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ATP synthesis consists of two mechanisms known as substrate-level
phosphorylation and oxidative phosphorylation. Substrate-level phosphorylation
involves the direct transfer of a phosphate group to change ADP into ATP. This
process occurs in the anaerobic process known as glycolysis and the aerobic
process known as the Krebs Cycle. In glycolysis, this process occurs in the
return phase and allows for the production of 4 ATP. In the Krebs Cycle, this
process produces 1 ATP per cycle. The advantage of substrate-level
phosphorylation is that is able to produce ATP quickly as opposed to oxidative
phosphorylation. Even though oxidative phosphorylation is a slower process, it
is capable of producing more ATP than substrate-level phosphorylation. This occurs
in the electron transport chain and is a chemiosmotic process that turns
potential energy into chemical energy. In the electron transport chain, NADH
and FADH give off their electrons, causing H+ to be pumped into the membrane.
This results in a gradient where the H+ wants to go back into the matrix of the
mitochondria. When the H+ goes down the ATP synthase, the gradient energy helps
attach the ADP and phosphate groups (Marieb 924).



Explain how short-term and long-term controls of
effect the hypothalamic command of appetite and food intake.

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The hypothalamus influences eating behaviors by affecting
neurons that deal with increasing appetite and decreasing appetite. It is
believed that a person’s behavior, when it comes to eating, is caused by neural
signals, signals dealing with energy, and hormones. There are two different
types of food regulation known as short and long term (Marieb 946).  Short-term regulation gets to the hypothalamus
through the brain stem. Short-term control is associated with signals from the
digestive tract, signals that deal with energy store and hormones. The brain is
able to determine how much someone ate by vagal nerve fibers and the receptors
that serve the purpose of stretching to eliminate the feeling of hunger. An
increase in glucose levels and blood levels of amino acids help with letting
someone know that they are full. Insulin and CCK are hormones that let someone
know that they are full (Marieb 947). Long-term controls are effected by
leptin, which shows how much energy is stored in fat. When leptin levels
increase NPY is blocked and CART is stimulated. The block in NPY causes a loss
of appetite. When the blood levels of leptin go down NPY is stimulated and CART
is blocked which causes a larger appetite. NPY can also be stimulated when
someone is under stress for long amounts of time and chooses to eat foods that
are unhealthy (Marieb 947-948).





Describe the regulation of the ovarian and
uterine cycles.


            As a child,
a female’s ovaries prevent the Gonadotropin-releasing hormone (GnHR) from being
released by constantly creating a little bit of estrogen. When GnHR is finally
released around the time of puberty, the follicle stimulating hormone (FSH) and
luteinizing hormone (LH) are produced as a response. Estrogen is directly released
by the granulosa cells while the LH cells release androgens that get turned
into estrogens. When these levels get too high, the hypothalamus and anterior
pituitary experience negative feedback and FSH and LH are no longer made. FSH
also experiences negative feedback from inhibin, which results in only one
living follicle that creates raised estrogen levels. Positive feedback happens
when the estrogen reaches a certain blood level, resulting in the release of
gonadotropin. When there is a lot of estrogen, LH is released which causes the
oocytle of the follicle to experience meiotic division resulting in another
oocyte. Ovulation takes place after about 14 days which is associated with an
ovary wall that becomes weaker. A portion of this wall breaks and the oocyte
goes through the broken hole. The follicle that burst turns into a corpus
luteum, which makes progesterone and estrogen. Negative feedback on the
hypothalamus and pituitary takes place when these progesterone and estrogen
levels get too high. If the egg is not fertilized, the blood levels go back
down, the estrogen and progesterone levels go back down and the corpus luteum
gets destroyed (Marieb 1058). The uterine cycle involves the changes that the endometrium
experiences in response to ovarian hormones. The changes experienced relate to
what is going on in the ovarian cycle. The first step of the uterine cycle is
called the menstrual phase and it occurs over a span of 1-5 days. In this phase
there is bleeding due to the shedding of the endometrium. On the last day, the
follicles make more estrogen. The next phase is the proliferative phase and its
span is 6-14 days. It involves the reformation of the endometrium that happens
under increased estrogen levels. At the end of this phase, ovulation occurs. The
secretory phase happens over a span of 15-24 days. This phase involves getting
ready for the embryo to implant. Progesterone levels increase to form the
cervical plug that keeps all unwanted things out, such as pathogens. This
increase also stops LH from being released. If fertilization does not occur, progesterone
levels decrease back to the normal range, LH blood levels go back down and the corpus
luteum deteriorates. Menstrual blood flow indicates the starting of this cycle
again (1059).



Define meiosis. Compare and contrast meiosis to


            Meiosis is a
type of nuclear division that typically takes place in the gonads. Meiosis
results in the production of four daughter cells that contain half as many
chromosomes as the normal chromosome number. This diploid chromosome number is
46. The cells are not identical and contain genetic components from each
parent. Meiosis goes through two separate divisions known as Meiosis I and Meiosis
II (Marieb 1036). Meiosis I consists of prophase I, metaphase I, anaphase I and
telophase I. In prophase I, the homologous pairs form tetrads. In metaphase I,
the tetrads line up on the spindle equator. In anaphase I, the sister
chromatids stay together and go to opposite sides of the cell. In telophase I, the
two haploid daughter cells go through interkinesis before going through the
steps of Meiosis II. Mitosis contains the steps of prophase, metaphase,
anaphase and telophase, but contains differences from Meiosis I. In prophase
the centrioles move to different ends of the cell and the nuclear membrane and nucleolus
disappear. In metaphase, the chromosomes line up in the center on the spindle
equate. In anaphase, the centrioles split and go to opposite ends of the cell.
This is different in the anaphase I stage of meiosis because the sister
chromatids stay together rather than splitting apart. In telophase, the chromosomes
uncoil to create chromatin (Marieb 98). Meiosis plays the role creating cells
involved in reproduction while mitosis creates cells involved with growth and
repair of tissues. Meiosis results in four non-identical haploid cells while
mitosis results in the production of two identical diploid cells. Meiosis and
mitosis both experience DNA replication and they both go through the same steps
of prophase, metaphase, anaphase and telophase. They also both contain the same
amount of DNA as one another (Marieb 1037).






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