Tutor profile: Teresa H.

how does a G-protein linked receptor work?

G-Protein receptors are the largest group of the cell-surface receptors. They will help to get signals across the cell membrane for any signal molecules that are unable to cross the cell membrane. Two Key Player: The receptor protein is called GPCR; it has 7 transmembrane domains. G-protein, it has three small subunits, α, β, and γ. There is a site on the α subunit where GDP or GTP can attach. The protein is active with GTP and inactive with GDP. Steps: 1. signal binds to GPCR, and GPCR has confirmational change. 2. The α subunit replaces its GDP with GTP and becomes active. 3. The α subunit + GTP detached from β, and γ subunits. 4. The α subunit + GTP finds the target protein. (Usually, it is an enzyme that can make secondary messengers or an ion channel for the secondary messengers) 5. the Target protein is activated and will repay its signal to the next target protein. Step 5 can keep repeating as long as the signaling ligand is bonded at the GPCR. 6. The RGS (regulator of G-protein signaling) will take away the GTP, and all the proteins will return to inactive forms and wait for the next signaling.

What is the development of oocyte?

An oocyte is an egg cell. The development of an oocyte is called oogenesis. Any gametes cells (sex cells) are formed after meiosis (2 division) and end up as a haploid (n) cell. During the prenatal period, a female fetus will set aside some oogonium (stem cell for making egg cells) asides. These stem cells will undergo mitotic divisions and enlargements to become a primary oocyte. These oocytes will start the first meiosis division and arrested in prophase of meiosis I. When the girl reaches puberty, the oocytes will finish meiosis I and make its first polar body. At this point, the oocyte is known as a secondary oocyte. About 3 hours before ovulation, the secondary oocyte will start the meiosis II and arrest in metaphase. Only when the oocyte is fertilized by a sperm will it complete meiosis II and make the second polar body. If the oocyte is not fertilized, it will stay in the meiosis II metaphase. The important take away: 1. At the moment when a girl is born, she has all the primary oocytes that she will need in her life, in the prophase meiosis I form. 2. During ovulation, the oocyte will be released as a secondary oocyte in the metaphase meiosis II form. 3. Only the fertilized oocyte will complete meiosis II.

-4x+7=15 Please find x

When salving equations, remember + and - are in a group, and x and ÷ are in a group. Think of the equation like a see-saw, so anything we do on one side, we need to do the same on the other side. The goal is to isolate the x by itself and move all the numbers to the other side of the equal sign. -4x+7=15 First, let's move the 7 to the opposite side. + and - are together, so to move +7 to another side we have to -7 on both sides. -4x = 15-7 -4x = 8 Now, we have to isolate x, so we need to the -4 to the other side. x and ÷ are in a group. so we are going to divide both sides by -4. x= 8/-4 x=-2