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Biochem > Biochemical Signaling > Flashcards

Biochemical Signaling Flashcards

1
Q

How do living things coordinate all activities?

A

Through complex signaling systems

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2
Q

What are hormones?

A

Extracellular signals mediated by chemical messengers (Maintained by synthesis or alteration of great variety of messengers)

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3
Q

What are the steps of every signaling pathway? (5 steps)

A

Summary: Hormone signals, binds to cell, mechanistically transmits hormone binding to cell interior, causes series of intracellular responses via secondary messengers, termination of signal

  1. Start with a signal, which is the hormone
  2. Receptor Protein will bind hormone (receptor in that hormone will be recognized by some sort of receptor on the target cell, causing it to bind to the target cell).
  3. Mechanism for transmitting hormone binding to cell interior (hormone transmitting a single signal into cell)
  4. Series of intracellular responses that “amplify” binding phenomena and illicit tons of responses (secondary messenger and/or chemical changes catalyzed by kinases and phosphatases — secondary messengers are produced by enzymes)
  5. Termination of the signal
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4
Q

Higher animals have specialized ductless ____________ that synthesize ___________.

A

Endocrine glands, endocrine hormones

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5
Q

After being syntheized in endocrine glands, what happens to endocrine hormones?

A

They’re released into the bloodstream in response to external stimuli, carried to target cells, and elicit a response

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6
Q

What are three things secreted hormones enable?

A
  1. Maintain homeostasis (steady state; i.e. insulin or glucagon)
  2. Respond to external stimuli (fight or flight)
  3. Enable cyclic and developmental programs (sexual differentiation/maturation)
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7
Q

Most hormones are:

A
  1. Polypeptides
    .2. Amino Acid Derivatives
  2. Steroids
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8
Q

Only cells with a specific receptor responds to the signal?

A

True (Signals are very specific in that only cells with specific receptors respond to signal even though all cell are exposed to signal)

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9
Q

Hormones may be under feedback control through…

A

secretion of other hormones

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10
Q

Endocrine glands are NOT a collection of independent secretory but are…

A

a complex and highly controlled network of glands (one gland affects another in many cases)

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11
Q

What are the major endocrine glands?

A

Hypothalamus, pituitary, parathyroid, thyroid, adrenal, pancreas, kidneys, ovaries & testes

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12
Q

Before polypeptide hormones are release, how are they synthesized?

A

Summary: Are synthesized, processed, matured, and packaged waiting for release

  • Are ribosomally synthesized as prohormones
  • Are processed in rough endoplasmic reticulum and golgi bodies forming mature hormones
  • Are packaged in secretory granules awaiting for release by exocytosis
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13
Q

Hormone release are influenced by what two things?

A
  1. Autonomic Nervous System (Involuntary)

2. Hormones secreted by gastrointestinal tract

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14
Q

What do pancreatic islet hormones control?

A

They fuel metabolism

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15
Q

What is the bulk of the pancreas?

A

An endocrine gland that produces digestive enzymes — Secreted via the pancreatic duct and release into the small intestine

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16
Q

A small portion (1-2%) of pancreatic tissue consists of what type of cells?

A

Islet of Langerhans

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17
Q

What are Islet of Langerhans?

A

Small clumps of cells that comprise the endocrine gland

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18
Q

What is the function of the Islet of Langerhans?

A

Maintaining energy homeostasis

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19
Q

What are the 3 types of cells that make up pancreatic islets?

A

α-cells – Glucagen (29 residues)
β-cells – Insulin (51 residues)
δ-cells – Somatosatin (14 residues)

Each have a specific polypeptide hormone

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20
Q

Insulin is Secreted in response to..

A

High Blood Glucose Levels

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21
Q

What the primary function of insulin?

A

Stimulate muscle, liver & adipose cells to take up glucose & store glucose for later use by synthesizing glycogen, protein & fat

22
Q

Glucagon is secreted in response to….

A

Low Blood Glucose Levels (opposite of insulin)

23
Q

What three things does Glucagon stimulate?

A
  1. Breakdown of glycogen and release glucose to general circulation
  2. Liver synthesis of glucose from noncarbohydrate precursors (gluconeogenesis)
  3. Adipose tissue to release fatty acids thru lipolysis
24
Q

What is the function of Somatostatin?

A

Release by hypothalmus and inhibits release of insulin and glucagon from islet cells

25
Q

What two types of distinct tissues do the adrenal glands consist of?

A

Medulla (core– an extension of autonomic nervous system) and cortex (outer layer)

26
Q

What two types of hormonally active catecholamines does the medulla synthesize?

A

Norepinephrine and epinephrine (methyl derivative of epinephrine)

–Both are synthesized by tyrosine and stored in granules awaiting exocytotic release

27
Q

Biological effects of catecholamines mediated by what type of receptors?

A

α- & β-adrenoreceptors

28
Q

What are α- & β-adrenoreceptors?

A

Transmembrane glycoproteins that occur on separate tissues. They generally respond differently and often oppositely to catecholamines.

29
Q

β-adrenoreceptors stimulate:

A
  1. Glycogenolysis & gluconeogenesis in liver
  2. Glycogenolysis in skeletal muscle
  3. Lipolysis in adipose tissue
  4. Relaxation smooth muscle (involuntary) in bronchi & blood vessels supplying skeletal muscles (voluntary)
  5. Increased heart action
30
Q

α-adrenoreceptors stimulate:

A

Smooth muscle contractions in blood vessels supplying peripheral organs such as skin & kidney
Smooth muscle relaxation in GI tract
Blood platelet aggregation

31
Q

The diverse effects of hormones are directed towards what to roles?

A
  1. Mobilization of energy resources

2. Shunting to prepare body for action (fight or flight)

32
Q

The adrenal cortex produces at least 50 different ________; classified according to _________.

A

adrenocortical, steroids physiological response

33
Q

What are three important adrenocortical steroids?

A
  1. Glucocorticoids
  2. Mineralocorticoids
  3. Androgens/Estrogens
34
Q

What are glucocorticoids?

A

Adrenocortical steroid that

  1. affects carbohydrate, protein, and lipid metabolism (opposite to insulin)
  2. influences inflammatory reaction and capacity to cope with stress
35
Q

Which adrenocortical steroid regulates kidney and water excretion?

A

Mineralocorticoids

36
Q

What are estrogen and androgen responsible for?

A

sexual development & maturation

37
Q

Glucocorticoids and Mineralcorticoids are all ___ compounds

A

C21

38
Q

Are steroids water soluble?

A

False — They are water insoluble (hydrophobic). Proteins are transported in blood by glycoprotein transcortin and, to a lesser extent, albumin.

39
Q

Which hormones spontaneously pass through membranes of target cells for cytosol binding to steroid receptors?

A

Steroid hormones (i.e. glucocorticoids and mineralocorticoids) and thyroid hormones. All other hormones will need a receptor to pass thought he membrane

Note: For steroids, after passing through membrane (without the need of a receptor), the steroid-receptor complex migrates to the cell nucleus functioning as transcription factors inducing/repressing transcription of specific genes. They influence expression numerous metabolic enzymes in target tissues

40
Q

What does the pituitary gland (anterior lobe) produce?

A

Growth hormone (19 residue polypeptide)

41
Q

When the growth hormone binds to receptors, it directly stimulates…

A

growth and metabolism in muscle, bone and cartilage cells

42
Q

Growth hormone in the pituitary gland also acts indirectly by stimulating the ….

A

liver to produce additional growth factors

43
Q

Growth hormone production is often the result of a

A

pituitary tumor (causes excessive growth)

44
Q

If overproduction of the growth hormone starts before growth plates are ossified, this can lead to

A

Gigantism

–Excessive GH inhibits testosterone necessary for growth plate ossification. This causes people to continue growing throughout abnormally short lives. People with gigantism have normal body proportions

45
Q

What is acromegaly and when does it occur?

A

When overproduction of GH begins after skeletal maturation. This causes only soft tissue to continue growing. People develp enlarged hands/feet and thickening facial features.

46
Q

What does growth hormone deficiency lead to?

A

Dwarfism (insufficient growth)

47
Q

What can GH deficiency can be treated with?

A

Can be treated before skeletal maturation with injections of human growth hormone (hGh)

  • -Animal GH is ineffective in humans
  • -Originally only available from cadaver pituitaries, but not can be synthesized
48
Q

What was the dark side of hGH?

A

Athletes would is it for athletic prowess

49
Q

What are adverse effects of hGH?

A

Hypertension, joint/muscle pain, and acromegaly

50
Q

What do receptor proteins do?

A

Transmit information into cell.

51
Q

What are the 3 major classes of membrane receptors?

A
  1. 7 Transmembrane receptors (associated with heterotrimeric G-Proteins)
  2. Dimeric Membrane Receptors (recruit protein kinases)
  3. Dimeric Protein receptors (are protein kinases)
52
Q

What are 7 transmembrane-helix receptors responsible for?

A

transmitting info initiated by signals such as photons, odorants, hormones

Biochem (2 decks)

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