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ATP synthesis consists of two mechanisms known as substrate-levelphosphorylation and oxidative phosphorylation. Substrate-level phosphorylationinvolves the direct transfer of a phosphate group to change ADP into ATP. Thisprocess occurs in the anaerobic process known as glycolysis and the aerobicprocess known as the Krebs Cycle. In glycolysis, this process occurs in thereturn phase and allows for the production of 4 ATP. In the Krebs Cycle, thisprocess produces 1 ATP per cycle. The advantage of substrate-levelphosphorylation is that is able to produce ATP quickly as opposed to oxidativephosphorylation. Even though oxidative phosphorylation is a slower process, itis capable of producing more ATP than substrate-level phosphorylation. This occursin the electron transport chain and is a chemiosmotic process that turnspotential energy into chemical energy.

In the electron transport chain, NADHand 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 themitochondria. When the H+ goes down the ATP synthase, the gradient energy helpsattach the ADP and phosphate groups (Marieb 924).  1.

    Explain how short-term and long-term controls ofeffect the hypothalamic command of appetite and food intake. The hypothalamus influences eating behaviors by affectingneurons that deal with increasing appetite and decreasing appetite. It isbelieved that a person’s behavior, when it comes to eating, is caused by neuralsignals, signals dealing with energy, and hormones.

There are two differenttypes of food regulation known as short and long term (Marieb 946).  Short-term regulation gets to the hypothalamusthrough the brain stem. Short-term control is associated with signals from thedigestive tract, signals that deal with energy store and hormones. The brain isable to determine how much someone ate by vagal nerve fibers and the receptorsthat serve the purpose of stretching to eliminate the feeling of hunger. Anincrease in glucose levels and blood levels of amino acids help with lettingsomeone know that they are full.

Insulin and CCK are hormones that let someoneknow that they are full (Marieb 947). Long-term controls are effected byleptin, which shows how much energy is stored in fat. When leptin levelsincrease NPY is blocked and CART is stimulated. The block in NPY causes a lossof appetite. When the blood levels of leptin go down NPY is stimulated and CARTis blocked which causes a larger appetite. NPY can also be stimulated whensomeone is under stress for long amounts of time and chooses to eat foods thatare unhealthy (Marieb 947-948).                                                                                             2.

    Describe the regulation of the ovarian anduterine cycles.             As a child,a female’s ovaries prevent the Gonadotropin-releasing hormone (GnHR) from beingreleased by constantly creating a little bit of estrogen. When GnHR is finallyreleased around the time of puberty, the follicle stimulating hormone (FSH) andluteinizing hormone (LH) are produced as a response. Estrogen is directly releasedby the granulosa cells while the LH cells release androgens that get turnedinto estrogens. When these levels get too high, the hypothalamus and anteriorpituitary experience negative feedback and FSH and LH are no longer made. FSHalso experiences negative feedback from inhibin, which results in only oneliving follicle that creates raised estrogen levels.

Positive feedback happenswhen the estrogen reaches a certain blood level, resulting in the release ofgonadotropin. When there is a lot of estrogen, LH is released which causes theoocytle of the follicle to experience meiotic division resulting in anotheroocyte. Ovulation takes place after about 14 days which is associated with anovary wall that becomes weaker. A portion of this wall breaks and the oocytegoes through the broken hole. The follicle that burst turns into a corpusluteum, which makes progesterone and estrogen. Negative feedback on thehypothalamus and pituitary takes place when these progesterone and estrogenlevels get too high. If the egg is not fertilized, the blood levels go backdown, the estrogen and progesterone levels go back down and the corpus luteumgets destroyed (Marieb 1058).

The uterine cycle involves the changes that the endometriumexperiences in response to ovarian hormones. The changes experienced relate towhat is going on in the ovarian cycle. The first step of the uterine cycle iscalled the menstrual phase and it occurs over a span of 1-5 days. In this phasethere is bleeding due to the shedding of the endometrium. On the last day, thefollicles make more estrogen. The next phase is the proliferative phase and itsspan is 6-14 days.

It involves the reformation of the endometrium that happensunder increased estrogen levels. At the end of this phase, ovulation occurs. Thesecretory phase happens over a span of 15-24 days. This phase involves gettingready for the embryo to implant. Progesterone levels increase to form thecervical plug that keeps all unwanted things out, such as pathogens.

Thisincrease also stops LH from being released. If fertilization does not occur, progesteronelevels decrease back to the normal range, LH blood levels go back down and the corpusluteum deteriorates. Menstrual blood flow indicates the starting of this cycleagain (1059).  3.    Define meiosis. Compare and contrast meiosis tomitosis.             Meiosis is atype of nuclear division that typically takes place in the gonads.

Meiosisresults in the production of four daughter cells that contain half as manychromosomes as the normal chromosome number. This diploid chromosome number is46. The cells are not identical and contain genetic components from eachparent. Meiosis goes through two separate divisions known as Meiosis I and MeiosisII (Marieb 1036). Meiosis I consists of prophase I, metaphase I, anaphase I andtelophase I. In prophase I, the homologous pairs form tetrads. In metaphase I,the tetrads line up on the spindle equator. In anaphase I, the sisterchromatids stay together and go to opposite sides of the cell.

In telophase I, thetwo haploid daughter cells go through interkinesis before going through thesteps of Meiosis II. Mitosis contains the steps of prophase, metaphase,anaphase and telophase, but contains differences from Meiosis I. In prophasethe centrioles move to different ends of the cell and the nuclear membrane and nucleolusdisappear. In metaphase, the chromosomes line up in the center on the spindleequate. 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 sisterchromatids stay together rather than splitting apart. In telophase, the chromosomesuncoil to create chromatin (Marieb 98).

Meiosis plays the role creating cellsinvolved in reproduction while mitosis creates cells involved with growth andrepair of tissues. Meiosis results in four non-identical haploid cells whilemitosis results in the production of two identical diploid cells. Meiosis andmitosis both experience DNA replication and they both go through the same stepsof prophase, metaphase, anaphase and telophase. They also both contain the sameamount of DNA as one another (Marieb 1037).     

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