Ch. 8 Heme

Front 1

What intermediate spun off from the Krebs cycle is an entry point into porphyrin synthesis?

Back 1

Succinyl CoA

Front 2

Porphobilinogen

Back 2

contains a single pyrrol ring. It converts to the quadruple-ringed porphyrinogens and porphyrins (which contain four pyrrhol rings attached like the petals of a pinwheel.

Front 3

Protoporphyrin IX

Back 3

Is famous for its combination with Fe++ to form heme.

Front 4

Examples of molecules that are derivatives of these build-up quadruple pyrrhols including:

Back 4

Vitamin B12, cytochromes, catalase, peroxidase, and chlorophyll

Front 5

Chlorophyll vs. heme

Back 5

intsead of an iron group, it contains a central magnesium atom instead of iron. It also contains an attached isoprenoid chain.

Front 6

Vitamin B12 is different from heme in that:

Back 6

It contains a central cobalt.

Front 7

Cytochromes (derivatives of pyrrhols)

Back 7

Important as electron transporters in the chain of oxidative phosphorylation.

Front 8

Hemoglobin

Back 8

Hemoglobin is formed by the combination of heme with a globin protein. "heme" is the prosthetic group for a number of important molecules including hemoglobin, myglobin, the cytochromes, and certain enzymes (e.g. catalase and peroxidase)

Front 9

Hemoglobin vs. cytochrome C

Back 9

Both have the same heme group but different associated proteins. The difference is that "heme" is a carrier of O2 and "cytochrome C" being a carrier of electrons.

Front 10

Hemoglobin vs. Myoglobin

Back 10

Both have heme prosthetic in globin peptide; however, hemoglobin consists of four polypeptide chains, while myglobin contains one polypeptide chain.

Front 11

Hemoglobin structure

Back 11

Two of the four polypeptide chains are alpha and two are beta. (Alpha 2 Beta 2 (or Hemoglobin A--HbA) for short). Embryos and fetus have HbF (which is alpha 2 gamma 2; HbA2).

Front 12

Breakdown products of hemoglobin

Back 12

Red cells get old and are destroyed primarily in the spleen. The globin is released and the heme ring breaks open, releasing Fe++--> forming "BILIVERDIN." Biliverdin changes to "unconjugated/indirect" bilirubin by reduction of central carbon. Following this, it must be taken to the liver via albumin.

Front 13

Bunconjugated bilirubin is insoluble in water, and in order to be taken into the liver, it must be carried by albumin. What steps follow this?

Back 13

1. The liver cells take up the unconjugated bilirubin. 2. The liver cells transform it into conjugated "direct" bilirubin by conjugating it with glucuronate--> resulting in a more polar/water soluble molecule. 3. The liver cells release conjugated bilirubin into biliary duct system, which carries it to small intestine. 4. In small intestine, conjugated bilirubin is transformed into "Urobilogen," some of which is excreted and some of which is reabsorbed and carried back to the liver and re-excreted as bile. URObilogen can be excreted in the URINE and is colorless.

Front 14

Dark color of stool

Back 14

Colorless urobilinogen can be converted to stercobilinogen (colorless) to stercobilin (brown) in the intestines.