S

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• Sümeyra OKCANOGLU
• Leyla CÜCÜGEN
• Perihan KILIÇ

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BIOSIGNALING
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CONTENTS

• 12.8 Regulation Of Transciption By Steroid
  Hormones
• 12.9 Signalling in Microorganism
  
  and Plant
• 12.10 Sensory Transduction in Vision, Olfaction,
  and Gustation

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12.8 Regulation Of Transciption By Steroid
Hormones
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• Steroid hormones
• For example Estrogen, progesterone, and cortisol
• Too hyrophobic to dissolve readily in the blood
• Transported on speciphic carrier proteins
• Pass to plasma membrane by simple diffusion

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• Steroid hormones enter the cell and bind to
  specific receptor proteins.
• This complex regulate the expression of nearby
  genes.
• Steroid hormones occur through a different,
  faster, signaling pathway.

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• Hormon binding triggers changes in the
  coformation of a receptor protein so that it
  becomes capable of interacting with specific
  regulatory sequences in DNA called hormon
  responce elements(HREs)

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Steroid analogs

• Steroid receptor interaction is exploited in the
  use of the drug tamoxifen to treat breast cancer
• The drug mifepristone(RU48) binds to progesterone
  receptorand block hormone action essential to
  implantation of the fertilized ovum in uterus.

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12.9 Signalling in Microorganism

and Plant

• Bacteria and eukaryotic microorganisms have a
  variety of sensory systems that allow them to
  sample and respond to their enviroment.
• some signals such as oxygen, nutrients, light,
  noxious chemicals

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The Two Compenent Signaling Mechanism in
Bacterial chemotaxis

• Receptor /His Kinase
• Response regulator(Asp)

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Signaling systems of plants

• Plants respond to many environmental stimuli and
  employ hormones and growth factors to coordinate
  the development and metabolic activities of their
  tissues.
• Two component signaling mechanisms common in
  bacteria are found in modified forms in plants
  used in the detection of chemical signals and
  light.

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• Plant have a rich collection of light detecting
  mechanism not found in animal tissues
• phytcroms and cryptochromes

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• Compound elicit signals in plant are smilar to
  certain signaling molecules in mammals
• Instead of prostoglandin, plants have
  jasmonate instead of steroid hormones,
  brassinosteroids.

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Ethylene

• CH2CH2
• Gaseous plant hormone
• Stimulates the ripening of fruit

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Transduction mechanism for detection of ethylene
by plants
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12.10 Sensory Transduction in Vision, Olfaction,
and Gustation

• The detection of light, odors and tastes in
  animals in a complished by specialized sensory
  neurons.
• light(vision)
• odors(olfaction)
• tastes(gustation)

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The visual system

• Light sensing cells are two types
• rod? sense low levels of light
• can not discriminate colors
• cone ? less sensitive of light
• discriminate colors

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