Unit 2: Cell: The Basic Units of Life
Photosynthesis and Respiration
is the metabolic process in plants and algae that captures
energy and uses it to turn CO
O into sugars
The process is
as a by-product.
is the series of reactions that uses the O
and glucose made during photosynthesis to
for cellular work, with
produced as by-products of the process. The breakdown of food molecules in this process is called aerobic
. Many of the reactions of respiration are compartmentalized in
The temporary storage and transfer of energy in both photosynthesis and respiration require the use of reduced electron
occurs in the chloroplast in two stages.
reactions occur on the
which separate the
(ETCs) are used to capture
energy, excite electrons, and manufacture
The "excited" electrons are
complex and are transferred from the chlorophyll to the ETC in Photosystem
receives the excess electrons and forms NADPH. A channel protein pumps protons into the
space, and are moved into the
by ATP synthase, producing
of photosynthesis occur in the
Products of the light reactions are used to energize CO
and make the sugar
in a process known as carbon
is the source of
is the source of high-energy
Other products of the dark reaction include the sugar
occurs in three stages.
takes place in the
and begins the breakdown of
and small amounts of
. In the absence of O
, the pyruvate made during glycolysis enters the anaerobic respiration of
is present, aerobic respiration takes place. Pyruvate is directed to the inner matrix of the
, where it enters the citric acid
is released as the
is degraded, yielding a few additional ATP and numerous molecules of
the electrons in NADH and O
are used during oxidative
(which occurs on the mitochondrial inner membrane) to manufacture more than 30 molecules of ATP, again through the
. In this process
is required and
Unit 2: Cell: The Basic Units of Life
cells multiply by
cells in a
An undifferentiated cell that can divide to produce one or more
cell types is called a
is packed with protein in strands called
. During cell division,
is condensed into visible bodies called
. Each species has a
of specific number and shape of chromosomes. Humans have 46 chromosomes consisting of 22
pairs and 2
the actively dividing state is
, while the period between mitotic division is
. Each daughter cell receives the full complement of DNA of the parent cell and is genetically identical to the parent; this is called DNA
and requires DNA
prepares the cell for division and is composed of 4 sub phases.
phase, the cell prepares for the DNA synthesis by producing necessary
and growing in size.
phase DNA synthesis occurs to prepare for DNA
. Each strand of DNA is
to form the two arms of
held together by
, each of which has two
phase, the cell prepares for mitosis by producing another set of proteins.
phase is a resting alternative to the G1 stage where cells do not prepare for mitosis. Most somatic cells are in this phase when they reach maturity.
Mitosis is composed of 5 sub phases.
, chromatins condense into
, and microtubules form the mitotic
, the nuclear
and the spindle microtubules connect kinetochores to opposing
, chromosomes line up in the middle of the cell called the metaphase
, or equatorial plate.
occurs when sister
separate at the kinetochore and the daughter
move toward the centrosomes at the
, spindle microtubules break down, nuclear
form around the new chromosomes, and the chromosomes unfold to their interphase state. In plants,
fuse to form a new cell
divide the cell in
In plants, new cell
formation is completed.
; each diploid parent cell yields four haploid
. The union of a male gamete called a
and a female gamete called an
results in a diploid
. This process of sexual
. The gender of a human zygote is determined by the
consists of two nuclear divisions, meiosis I and meiosis II.
homologous chromosomes form pairs of
. Microtubules from only one pole attach to each chromosome of a homologous pair, and each daughter cell receives only one of the pair. This
division produces two haploid cells, each with two chromatids on each chromosome.
in each daughter cell separate. The
is four haploid
Apr 4, 2006