Question 1. Monotremes use the monosaccharide fucose as their milk sugar; eutherian mammals (like us) use the disaccharide lactose as theirs

a. (5 pts) On the structures of these two sugars below, please label: i. the glycosidic bond ii. the modified “group” on fucose

b. (4 pts) What monomers make up the lactose disaccharide? Include the identity of the two monomers and the proper bond designation betveh–them.

c. (3 pts) Hypothesize the role of the modification seen on Fucose. Focus on chemistry not complex biological function.

d. (5 pts) The inability of some individuals to digest lactose is called “lactose intolerance” and leads to digestive distress as the result of undigested sugar accumulating in the gut. This condition stems from the reduced expression of an enzyme that breaks a particular kind of bond. Which bond in lactose do you think is the problem (and why) 3-5 sentences?

 

Question 2. Hormone that stimulates growth binds a receptor tyrosine kinase in the membrane of its Question 8 A target cells opts)

a. (0pts) Why does the hormone require a receptor to work properly? Focus on the cell membrane in vour answer (1-2 sentences)
b. (opts) Explain why a receptor tyrosine kinase contains both a kinase domain and a SH2 domain (2-3 sentences)
c. (7pts) A mutation discovered in this process leads to the Sos protein having a much lower affinity for binding Ras. Explain the effect this would have on the signaling process and protein transcription. Predict the effect of this mutation on organismal growth (5-7 sentences)

Question 3 The amino acid histidine is very important biologically and can also be used as a buffer

H3N—CH I CH2 1 H C—NN 1\ , CH CH —N, H A
OOH H2N—CH I CH2 z H C—N 11 NCH CH —N .1
OOH H3N—CH I CH2 1 H C—NN II + CH CH—N’
COO-_± I H3N—CH I CH2 1 H C—NN 11 CH CH—N,
co971/ I H2N—CH I CH2 1 H C—NN 11 CH CH—N,
B C D E
a. (4 pts) The structures above show forms of histidine. Using the letters “A, B, C, D, E” to name the forms, fill in the blanks in the acid/base equilibria below.

b. (4 pts) The pl of histidine is 7.6. What is the predominant form of histidine at pH 7.6 and what is its net charge? Give your answer as “A, B, C, D, E.”

c. (5 pts) There are two Henderson-Hasselbach equations you cou. win., Lui ifistidine buffer at pH 7.6. Write them both, using the relevant term pKi, pK2, or pKR, and the correct letters (A, B, C, D or E) for the conjugate acid and base forms.

d. (3 pts) Using “D” as the conjugate base species, calculate the ratio of conjt____Ilatel)asep its weak acid at pH 7.6. Show all wnrk

 

 

Question 6 After passing biochemistry with an A, you accept a position in a biochemistry lab that studies oxygen transport in limpets (a type of mollusk). You are tasked with characterizing the copper containing oxygen transport protein known as Hemocyanin. a. (3pts) How are the alpha helices that make up hemocyanin held together? Identify the atoms that interact and the nature of their interaction)-3 sentences
b. (8pts) A segment of the hemocyanin primary structure is of particular interest: TTYHIHKSC Pick one of the residues that has an ionizable R group for part C. Write the full name, pKr and charge at pH=8.0, draw the R group

c. (6pts) Pick one of the residues (from the peptide in part c) that does not have a charged R group for part D. Write the full name and net charge at pH=8.0, draw the R group

 

 

Question 7 Hemoglobin utilizes quaternary structure to transport oxygen efficiently.

a. (lOpts) A mutant version of hemoglobin (Heme M) lacks the ion pairs at the interface between the a and 5 subunits. Explain what effect the lack of these ion pairs has on 02 transport. As part of your explanation you must include your hypothesized effect on Heme M’s p02 and its ability to perform its normal function. 6-8 Sentences  nots1 Do you predict Heme M to be a lethal mutation? Why or why not? (2-3 sentences)