2. Within a cellular environment, draw the sequence of events that occur when extracellular LDL binds to the LDL receptor through generation of cholesterol. Represent the sequence of events numerically. Label all relevant cellular structures. Details to include: components of the endocytic pathway and the pH of the compartments representation of the LDL binding domain and beta-propeller domain of the LDL receptor. Conformation of LDL receptor Use a "+"to indicate when histidine(s) become protonated on the LDL receptor. V-ATPases

S-adenosylmethionine is an activated carrier molecule that transfers which of the following groups? the carboxylic acid group (with one carbon) the phosphate group (with zero carbons) the glucose group (with six carbons) the methyl group (with one carbon) the acetyl group (with two carbons)

2. Provide a short phrase or word to anwer each of the following: (a) What is the organ where glycogen is stored in humans? (b) What type of enzyme digests carbohydrates? (c) What is the name of the pathway that corresponds to Stage 2 for lipids? (d) Name the pathway that corresponds to Stage 3, assuming aerobic conditions (e) Name the pathway that transforms pyruvate into ethanol and carbon dioxide (f) What is the number of reactions in glycolysis? (g) What is the net gain of ATP in glycolysis? (h) Name the product when pyruvate is metabolized anaerobically.

3. The image below depicts 2,3-bisphosphoglycerate depicted in dark gray, and ß subunits are depicted in light gray. (BPG) bound to hemoglobin. The a subunits are BPG (a) Briefly explain how BPG regulates oxygen transport by hemoglobin and describe the critical chemical properties of BPG and its binding pocket.

9. In E. coli the synthesis of phosphatidylethanolamine directly involves: acyl carrier protein. biotin. CDP-choline. phosphatidylglycerol. serine.

2. The diagram to the right shows the change in the structure of the C-terminal portion of each of the ẞ-subu- nits of human hemoglobin (HbA) in the oxyHb to deox- yHb or R-to-T transition. The hydrogen bonding interac- tion of the C-terminal ẞHis 146 residue with the side chain of Asp94, highlighted by the red ellipse, has been shown to be responsible for a major portion of the proton uptake associated with the Bohr effect. Treatment of HbA with the enzyme carboxypeptidase A (CPA) results in loss of the C-terminal ẞHis 146 and ẞTyr145 residues of the ẞ- subunits. (a) ( ) Draw a Hill plot [log(Y/[1-Y]) vs. log(pO2), Y = fraction of heme groups occupied by O2] to compare the values of the Hill coefficient nн and the O2-binding affinity at pH 7.4 of normal HbA before and after treat- ment of with CPA. (b) (' ) How will the plot for CPA-digested HbA change at pH 7.2? (c) 1 Hi5146 HN- ✓ Low PK B-chain. CH2 CH-NH-CO-CH-NH- CH₂ Tyr145 он HbO2 or R state Туг145 CH-CH2- OH co NH CH CH₂ His…

5. Shown below are the first steps in the mechanism of a cysteine protease, which catalyses amide bond hydrolysis in a similar manner as serine proteases. (a) Complete this mechanisms, and (b) sketch the approximate reaction coordinate diagram for this catalyzed reaction relative to the uncatalyzed proteolysis. HN N HN cysteine protease

2. “Most enzymes are gene-encoded proteins." Using this lens, explain: A) effects of increased temperature on the rate of enzymatic reactions, and B) effects of decreased temperature on enzymatic reactions, and C) importance of optimal pH and ionic strength on enzymatic reactions.

2. What is the chemical reaction that lactase catalyzes? Write it below in word form as well as in its chemical equation.

Which of the following steps in glycoylsis is a substrate level phosphorylation? 1,3-BPG --> 3PG GAP --> 1,3-BPG DHAP --> GAP --> Glc-6-P