1. The advantage of substrate-level phosphorylation is

Explain how substrate-level phosphorylation and oxidative
phosphorylation produce ATP.


            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).

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





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. The FSH causes the granulosa cells to release
estrogen and the LH causes the cells to release androgens that are turned into
estrogens. When estrogen levels get too high, the hypothalamus and anterior
pituitary experience negative feedback and FSH and LH are not able to be
produced. FSH also experiences negative feedback from inhibin. Only one
follicle remains alive after this and it 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.
This is associated with vascular permeability and the release of
metalloproteinase enzymes. A portion of the follicle wall breaks and leaves a
hole for the oocyte to go through. The follicle that burst turns into a corpus
luteum, which makes progesterone and estrogen. Negative feedback on the
hypothalamus and pituitary takes place when the 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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