Homework 4.  (a practical problem)           Ans to # 3

ANSWERS to Homework 4 =   

1.  0.5 ml = Abs of 0.32, which equals 5 microgram of protein, thus
       the 20 ml homogenate contains (40 x 5) = 200 micrograms of protein.
    Since  the homogenate represents 6 gm of liver and the average liver
       has 25 gm of liver, then if we multiply the 200 ugm of protein by 4.16 
       we should get the amount of protein in the whole liver = 833.33 micrograms

    2. a,  3.b,  4.b,  5.b,  6.c,  and 7.c


1. Shown below is a Bovine Serum Albumin Protein Standard Curve.
It plots the amount of light absorbed for coomassie blue treated
bovine serum albumin against known amounts of the albumin.

Using this curve tell me how much cell protein is in the following
liver tissue homogenate. 

Six gm of rat liver were homogenized in 25 ml of 0.25M HEPES
buffer at pH 7.1.  After centrifugation at 35,000xG, 20 ml of
of supernatant were collected and 0.5 ml of the supernatant
was treated with coomassie blue.  It showed an absorbance of
0.32; how much total protein is in the supernatant fraction of
this liver sample? If the average rat liver weighs 25 gm, how much
soluble supernatant protein might you expect to be able to isolate?

2. The amino acid to the right, at pH 9.3, would have the following charge?

a)  -2
b)  -1
c)  +2
d)  +1
e)  none of these is correct

3. An ampholyte or zwitterion contains ?
  a) 2 carboxyl groups
b) 2 groups of opposite sign
c) 2 amino groups
d) a dextro-rotary group
  e) choose this answer if none of the above is correct

4. When a peptide bond is formed between 2 amino acids?
  a) the R groups all occur on the same side of the bond  
b) free rotation of groups is lost
        c) the new bond length is longer than a C-C
d) the 2 carboxyl ends are linked together
  e) choose this answer if none of the above is correct

5. The aromatic amino acids are those that are negatively charged
at pH's above 7.0, are hydrophilic, and contain only linear,
long chain (aliphatic) side groups?               
a) true             
b) false

6. Life is thermodynamically possible because living things?
        a) increase the degree of order in the universe          
        b) reproduce themselves
  c) release heat to the environment                                 
        d) it carries out only energetically favored reactions
  e) choose this answer if none of the above is correct

7. The energy required by cells to grow, differentiate,
         and reproduce is provided by?
        a) its anabolic reactions               
b) the generation of order inside it
c) its catabolic reactions
  d) condensation reactions            
        e) none of these is correct


Answer to homework # 3

3.1) b        2) c        3) b        4) d        5) a

  6) e [hydrogen bond]        7) c        8) c        9) a