Cell and Molecular Biology Flashcards

Vocabulary flashcards for Cell and Molecular Biology, covering key terms and definitions from lecture notes.

Nuclear Envelope

A double membrane that encloses the DNA in eukaryotic cells.

Compartmentalization

Increases control of processes but creates a problem as large molecules (mRNA and proteins) have to move in and out of the nucleus.

Nuclear pore

Enables movement of molecules in and out of the nucleus.

Prokaryotes

Lack nucleus and membrane-bound organelles, are small ~1.0 µm in diameter, with a simple structure, unicellular or acellular (viruses)

Eukaryotes

Have membrane-bound organelles and nucleus, ~10-100 µm, can be uni or multicellular

Endoplasmic Reticulum Contiguity

the space between the inner and outer nuclear membranes is directly connected with the lumen of the ER

Inner Nuclear Membrane

Carries nuclear specific proteins such as the membrane proteins that organize the nuclear lamina, a fibrous network that provides structural support to the nucleus

Nuclear pore complexes

The sole channels through which polar molecules and macromolecules pass through the nuclear envelope

Nuclear localization signals (NLS)

Is a protein tag that identifies proteins destined for the nucleus.

Importins

Carry proteins into the nucleus.

Exportins

Carry proteins out of the nucleus.

RAN

The energy supplied by GTP hydrolysis drives nuclear transport.

Nucleolus

Most prominent structure in the nucleus and the site of ribosome biogenesis where transcribed and processed rRNA are combined with proteins to form the ribosomal subunits

Ribosomes

Translate mRNA into proteins in the cytoplasm (rough ER and in cytosol)

Nucleosome Core Particle

Consists of 147 base pairs of DNA wound around a protein core of histones

Histone H1

Binds to both the DNA and nucleosome in the area where the DNA exits the nucleosome stabilizing the chromatin fibre

Euchromatin

Transcriptionally active, relatively loose nucleosome arrangement

Heterochromatin

Transcriptionally inactive associated chromatin conformations that are highly compacted – inactive genes, long repeat sequence arrays or regions adjacent to repeats.

Nucleosome sliding

The enzyme activity performed by histone remodelers to promote either euchromatin or heterochromatin structure and accessibility

Histone modification

Each core histone has a ‘tail’ that extends out of the nucleosome core that can be modified by methylation and acetylation to influence chromatin structure and thus gene expression

X chromosome inactivation

To ensure equal gene expression between XY and XX individuals the extra X is transcriptionally silenced in early development

G1 Phase

Cell recovers from previous division, Cell grows and increases in volume; high amount of protein synthesis, Organelles, such as the mitochondria and ribosomes, are duplicated

S Phase

DNA is replicated, resulting in two identical copies (or sister chromatids) of each chromosome joined at the centromere

G2 Phase

Cell continues to grow and increase in volume; proteins required for chromosome manipulation are produced

Prophase

At prophase, the replicated chromosomes, each consisting of two closely associated sister chromatids, condense. Outside the nucleus, the mitotic spindle assembles between the two centrosomes, which have begun to move apart.

Prometaphase

Prometaphase starts abruptly with the breakdown of the nuclear envelope. Chromosomes can now attach to spindle microtubules via their kinetochores and undergo active movement.

Metaphase

At metaphase, the chromosomes are aligned at the equator of the spindle, midway between the spindle poles. The paired kinetochore microtubules on each chromosome attach to opposite poles of the spindle.

Anaphase

At anaphase, the sister chromatids synchronously separate, and each is pulled slowly toward the spindle pole it is attached to. The kinetochore microtubules get shorter, and the spindle poles also move apart, both contributing to chromosome segregation.

Telophase

During telophase, the two sets of chromosomes arrive at the poles of the spindle. A new nuclear envelope reassembles around each set, completing the formation of two nuclei and marking the end of mitosis. The division of the cytoplasm begins with the assembly of the contractile ring.

Cytokinesis

The cytoplasm is divided in two by a contractile ring of actin and myosin filaments, which pinches in the cell to create two daughters, each with one nucleus.