VL 1

Question 1

transduction

Answer 1

Transduction is the action of bringing or leading something across

processes, by which extracellular stimuli
are transferred into intracellular answers

Question 2

What are the two main types of signal transduction?

Answer 2

intercellular
–> between cells
* chemical messengers (receptor and extracellular signal)
* gap junctions (cell-cell contact)
* cell-cell-interactions (surface proteins)

intracellular
–> within a cell
* second messengers
* kinases
* phosphatases
* G-proteins
* adapters

Question 3

What are some key mechanisms of cellular signal transduction?

Answer 3

• receptors
• heterotrimeric G-Proteins
• small GTP-binding proteins
• second messengers
• kinases
• phosphatases
• protein domains

Question 4

What are the major human glands and what do they have to do woth signal transduction?

Answer 4

–> endocrine glands secrete gormones, which act as extracelullar signals and regulate various phsiological processes.

Question 5

Why is there a hierarchical secretion of hormones?

Answer 5

1. Step: Brain control
* The CNS detects environmental signals.
* The Hypothalamus releases hormones to control the pituitary gland.
2. Step: Pituitary Gland Activation
* The Anterior Pituitary releases hormones that stimulate target glands.
* The Posterior Pituitary directly releases hormones into the blood.
3. Step: Target Glands & their Hormones
* Adrenal Cortex → Cortisol & Aldosterone (stress, salt balance)
* Thyroid → T3 & T4 (metabolism)
* Ovaries/Testes → Estrogen, Progesterone, Testosterone (reproduction)
* Liver & Bones → Growth Hormone (growth, metabolism)
* Mammary Glands → Prolactin (milk production)
* Smooth Muscle/Mammary Glands → Oxytocin (contractions, lactation)
* Arterioles → Vasopressin (blood pressure, water balance)
* Pancreas → Insulin & Glucagon (blood sugar control)
* Adrenal Medulla → Epinephrine (fight-or-flight response)
4. Step: Target Organs & Rsponse
* Hormones act on muscles, liver, heart, and reproductive organs to trigger responses.

Question 6

Key Steps in Signal Transduction

Answer 6

1. Extracellular signal binds to Receptor
   z.B Hormones, growth factors, Cytokines
2. Receptor initiates intracellular signaling
   z.B Second messengers, Protein kinases and G-Proteins
   * Second messengners lead to transcription
   * protein kinases lead to transcription
   * G-Proteins lead to enzymatic regulations
3. Transcription & Celullar Response
   When the signal reaches the nucleus, which leads to transcription (gene expression) or enzymatic regulation.
   –> this leads to cellular responses
   (Growth, Differntiation and apoptosis)

Question 7

Types of Intercellular Signaling

Answer 7

• paracrine Signaling
  –> The ligand diffuses to nearby target cells. Receptor of target cell binds ligand.
• juxtacrine signaling
  –>The ligand remains bound to the secreting cell and interacts directly with Receptor adjacent cells.
• autocrine signaling
  –> A feedback loop where a cell signals itself. Cell relases ligand and the receptor of the same cell binds ligand.
• intracrine signaling
  –> The ligand remains inside the cell and binds intracellular receptors.
• endocrine signaling
  –> The ligand is transported through the vasculat transport sytsem (bloodstream) to distant target cells.

Question 8

What are the main types of extracellular signaling molecules?

Answer 8

Hormones, cytokines, growth factores and neurotransmitters

Question 9

What are second messengers?

Answer 9

Small intracellular signaling molecules that amplify signals (e.g., cAMP, Ca²⁺, IP3).

Question 10

What is the role of protein kinases in signal transduction?

Answer 10

They phosphorylate target proteins to regulate their activity.

Question 11

What is the role of phosphatases in signal transduction?

Answer 11

They remove phosphate groups from proteins to deactivate signaling.

Question 12

What are G-proteins?

Answer 12

Guanine nucleotide-binding proteins that relay signals from receptors to effectors.

Question 13

What are the 2 key mechanisms of gene regulation in signaling?

Answer 13

Regulation of gene expression
* protein-DNA-interactions
* regulation of transcription
* posttranscriptional regulation

regulation of enzymatic activities
* allosterie
* inhibitors/activators
* phosphorylation
* proteolysis

Allosterie ist die Eigenschaft vieler aus mehreren Untereinheiten zusamm

Question 14

What are examples of dysregulated signaling in disease?

Answer 14

• p53 mutations (50% of human tumors)
  –> Tumorsuppressor protein,
  mutated in 50% of all human tumors
• p21ras mutations
  –> mutated in 30% of all human tumors (rat sarcoma)
• Retinoblastoma protein (tumor suppressor dysfunction)
  –> first identified and characterized
  human tumorsuppressor