Hydrogen has a 1s1, while Carbon has a 1s22s22p2 configuration
• Elements with complete outermost shells are stable (noble gases)
• An unfilled electron shell is less stable than a filled one, atoms with incomplete outer shells have a strong tendency to interact with other atoms in a way that causes them to share or either gain/lose enough electrons to achieve a stable configuration.

Question 4

Covalent Bonds

• Electrons are ____between atoms to complete the outer shells, rather than being transferred between them to achieve a stable configuration.
• Occurs where the electronegativity difference is___ between the atoms.

Answer 4

• Electrons are shared between atoms to complete the outer shells, rather than being transferred between them to achieve a stable configuration.
• Occurs where the electronegativity difference is small between the atoms.

Question 5

Single vs Double vs Triple

•Covalent bonds between carbon atoms can be single, double or triple bonds.
•A single covalent bonds allows
•Double bonds and triple bonds are ___and___
•However, there is ____
•This affects the spatial arrangement of chemical group and influences the overall shape of molecules.
•
Get more stability if you can rotate to avoid steric hinderence

Answer 5

•Covalent bonds between carbon atoms can be single, double or triple bonds.
•A single covalent bonds allows rotation of one part of the molecule relative to other around bond axis
•Double bonds and triple bonds are shorter and stronger.
•However, there is little rotation along the bond axis relative to a single bond.
•This affects the spatial arrangement of chemical group and influences the overall shape of molecules.
•
Get more stability if you can rotate to avoid steric hinderence

Question 6

Ionic Bonds/Electrostatic Interactions

(One ionic bond not whole lattice)

• Occurs between atoms that have just one or two electrons in addition to a filled outer shell or are just one or two electrons short of acquiring a filled outer shell.
• Occurs where the electronegativity difference is ____between the atoms.
• Electron____occurs between the atoms.
• Results in ____.
• The oppositely charged ions attract each other and are held together in an ionic bond or an electrostatic interaction.

Answer 6

• Occurs between atoms that have just one or two electrons in addition to a filled outer shell or are just one or two electrons short of acquiring a filled outer shell.
• Occurs where the electronegativity difference is large between the atoms.
• Electron transfer occurs between the atoms.
• Results in electrically charged ions.
• The oppositely charged ions attract each other and are held together in an ionic bond or an electrostatic interaction.

Question 7

Hydrogen Bonds

The hydrogen atom in a hydrogen bond is partly ____ between two relatively _____ atoms such as nitrogen or oxygen.
•The hydrogen-bond donor is the group that includes both the _____ and the_____ itself.
•The hydrogen-bond acceptor is the atom _____________.
•The relatively electronegative atom to which the hydrogen atom is covalently bonded ____ ____ ____ away from the hydrogen atom so that it develops a partial _____ charge (δ+). Thus, it can interact with an atom having a partial ____ charge (δ-) through an ____ ____

Answer 7

• The hydrogen atom in a hydrogen bond is partly shared between two relatively electronegative atoms such as nitrogen or oxygen.
• The hydrogen-bond donor is the group that includes both the atom to which the hydrogen is more tightly linked and the hydrogen atom itself.
• The hydrogen-bond acceptor is the atom less tightly linked to the hydrogen atom.
• The relatively electronegative atom to which the hydrogen atom is covalently bonded pulls electron density away from the hydrogen atom so that it develops a partial positive charge (δ+). Thus, it can interact with an atom having a partial negative charge (δ-) through an electrostatic interaction.

Question 8

Dipole – dipole Interactions &
van der Waals Interactions

• The ____ ____ around any nonpolar atom will fluctuate, producing a flickering dipole.
• Such dipoles will transiently induce an ____________

This interaction generates an attraction between atoms that is very ____

•Molecules with ________dipoles exist too.

Answer 8

•The electron cloud around any nonpolar atom will fluctuate, producing a flickering dipole.•Such dipoles will transiently induce an oppositely polarized flickering dipole in a nearby atom. This interaction generates an attraction between atoms that is very weak.
•
•Molecules with permanent dipoles exist too.

Question 9

Relative Strengths of Interactions

Answer 9

•Typical single C-C bond ~ 85 kcal mol-1 (356 kJ mol-1)
•
•Typical double C-C bond ~ 175 kcal mol-1 (732 kJ mol-1)
•
•Electrostatic interaction between two atoms bearing single opposite charges separated by 3 Å in water (has an energy of 1.4 kcal mol-1 (5.9 kJ mol-1)
•
•H-bonds have energies of 1–3 kcal mol-1 (4–13 kJ mol-1)
•
•van der Waals interactions have energies of 0.5 to 1.0 kcal mol-1 (from 2 to 4 kJ mol-1)

Question 10

First Law of Thermodynamics

The total energy of a______ and _____s constant.

–The energy content of the universe is _____
–Energy can be neither _____ nor ___________
–Energy can take___________ (Ex: – conversion of potential to kinetic energy)

A system is defined as part of the universe _________. Ex – the organism

The rest of the universe is called the_________

Answer 10

The total energy of a system and its surroundings is constant.

–The energy content of the universe is constant.
–Energy can be neither created nor destroyed.
–Energy can take different forms. (Ex: – conversion of potential to kinetic energy)

A system is defined as part of the universe that is of interest. Ex – the organism

The rest of the universe is called the surroundings.

Question 11

enthalpy

measure of

it includes

H=

The total enthalpy, H, of a system cannot be

Change in enthalpy, ΔH, is

Answer 11

The enthalpy (H ) - measure of the total energy of a thermodynamic system (the energy content).

It includes the internal energy (U) required to create the system and the work necessary to establish the volume (V) and pressure (P) of the system.

H= U + pV ; w= PV

The total enthalpy, H, of a system cannot be measured directly.

Change in enthalpy, ΔH, is a more useful quantity than its absolute value:

Question 12

§If ΔH is positive/negative

Answer 12

If + it is an endothermic reaction (heat is absorbed from the surroundings)
§If ΔH is negative it is an exothermic reaction (heat is released to the surroundings)

Question 13

Second Law of Thermodynamics

The total entropy of a system and its surroundings always

Entropy (S) is a measure

The spontaneity of system can not be determined from a knowledge

The true criterion for spontaneity is given by the formula

Answer 13

The total entropy of a system and its surroundings always increases for a spontaneous process. DS>0

Entropy (S) is a measure of the level of randomness or disorder in a system.

The spontaneity of system can not be determined from a knowledge of the system’s entropy change alone.

The true criterion for spontaneity is given by the formula

Question 14

•When DG<0 the reaction is

• When DG>0 the reaction is
• When DG=0 the reaction is
• Gibb’s free energy, enthalpy and entropy are all

Answer 14

•When DG<0 the reaction is exergonic
•When DG>0 the reaction is endogonic
•When DG=0 the reaction is in equilibrium
Gibb’s free energy, enthalpy and entropy are all state functions.

Question 15

Standard State (DGo) has set reference conditions:

Biological Standard State

Answer 15

Standard State (DGo) has set reference conditions:

–Temperature = 298 K (25oC)
–Pressure = 1 atmosphere
–All solutes at 1 Molar concentration ( 1M)

Biological Standard State (DGo’) includes a standard H+ concentration of 10-7 M (pH 7) rather than 1 M.

Question 16

Relationship between Concentration and Gibb’s Free Energy

• Entropy is a function of ___
• Therefore, ____

The equilibrium constant for above reaction is given by Keq

ΔG = ΔG° +

At equilibrium

ΔG°=

Where ln =

Answer 16

• Entropy is a function of concentration
• Therefore, if entropy varies with concentration, so must the Gibb’s free energy

The equilibrium constant for above reaction is given by Keq

ΔG = ΔG° + RT ln [prod]/[reac]

ΔG°= -RT ln(Keq) = -2.3RTlog10 Keq

Where ln = 2.3 log10

Question 17

Acids and Bases

Answer 17

Defined by the Bronsted-Lowry theory

•Acid – Substance that gives up a hydrogen ion (proton)•Base – Substance that accepts a hydrogen ion (proton)

Question 18

pH

Answer 18

• The concentration of H+ ions determines the acidity of the solution.
• It is expressed as pH of the solution

pH = -log[H+]

Negative log10 of the hydrogen concentration expressed in moles per liter (mol/L)

pH scale

Question 19

Dissociation Constant Kd

Answer 19

•The dissociation constant for water is

Kd=[H+][OH-]

[H2O]

•Because water dissociates to a small extent, the concentration of water [H2O] remains the same
•

Kd[H2O] = Kw = [H+][OH-] = 1X10-14

Kw is the ionic product of water

•

Question 20

Strong acids

Question 21

Weak acids

• Weak acids only ____ ____ in solution releasing a fraction of their protons.
• The resulting acid is converted to a ____ ___
• Weak acids have a characteristic ____ ____

Ka =

pka=

Answer 21

• Weak acids only dissociate partially in solution releasing a fraction of their protons.
• The resulting acid is converted to a conjugate base.
• Weak acids have a characteristic dissociation constant Ka:

Ka =[conjugate base][H+] and pKa=-log(ka)

[acid]

Question 22

Buffers

•A mixture of an ____ and ____.
•Causes a solution to resist changes in pH when small volumes of H+ or OH- ions are added.
•Buffers have the greatest buffering capacity when __________
The____ and the _____ of a buffer relative to the pH of the solution determines the effectiveness of a buffer

Answer 22

•A mixture of an undissociated acid and it’s conjugate base.
•Causes a solution to resist changes in pH when small volumes of H+ or OH- ions are added.
•Buffers have the greatest buffering capacity when the pH range is near it’s pKa.
The concentration and the pKa of a buffer relative to the pH of the solution determines the effectiveness of a buffer

Question 23

Henderson-Hasselbalch Equation

Question 24

Buffer Systems in the Human Body and where found

_____

____
____
____

•Salivary system employs 3 buffer systems
–___
–____
–____
•pH ranges between ______(Depends on the__________)
•Drop in pH below _____ results in harm to hard (enamel and dentin) and soft tissues.

Answer 24

• Bicarbonate (Extracellular fluids)
• Hemoglobin (Red blood cells)
• Phosphate (In all cells)
• Proteins (In most cells)

•Salivary system employs 3 buffer systems
–Bicarbonate
–Phosphate
–Proteins
•pH ranges between 6.0 – 7.5 (Depends on the saliva secretion rate)
•Drop in pH below 5.5 results in harm to hard (enamel and dentin) and soft tissues.