Download In order to gain 1lb in body fat over 1 year a person would have to

NST103 Spring2006
Midterm Exam II (5pages, 100pts)
Name____________________________SID___________
I. (@3 pts ea = 12pts) Choose the SINGLE best answer to each of the following questions:
In order to gain 1lb in body fat over 1 year a person would have to consume on average
a. +15 kcal/day
b. +10 kcal/day
c. +5 kcal/day
d. +1 kcal/day
Answer B
Which of the following is NOT a function of insulin
a. decrease lipolysis
b. increase glucose uptake
c. increase ketogenesis
d. decrease glycogen breakdown
Answer C
Which of the following is the best indicator of the fatty acid makeup of the diet?
a. Fatty acid composition in adipocyte
b. Free fatty acid level in plasma
c. TAG composition in adipocyte
d. Number of circulating CM
Answer A
Choose the phosphate bond which releases the most energy when hydrolyzed
a. ATP  ADP + Pi
b. Pyrophosphate  2 Pi
c. ADP  AMP + Pi
d. AMP  Adenosine
Answer C
II. (7pts) Fill in the blank with the appropriate word or phrase.
adrenal cortex
Tissue which secretes glucocorticoids
bomb calorimeter
Instrument used to measure energy in food where w=0
NAD or NADH
Universal electron carrier made from niacin
FMN or FAD
Universal electron carrier made from riboflavin
Pellagra
Niacin deficiency disease
Araboflavinosis
Riboflavin deficiency disease
Glycogenin
Protein required for initiation of glycogen synthesis
1
III. (8pts) Match the following proteins to their function. You may use one answer more than once but use
only one answer for each blank.
Apo A-I
Apo B-48
Apo B-48
Apo A-I
Apo C-II
Apo E or Apo B-100
Apo B-100
Apo C-II
Apo E
Is required for excretion of nascent CM from enterocyte
Recognizes and binds to HDL receptor
Activates lipoprotein lipase activity
Binds to LDL receptor for liver uptake
IV. (12pts) Match the lipoprotein particles with the statements that follow. You may use one answer
more than once but use only one answer for each blank.
CM
CM
VLDL
LDL
CM
HDL
HDL
LDL HDL VLDL
Is synthesized solely in intestinal cells
Delivers endogenous TAG from liver to peripheral tissues
Is formed in blood
Delivers dietary lipid from intestine to peripheral tissues
Cholesterol is transferred via this molecule to other circulating lipoproteins
Delivers cholesterol from extrahepatic tissues to liver
V. (5pts) Match enzymes to their proper functions.
A.
B.
C.
D.
E.
B
E
D
A
C
hormone sensitive lipase (HSL)
lecithin cholesterol acyltransferase (LCAT)
diacylglycerol acyltransferase (DGAT)
lipoprotein lipase (LPL)
cholesterol ester transfer protein (CEPT)
conjugates cholesterol with fatty acid in HDL particles
interchanges cholesterol esters among different lipoproteins
releases FFA from digests TAG in VLDL
releases FFA from TAG in adipose tissue
catalyzes formation of TAG in adipose tissue
VI. (2pts) Fill in the blanks
Thiamine is an essential nutrient. Its coenzyme form is
Thiamine pyrophosphate (TPP) and it is
involved in decarboxylation
of keto-acids. Examples of enzymes requiring this coenzyme
include
pyruvate dehydrogenase (PDH)
and -ketoglutarate dehydrogenase (KDGH).
2
VI. (18pts) State whether each of the following statements is TRUE or FALSE. In either case briefly
explain why.
1. (3pts) The brain uses ketone bodies and glutamine as sources of energy
FALSE (1 pt). KB are used for a portion of brain energy (1 pt) but glutamine is not (1 pt)
2. (3pts) Pantothenic acid is an essential nutrient.
TRUE (1 pt). AcCoA (1 pt) and Acyl carrier protein (1 pt) both contain pantothenic acid as part of
their chemical structure, and both of these pantothenic acid-containing molecules are needed for essential
metabolic reactions
3. (6pts) Upon starvation plasma glucose levels spike, while ketone and FFA levels remain constant.
Provide an appropriate graph as part of your answer.
FALSE (2 pts) Glucose decreases (1 pt) then levels off (1 pt), KB increase and stay high (1 pt),
FFA increase to a lesser extent than KB and then level off (1 pt)
Plasma
Concentration
KB
Glucose
FFA
Duration of Starvation
4. (3pts) PFK-2 is an important modulator of glycolysis
TRUE (1 pt). PKF-2 activation produces F-2,6 BP (1/2 pt) which is an activator of PFK-1 (1/2
pt), an important regulatory step in the glycolytic pathway (1 pt).
5. (3pts) Glycogen degradation in some tissues can cause blood glucose to increase, while degradation of
glycogen in other tissues does not directly increase blood glucose.
TRUE (1 pt). Glycogen degradation in liver increases blood glucose (1 pt), glycogen degradation
in muscle does not (1 pt).
3
IX. (37pts) Provide brief answers to the following questions:
1. (4pts) Give ONE physiological example of glucose sparing. What is the significance of this example
to whole body energy metabolism?
Glucose sparing is the utilization of substrates other than glucose for energy by tissues that are not
obligatory glucose users. Examples: muscle uses FA predominately for energy (2 pt), sparing glucose
for tissues (such as brain, retina and RBS’s) that require glucose for energy (2 pt), and sustaining life.
2. (4pts) Describe the mechanism by which thyroid hormone exerts its effect on BMR
Increases BMR (2 pt) by uncoupling and increasing Na/K ATPase activity (2 pt).
3. (4pts) What is the importance of the anaplerotic reactions of the TCA cycle?
Anaplerotic reactions refers to the flow of intermediates out of “cycle” and their replenishment via
alternative synthetic reactions (1 pt). As an example, if OAA or Malate were used in reactions other than
those of the TCA cycle, the concentration of these intermediates would drop. Unless replenished via
increased influx via a prior TCA cycle intermediate, the OAA concentration would eventually get too low
to allow condensation with acetyl CoA (1 pt). This would effectively stop metabolism of acetyl CoA via
the TCA cycle (2 pt).
4. (6pts) Describe the factors that are responsible for delivery of dietary TAG primarily to the adipose
tissue.
Insulin will preferentialy activate the LPL in the adipose. LPL will recongize apo-CII and begin
hydrolysis of TAG into FFA which they will enter the adipocyte via diffusion. FABP will maintain the
gradient of FFA so that more diffusion can occur. Formation of the glycerol backbone via glycolysis of
intaken glucose and activation of DGAT promote TAG formation in the adipose (this last part not
required for full credit).
5. (6pts) How do insulin and acylation-stimulating protein work together to promote storage and retention
of TAG in adipose tissue?
Both insulin and ASP stimulate glucose uptake into cells (1 pt), thus inducing glycolysis in the
cell. This provides the glycerol backbone (glycolytic intermediate) needed for esterification of FFA to
TAG (1 pt). ASP promotes TAG formation in the adipocytes by activating the rate-limiting enzyme in
TAG re-esterification (diacylglycerol acyl transferase, DGAT) (2 pt). Insulin suppresses the activity of
HSL impairing TAG hydrolysis. (2 pt)
4
6. (3pts) Explain the significance of hexokinase in the glycolytic pathway
Once glucose is metabolized via hexokinase to G-6-P (1 pt) it must be metabolized within that cell
(unless the phosphatase exists also within that cell) since G-6-P can’t cross membranes (2 pt).
7. (3pts) What role does magnesium play in metabolism.
Required for all reactions involving ATP (3 pt)
Cellular energy metabolism
Synthesis of nucleic acids and proteins
Signaling
Function of ion channels
8. (4pts) When the cells of an individual are in low energy status, the enzyme AMPK is activated.
Explain how low energy status activates AMPK.
When a cell is in low energy status [ATP] is reduced while [AMP] is increased (2 pt). AMP
activates AMPK via two mechanisms (1) complexes form between AMP and AMPK, and between AMP
and AMPKK (1 pt), and (2) phosphorylation of AMPK via the activated AMPKK. (1 pt)
9. (3pts) Why is thiamine repeatedly phosphorylated and dephosphorylated?
dephosphorylated to enter/exit cells (1.5 pg) , phosphorylated to be active (1.5
pt)decarboxylation rxns, transketolation rxns
5