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Biochemistry > Feeding Fasting cycle > Flashcards

Feeding Fasting cycle Flashcards

1
Q

What are the major organs involved in feeding/appetite?

A

GI tract, liver, muscle, adipose tissue, brain, kidney

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2
Q

What is the function of the GI tract?

A

Mixing, digesting, absorbing, and propelling food

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3
Q

What are the major digestion/metabolism/appetite hormones

A

Ghrelin, leptin, cholecystokinin, insulin, glucagon

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4
Q

What hormone is secreted by pancreatic beta-cells

A

Insulin

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5
Q

What hormone is secreted by pancreatic alpha-cells?

A

Glucagon

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6
Q

What is the biological role of the liver?

A

Carbohydrate/lipid/amino acid metabolism
Regulate blood glucose
Detox

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7
Q

What is the energy source for cardiac muscle?

A

Glucose in fed state

Fatty acids in fasting state

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8
Q

How is glucose transport into muscle cells activated?

A

By insulin, which activates translocation of GLUT 4

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9
Q

What is the function of adipose tissue?

A

Store triacylglycerols

Secretes leptin

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10
Q

What is the function of the leptin hormone?

A

Satiety-inducing

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11
Q

How does the brain regulated appetite? What is its energy source?

A

Regulates via the hypothalamus

Glucose is sole energy source

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12
Q

What is the biological role of the kidneys?

A

Filter blood plasma
Reabsorption of electrolytes and nutrients
Regulate pH
Regulate water content

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13
Q

What is the postprandial state?

A

After meal, when nutrient levels are high

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14
Q

What is the postabsorptive state?

A

After fasting [e.g. overnight] when nutrient levels are low

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15
Q

Describe the features of food digestion and absorption [aka feeding phase]

A

In early postprandial state…

1) Sugars and AAs absorbed and transported in blood to liver through portal vein
2) Lipids transported in lymph as chylomicrons
3) Chylomicrons pass to the bloodstream, which provides triacylglycerol to muscle and adipose tissue
4) Glucose movement from small intestine to liver stimulates beta cells
5) Beta cells release insulin, which promotes glucose uptake
6) Glycogenesis, fat + protein synthesis are promoted

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16
Q

Describe the fasting phase

A

1) Glucose/insulin levels decrease
2) Glucagon is released–prevents hypoglycemia by stimulating glycogenolysis and gluconeogenesis

If fasting is prolonged–maintain glucose levels via fatty acid mobilization–alternative to glucose for muscle, so glucose can be saved for brain

Starvation–additional fatty acids from adipose tissue and ketone bodies from liver are mobilized

  • gluconeogenesis
  • large amounts of AAs from muscle are used
  • eventually brain adapts to new energy source
17
Q

What neural circuit regulates appetite? How does it work?

A

Arcuate nucleus (ARC)

Depending on signal produced by ARC, appetite suppressed or stimulated

Insulin reduces uptake via same mechanism

mTORC also regulates ARC

18
Q

How does AMPK work to regulate appetite? What hormones inhibit it?

A

AMPK mediates appetite-regulating integration

- inhibited by insulin and leptin

19
Q

What is the cause of type 1 diabetes? What are its effects?

A

Inadequate insulin secretion

Why? Autoimmune destruction of pancreatic beta-cells

Can cause? Ketoacidosis

20
Q

What is the cause of type 2 diabetes–proximate and ultimate? What are the symptoms?

A

Ultimate cause = insulin resistance of target cells

Proximate cause = hyperglycemia

Symptoms…
glucosuria -> osmotic diuresis, polyuria, excessive thirst

dyslipidemia -> abnormal blood lipid/lipoprotein levels -> deposits around cells can further block insulin

21
Q

What conditions make up the metabolic syndrome cluster?

A

Obesity, hypertension, dyslipidemia, insulin resistance

22
Q

What are the causes of metabolic syndrome?

A

Hyperinsulinemia

Excess glucose production

Decreased insulin-dependent glucose uptake in muscle

Excess free fatty acids–disrupt signal transduction in insulin dependent tissues

Type 2 diabetes

23
Q

What is the formula for BMI calculation?

A

BMI = Weight (kg) / height (m) ^2

Biochemistry (43 decks)

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