Cell Communication AP BIO youtube notes

What is the G0 phase in the cell cycle?

A resting state where cells exit the cycle and do not divide, often permanently in specialized cells like neurons.

What is quorum sensing in bacteria?

A cell communication process where bacteria release signaling molecules that activate gene expression when a threshold concentration is reached.

What occurs in type 2 diabetes regarding insulin function?

Cells become resistant to insulin, leading to high blood glucose levels despite insulin presence.

What is the significance of cyclins and CDKs in cell cycle regulation?

Cyclins activate CDKs to promote progression through cell cycle checkpoints.

How does insulin regulate blood glucose levels?

Insulin triggers glucose uptake and storage, decreasing blood glucose to maintain homeostasis.

What are the key differences between positive and negative feedback loops?

Negative feedback reduces output to maintain stability, while positive feedback amplifies activity to drive processes to completion.

How does the binding of a ligand to its receptor initiate cell signaling?

The ligand binds based on complementary shape, causing the receptor to change shape and activate downstream signaling.

What is the inactive state of a G protein in G protein-coupled receptor signaling?

The G protein is bound to GDP and not interacting with adenylyl cyclase.

What are the two main types of ligands involved in cell signaling?

Hormones that travel long distances through the bloodstream
Local regulators for short-distance communication.

What triggers the G0 phase in cells?

Cells exit the cycle into G0 in response to differentiation signals or lack of growth signals, often permanently.

What change occurs in the G protein when epinephrine binds to its receptor?

The G protein discharges GDP and binds GTP, becoming activated.

What is the role of cyclic AMP (cAMP) in G protein-coupled receptor signaling?

cAMP is a second messenger produced by adenylyl cyclase that activates kinase cascades leading to cellular responses.

Explain the role of insulin and glucagon in blood glucose homeostasis.

Insulin decreases blood glucose by promoting uptake and storage after eating, while glucagon increases blood glucose by inducing glycogen breakdown during fasting.

What occurs during the S phase of interphase?

DNA replication or chromosome duplication takes place.

What distinguishes steroid hormones from water-soluble hormones in cell signaling?

Steroid hormones diffuse through the membrane and bind to cytoplasmic receptors, acting as transcription factors,

Water-soluble hormones bind to membrane receptors and activate second messengers.

What is the function of protein kinases in the signal transduction pathway triggered by epinephrine?

They are relay molecules that get activated sequentially, amplifying the signal through phosphorylation.

How does the p53 protein prevent cancer?

p53 halts the cell cycle to allow DNA repair or initiates apoptosis if damage is irreparable.

What is the difference between negative and positive feedback in biological systems?

Negative feedback decreases the output to return to a set point, promoting stability, while positive feedback amplifies activity to drive a process to completion.

What role do cell cycle checkpoints play?

Checkpoints assess internal conditions and determine whether to proceed to the next phase, halt, or initiate apoptosis if conditions are not met.

How does p53 contribute to preventing cancer?

p53 halts the cell cycle for DNA repair or induces apoptosis if damage is irreparable.

What occurs during anaphase of mitosis?

Spindle fibers pull sister chromatids apart and move them to opposite poles of the cell, elongating the cell.

What is the role of second messengers like cAMP in signal transduction?

Second messengers relay and amplify signals within the cell after receptor activation, leading to cellular responses such as enzyme activation.

How does disregulation of the cell cycle lead to cancer?

Mutations in proto-oncogenes and tumor suppressor genes cause unregulated cell division, leading to tumor formation and cancer.

What is apoptosis and why is it important?

Apoptosis is programmed cell death that prevents damaged or unnecessary cells from harming the organism.

Define homeostasis in biological systems.

Homeostasis is the tendency of a living system to maintain its internal conditions at a relatively constant, optimal level.

What happens during the G2 phase of interphase?

The cell grows additional structures required for cell division.

How does a set point function in negative feedback systems?

A set point is the target value around which a homeostatic process fluctuates, and feedback mechanisms act to maintain this value.

Describe the main effect of epinephrine on liver cells during the fight-or-flight response.

Epinephrine triggers glycogen hydrolysis into glucose, which is released into the bloodstream for energy.

What is the mechanism of positive feedback during childbirth?

Baby's growth stretches the uterus, triggering oxytocin release, which increases contractions, leading to more oxytocin release until birth occurs.

What happens if p53 is nonfunctional due to mutation?

Cells with damaged DNA continue dividing, increasing the risk of further mutations and cancer.

What are the three phases of cell signaling?

Reception, transduction, and cellular response.

How do cyclins and CDKs regulate the cell cycle?

Cyclins rise and fall in concentration to activate CDKs, which then promote progression through cell cycle phases; MPF is an example of a cyclin-CDK complex.

What occurs in type 2 diabetes regarding insulin sensitivity?

Cells become insulin resistant, so insulin binding does not trigger the signaling cascade, resulting in high blood glucose levels.

What role does feedback play in homeostasis?

Feedback mechanisms regulate internal conditions, with negative feedback restoring set points and positive feedback amplifying processes.

What triggers the rapid shutdown of the epinephrine signaling pathway after a threat is removed?

The receptor dissociates epinephrine, the G protein hydrolyzes GTP to GDP, and phosphatases remove phosphates from kinases, stopping the cascade.

Describe the sequence of events in mitosis.

Prophase, metaphase, anaphase, telophase, followed by cytokinesis.

What is apoptosis and why is it important?

Programmed cell death that removes damaged or unnecessary cells, preventing potential tumor formation.

What is the function of tumor suppressor genes like p53?

p53 detects DNA damage, halts the cell cycle to allow repair, or induces apoptosis if damage is irreparable, preventing cancer.

What is the primary function of mitosis in eukaryotic cells?

Mitosis duplicates the chromosomes, transmitting the cell's entire genome to its daughter cells, enabling growth, repair, and reproduction in multicellular and unicellular organisms.

What is cytokinesis?

The division of the cytoplasm that results in two daughter cells.

What are the main phases of the cell cycle?

The main phases are interphase (G1, S, G2) where the cell grows and prepares, and M phase (mitosis and cytokinesis) where the cell divides.

How does the mutation of the Ross proto-oncogene contribute to cancer?

Mutated Ross becomes constitutively active, continuously promoting cell division even without external signals, contributing to about 30% of human cancers.

What is the role of spindle fibers during metaphase?

Spindle fibers attach to chromosomes and align them at the cell's equator.

What are the main phases of the cell cycle?

Interphase (G1, S, G2) and M phase (mitosis and cytokinesis).

What is the significance of the S phase in the cell cycle?

DNA replication or chromosome duplication occurs during the S phase.

What is the G0 phase and why do some cells enter it?

G0 is a resting state where cells exit the cell cycle and do not divide; highly specialized cells like nerve or muscle cells enter G0 permanently.

How does epinephrine trigger glycogen breakdown in liver cells?

Epinephrine binds to G protein-coupled receptors, activating a phosphorylation cascade that leads to activation of glycogen phosphorylase, which breaks down glycogen into glucose.

What is the function of MPF (maturation promoting factor)?

MPF, formed by cyclin and CDK, triggers the cell's entry into mitosis by passing the G2 checkpoint.

How do kinases become activated in a phosphorylation cascade?

Kinases are activated by gaining a phosphate group through phosphorylation, which enables them to activate the next kinase in the chain.

Describe how antagonistic negative feedback loops work to regulate body temperature.

One loop activates cooling mechanisms when temperature is high, and another activates heating when temperature is low, both working to maintain a stable temperature.

What is apoptosis and why is it important?

Apoptosis is programmed cell death, a regulated process that prevents damaged or unnecessary cells from damaging surrounding tissue.

What is the role of proto-oncogenes and how can they become oncogenes?

Proto-oncogenes promote cell division; mutations can turn them into oncogenes, which are constitutively active and cause excessive cell proliferation.

What is the main event of telophase?

A new nuclear membrane forms around each set of separated chromosomes, which then spread out into interphase form, and nucleoli reappear.

What is the primary function of phosphorylation cascades in cell signaling?

They amplify a signal by sequentially activating kinases through phosphorylation, leading to a large cellular response from a single signal molecule.

How does type 1 diabetes differ from type 2 diabetes?

Type 1 is an autoimmune disorder where pancreatic cells cannot produce insulin, requiring injections; type 2 involves insulin resistance despite normal or high insulin levels.

How does ethylene facilitate fruit ripening through positive feedback?

Ripening fruit releases ethylene, which induces nearby fruit to produce more ethylene, accelerating ripening until all fruit are ripe.

What role do cyclins and CDKs play in cell cycle regulation?

Cyclins bind to CDKs to form MPF, which promotes progression through cell cycle checkpoints; cyclin levels fluctuate during the cycle.

What occurs during the G1 phase of interphase?

The cell increases in size and prepares for DNA replication.

Describe the key events of prophase in mitosis.

Chromosomes condense into X-like structures, the nuclear membrane disintegrates, and spindle apparatus begins to form from centrosomes.