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PHM 532 Exam2 > Flashcards lecture 9-11 > Flashcards

Flashcards lecture 9-11

1
Q

What is the action of glucagon on adipose tissue?

A

Glucagon activates the release of cyclic AMP, which activates Protein Kinase A. This phosphorylates and activates hormone-sensitive lipase.

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2
Q

What is the role of hormone-sensitive lipase in adipose tissue?

A

It hydrolyzes the ester bonds between glycerol and fatty acids, releasing free fatty acids into the bloodstream.

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3
Q

What happens to free fatty acids released from adipose tissue?

A

They circulate in the bloodstream and are transported to the liver for conversion to Acetyl CoA and further processed in ketogenesis.

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4
Q

What is the first step of lipogenesis from carbohydrates?

A

Glucose is converted to pyruvate through glycolysis, which then enters the mitochondria to form Acetyl CoA.

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5
Q

What must Acetyl CoA combine with to exit the mitochondria?

A

Acetyl CoA must combine with oxaloacetate to form citrate, as there are no pathways for Acetyl CoA to leave the mitochondria directly.

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6
Q

What occurs to citrate in the cytoplasm?

A

Citrate is converted back into Acetyl CoA and oxaloacetate. Oxaloacetate is recycled into the mitochondria, while Acetyl CoA proceeds to fatty acid or cholesterol biosynthesis.

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7
Q

What is the rate-determining enzyme in fatty acid biosynthesis?

A

Acetyl CoA Carboxylase, which converts Acetyl CoA into Malonyl CoA.

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8
Q

What coenzyme is involved in the conversion of Acetyl CoA to Malonyl CoA?

A

Biotin (Vitamin B7), which captures CO2 for the reaction.

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9
Q

What is the main product of Phase II of fatty acid biosynthesis?

A

Palmitic acid (16:0), formed by the addition of multiple Malonyl CoA molecules through the action of fatty acid synthase.

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10
Q

What are the types and sources of Vitamin D?

A

D2: Found in plants, fungi, and yeast (1/3 to 1/9 potency of D3)
D3: Produced in the skin from sunlight and found in animal products (includes cholecalciferol, calcidiol, calcitriol).

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11
Q

Where is Vitamin D3 synthesized?

A

In the skin upon exposure to sunlight.

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12
Q

How does calcitriol (active Vitamin D3) affect calcium absorption?

A

It binds to receptors in intestinal cells, promoting the expression of calcium transporter proteins, Calbindin, and ATP-dependent calcium pumps.

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13
Q

What is the effect of Vitamin D on phosphate absorption?

A

Vitamin D stimulates the reabsorption of phosphate from the gastrointestinal tract and kidneys.

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14
Q

What role does Vitamin D play in bone health?

A

By promoting calcium absorption, it helps prevent the release of parathyroid hormone (PTH), reducing the risk of osteoporosis.

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15
Q

What are the roles of Vitamin D in immune and muscle function?

A

Immune Function: Activates lymphocytes and macrophages.
Muscle Function: Facilitates calcium binding in muscle contraction by allowing myosin to bind to actin.

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16
Q

What triggers the activation of glucagon in the body?

A

Glucagon is primarily released in response to low blood glucose levels.

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17
Q

What is the role of Protein Kinase A in glucagon signaling?

A

Protein Kinase A phosphorylates target proteins, leading to the activation of hormone-sensitive lipase and promoting lipolysis.

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18
Q

What is the significance of free fatty acids in metabolism?

A

Free fatty acids serve as an important energy source and can be converted into ketones in the liver for use by other tissues.

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19
Q

What is the first step in converting pyruvate to Acetyl CoA?

A

Pyruvate undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex.

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20
Q

Why is the conversion of Acetyl CoA to citrate necessary?

A

Acetyl CoA cannot cross the mitochondrial membrane directly; it must be converted to citrate for transport into the cytoplasm.

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21
Q

What happens to oxaloacetate once it is formed in the cytoplasm?

A

Oxaloacetate is converted back into malate, which can then re-enter the mitochondria or be converted into pyruvate.

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22
Q

What additional substrates are needed for fatty acid biosynthesis in Phase II?

A

NADPH is required as a reducing agent for the elongation of fatty acid chains.

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23
Q

What is the role of fatty acid synthase in fatty acid biosynthesis?

A

Fatty acid synthase catalyzes the sequential addition of malonyl CoA to build up the fatty acid chain, ultimately producing palmitic acid.

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24
Q

How does vitamin D3 differ from calcidiol and calcitriol?

A

Vitamin D3 (cholecalciferol) is synthesized in the skin; calcidiol is its hydroxylated form in the liver; calcitriol is the active form produced in the kidneys.

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25
Q

What is the primary action of calcitriol on the kidneys?

A

Calcitriol promotes the reabsorption of calcium and phosphate in the renal tubules.

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26
Q

How does Vitamin D influence bone remodeling?

A

Vitamin D reduces the need for bone reabsorption and supports bone mineralization.

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27
Q

In what way does Vitamin D affect muscle performance?

A

Adequate Vitamin D levels are linked to improved muscle strength and function, potentially reducing the risk of falls in the elderly.

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28
Q

What is the effect of glucagon on lipogenesis?

A

Glucagon inhibits lipogenesis, promoting lipolysis and the release of fatty acids instead.

29
Q

What is the feedback mechanism involving calcium in the context of Vitamin D?

A

Sufficient calcium absorption prevents the release of PTH, which regulates calcium levels in the body.

30
Q

What dietary sources provide Vitamin D3?

A

Fatty fish (like salmon), cod liver oil, fortified dairy products, and egg yolks are rich in Vitamin D3.

31
Q

What are the main groups of lipoproteins?

A

Chylomicrons: Largest volume, lowest density.
VLDL/IDL/LDLs: VLDLs are metabolized into IDLs, which are further metabolized into LDLs.
HDLs: Smallest volume, highest density.

32
Q

What are the identity markers for different lipoproteins?

A

Chylomicrons: Apo B48
VLDL/IDL/LDLs: Apo B100
HDLs: Apo A1

33
Q

What is the function of Apo E in lipoproteins?

A

ApoE interacts with receptors for lipoprotein internalization, facilitating endocytosis of the lipoprotein.

34
Q

What role does Apo C2 (CII) play in lipid metabolism?

A

Apo C2 activates lipase to break down triglycerides in lipoproteins, allowing for fatty acid storage in adipose cells.

35
Q

Why do LDLs circulate longer in the bloodstream compared to other lipoproteins?

A

LDLs lose their Apo E marker during conversion from IDLs, leading to delayed endocytosis as they rely on the LDL receptor-B100 interaction.

36
Q

What risk is associated with prolonged circulation of LDLs?

A

Without Apo E, LDLs are at greater risk of oxidation by free radicals, increasing the risk of atherosclerosis.

37
Q

What is the forward transport pathway of cholesterol?

A

Cholesterol is released from the liver into the bloodstream as VLDLs, which are converted to IDLs and LDLs, delivering cholesterol to local tissues.

38
Q

What is the Bohr effect in relation to hemoglobin?

A

The Bohr effect refers to the change in hemoglobin’s affinity for oxygen based on conditions such as pCO2, pH, 2,3-DPG levels, and temperature.

38
Q

Describe the reverse transport pathway of cholesterol.

A

HDLs are released from the liver and intestines to collect cholesterol from local tissues and transport it back to the liver.

39
Q

What factors decrease hemoglobin’s affinity for O2?

A

Increase in pCO2
Decrease in pH (increase in [H+])
Increase in 2,3-DPG
Increase in temperature

40
Q

What factors increase hemoglobin’s affinity for O2?

A

Decrease in pCO2
Increase in pH (decrease in [H+])
Decrease in 2,3-DPG
Decrease in temperature

41
Q

What is the purpose of the HbA1c test?

A

It measures average blood glucose levels over the past 2-3 months, providing insight into the risk of diabetic complications.

42
Q

What does jaundice indicate?

A

Jaundice is a sign of liver disease, resulting from the accumulation of bilirubin from hemoglobin degradation.

42
Q

How does glucose affect hemoglobin in the HbA1c test?

A

Glucose forms an irreversible covalent bond with hemoglobin, leading to more glycation reactions with higher blood glucose levels.

42
Q

Where does the glycation reaction of hemoglobin occur?

A

In red blood cells, specifically between glucose and the valine of beta-globin chains in hemoglobin.

43
Q

What causes the yellow coloration in the skin and tissues in jaundice?

A

Bilirubin, which is not conjugated with glucuronic acid, is reabsorbed into the bloodstream and is lipid-soluble, leading to yellowing.

44
Q

What is the importance of the pentose phosphate pathway (PPP)?

A

The PPP generates NADPH, which acts as a major antioxidant in the body.

45
Q

How does glutathione (GSH) function as an antioxidant?

A

GSH oxidizes to form a disulfide complex (G-S-S-G), neutralizing hydrogen peroxide and converting it into water.

46
Q

What enzyme is involved in the oxidation of glutathione?

A

Glutathione Peroxidase, with selenium as a co-enzyme.

47
Q

How is oxidized glutathione (G-S-S-G) reduced back to GSH?

A

Through the action of glutathione reductase, using NADPH as the co-enzyme that donates electrons.

48
Q

How does G6PDH deficiency affect NADPH production?

A

A deficiency in G6PDH leads to insufficient NADPH, compromising the body’s antioxidant defenses and increasing susceptibility to oxidative damage.

48
Q

What is favism and what causes it?

A

Favism is a condition caused by a deficiency in glucose-6-phosphate dehydrogenase (G6PDH), leading to dysfunction in the pentose phosphate pathway and resulting in hemolytic anemia when exposed to fava beans.

49
Q

What is the role of glucose-6-phosphate dehydrogenase (G6PDH) in the pentose phosphate pathway?

A

G6PDH catalyzes the rate-limiting step of the pentose phosphate pathway, producing NADPH, which is essential for combating oxidative stress.

50
Q

What coenzyme is required for transamination reactions and what is its function?

A

Vitamin B6 is the coenzyme that holds the amine group within the enzyme’s active site and transfers it to the alpha-ketoacid.

50
Q

What occurs during a transamination reaction?

A

The amine group is transferred from an amino acid to an alpha-ketoacid, converting the amino acid into an alpha-ketoacid and the alpha-ketoacid into an amino acid.

51
Q

What is the enzyme involved in transamination reactions?

A

The enzyme for transamination reactions is transaminase.

52
Q

What reaction is catalyzed by alanine transaminase (ALT)?

A

The reaction catalyzed by ALT is: Glutamate + Pyruvate ↔ alpha-ketoglutarate + Alanine.

53
Q

What is another name for alanine transaminase (ALT)?

A

Serum Glutamate-Pyruvate Transaminase (SGPT).

54
Q

What are the amino acids involved in transamination reactions?

A

The amino acids are alanine, aspartate, and glutamate.

55
Q

What are the alpha-ketoacids involved in transamination reactions?

A

The alpha-ketoacids are pyruvate, oxaloacetate, and alpha-ketoglutarate.

56
Q

What are the metabolic pathways involved in the glucose-alanine cycle?

A

The pathways are glycolysis, transamination, and gluconeogenesis.

57
Q

What happens to alanine in the liver during the glucose-alanine cycle?

A

In the liver, alanine loses its amine group via transamination to form pyruvate, which then undergoes gluconeogenesis to produce glucose.

57
Q

How does glucose convert to alanine in the muscles?

A

In the muscles, glucose undergoes glycolysis to form pyruvate, which then picks up an amine group via transamination to become alanine.

58
Q

Where does the urea cycle occur in the body?

A

The urea cycle occurs primarily in the liver.

58
Q

How does the glucose-alanine cycle compare to the Cori cycle?

A

Both cycles involve glycolysis and gluconeogenesis, but the glucose-alanine cycle includes transamination, while the Cori cycle involves lactic fermentation.

59
Q

Which amino acids are involved in the urea cycle?

A

The amino acids involved are aspartate and arginine.

60
Q

What is the metabolic importance of the urea cycle?

A

The urea cycle allows for the excretion of excess ammonia, preventing toxic accumulation that can lead to conditions like hepatic encephalopathy.

61
Q

What role does aspartate play in the urea cycle?

A

Aspartate transports an amine group into the urea cycle.

62
Q

What is the role of arginine in the urea cycle?

A

Arginine serves as an intermediate in the urea cycle.

PHM 532 Exam2 (5 decks)

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