Chemical Bonds & Buffers

Question 1

What is a lysate?

Answer 1

general term describing the internal parts of a broken apart cell

Question 2

What is the equation for Gibb’s free energy?

Answer 2

deltaG=deltaH - TdeltaS

Question 3

What is anabolism vs catabolism? Is energy used or produced?

Answer 3

anabolism is building things up (uses energy) catabolism is breaking things down (releases energy)

Question 4

What are considered the energy currencies of the cell? Why?

Answer 4

ATP and NADH

carry energy and when broken apart can be used to power the cell

Question 5

What is the difference between endergonic reactions and exergonic reactions? (in terms of ATP)

Answer 5

endergonic use ATP, exergonic make ATP

Question 6

What laws do all chemical/biochemical phenomena follow?

Answer 6

thermodynamics

Question 7

What do enzymes do?

Answer 7

speed up reactions by lowering the activation energy

Question 8

What are the most common elements in organic molecules?

Answer 8

sulfur, phosphorous, oxygen, nitrogen, carbon, hydrogen (SPONCH)

Question 9

When carbon has four single bonds what are the bond angles?

Answer 9

tetrahedral, 109.5

Question 10

When carbon has a double bond what are the bond angles?

Answer 10

planar, 120

Question 11

Why do some biological interactions occur between molecules not covalently bonded?

Answer 11

allows for continual forming/breaking, allows for reversible association

Question 12

What are some things that make water important?

Answer 12

most all biological molecules assume their shape in response to water, most biochemical reactions happen in water, it also often participates in reactions, oxidation of water is also important for photosynthesis

Question 13

Why is water such a good solvent for polar compounds?

Answer 13

asymmetry of the water molecules makes a significant dipole moment

Question 14

What is the hydrophobic effect?

Answer 14

non polar groups will orient themselves to minimize their contact with water

Question 15

How do lipids orient themselves when in water? How does this affect entropy?

Answer 15

dispersed, clusters, micelles

entropy is lowest when the lipids on are their own and it increases as they cluster and when they form a spherical micelle entropy is increased even more

Question 16

Why do micelles have higher entropy than dispersed lipids?

Answer 16

more water molecules are ordered by the fatty acid tails but in micelles the tails are completely seperate from water, therefore they are not being ordered

Question 17

What does amphiphilic mean? How will they orient themselves?

Answer 17

contains both polar and non polar sections

maximize polar contacts with water and the non polar parts w/other non polar parts

Question 18

How can hydrogen bonds be broken?

Answer 18

heat or high salt

Question 19

Are hydrogen bonds stronger than covalent bonds?

Answer 19

no but they still have a big effect (boiling point)

Question 20

What is proton hopping?

Answer 20

a very small portion of the water is dissociated and a proton is picked up by another water molecule, this proton is passed between water molecules

Question 21

What is the equation used to describe the ionization of water? What does the 55.5 mean?

Answer 21

K=[H+][OH-]/55.5

55.5 is the molarity of pure water, we susbtitute it because such a small amount of water is ionzied

Question 22

What is the autoionization of water?

Answer 22

Kw= 1.0 x 10^-14

Question 23

How can you calculate pH?

Answer 23

pH = -log[H+]

Question 24

How can you calculate [H+] using pH?

Answer 24

[H+] = 10^-pH

Question 25

How can you find the pKa?

Answer 25

pKa = -logKa, also the pH where acid is half ionized [A-]=[HA]

Question 26

What is the buffering capacity of a weak acid with a pKa of 4.76?

Answer 26

3.76 to 5.76 (+- 1 from pKa)

Question 27

What is the henderson-hesselbach equation?

Answer 27

pH = pKa + log[A-]/[HA]

Question 28

What are polyprotic acids?

Answer 28

weak acids with more than one ionizable group

Question 29

How can you find the pH after adding 0.1 mol NaOH to 1 mol acetic acid?

Answer 29

naoh reacts completely cause its a strong base and it makes 0.1 mol acetate leaving 0.9 mol acetic acid, plug these numbers as well as the pKa into HH equation will give you pH

Question 30

What are examples of some biological buffers?

Answer 30

phosphate, carbonate, protein and peptides

Question 31

How would you approach a problem using an acid with multiple pKas and you are trying to find the final pH when 10mL of a strong acid is added to the buffer with a given pH?

Answer 31

using the given pH choose the pKa that we will be buffering in (similar), convert everything to mol/L then add the strong acid added to the compound with more H+ and subtract it from the one with less, plug into HH