HONR 1034 Chapter Notes - Chapter 2: Nucleolus Organizer Region, Endoplasmic Reticulum, Cell Membrane
Chapter 2: Mitosis and Meiosis (1/23 Lecture 2)
I. Definitions
A. Chromosomes: serve as vehicles for transmitting genetic information; chromosomes made up of
two sister chromatids, one of which was duplicated to make the other and joined together at the
centromere
1. Two chromosome pairs are homologous chromosomes
2. Different in size and shape
B. Chromatin: the genetic material making up chromosomes that unfolds and uncoils into a diffuse
network within the nucleus
II. Cell Structure and Genetic Function (2.1)
A. Great discoveries about the cell after 1940
B. Plasma membrane: an outer covering that defines a cell boundary and delimits the cell from its
immediate external environment; uses active transport to control movement of materials
C. Cell wall: the outer covering of a plant cell, largely composed of cellulose (polysaccharide)
D. Cell coat/glycocalyx: covering over the plasma membrane in many animal cells
1. Consists of glycoproteins and polysaccharides
2. Provides biochemical identity at the surface of cells and establish cellular identity
E. Receptor molecules: found on the surface of cells, they act as recognition sites that transfer
specific chemical signals across the membrane into the cell
F. The two categories of living organisms
1. Eukaryotic organisms: organisms with a nucleus and other membranous organelles
a) Nucleus: a membrane-bound structure that houses the
genetic material, DNA, which is complexed with an array of acidic and basic
proteins into thin fibers
b) Fibers are uncoiled and dispersed into chromatin during
nondivisional phases of cell cycle
c) During mitosis/meiosis, chromatin fibers coil and
condense into chromosomes
d) Nucleolus: an amorphous component where rRNA is
synthesized and the initial stages of ribosome assembly occur
e) Nucleolus organizer region (NOR): the portions of DNA that encode rRNA
2. Prokaryotic organisms: lack a nuclear envelope and membranous organelles
a) Eubacteria/archaea: genetic material is present as a long, circular DNA
molecule that is compacted into an unenclosed region called the nucleoid
G. Cytoplasm: the remainder of the eukaryotic cell within the plasma membrane (w/o nucleus)
1. Cytosol: surrounds cellular organelles in the cytoplasm
2. Contains extensive system of tubules and filaments → comprise cytoskeleton
3. The cytoskeleton is mainly composed of microtubules (made of protein tubulin) and
microfilaments (come from protein actin) → maintains shape, facilitates cell mobility,
and anchors the various cell organelles
H. Endoplasmic reticulum: compartmentalizes the cytoplasm, increasing surface area for
biochemical synthesis
I. Ribosomes act as sites where genetic info in mRNA is translated into proteins
J. Important cytoplasmic structures
1. Mitochondria: sites of oxidative phases of cell respiration → create ATP
2. Chloroplasts: associated with photosynthesis
a) Both have DNA in a form distinct from found in the nucleus
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