Unit 4 review
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Unit 4 Review. Explain what happens in the signaling pathway between yeast mating cells. Explain what happens in the signaling pathway between yeast mating cells. Exchange of mating factors A cell secretes an a mating factor, which binds to receptors on the alpha cell

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Unit 4 Review

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Unit 4 Review


  • Explain what happens in the signaling pathway between yeast mating cells.


  • Explain what happens in the signaling pathway between yeast mating cells.

    • Exchange of mating factors

      • A cell secretes an a mating factor, which binds to receptors on the alpha cell

      • Alpha cell secretes an alpha mating factor, which binds to receptors on the a cell

    • Mating

      • The two mating factors cause the cells to grow towards each other and result in fusion

    • New a/alpha cell

      • Fused cell includes all the genes from the original cell


  • What are the two types of local signaling? Explain how they work.

  • What is the type of long-distance signaling? Explain how it works.


  • What are the two types of local signaling? Explain how they work.

    • Paracrine signaling: secreting cell acts on nearby target cell by discharging molecules of a local regulator

    • Synaptic signaling: nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell

  • What is the type of long-distance signaling? Explain how it works.

    • Hormone signaling: specialized endocrine cells secrete hormones into body fluids; travel all over the body but only affect specialized target cells


Match the words below with their definition.

_____Hormones

_____Ligand

_____Local Regulators

_____Signal transduction pathway

_____Transcription factor

  • A molecule that specifically binds to another molecule

  • Circulating chemical signal that act on specific target cells to change their function

  • Control which genes are turn on

    4. Messenger molecules that influence cells nearby

    5. The process by which a signal on a cell’s surface is converted into a specific cellular response


Match the words below with their definition.

__2__Hormones

__1__Ligand

__4__Local Regulators

__5__Signal transduction pathway

__3__Transcription factor

  • A molecule that specifically binds to another molecule

  • Circulating chemical signal that act on specific target cells to change their function

  • Control which genes are turn on

    4. Messenger molecules that influence cells nearby

    5. The process by which a signal on a cell’s surface is converted into a specific cellular response


  • What do signal molecules have to be in order to reach an intracellular receptor?

  • What happens to an intracellular receptor after a signal molecule has bonded to it?


  • What do signal molecules have to be in order to reach an intracellular receptor?

    • Small

    • Hydrophobic

  • What happens to an intracellular receptor after a signal molecule has bonded to it?

    • It enters the nucleus and turns on specific genes

      • Bound protein stimulates the transcription of the genes into mRNA

      • mRNA moves to the cytoplasm and is translated into a specific protein by the ribosomes


  • Explain how a G-protein-linked receptor works.

  • Explain how a receptor tyrosine kinase works.


  • Explain how a G-protein-linked receptor works.

    • Signal molecule binds to receptor protein, which causes receptor protein to change shape

      • Attaches to G protein

        • GDP replaced by GTP, which activate the G protein

    • Activated G protein binds to an activated enzyme

    • G protein hydrolyzes the GTP to GDP, which deactivates the protein


  • Explain how a receptor tyrosine kinase works.

    • Signal molecule binds to receptor protein

      • Two polypeptides come together to form a dimer

    • Dimerization activates tyrosine-kinase region of polypeptide

      • Tyrosine kinase adds a phosphate from ATP

    • Relay proteins bind to the each tyrosine, which activates the proteins

      • Each activated protein triggers a transduction pathway


  • Explain how an ion-channel receptor works.

  • Briefly explain what two things Sutherland discovered from his experiment with epinephrine.


  • Explain how an ion-channel receptor works.

    • Ligand binds to receptor

      • Ion gate opens

    • Specific ions flow through the open channel

    • Ligand then dissociates

      • Closes the ion gate

  • Briefly explain what two things Sutherland discovered from his experiment with epinephrine.

    • Epinephrine does in directly interact with the enzyme

    • Plasma membrane is involved in transmitting the epinephrine signal


Match the signaling molecule to the appropriate pathway:

_____Neurotransmitter

_____Growth factor

_____Hormones

_____Yeast mating factors

  • Receptor tyrosine kinase

  • G-protein-linked receptor


Match the signaling molecule to the appropriate pathway:

__B__Neurotransmitter

__A__Growth factor

__B__ Hormones

__B__ Yeast mating factors

  • Receptor tyrosine kinase

  • G-protein-linked receptor


  • When does transduction begin?

  • Which molecules are the most common second messengers?


  • When does transduction begin?

    • When the signal molecule binds to the receptor protein and changes in the protein in some way

  • Which molecules are the most common second messengers?

    • cAMP

    • Calcium ions


  • Explain the role of the following enzymes:

    • Protein kinase

    • Protein phosphatase

    • Adenylylcyclase

    • Phosphodiesterase

    • Phospholipase C

  • Explain the role of the following second messengers:

    • cAMP

    • IP3

    • Calcium ions


  • Explain the role of the following enzymes:

    • Protein kinase

      • Transfers phosphate groups from ATP to a protein

    • Protein phosphatase

      • Removes phosphate groups from proteins

    • Adenylylcyclase

      • Converts ATP to cAMP

    • Phosphodiesterase

      • Converts cAMP to AMP

    • Phospholipase C

      • Cleaves a plasma membrane phospholipid into DAG and IP3


  • Explain the role of the following second messengers:

    • cAMP

      • Activates a protein kinase

    • IP3

      • Binds to a ligand-gated ion channel in the ER

        • Opens the channel and allows calcium to flow from ER to cytosol

    • Calcium ions

      • Increased concentrations cause various responses

        • Ex: muscle contraction, secretion of substances, cell division


  • Explain the phosphorylation cascade model.

  • How is cAMP made? (Explain the process.)


  • Explain the phosphorylation cascade model.

    • Signal molecule binds to receptor

    • Receptor passes signal to relay molecule

    • Relay molecule activates protein kinase 1

    • Active protein kinase 1 transfers a phosphate from ATP to inactive protein kinase 2

      • Activates PK2

    • Protein kinases are activated throughout the entire phosphorylation cascade

    • Final protein kinasephosphorylates a protein that causes the cell’s response to the signal


  • How is cAMP made? (Explain the process.)

    • First messenger (signal molecule) binds to receptor protein

    • Receptor protein activates G protein by hydrolyzing GDP to GTP

    • Activated G protein activates the adenylylcyclase enzyme

    • ATP is converted into cAMP

    • Camp activates protein kinase


  • Explain how the cholera bacteria (Vibriocholerae) disrupts a G protein signal transduction pathway.

  • Where are calcium ion concentrations highest?


  • Explain how the cholera bacteria (Vibriocholerae) disrupts a G protein signal transduction pathway.

    • Cholera bacteria produces a toxin

      • Toxin modifies G protein

    • G protein can’t hydrolyze GTP back to GDP

      • So pathway is always active

    • cAMP is constantly being made

      • High levels of cAMP in intestinal cells cause lots of water and salt to be secreted

  • Where are calcium ion concentrations highest?

    • Outside the cell (interstitial fluid) or inside the ER


  • Explain how calcium ions are released from the ER (know the entire process).

  • What are the two types of responses (the last step of the signal transduction pathway—where do they occur)?


  • Explain how calcium ions are released from the ER (know the entire process).

    • Signal molecule binds to receptor protein

    • Receptor protein activates G protein

    • G protein activates Phospholipase C

    • Phospholipase C cleaves a membrane protein into DAG and IP3

    • IP3 travels through cytosol to ER

    • IP3 binds to an IP3-gated calcium channel in the ER’s membrane

    • Causes ion channel to open and release calcium into the cytosol

  • What are the two types of responses (the last step of the signal transduction pathway—where do they occur)?

    • Nucleus and Cytoplasm


  • What are scaffolding proteins?

  • How is the signal in a signal transduction pathway “turned off”?


  • What are scaffolding proteins?

    • Large relay proteins to which several other relay proteins are simultaneously attached

      • Increases signaling efficiency

  • How is the signal in a signal transduction pathway “turned off”?

    • Signaling molecule dissociates from receptor protein

      • Receptor protein reverts to inactive form which causes all other parts of the pathway to become inactive again


Match the following terms with their correct definition.

____Conformer

____Homeostasis

____Interstitial fluid

____Regulator

____Thermoregulation

  • Internal environment that exchanges nutrients and wastes

  • Internal balance

  • Moderates internal conditions as external conditions change

  • Allows internal conditions to vary with certain external conditions

  • Process by which animals maintain an internal temperature, within a tolerable range


Match the following terms with their correct definition.

__D__Conformer

__B__Homeostasis

__A__Interstitial fluid

__C__Regulator

__E__Thermoregulation

  • Internal environment that exchanges nutrients and wastes

  • Internal balance

  • Moderates internal conditions as external conditions change

  • Allows internal conditions to vary with certain external conditions

  • Process by which animals maintain an internal temperature, within a tolerable range


  • Explain how a negative feedback loop works. Give an example.

  • Explain how a positive feedback loop works. Give an example.


  • Explain how a negative feedback loop works. Give an example.

    • A change in a variable being monitored triggers a response that counteracts the initial fluctuation

      • Ex: body temperature, blood glucose levels

  • Explain how a positive feedback loop works. Give an example.

    • A change in a variable triggers mechanisms that amplify the change

      • Ex: childbirth, breast feeding


_________________ (Ectotherms or Endotherms) gain most of their heat from their environment.

_________________ (Ectotherms or Endotherms) can use metabolic heat to regulate their body temperature.


___Ectotherms____ (Ectotherms or Endotherms) gain most of their heat from their environment.

___Endotherms ___ (Ectotherms or Endotherms) can use metabolic heat to regulate their body temperature.


  • Explain how the mechanism of homeostasis works (**hint: think receptor, control center, effector).

  • What is the set point in a homeostatic mechanism?


  • Explain how the mechanism of homeostasis works (**hint: think receptor, control center, effector).

    • Receptor detects a change in some variable

    • Control center processes information it receives and directs an appropriate response

    • Effector carries out the desired response

  • What is the set point in a homeostatic mechanism?

    • The point of homeostasis; the point around which the system is based


  • Which part of the brain controls thermoregulation? This part of the brain contains nerve cells that function as our body’s “thermostat”.

  • List the types of local regulators.


  • Which part of the brain controls thermoregulation? This part of the brain contains nerve cells that function as our body’s “thermostat”.

    • Hypothalamus

  • List the types of local regulators.

    • Neurotransmitters

    • Cytokines

    • Growth factors

    • Nitric acid

    • Prostaglandins


  • Why do cells react differently to the binding of the same signal molecule?

  • List three characteristics of a hormone.


  • Why do cells react differently to the binding of the same signal molecule?

    • Signaling pathways can use different proteins

  • List three characteristics of a hormone.

    • Secreted into extracellular fluid

    • Carried by circulatory system

    • Communicates messages within the body

    • Travel throughout the entire body


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