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SFM Exam 2 > Integration Of Metabolism > Flashcards

Integration Of Metabolism Flashcards

1
Q

Which organ is the only one capable of carrying out all the major pathways of metabolism?

A

Liver

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2
Q

Which three key molecules act as metabolic junction points?

A

Glucose 6 phosphate, pyruvate and acetyl CoA

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3
Q

The liver receives blood from the enteric circulation via

A

Portal vein and from the periphery via the hepatic artery

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4
Q

Describe why the liver is considered the MVP of metabolism

A

Processes most incoming nutrients
Responds quickly to dietary conditions
Maintains constant concentrations of nutrients in blood regardless of food intake
Synthesizes and secretes proteins
Processes and detoxifies toxins and wastes

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5
Q

What does the liver primarily depend on for its own energy needs?

A

Beta oxidation of FAs

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6
Q

Describe metabolic pathways used by adipose

A

Synthesizes and stores TAGs as signaled by insulin/fed state
Uses FAs from chylomicrons and VLDL to make TAGs
Degrades TAGs and releases FAs and glycerol for other tissues to use as signaled by glucagon/epinephrine (hunger and exercise)

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7
Q

White adipose

A

Accumulated fat from surplus calories

Subcutaneous, large effect on hormone regulation

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8
Q

Brown adipose

A

Has high levels of thermogenin

Burns calories and generates them as heat (the good fat)

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9
Q

The brain highly depends on what for energy?

A

Blood glucose

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10
Q

Explain astrocytes function in metabolism in the brain

A

Astrocytes contain some glycogen
Breaks down to release glucose which can be used by neurons
Lactate released from astrocytes used as well

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11
Q

What occurs in the brain during starvation?

A

Brain switched to metabolism of KBs for energy needs
Metabolized by the TCA cycle
Prevents protein breakdown for energy purposes
Uses amino acids for synthetic purposes instead (i.e. make neurotransmitters and peptide hormones)

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12
Q

Cardiac muscle is exclusively aerobic or anaerobic?

A

Aerobic as evidenced by the density of mitochondria in heart muscle

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13
Q

Metabolic pathways in cardiac muscle

A

Complete oxidation of glucose via TCA cycle, oxphos and beta oxidation of FAs serve as major fuel
Also use KBs (consumes acetoacetate in preference to glucose)
Also can use (branched) amino acids

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14
Q

Describe metabolic pathways in skeletal muscle

A

Rich in glycogen (contains 75% of the body’s glycogen stores)
Glycogen readily broken down to G6P and used by muscle for glycolysis
Lacks glucose 6 phosphatase so muscle retains glucose (proffered fuel)
Also uses FAs and KBs

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15
Q

Describe the phosphagen system

A

Phosphocreatine + ADP -> creatine -> ATP
Reversible reaction: forward during activity and reversed during recovery
Highest speed but lowest energy produced
Quick exhaustion of ATP stores replenished by metabolism of phosphocreatine

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16
Q

Describe the generation of ATP by anaerobic glycolysis and glycogenesis

A

Further intense activity (past the ATP-PC phase)
Oxidation of free blood glucose or glycogen
Glycogen -> G6P -> pyruvate -> lactate
Must shift to longer more sustainable energy production system

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17
Q

Describe the generation of ATP by oxphos and FA metabolism

A

Lowest speed, highest total energy produced
Metabolic processes involving ETC in mitochondria results in the reduction of co-enzymes
Oxphos and pumping proteins out of the mito matrix to produce ATP via ATP synthase

18
Q

Which hormones function as appetite suppressors?

A

CCK and GLP-1

19
Q

CCK is a family of

A

Peptide hormones thats secreted into the blood by cells in the duodenum and jejunum regions of the SI as postprandial signal

20
Q

Describe CCK’s signaling pathway to induce satiety

A

CCK binds to its GPCR located in various peripheral neurons that relay signals to the brain
Binding initiates a signal transduction pathway in the brain that generates a feeling of satiety
Also helps in digestion stimulating secretion of pancreatic enzymes and bile salts from gallbladder

21
Q

Describe the hormone glucose like peptide 1 (GLP-1)

A

Secreted by intestinal L cells which are hormone secreting cells present throughout the lining of the GI tract
Has a variety of effects mediated via binding to its receptor (GPCR)
Induces feelings of satiety that inhibit further eating
Also potentiates glucose induced insulin secretion by beta cells of pancreas while inhibiting glucagon secretion

22
Q

GLP-1 receptor agonists

A

Effects of GLP-1 only lasts for a few minutes but GLP-1 receptor agonists can lasts for hours/days
Increases insulin synthesis and release
Decrease glucagon release
Slow emptying of the stomach contents into the intestines
Helps feel full after a meal so you eat less (ex. Trulicity, Victoza)

23
Q

What are Na glucose co-transporter-2 (SGLT-2) inhibitors?

A

Being used as another class of medications for regulating blood sugar in T2DM
Associated with weight loss and improved blood sugar control
Ex. Invokana, Jardiance

24
Q

What is an example of an appetite enhancer?

A

Ghrelin is a peptide secreted by the stomach and acts on the regions of the hypothalamus to stimulate appetite through its GPCR
It’s secretion increases before a meal and decreases afterwards

25
Q

How is adipose tissue a very active endocrine tissue?

A

It secretes adipokines (e.g. leptin and adiponectin) which regulate a host of physiological processes

26
Q

Describe the hormone leptin

A

Secreted by adipose tissue in direct proportion to fat mass
Leptin receptors present all over the body and the brain (most importantly the hypothalamus)
Regulates body weight by inhibiting food intake and stimulating energy expenditure

27
Q

What are the effects of leptin signaling?

A

Increase sensitivity of muscle and liver to insulin, stimulate beta oxidation of FAs and decrease TAG synthesis

28
Q

Explain leptin’s role in insulin resistance

A

Contributes to obesity
Role of a group of protiens called the suppressors of cytokine signaling (SCOS)
Inhibit receptor action by binding to receptor, binding to other components of the signaling pathway, enhancing proteolytic degradation of the receptor

29
Q

Which two key molecules regulate energy homeostasis over the time scale of hours or days?

A

Leptin and insulin

30
Q

Leptin reports on the status of ____ whereas insulin reports on the status of _____

A

TAG stores; blood glucose (carb availability)

31
Q

Cells constantly adapt to what?

A

Their metabolism to meet their energy needs and respond to nutrient availability

32
Q

Describe how eukaryotes have evolved to sense low cellular ATP

A

Have evolved a very sophiscated system to sense low cellular ATP levels
This is accomplished via the serine/threonine kinase AMP-activated protein kinase (AMPK) complex

33
Q

What does AMPK do under low energy conditions?

A

AMPK phosphorylates specific enzymes and growth control nodes to increase ATP generation and decrease ATP consumption

34
Q

What is the cellular energy sensor?

A

AMPK

35
Q

When is AMPK inactive?

A

When ATP is high

36
Q

When is AMPK active?

A

When ATP is low

37
Q

When ATP is low, what happens to AMPK?

A

It is allosterically activated and phosphorylates many targets controlling cellular energy production and consumption

38
Q

Activation of AMPK leads to a shift in which type of pathways?

A

Leads to a decrease in anabolic pathways and increase in catabolic pathways

39
Q

What can stimulate AMPK?

A

Exercise as well as leptin and adiponectin (from adipose) can stimulate AMPK

40
Q

AMPK can positively influence which events?

A

Food intake in the hypothalamus
FA uptake and oxidation, glucose uptake and glycolysis in the heart
FA uptake and oxidation, glucose uptake and mitochondria biogenesis in skeletal muscle

41
Q

AMPK can negatively influence which events?

A

FA synthesis and lipolysis in adipocytes
FA synthesis, cholesterol synthesis and gluconeogenesis in the liver
Insulin secretion from the pancreas

42
Q

Reminder

A

Look at pics on how liver changes its metabolic pathways in a fed, fasting and starving state

SFM Exam 2 (25 decks)

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