The Nucleus Flashcards
what is the nucleus
a large, membrane-bound structure usually located near the center of the cell
what can the nucleus be in terms of shape
spherical, elongated, or lobed, depending on the cell type.
what kind of cells loose their nucleus as they develop
RBC
what cells contain more than one nucleus
skeletal muscle cells and certain bone cells, called osteoclasts
the nucleus consists of three main things
nucleoplasm, nuclear envelope, nuclear pores, nucleolus, nucleolar organizer regions
what surrounds the nucleoplasm
the nuclear envelope
what is the nuclear envelope made of
two membranes separated by a space
what are nuclear pores
at many points on the surface of the nuclear envelope the inner and outer membranes of the nuclear envelope fuse they form pore like structures called nuclear pores
through what do molecules move from nucleus to cytoplasm
through nuclear pores
Deoxyribonucleic acid (DNA) is mostly found where
within the nucleus, although small
amounts of DNA are also found within mitochondria
Nuclear DNA and associated proteins are
organized into discrete structures called
chromosomes
the proteins of chromosomes are called
histones
During most of the life cycle of a cell, the chromosomes are dispersed
throughout the nucleus as delicate filaments referred to as
chromatin
what happens to chromatin during cell division
the dispersed chromatin becomes densely coiled,
forming compact chromosomes
At the beginning of cell division, each chromosome consists of
two chromatids attached at a single point called centromere
the centromere has what proteins
kinetochore
what is kinetochore
a protein structure within the centromere, provides a point of attachment for microtubules during
cell division.
what does DNA determine
the structural and functional characteristics of the cell by specifying the structure
of proteins
how does DNA establish the structure of proteins
by specifying the sequence of their amino
acids
does DNA leave the nucleus
no its too large
how does DNA function and leave the nucleus
by the means of an intermediate ribonucleic acid (RNA), which can leave the nucleus through nuclear
pores.
DNA determines the structure of three things what are they
messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
A sequence of nucleotides in a DNA molecule that specifies the structure of a protein or RNA molecule is called a
gene
where does mRNA synthesis occurs
inside the nucleus
how do cells without nuclei accomplish proteins synthesis
only as long as the mRNA produced before the
nucleus degenerates remains functional
the nucleus of RBC is expelled elaborate on this
The nuclei of developing red blood cells are expelled
from the cells before the red blood cells enter the blood, where they survive without a nucleus for
about 120 days.
do cells with nuclei survive longer than RBC
yes example skeletal cells and muscle cells and nerve cells survive as long as the person survives
nucleolus
somewhat rounded, dense region within the nucleus that lacks a surrounding
membrane
Usually, one nucleolus exists per nucleus, but several nucleoli may also be
seen in the
nuclei of rapidly dividing cells
The nucleolus incorporates portions of
10 chromosomes (5 pairs) called nucleolar organizer regions
what do nucleolar organizer regions contain
DNA from which rRNA is
produced.
where are the subunits of ribosomes manufactured
inside the nucleolus
