Podcast
Questions and Answers
What is the structure of a G protein-coupled receptor (GPCR)?
What is the structure of a G protein-coupled receptor (GPCR)?
- Single membrane spanning protein
- Receptor with seven transmembrane helices (correct)
- Lipid-anchored protein
- Double membrane structure
Where are the binding sites for ligands located in a GPCR?
Where are the binding sites for ligands located in a GPCR?
- Extracellular regions or between helices (correct)
- Cytoplasmic membrane only
- Within the nucleus
- Intracellularly only
What effect can activated protein kinase A (pkA) have following GPCR activation?
What effect can activated protein kinase A (pkA) have following GPCR activation?
- Reduction in DNA replication
- Regulation of metabolic pathways (correct)
- Inhibition of glycolysis
- Decrease in cell membrane permeability
Which function is NOT associated with the phosphorylation effects of pkA?
Which function is NOT associated with the phosphorylation effects of pkA?
Which of the following best describes GPCRs' interaction with G proteins?
Which of the following best describes GPCRs' interaction with G proteins?
How does the phosphorylation of channel proteins affect the cell?
How does the phosphorylation of channel proteins affect the cell?
What property do water-soluble proteins have that prevents them from easily penetrating the cell membrane?
What property do water-soluble proteins have that prevents them from easily penetrating the cell membrane?
Which type of hormone requires a receptor on the cell membrane to exert its effects?
Which type of hormone requires a receptor on the cell membrane to exert its effects?
Which hormone is classified as a lipid-soluble hormone?
Which hormone is classified as a lipid-soluble hormone?
What is the function of GTPase in the context of G protein-coupled receptors?
What is the function of GTPase in the context of G protein-coupled receptors?
What is the role of adenylate cyclase in the signaling pathway initiated by G proteins?
What is the role of adenylate cyclase in the signaling pathway initiated by G proteins?
What is the 'off' state of the receptor characterized by?
What is the 'off' state of the receptor characterized by?
What happens to the G protein when a peptide hormone binds to the receptor?
What happens to the G protein when a peptide hormone binds to the receptor?
Which statement correctly describes a property of lipid-soluble hormones?
Which statement correctly describes a property of lipid-soluble hormones?
Which of the following hormones is NOT classified as a steroid hormone?
Which of the following hormones is NOT classified as a steroid hormone?
Which of the following is NOT a peptide hormone?
Which of the following is NOT a peptide hormone?
What characterizes water-soluble hormones in contrast to lipid-soluble hormones?
What characterizes water-soluble hormones in contrast to lipid-soluble hormones?
What indicates the 'on' state of the receptor?
What indicates the 'on' state of the receptor?
Which of the following hormones is included in the list of peptide hormones?
Which of the following hormones is included in the list of peptide hormones?
What role does GTP play in the function of the G protein?
What role does GTP play in the function of the G protein?
Which type of receptor is primarily associated with the described G protein pathways?
Which type of receptor is primarily associated with the described G protein pathways?
What is the consequence of the activated G protein moving along the membrane?
What is the consequence of the activated G protein moving along the membrane?
What happens when IP3 binds to its specific receptor on the reticulum?
What happens when IP3 binds to its specific receptor on the reticulum?
What role does calcium play in the mechanism used by oxytocin?
What role does calcium play in the mechanism used by oxytocin?
Which enzyme is responsible for breaking down cAMP to regulate signal pathways?
Which enzyme is responsible for breaking down cAMP to regulate signal pathways?
Where are peptide hormones, such as oxytocin, primarily located?
Where are peptide hormones, such as oxytocin, primarily located?
Which of these is NOT a peptide hormone?
Which of these is NOT a peptide hormone?
What initiates muscle contractions in the context of calcium signaling?
What initiates muscle contractions in the context of calcium signaling?
What is the state of receptors for steroid hormones when activated?
What is the state of receptors for steroid hormones when activated?
Which hormone is peptide in nature?
Which hormone is peptide in nature?
Which mechanism prevents persistent activation of signaling pathways in cells?
Which mechanism prevents persistent activation of signaling pathways in cells?
Which hormone is steroid in nature?
Which hormone is steroid in nature?
What is a typical property of peptide hormones?
What is a typical property of peptide hormones?
What is a typical property of steroid hormones?
What is a typical property of steroid hormones?
Which enzyme activates the GPCR?
Which enzyme activates the GPCR?
Which of the following is NOT a property of peptide hormones?
Which of the following is NOT a property of peptide hormones?
Which hormone is primarily involved in glucose metabolism and is peptide in nature?
Which hormone is primarily involved in glucose metabolism and is peptide in nature?
What type of receptor do steroid hormones typically interact with?
What type of receptor do steroid hormones typically interact with?
Study Notes
Hormones
- Peptide hormones include oxytocin, insulin, glucagon, FSH, LH, GH, PTH, and ADH.
- Peptide hormones are water-soluble, hydrophilic, and large, preventing them from freely crossing the phospholipid bilayer.
- Require receptors on the cell membrane and utilize 2nd Messenger Systems (Gs, Gq, Gi).
- Steroid hormones include testosterone, estrogen, progesterone, aldosterone, cortisol, and gonadocorticoids.
- Steroid hormones are lipid-soluble, derived from cholesterol, and can pass through cell membranes to bind with intracellular receptors.
G Protein-Coupled Receptors (GPCR)
- GPCRs have a structure comprising seven transmembrane helices.
- Binding sites for ligands are external, with intracellular sites for G proteins.
- The G protein is normally bound to GDP in an inactive state; hormone binding switches it to an active state by exchanging GDP for GTP.
- Activated G proteins move along the membrane to interact with effector enzymes like adenylate cyclase.
Adenylate Cyclase and cAMP
- Activated G stimulatory (Gs) protein activates adenylate cyclase, increasing its activity.
- Adenylate cyclase converts ATP to cyclic AMP (cAMP); GTPase activity of Gs turns GTP back to GDP, deactivating the G protein.
- cAMP activates Protein Kinase A (PKA), which phosphorylates various proteins, influencing:
- Membrane permeability for ions through channel proteins.
- Metabolic pathways including glycolysis by phosphorylating enzymes.
- Gene transcription and cell proliferation via phosphorylation of transcription factors.
Calcium and Calmodulin
- Calcium ions (Ca²⁺) activate calmodulin, leading to kinase activation for downstream effects.
- This mechanism, notably used by oxytocin, enhances intracellular calcium levels to trigger contractions.
Inhibition Mechanisms
- Phosphodiesterase (PDE) breaks down cAMP to regulate signaling pathways, preventing continuous activation.
- Phospholipase C may also contribute to inhibition of pathways.
Summary of Hormone Characteristics
- Peptide hormones (e.g., oxytocin, insulin) are water-soluble and act on cell membranes.
- Steroid hormones (e.g., testosterone, cortisol) are lipid-soluble and act within the cell or nucleus.
Review Questions
- Identify peptide and steroid hormones based on their properties and roles in the body.
- Understand the mechanisms of GPCR activation and the roles of G proteins and adenylate cyclase in cellular signaling.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on receptor pathways in endocrinology. This quiz covers hormone interactions and the role of G proteins in signaling. Enhance your understanding of how peptide hormones function in the body.
