MODULE 7: Chapter 8.1 Flashcards
What is the basis of biological diversity?
Complexity and high-level organization.
Why is communication critical in multicellular organisms?
To organize individuals to function as a group and respond to environmental changes.
What is the molecular basis of cell communication?
A biochemical pathway involving protein structural changes triggered by ligand binding.
What is the role of ligands in cell signaling?
They bind to receptor proteins to initiate cellular responses.
Give an example of a ligand and its corresponding receptor.
Glucagon binds to the glucagon receptor.
What is signal transduction?
The biochemical mechanism for transmitting extracellular signals across the plasma membrane.
What are the three types of biochemical responses involved in receptor protein activation?
- Covalent protein modifications
- Protein conformational changes
- Altered rates of protein expression.
What is a cell signaling pathway?
A linked set of biochemical reactions initiated by ligand-induced activation of a receptor protein.
What is the difference between upstream and downstream events in a signaling pathway?
Upstream events are early steps, while downstream events involve target protein modification.
What percentage of protein-coding genes in the human genome are involved in signal transduction?
9%.
How many G protein–coupled receptors are encoded in the human genome?
616.
What type of hormones are considered first messengers?
Biologically active compounds released into the circulatory system.
What are the three mechanisms through which hormones can act?
- Endocrine
- Paracrine
- Autocrine.
What is the significance of the discovery of insulin?
It controls blood glucose levels and treats human diabetes.
Who were the key figures in the discovery of insulin?
Frederick Banting and Charles Best.
What is an example of a first messenger that is not a peptide hormone?
Nitric oxide.
Fill in the blank: Hormones are released into the _______ system.
circulatory.
What biological effect does acetylcholine have?
Muscle contraction.
What is the biological response of epinephrine?
Increased pulse rate and glycogen degradation.
What role do prostaglandins play in the body?
Inflammation.
Which hormone is produced by the adrenal gland and has anti-inflammatory effects?
Cortisol.
How do hormones function locally?
As paracrine or autocrine signals.
What is the main function of insulin?
Glucose uptake.
What are metabolites?
Metabolites are small molecules, such as amino acids and nucleotides, released from other cells in the organism.
What are prostaglandins involved in?
Prostaglandins are involved in inflammation.
Where is testosterone produced?
Testosterone is produced in the testes (males only) and adrenal glands.
What role does nitric oxide (NO) play in signaling?
Nitric oxide activates signaling pathways by diffusing across cell membranes and directly activating signaling proteins.
What is the function of guanylate cyclase in NO signaling?
Guanylate cyclase generates the second messenger cyclic GMP (cGMP) in response to nitric oxide.
What effect does nitric oxide have on smooth muscle cells?
Nitric oxide causes muscle relaxation and vasodilation, leading to increased blood flow.
What is sildenafil, and what is its primary use?
Sildenafil, marketed as Viagra, is an inhibitor of cGMP phosphodiesterase used to treat erectile dysfunction.
What is the role of cyclic GMP (cGMP) in vasodilation?
cGMP activates protein kinase G (PKG), leading to muscle relaxation and vasodilation.
What are the three other second messengers besides cAMP and cGMP?
- Diacylglycerol (DAG)
- Inositol-1,4,5-trisphosphate (IP3)
- Calcium ion (Ca2⁺)
How does phospholipase C (PLC) generate second messengers?
PLC hydrolyzes phosphatidylinositol-4,5-bisphosphate (PIP2) to form diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (IP3).
What is the effect of diacylglycerol (DAG) in signaling pathways?
DAG binds to and activates protein kinase C (PKC), which phosphorylates downstream targets.
What is the function of calmodulin in intracellular signaling?
Calmodulin binds to Ca2⁺ ions and activates a wide variety of target proteins.
What is signal amplification in the context of second messengers?
Signal amplification occurs when a first messenger activates multiple downstream enzymes, leading to a multiplicative effect on signaling.
Name the five abundant classes of receptor proteins in higher eukaryotes.
- G protein–coupled receptors
- Receptor tyrosine kinases
- Tumor necrosis factor receptors
- Nuclear receptors
- Ligand-gated ion channels
What is the function of G protein–coupled receptors (GPCRs)?
GPCRs activate heterotrimeric G proteins, leading to the activation of enzymes that generate second messengers.
How do receptor tyrosine kinases (RTKs) transmit signals?
RTKs phosphorylate tyrosine residues in target proteins, creating docking sites for intracellular signaling proteins.
What is the role of tumor necrosis factor (TNF) receptors?
TNF receptors regulate signaling pathways that control inflammation and apoptosis.
What is the primary function of ligand-gated ion channels?
Ligand-gated ion channels control the flow of ions across cell membranes in response to ligand binding.
What is the well-characterized ligand-gated ion channel mentioned?
The nicotinic acetylcholine receptor, which mediates ion transport in response to acetylcholine.
What is the mechanism by which acetylcholine transmits signals across neuromuscular junctions?
Acetylcholine is released from vesicles in the presynaptic neuron and binds to receptors on the postsynaptic membrane.
What type of protein is the nicotinic acetylcholine receptor?
GPCR protein
GPCR stands for G protein-coupled receptor.
What is the function of the nicotinic acetylcholine receptor?
Transmit physiologic signals across neuromuscular junctions in response to neuronal stimuli
What triggers the release of acetylcholine from presynaptic neurons?
Nerve impulse transmitted by membrane depolarization
Where do acetylcholine molecules bind in the nicotinic acetylcholine receptor?
To α subunits in the plasma membrane of muscle cells
What happens when acetylcholine binds to the nicotinic acetylcholine receptor?
Triggers a conformational change that opens the ion channel
Which ions flow into the muscle cell upon ion channel opening?
- Na⁺ * K⁺
What is the result of membrane depolarization in muscle cells?
Induces Ca2⁺ release from the sarcoplasmic reticulum
What initiates muscle contraction in response to calcium release?
Conformational change in muscle proteins
What is the subunit composition of the nicotinic acetylcholine receptor?
α2βγδ
What type of protein complex is the nicotinic acetylcholine receptor?
Pentameric transmembrane protein
What is the role of ligand binding in signal transduction?
Induces conformational changes that alter receptor function
What is a first messenger?
An extracellular ligand that binds to a receptor protein
What is a second messenger?
A molecule that transmits, amplifies, and terminates a biochemical signal
What does insulin control in the body?
Blood glucose levels
What is the role of nitric oxide (NO) in muscle cells?
Causes muscle relaxation and vasodilation
What is cyclic GMP (cGMP)?
A second messenger for numerous signaling pathways
What is the function of adenylate cyclase?
Produces the second messenger cAMP from ATP
What does calmodulin bind to?
Four Ca2⁺ ions
What is signal amplification?
Process where initial signals lead to multiple downstream events
What are receptor tyrosine kinases (RTKs)?
Receptor proteins that phosphorylate tyrosine residues in target proteins
What is the function of phospholipase C (PLC)?
Hydrolyzes PIP2 to form DAG and IP3
What does the term ‘autocrine’ refer to?
A hormone that activates receptors on the same type of cell
What is the role of cyclic AMP (cAMP)?
Activates numerous signaling proteins and target proteins
What happens when acetylcholine binds to the nicotinic acetylcholine receptor?
Opens the ion channel and allows Na⁺ and K⁺ to flow across the membrane
What is the primary function of ligand-gated ion channels?
Control the flow of ions across cell membranes in response to ligand binding
What does inositol-1,4,5-trisphosphate (IP3) activate?
Ca2⁺ channels in the endoplasmic reticulum
