Chromatin Structure and Function Exam 1

The difference in electrical charge across a neuron's membrane when it's not transmitting a signal.

Neurons that depolarize the membrane, increasing the likelihood of an action potential.

Neurons that hyperpolarize the membrane, decreasing the likelihood of an action potential.

Voltage-gated channels that open when an action potential reaches the axon terminal, allowing calcium ions (Ca²⁺) to enter.

The process of using the energy stored in a proton (H⁺) gradient across a membrane to generate ATP.

A process that marks histones for remodeling or degradation. It involves attaching a small protein called ubiquitin to histones, changing their structure and function.

Specialized protein complexes that use energy from ATP to reposition or remove nucleosomes from DNA. This allows access for transcription factors and other regulatory proteins.

Repetitive DNA sequences found at the ends of chromosomes. They prevent degradation and ensure complete replication of the chromosome.

The region on a chromosome where kinetochores attach, enabling proper chromosome segregation during cell division. It's made up of heterochromatin and satellite DNA.

Specific DNA sequences where DNA replication begins. Eukaryotic chromosomes have multiple origins of replication to speed up the process.

The less condensed form of chromatin, allowing for active transcription. It's found in regions where genes are actively being expressed.

The tightly packed form of chromatin, limiting transcription. It's often found in regions of the genome that are inactive.

Programmed cell death, a controlled process where a cell self-destructs to prevent damage to surrounding cells.

A small protein tag that marks misfolded proteins for degradation.

A protein complex responsible for breaking down misfolded proteins tagged with ubiquitin.

Degradation of misfolded proteins in the endoplasmic reticulum (ER).

These proteins facilitate the fusion of vesicles with target membranes, ensuring correct delivery of cargo.

These proteins are located on vesicles and help guide them to the correct target membranes.

These proteins are located on target membranes and work with v-SNAREs for vesicle fusion.

These small GTPases regulate vesicle targeting and docking, ensuring vesicles go to the right location.

These proteins coat vesicles during formation, shaping the membrane and selecting cargo for transport.

Proteins like +TIPs bind to the growing (+) end of microtubules, stabilizing them and influencing microtubule dynamics. GTP-tubulin caps the growing end, promoting stability. When this cap is lost, microtubules rapidly depolymerize.

Microtubules are nucleated from the microtubule organizing center (MTOC), primarily within the centrosome. Gamma-tubulin complexes form rings that serve as templates for the addition of alpha- and beta-tubulin dimers, initiating microtubule growth.

Astral microtubules radiate outward from the centrosome, connecting the spindle to the cell membrane. Kinetochore microtubules attach to kinetochores on chromosomes, responsible for pulling chromatids apart. Interpolar microtubules overlap at the spindle's center, pushing the poles apart and stabilizing the spindle structure.

In metaphase, chromosomes align centrally at the metaphase plate with each sister chromatid's kinetochore attached to kinetochore microtubules from opposite spindle poles. Anaphase marks the separation of sister chromatids: kinetochore microtubules shorten (Anaphase A), pulling chromatids apart, while interpolar microtubules lengthen (Anaphase B), pushing poles further apart.

Dynein moves towards the (-) end of microtubules, typically towards the cell center. It transports cargoes inwards, like vesicles and organelles. Kinesin moves towards the (+) end of microtubules, usually towards the cell periphery. It carries cargoes outwards, like vesicles and organelles.

The actin cytoskeleton is present throughout the cell, but it's particularly concentrated near the cell cortex (just under the plasma membrane). It provides structural support, influencing cell shape, adhesion, and movement.

Intermediate filaments are strong, rope-like structures made of fibrous proteins. They provide support to the cell and help regulate DNA processes.

Intermediate filaments assemble through a specific process involving monomers, dimers, tetramers, and protofilaments, creating a complex interwoven structure.

Intermediate filaments differ from actin and microtubules by lacking polarity, meaning they don't have distinct ends like the others.

Phosphorylation typically leads to the disassembly of intermediate filaments, while dephosphorylation promotes their reassembly, regulating their structure and function.

Microtubules are hollow tubes formed by alpha- and beta-tubulin dimers arranged in a precise pattern, crucial for many cellular processes.

Microtubules have distinct ends: the plus end (beta-tubulin exposed) grows faster, while the minus end (alpha-tubulin exposed) grows slower.

Dynamic instability refers to the continuous growth and shrinkage of microtubules at the plus end, driven by GTP hydrolysis, allowing them to explore space.

The minus end of a microtubule is often anchored at the microtubule-organizing center (MTOC), such as the centrosome.

The plus end of microtubules extends towards the cell periphery, reaching out to the cell's outer edges.

Microtubules play a crucial role in cell division, transporting cargo, and maintaining cell shape, showcasing their dynamic and essential nature.