NST 103: MIDTERM 3 Flashcards
What is HMG-CoA ?
- HydroxyMethylGlutaryl-Coenzyme A
- it is an intermediate in ketone body synthesis
ketone bodies are synthesized in mitochondria
Why is it important that ketone bodies are synthesized in the mitochondria ?
- this is important because production of acetyl-CoA, the substrate for synthesis of ketone bodies, occurs in the mitochondria via β-oxidation of fatty acids
ketone bodies are synthesized in mitochondria
What is acetyl-CoA ?
- acetyl-CoA is a metabolite derived from glucose, fatty acid, and amino acid catabolism. During glycolysis, glucose is broken down into two three-carbon molecules of pyruvate.
How is acetyl-CoA carboxylase regulated ?
- activated by citrate
- inhibited by long chain acyl-CoA
- inhibited by AMPK
- activated by insulin
all are true
Which of the following is false about **chylomicron metabolism **?
A) Uptake by hepatocytes is via interaction of apoB-48 with the LRP
B) Uptake by hepatocytes is via interaction of **apoE **with **LDL receptor **
C) The majority of **TAG **in chylomicron is hydrolized in the capillary of adipose tissue
D) Chylomicron remnants does NOT contain ApoC-ll
E) Chylomicron is generated from LDL in the liver
E) Chylomicron is generated from LDL in the liver
A-D are true about chylomicron metabolism
apoB-48 = shorter form of apo B (chylomicrons and their remnants contain one molecule of apoB-48)
LRP = LDL receptor-like protein (Chylomicron remnant receptor)
apoE = apolipoprotein E
LDL = low-density lipoprotein
TAG = triacylglycerol
apoC-II = apolipoprotein C-II
Which lipoprotein particles have higher triaglycerol percentage ? Choose the right order.
choices: IDL, LDL, CM, HDL
CM > IDL > LDL > HDL
CM = chylomicron
IDL = intermediate density lipoprotein
LDL = low-density lipoprotein
HDL = high-density lipoprotein
Which particle delivers cholesterol to peripheral tissues ?
LDL (low-density lipoprotein)
They bind to a specific cell receptor (LDL-receptor), and after endocytosis the intracellular cholesterol will be used to build cell membranes and to synthesize other molecules (biliary acids, hormones). The cholesterol present in peripheral tissues is taken up by high-density lipoproteins (HDL) and transferred to LDL.
T/F: Activation of one fatty acid requires two ATP equivalents of energy.
TRUE
T/F: Entry of fatty acids into the mitochondria is regulated by malonyl-CoA.
TRUE
T/F: Glucagon can inhibit HSL activity in humans.
FALSE
HSL = hormone-sensitive lipase
Several hours after a meal, insulin levels decrease, resulting in:
Increased B-oxidation as the major source of energy in muscle and adipose tissue.
Which of the following are activator(s) of mTOR signaling ?
A) Insulin signaling
B) Glucose
C) Leucine
D) Cholesterol
E) Glucagon signaling
Select all that apply
**A) Insulin signaling
**B) Glucose **
C) Leucine
Which of the following is true in regards to the Ping Pong reaction ?
A) APALP is required as a coenzyme
B) The transaminase enzyme can bind to both substrates at the same time
C) A keto acid accepts the NH2 group to form a new amino acid
D) The purpose is to expend the energy after a high protein meal
E) Involves formation of a Schiff base
Select all that apply
A) APALP is required as a coenzyme
C) A keto acid accepts the NH2 group to form a new amino acid
E) Involves formation of a Schiff base
Which of the following is true ?
A) Reactions that produce ammonia are often coupled with reactions that reincorporate it
into an amino acid because our body has no way to excrete the toxic metabolite
B) Alanine and glutamine are favored as “nitrogen carriers” over glutamate, since glutamate can be neurotoxic at high levels
C) Citrulline and arginine combine to form Argininosuccinate in the third step of the urea cycle
D) Pyridoxine is a non-essential nutrient
B) Alanine and glutamine are favored as “nitrogen carriers” over glutamate, since glutamate can be neurotoxic at high levels
T/F: In the postprandial state HSL is active in adipose tissue.
**FALSE **
T/F: Biotin is involved in the generation of Acetyl-ACP.
FALSE
T/F: NADPH is used for ketone body synthesis
FALSE
T/F: Citrate is an allosteric inhibitor of Acetyl-CoA Carboxylase.
FALSE
T/F: During fasting, cAMP signaling results in phosphorylation of HSL by PKA activates
lipolysis
TRUE
T/F: CPT1 is activated by high levels of malonyl-CoA.
FALSE
T/F: Glutamate is the only amino acid that can undergo deamination.
TRUE
FILL IN THE BLANK
The rate-limiting step of the pentose phosphate pathway is catalyzed by ________________, which produces ________________.
- glucose-6-phosphate dehydrogenase
- NADPH or 6-Phosphogluconolactone.
FILL IN THE BLANK
When cholesterol levels are low, _____ moves to ER and then golgi to get cleaved, which then acts as a transcription factor to increase the transcription of _______ reductase and _______ (enzymes)
- SREBP
- HMG-CoA reductase
- LDL receptor
FILL IN THE BLANK
When cholesterol levels are low, _____ moves to ER and then golgi to get cleaved, which then acts as a transcription factor to increase the transcription of _______ reductase and _______ (enzymes)
- SREBP
- HMG-CoA reductase
- LDL receptor
FILL IN THE BLANKS
In amino acid metabolism, _____ is an important coenzyme required to form ____ intermediates involved in ____ reactions.
- PALP/Vitamin B6
- Schiff base
- transamination
SHORT ANSWERS: Reverse Cholesterol Transport
Which tissue is the major site for HDL production? (1)
LIVER
SHORT ANSWERS: Reverse Cholesterol Transport
Briefly explain how HDL takes up cholesterol from peripheral cells? (2)
A1 on HDL binds ABCA1 on peripheral cells, allowing cholesterol uptake into HDL.
SHORT ANSWERS: Reverse Cholesterol Transport
What is the enzyme that esterifies the cholesterol in HDL? What activates this enzyme? Where does the fatty acid for the esterification come from? (3)
- LCAT.
- ApoA1.
- Lecithin on peripheral cell membrane.
SHORT ANSWERS: Reverse Cholesterol Transport
What are the 2 fates of cholesterol taken up by HDL? In other words, where does the cholesterol go? Make sure to mention proteins involved that are discussed in the class. (4)
Transferred to VLDL/IDL/LDL by CETP in exchange for TAG.
Taken up by the liver via SR-B1, converted into bile and secreted into the intestine.
SHORT ANSWERS: Urea Cycle
What is the purpose of the urea cycle? Why is it important? (2 pts)
The purpose of the urea cycle is to excrete NH4+, produced from protein
catabolism. The urea cycle is important because NH4+ is toxic.
SHORT ANSWERS: Urea Cycle
Which intracellular compartment(s) are required for the urea cycle (i.e. in which cellular compartment(s) does the urea cycle take place)? (1 pt)
Mitochondria and cytosol
SHORT ANSWERS: Urea Cycle
How many nitrogen groups are in urea? Where are these nitrogen groups derived from? (2 pts)
The two nitrogen groups are from NH4+ (carbamoyl phosphate) and
aspartate
SHORT ANSWERS: Urea Cycle
In what conditions is the urea cycle upregulated? Explain why these conditions stimulate the urea cycle (2pts)
High protein diet - amino acids are used as fuel (broken down) because of abundance
Prolonged starvation - muscle proteins are broken down for energy
(glucose sparing)
SHORT ANSWERS: Urea Cycle
The urea cycle produces a byproduct that can be shuttled into the gluconeogenesis pathway. What is this intermediate? (1 pt)
Fumarate
Which of the following will not increase urea cycle enzymes?
A) Low protein but adequate energy diet
B) High protein diet
C) High muscle catabolism
D) Starvation
Low protein but adequate energy diet
Which intermediate links the urea cycle to the TCA cycle?
A) Aspartate
B) Fumarate
C) Alpha-ketoglutarate
D) Citrate
E) Oxaloacetate
Fumarate
Which intermediate links the urea cycle to the TCA cycle?
A) Aspartate
B) Fumarate
C) Alpha-ketoglutarate
D) Citrate
E) Oxaloacetate
Fumarate
Which of the following is not an intermediate of the urea cycle?
A) Citrulline
B) Ornithine
C) Aspartate
D) Arginine
Aspartate
In low cholesterol conditions in a cell, which of the following will take place?
A) Decrease in number of LDL receptors at the cell membrane
B) Transcription factor SREBP will be cleaved (cut) from the golgi membrane and targeted to DNA
C) Decreased transcription of HMG CoA Reductase
D) Esterification of cholesterol will increase via ACAT enzyme
Transcription factor SREBP will be cleaved (cut) from the golgi membrane and targeted to DNA
What enzyme is responsible for the transfer of free cholesterol into HDL particles?
A) SR-B1
B) LCAT
C) CETP
D) ABCA1
ABCA1
What enzyme is responsible for the transfer of free cholesterol into HDL particles?
A) SR-B1
B) LCAT
C) CETP
D) ABCA1
ABCA1
The transport of fatty acids from cytosol to the mitochondria matrix is inhibited by _______.
A) Carnitine (non-essential amino acid)
B) High levels of fatty acyl-CoAs in the cytosol
C) Fasting
D) Malonyl-CoA (from activation of acetyl CoA in fatty acid synthesis)
Malonyl-CoA (from activation of acetyl CoA in fatty acid synthesis)
Which apolipoprotein is an activator of LCAT?
A) B48
B) CII
C) A1
D) B100
A1
Compared to a fed state, which metabolite decreases during fasting/starvation state?
A) FFA
B) TAG
C) KB
TAG
Where does LPL act in the body?
A) Adipose tissue (AT)
B) Brain
C) Capillaries of liver
D) Capillaries of AT
E) Liver
Capillaries of AT
T/F: Oxoaloacetate is considered glucogenic because it can only be metabolized into glucose.
FALSE
High concentrations of which TCA cycle intermediate will drive FA synthesis?
A) Oxaloacetate
B) Citrate
C) Succinate
D) Acetyl-CoA
E) Pyruvate
Citrate
T/F: Glucose is a required substrate for TAG synthesis in adipose tissue.
TRUE
