MODULE 7: Chapter 8.1

Question 1

What is the basis of biological diversity?

Answer 1

Complexity and high-level organization.

Question 2

Why is communication critical in multicellular organisms?

Answer 2

To organize individuals to function as a group and respond to environmental changes.

Question 3

What is the molecular basis of cell communication?

Answer 3

A biochemical pathway involving protein structural changes triggered by ligand binding.

Question 4

What is the role of ligands in cell signaling?

Answer 4

They bind to receptor proteins to initiate cellular responses.

Question 5

Give an example of a ligand and its corresponding receptor.

Answer 5

Glucagon binds to the glucagon receptor.

Question 6

What is signal transduction?

Answer 6

The biochemical mechanism for transmitting extracellular signals across the plasma membrane.

Question 7

What are the three types of biochemical responses involved in receptor protein activation?

Answer 7

• Covalent protein modifications
• Protein conformational changes
• Altered rates of protein expression.

Question 8

What is a cell signaling pathway?

Answer 8

A linked set of biochemical reactions initiated by ligand-induced activation of a receptor protein.

Question 9

What is the difference between upstream and downstream events in a signaling pathway?

Answer 9

Upstream events are early steps, while downstream events involve target protein modification.

Question 10

What percentage of protein-coding genes in the human genome are involved in signal transduction?

Answer 10

9%.

Question 11

How many G protein–coupled receptors are encoded in the human genome?

Answer 11

616.

Question 12

What type of hormones are considered first messengers?

Answer 12

Biologically active compounds released into the circulatory system.

Question 13

What are the three mechanisms through which hormones can act?

Answer 13

• Endocrine
• Paracrine
• Autocrine.

Question 14

What is the significance of the discovery of insulin?

Answer 14

It controls blood glucose levels and treats human diabetes.

Question 15

Who were the key figures in the discovery of insulin?

Answer 15

Frederick Banting and Charles Best.

Question 16

What is an example of a first messenger that is not a peptide hormone?

Answer 16

Nitric oxide.

Question 17

Fill in the blank: Hormones are released into the _______ system.

Answer 17

circulatory.

Question 18

What biological effect does acetylcholine have?

Answer 18

Muscle contraction.

Question 19

What is the biological response of epinephrine?

Answer 19

Increased pulse rate and glycogen degradation.

Question 20

What role do prostaglandins play in the body?

Answer 20

Inflammation.

Question 21

Which hormone is produced by the adrenal gland and has anti-inflammatory effects?

Answer 21

Cortisol.

Question 22

How do hormones function locally?

Answer 22

As paracrine or autocrine signals.

Question 23

What is the main function of insulin?

Answer 23

Glucose uptake.

Question 24

What are metabolites?

Answer 24

Metabolites are small molecules, such as amino acids and nucleotides, released from other cells in the organism.

Question 25

What are prostaglandins involved in?

Answer 25

Prostaglandins are involved in inflammation.

Question 26

Where is testosterone produced?

Answer 26

Testosterone is produced in the testes (males only) and adrenal glands.

Question 27

What role does nitric oxide (NO) play in signaling?

Answer 27

Nitric oxide activates signaling pathways by diffusing across cell membranes and directly activating signaling proteins.

Question 28

What is the function of guanylate cyclase in NO signaling?

Answer 28

Guanylate cyclase generates the second messenger cyclic GMP (cGMP) in response to nitric oxide.

Question 29

What effect does nitric oxide have on smooth muscle cells?

Answer 29

Nitric oxide causes muscle relaxation and vasodilation, leading to increased blood flow.

Question 30

What is sildenafil, and what is its primary use?

Answer 30

Sildenafil, marketed as Viagra, is an inhibitor of cGMP phosphodiesterase used to treat erectile dysfunction.

Question 31

What is the role of cyclic GMP (cGMP) in vasodilation?

Answer 31

cGMP activates protein kinase G (PKG), leading to muscle relaxation and vasodilation.

Question 32

What are the three other second messengers besides cAMP and cGMP?

Answer 32

* Diacylglycerol (DAG) * Inositol-1,4,5-trisphosphate (IP3) * Calcium ion (Ca2⁺)

Question 33

How does phospholipase C (PLC) generate second messengers?

Answer 33

PLC hydrolyzes phosphatidylinositol-4,5-bisphosphate (PIP2) to form diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (IP3).

Question 34

What is the effect of diacylglycerol (DAG) in signaling pathways?

Answer 34

DAG binds to and activates protein kinase C (PKC), which phosphorylates downstream targets.

Question 35

What is the function of calmodulin in intracellular signaling?

Answer 35

Calmodulin binds to Ca2⁺ ions and activates a wide variety of target proteins.

Question 36

What is signal amplification in the context of second messengers?

Answer 36

Signal amplification occurs when a first messenger activates multiple downstream enzymes, leading to a multiplicative effect on signaling.

Question 37

Name the five abundant classes of receptor proteins in higher eukaryotes.

Answer 37

* G protein–coupled receptors * Receptor tyrosine kinases * Tumor necrosis factor receptors * Nuclear receptors * Ligand-gated ion channels

Question 38

What is the function of G protein–coupled receptors (GPCRs)?

Answer 38

GPCRs activate heterotrimeric G proteins, leading to the activation of enzymes that generate second messengers.

Question 39

How do receptor tyrosine kinases (RTKs) transmit signals?

Answer 39

RTKs phosphorylate tyrosine residues in target proteins, creating docking sites for intracellular signaling proteins.

Question 40

What is the role of tumor necrosis factor (TNF) receptors?

Answer 40

TNF receptors regulate signaling pathways that control inflammation and apoptosis.

Question 41

What is the primary function of ligand-gated ion channels?

Answer 41

Ligand-gated ion channels control the flow of ions across cell membranes in response to ligand binding.

Question 42

What is the well-characterized ligand-gated ion channel mentioned?

Answer 42

The nicotinic acetylcholine receptor, which mediates ion transport in response to acetylcholine.

Question 43

What is the mechanism by which acetylcholine transmits signals across neuromuscular junctions?

Answer 43

Acetylcholine is released from vesicles in the presynaptic neuron and binds to receptors on the postsynaptic membrane.

Question 44

What type of protein is the nicotinic acetylcholine receptor?

Answer 44

GPCR protein ## Footnote GPCR stands for G protein-coupled receptor.

Question 45

What is the function of the nicotinic acetylcholine receptor?

Answer 45

Transmit physiologic signals across neuromuscular junctions in response to neuronal stimuli

Question 46

What triggers the release of acetylcholine from presynaptic neurons?

Answer 46

Nerve impulse transmitted by membrane depolarization

Question 47

Where do acetylcholine molecules bind in the nicotinic acetylcholine receptor?

Answer 47

To α subunits in the plasma membrane of muscle cells

Question 48

What happens when acetylcholine binds to the nicotinic acetylcholine receptor?

Answer 48

Triggers a conformational change that opens the ion channel

Question 49

Which ions flow into the muscle cell upon ion channel opening?

Answer 49

* Na⁺ * K⁺

Question 50

What is the result of membrane depolarization in muscle cells?

Answer 50

Induces Ca2⁺ release from the sarcoplasmic reticulum

Question 51

What initiates muscle contraction in response to calcium release?

Answer 51

Conformational change in muscle proteins

Question 52

What is the subunit composition of the nicotinic acetylcholine receptor?

Answer 52

α2βγδ

Question 53

What type of protein complex is the nicotinic acetylcholine receptor?

Answer 53

Pentameric transmembrane protein

Question 54

What is the role of ligand binding in signal transduction?

Answer 54

Induces conformational changes that alter receptor function

Question 55

What is a first messenger?

Answer 55

An extracellular ligand that binds to a receptor protein

Question 56

What is a second messenger?

Answer 56

A molecule that transmits, amplifies, and terminates a biochemical signal

Question 57

What does insulin control in the body?

Answer 57

Blood glucose levels

Question 58

What is the role of nitric oxide (NO) in muscle cells?

Answer 58

Causes muscle relaxation and vasodilation

Question 59

What is cyclic GMP (cGMP)?

Answer 59

A second messenger for numerous signaling pathways

Question 60

What is the function of adenylate cyclase?

Answer 60

Produces the second messenger cAMP from ATP

Question 61

What does calmodulin bind to?

Answer 61

Four Ca2⁺ ions

Question 62

What is signal amplification?

Answer 62

Process where initial signals lead to multiple downstream events

Question 63

What are receptor tyrosine kinases (RTKs)?

Answer 63

Receptor proteins that phosphorylate tyrosine residues in target proteins

Question 64

What is the function of phospholipase C (PLC)?

Answer 64

Hydrolyzes PIP2 to form DAG and IP3

Question 65

What does the term 'autocrine' refer to?

Answer 65

A hormone that activates receptors on the same type of cell

Question 66

What is the role of cyclic AMP (cAMP)?

Answer 66

Activates numerous signaling proteins and target proteins

Question 67

What happens when acetylcholine binds to the nicotinic acetylcholine receptor?

Answer 67

Opens the ion channel and allows Na⁺ and K⁺ to flow across the membrane

Question 68

What is the primary function of ligand-gated ion channels?

Answer 68

Control the flow of ions across cell membranes in response to ligand binding

Question 69

What does inositol-1,4,5-trisphosphate (IP3) activate?

Answer 69

Ca2⁺ channels in the endoplasmic reticulum