Where do most of the hydrogen ions in the blood originate from

3. The second stage of urine formation is called _________. Cells lining the proximal convoluted tubules (PCTs) have special projections called _________ which increase their surface area, thus enabling the PCTs to transport about 70% of filtrate back into blood. 4. When a person is dehydrated, their blood volume and blood pressure are too low. Two hormones reduce the loss of sodium and water from the body during dehydration by concentrating urine to prevent further water loss. The first hormone is secreted by the adrenal cortex and is called __________; this hormone stimulates sodium retention by nephrons. The second hormone is released by the posterior pituitary gland and is called _________; this hormone cause water retention by nephrons. 5. ___________is the waste product of cellular respiration (ATP synthesis). This waste product must be eliminated from the body because it becomes toxic at high levels. This waste product combines with water in blood to form carbonic acid, which is then converted into bicarbonate ions (HCO3-) and hydrogen ions (H+). Hydrogen ions lower blood pH, causing it to become too acidic. Kidneys are able to sense high H+ levels in blood and actively transport hydrogen ions (and other toxic blood borne chemicals) from blood into urine during ___________, the third stage of urine formation.

1) Describe how do cell shape and changes in cell adhesiveness collaborate in the formation of the neural tube?

2) Somite formation in chick embryos proceed from anterior to posterior in reponse to a gradient of FGF8 gene expression. Describe this gradient:

a) Where does FGF8 originate?

b)Why does it form a gradient

c)How does the gradient trigger somite formation?

You may have noticed in some hard boiled eggs a grey-green ring surrounding the yolk. The color is from iron sulfide (FeS) which is harmless but kind of disgusting looking. Explain where the iron and sulfur originate from in the egg and how cooks can easily avoid its appearance in their boiled eggs