CELS191 Lecture 9 - Nucleus Vocabulary

Flashcards for CELS191 Lecture 9 Nucleus, focusing on vocabulary related to cell structure, DNA organization, and nuclear functions.

Ribosomes

Complexes made of ribosomal RNAs and proteins, found attached to the rough ER or free in the cytoplasm, responsible for protein synthesis.

Nucleus

The most prominent organelle in the cell, containing most of the cell's genes and serving as the repository of inherited genetic information and the cell’s control center.

Nuclear Envelope

The double membrane surrounding the nucleus, consisting of outer and inner membranes with a perinuclear space in between.

Nucleolus

A prominent area within the nucleus where ribosomal RNA is synthesized.

Nuclear Pores

Channels made of proteins (nucleoporins) that span the nuclear envelope, controlling the movement of molecules (e.g. RNA) into and out of the nucleus.

Nuclear Lamina

The inner surface of the nuclear envelope, lined by intermediate filaments, which maintains the shape of the nucleus and helps organise DNA packing. Defective lamina leads to Hutchinson-Gilford-Progeria syndrome (accelerated ageing)

mRNA, tRNA, and ribosomal subunits

Molecules such as messenger RNA, transfer RNA, and ribosomal subunits, which move from the nucleus to the cytoplasm.

Control Signals, Building Materials, and Energy

Molecules such as control signals, building materials, and energy, which move from the cytoplasm to the nucleus.

Histones

Specific proteins that interact with the DNA helix to form a 10-nm diameter fiber, with each 'bead' called a nucleosome.

Euchromatin

Less electron-opaque DNA, containing genes being used by the cell. It is less tightly packed, allowing access for transcriptional machinery.

Heterochromatin

More electron-opaque DNA, containing genes not being used by that cell. It is more tightly packed.

DNA

A nucleotide polymer that must be very well packed within the nucleus but still accessible — double helix.

Nucleolus

Non-membrane bound specialized region within the nucleus that is responsible for making ribosomal RNA and ribosomal subunits.

DNA structure

DNA + histone proteins = chromatin fibres, specific proteins called histones (H2–H4) coil DNA into a ‘bead’ called a nucleosome. Nucleosome units are formed, allowing further packing into fibres → condensed chromasomes.

Heterochromatin

Heterochromatin is more dense/ compact, and not genetically active.

Euchromatin

Less dense/ compact, and more genetically active.