cell cycle and cell communication

anaphase

-centromeres split, and the sister chromatids separate

-daughter chromosomes moves toward opposite poles, pulled by shortening spindle fibers

G1

-cell grows rapidly and performs metabolic functions

-organelles are duplicated and proteins needed for DNA synthesis are produced

-ensures the cell has enough energy and materials to prepare for DNA replication

cytokinesis

cytoplasm divides, completing cell division

in animals cells, a cleavage furrow forms and pinches inward until two daughter cells separate

in plant cells, a cell plate forms in the middle of the cell, developing into a new cell wall

result = two genetically identical daughter cells

S phase

-cell replicates its DNA, producing two identical copies of each chromosome

-each chromosome now consists of two sister chromatids joined at the centromere

-guarantees that both daughter cells will receive a complete set of genetic information

Metaphase

-Chromosomes line up single file along the metaphase plate at the center of the cell

-Each chromosome’s centromere is attached to spindle fibers from opposite poles

-stage identified by chromosomes perfectly aligned along the cell’s equator

G2

-Cell continues to grow and produce proteins required for mitosis

-Organelles such as mitochondria and centrioles are duplicated, cytoplasm expands

-Final preparation for cell division, ensuring everything is ready for mitosis

prophase

-Chromatin condenses into visible chromosomes; each chromosome has two sister chromatids joined at the centromere

-nucleolus disappears and the nuclear envelope begins to break down

-centrosomes move toward opposite poles, and spindle fibers negin forming from microtubules

-first stage where chromosomes are visible under a microscope

g1 checkpoint

cell verifies that is has grown sufficiently and that the DNA is undamaged

• if yes → S phase; if no → G0 state

determines whether division could continue

telophase

chromosomes reach opposite poles and begin to uncoil back into chromatin

nuclear envelopes reform, and nuceloli reappear

spindle apparatus breaks down

final stage of nuclear division

G2 checkpoint

checks if any of the DNA was damaged and if it was completely copied during S phase

• if errors are detected the cell cycle pauses for repair before mitosis begins

M checkpoint

cell examines whether all the sister chromatids are correctly attached to the spindle microtubules

paracrine signaling

molecules that travel short distances to stimulate nearby cells like neurotransmitters diffusing across a synapse

ex. quorum sensing in bacteria

endocrine signaling

involves hormones that travel through the bloodstream to reach distant target cells

autocrine signaling

occurs when a cell releases a signal that binds to receptors on the same cell

signal transduction pathways steps

Reception

Transduction

Response

signal transduction

• G-protein coupled receptor activates a G protein, which in turn activates the enzyme Adenylyl Cyclase, converting ATP into cAMP, a second messenger, second messenger triggers an intracellular signaling cascade

• receptor tyrosine kinases (RTKs), ligand binding causes monomers to form a dimer which activates kinase activity and leads to phosphorylation cascades (each kinase adds a phosphate from an ATP molecule to tyrosines on the other monomer)

• ion channel receptors: contain a portion of the protein that changes shape and acts like a gate when its ligand binds to it

cellular response

• gene expression changes

• enzyme activation

• apoptosis (programmed cell death carried out by caspases)

rtks and cancer

• rtks are often involved in pathways that stimulate cell division; such rtks are oncogenic which means they accelerate cell division causing cancer to develop

• many cancer treatments interfere w/ rtk signaling pathways