8 Questions on Life Sciences - Exam 2 | BCMB 4020 | Exams Biology

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Last 4-digit 810:

Biochemistry 4020/6020

Second Examination, March 1, 2013

1.25 - 2.15 pm, C127, Life Sciences

This examination represents 20% of the final grade. Answer all four questions.

The number of total points = 100. The value for each question is given in parenthesis.

Question 1.

Fatty acid biosynthesis takes place in the cytoplasm but the carbon is provided by the

mitochondria. Draw a cycle to show how carbon is transported out of, and back into, the

mitochondria while supplying the carbon for fatty acids (give the names of metabolites

but structures and enzymes are not required) (14). How does glucose feed into this cycle

(2)? What is the name of the key ATP-dependent enzyme that generates acetyl CoA for

fatty acid synthesis (2)? Draw the structures of the carbon substrate and products of this

enzyme (2).

(20 pts total)

Question 2.

You are starving. With the help of a diagram, explain how glucagon enables

triacylgycerides to be used as an energy source while preventing the synthesis of fatty

acids (16). With the help of dotted or dashed lines and arrows on your diagram, show

how insulin has the opposite effect (6). Briefly describe the roles of malonyl CoA in fatty

acid biosynthesis both as a pathway intermediate and as a regulatory molecule (4).

(26 pts total)

Question 3.

Draw the oxidative branch of the pentose phosphate pathway (enzymes and structures are

required) (12)? Which metabolites regulate the activity of this pathway, how do they

accomplish this, and why (8)? What are the two main functions of the pentose phosphate

pathway and how are these functions achieved at the same time (the name(s) of

enzyme(s) and structures of all additional substrates/products are required) (8).

(28 pts total)

Question 4.

The β-oxidation pathway oxidizes the CoA-derivatives of saturated Cn fatty acids, where

n is even, to acetyl CoA, which then enters the TCA cycle. What additional enzymes

(and include structures of their substrates and products) are required to metabolize Cn

acyl CoAs when n is odd? Use heptadecanoic acid (C17:0) to answer this question (14).

What additional enzyme (and include structures of its substrate and product) is required

to metabolize unsaturated fatty acyl CoAs? Use oleic acid (C18:1, cis Δ9) to answer this

question (12).

(26 pts total)

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NAME:

Last 4-digit 810: 1 Biochemistry 4020/ Second Examination, March 1, 2013 1.25 - 2.15 pm, C127, Life Sciences This examination represents 20% of the final grade. Answer all four questions. The number of total points = 100. The value for each question is given in parenthesis. Question 1. Fatty acid biosynthesis takes place in the cytoplasm but the carbon is provided by the mitochondria. Draw a cycle to show how carbon is transported out of, and back into, the mitochondria while supplying the carbon for fatty acids (give the names of metabolites but structures and enzymes are not required) (14). How does glucose feed into this cycle (2)? What is the name of the key ATP-dependent enzyme that generates acetyl CoA for fatty acid synthesis (2)? Draw the structures of the carbon substrate and products of this enzyme (2). ( 20 pts total ) Question 2. You are starving. With the help of a diagram, explain how glucagon enables triacylgycerides to be used as an energy source while preventing the synthesis of fatty acids (16). With the help of dotted or dashed lines and arrows on your diagram, show how insulin has the opposite effect (6). Briefly describe the roles of malonyl CoA in fatty acid biosynthesis both as a pathway intermediate and as a regulatory molecule (4). (26 pts total) Question 3. Draw the oxidative branch of the pentose phosphate pathway (enzymes and structures are required) (12)? Which metabolites regulate the activity of this pathway, how do they accomplish this, and why (8)? What are the two main functions of the pentose phosphate pathway and how are these functions achieved at the same time (the name(s) of enzyme(s) and structures of all additional substrates/products are required) (8). (28 pts total) Question 4. The β-oxidation pathway oxidizes the CoA-derivatives of saturated Cn fatty acids, where n is even, to acetyl CoA, which then enters the TCA cycle. What additional enzymes (and include structures of their substrates and products) are required to metabolize Cn acyl CoAs when n is odd? Use heptadecanoic acid (C17:0) to answer this question (14). What additional enzyme (and include structures of its substrate and product) is required to metabolize unsaturated fatty acyl CoAs? Use oleic acid (C18:1, cis Δ 9 ) to answer this question (12). ( 26 pts total )

NAME:

Last 4-digit 810: 2 Biochemistry 4020/ Second Examination, March 2, 2012 1.25 - 2.15 pm, C127, Life Sciences This examination represents 20% of the final grade. Answer all four questions. The number of total points = 100. The value for each question is given in parenthesis.

Draw the oxidative branch of the pentose phosphate pathway (enzymes and structures are required) (12)? Which metabolites regulate the activity of this pathway, how do they accomplish this, and why (8)? The primary functions of the pentose phosphate pathway are to produce ribose- 5 - phosphate and NADPH. How are both of these achieved at the same time (the name(s) of enzyme(s) and structures of all additional substrates/products are required) (8)? (28 pts total)
During CO 2 fixation in photosynthesis, what is the product when ribulose-1,5- bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the addition of 6 moles of CO 2 to 6 moles of ribulose-1,5-bisphosphate (RuBP)? (2)? Show how this product is converted to 1 mole of glucose and how 6 moles of RuBP are regenerated (20). Give the names of all intermediates (no structures are required) and the names or numbers of all of the enzymes. Clue – in addition to Rubisco, seven enzymes are required to produce glucose, and using the intermediates that remain after glucose production, another seven enzymes are used to convert those intermediates to RuBP. (22 pts total)
Draw the pathway by which two molecules of acetyl CoA are converted to a C-4 unit (butyryl-S.ACP). Include structures and the names of the enzymes involved (20). Why is a malonyl (C-3) unit used as an intermediate (2)? Write the overall equation by which palmitic acid is produced from acetyl CoA (2). (24 pts total)
Show how ketone bodies are generated from acetyl CoA (names of enzymes and structures are required) (10)? Where are they produced and what is their function (4)? Which intermediate in the formation of ketone bodies is also used for the synthesis of cholesterol (2)? What is the first enzyme in the pathway of cholesterol biosynthesis and what reaction does it catalyze (structure of the product is required) (4)? Why is this enzyme of medical significance (2)? Draw the structure of cholesterol (4). (26 pts total)

8 Questions on Life Sciences - Exam 2 | BCMB 4020, Exams of Biology

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