Biochem Course Notes Q And A

Front 1

1.1 Why is the boiling point of water higher then that of other solvents? What about its melting point and its heat of evaporation?

Back 1

- because of the hydrogen bonds
- hydrogen bonds require high energy to break. .

Front 2

1.1 Is the attraction between Na+ and Cl- higher in water or in methanol? why ?

Back 2

Repulsion: F=kq1Q2/ Dr^2
= fm/fh= Dh/Dm = 78/32= 2.5

therefore: 2.5 x better in methanol
- attract 2.5 better in methanol, and repel 2.5 better in water/

Front 3

2 But in the most important reaction of life, the burning of carbon to produce energy. is water a substrate or is it a product.

Back 3

water is both a substrate and product
- hydro carbons burn to give both CO2 and water

Front 4

3.1 Give three very general hydrophilic groups:

Back 4

POLAR
- groups with positive charge
- groups with negative charge

Front 5

3.2 What compartment does oxygen prefer? salt? benzene?

Back 5

Oxygen: hydrophobic
Salt: hydrophilic
Benzene: hydrophobic

Front 6

3.3 How will you tell if a molecule is hydrophobic or hydrophilic?

Back 6

1. polarity
2. if it is charged
3. h-bonds

Front 7

3.4 Where will a molecule that contains both types of groups go?

Back 7

depends on relative amount of each group

Front 8

Q 3.5. If you add D20 to an aqueous solution of a biological molecule, will it exchange with the bound water?

Back 8

there will be D2)s replacing the H2O this is a method used to measure the amount of bound water

Front 9

Why can't you use a membrane to pump solution up a building?

Back 9

practically: osmotic pressure so high that it would break membrane.

theroetically: will want to remove water at the top, causing loss in osmotic pressure

Front 10

What is the osmotic pressure create by 1M protein solution? answer in ATM

Back 10

MM protein= 100 g/mol
1M= 1 mol/L= 100 g/L

pie= cRT
pie= (1) (0.8)x 300= 24 ATM

(1 atm= 10 m)
Therefore 24 ATM = 240 m of water.

Front 11

How do you make a 1 molar protein solution?

Back 11

- USE aa weight= 100
- can't put ten bags of sugar into a bottle of wine.

Front 12

5.1 to work with the content of a cell, you have to break open the cell. This is sometimes done by putting the cell in a hypotonic solution. Explain>

Back 12

the cell has high osmotic pressure and draws in so much water that is explodes/

Front 13

5.2 A plant sprayed with concentrated fertilizer wilts. Why>

Back 13

fertilizer draws out so much water. osmotic pressure is lessened= wilt

Front 14

6.2 what is the value of the term H2) that was left out of the second equation? or, what is the conc. of water?

Back 14

conc= mol/L
water= 1000 g
MM of water= 18= 20 g/mol
Mol/g= 1000/ 18
= 50

Front 15

6.3 what is the conc. of water in a aqueous solution that is 150 nM in NaCl?

Back 15

same = 50
salt is negilible

Front 16

6.4 if a neutral aqueous solution contains 10^(-4) M H+ what is the concentration of OH-?

Back 16

neutral solution has 10 to power of -7 NOTHING ELSE

Front 17

6.5 what is the ratio of H+ to H2O in pure water?

Back 17

10^(-7) / 55 amount og H+ is trivial .

Front 18

C1.2 imagine you are a human robot that approaches carbon two of glycerol from the H and OH bond side.Takes H of carbon 2 in left hand, and OH of C2 in right hand. take OH with mouth. oxidizes it into an aldehyde. Will it produce, D-glyceraldehye, or L? OR A RACEMIC MIXTURE?

Back 18

JUST D-

Front 19

C1.2 What would be the general size of that robot> mm, um, nm, pm?

Back 19

nm

Front 20

WHy is life stereospecific?

Back 20

enzymes, must fit.

Front 21

C1.4 what kinds of enzymatic reactions produce chiral centres?

Back 21

hydrolysis.

Front 22

C1.4 Which enzymes act on both the D and L forms of a compound?

Back 22

those that don't act on the chiral centre

Front 23

C1.5 a. when two hydroxyl groups on adjacent carbons complex with the anion periodate (IO4-) the reagent oxidatively cleaves the c-c bond between two carbons. Both OHs must be in the plane of the C-C bond. Will this ion cut the four compounds identically?

Back 23

yes!

Front 24

C 1.5b Assume that the first molecule above, L-glucose, has the 3D structure depicted by the drawing; we will call this a front view. What is the shape of the backbone if you were viewing it from the side (imagine that you are in the plane of the paper to the right or left of the molecule: Line? Zig-zag? Circle? Spiral? Helix?


Back 24

circle

Front 25

C2.1 a How does glucose conc. compare to 1) H+ 2) water?

Back 25

Water = 1000/18 = 55 M : about 10,000 x more concentrated. H+ : pH 7 = 10-7 M : about 10,000 x less concentrated. Definitely enough water to make H-bonds with glucose!

Front 26

Q#2.1b Assume that you need 400 g of glucose a day to stay alive.
How long will you survive using just the glucose found in your blood?
Your blood volume is 5 l. Do this problem using ONLY the information found on this page.

Back 26

blood contains: 5mM x 5 L = 25 mmol

Mol Weight C6(H2O)6 = (6x12=72) + (6x18 = 108) = 180 F 200 (rounded off for quick math).

400 g/ 200g = 2 mol / day
= 2000 mmol//day
2000/ 25 hr day= 80 mmol/hr

80/25 = 1/3 of an hour!

Front 27

Q#2.2aWithout going back to previous page: What is the weight of all the glucose (5 mM) in your blood (5l)?

Back 27

Even with the structures available, it is not worth changing the method of estimation: do as in #2.1b: 25 mMol x “200" mg/mMol = 5,000 mg = 5g

Front 28

fructose sugar is: freely soluble in water? quite soluble? poorly soluble? slightly soluble? more soluble in alcohol than in water?

Back 28

freely soluble
- all of the OH groups - polar groups

Front 29

Q#2.4.2b The crystalline form of glucose is á-D-glucopyranose. Since it is prepared from a solution that contains both anomers, why is the crystalline form of glucose á-D-glucopyranose and not a mixture of the two anomers?

Back 29

- constantly changing
- crystals are defined as deposits of the same structure that form when a product precipitates.
- therefore the alpha anomer must have a lower solubility and keep precipitating out.
- more and more alpha will be made from beta to keep equilibrium.

Front 30

#2.4.2c Suppose you wanted to prepare crystalline â-D-glucopyranose. What would you propose?

Back 30

try and make the beta glucopyranose less soluble

Front 31

Q#2.4.2d What is the biggest atom that you could fit inside a pyranose ring: H, Li, Na, K, Rb, Cs, Fr ?

Back 31

NONE

Front 32

Do Q 2.4.3a

Back 32

answer in book

Front 33

Q#2.4.3b Free fructose (the sweet taste of honey) is mainly â-D-pyranose yet the fructose found in most biological compounds is ONLY the furanose form (illustrated above and in most textbooks {359}). Explain.

Back 33

in book