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25 May 2018

A. Hemoglobin is a heterotetramer with two alpha subunits and two beta subunits. Each subunit has the capability of binding to one oxygen molecule.

a. True

b. False

B. Which hemoglobin subunit is most likely to be in the R state?

a. a de-oxygenated beta subunit in a tetramer where two other subunits are de-oxygenated

b. a de-oxygenated alpha subunit in a tetramer where the other three subunits are oxygenated

c. a de-oxygenated beta subunit in a tetramer where the other three subunits are also de-oxygenated

d. a de-oxygenated alpha subunit in a tetramer where two other subunits are oxygenated

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Jean KeelingLv2

25 May 2018

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1.Bacteriorhodopsin is a protein that has 7 alpha helices embedded in the cell membrane. As such, how many start-transfer and stop-transfer sequences would it need?

7 start transfer sequences, 6 stop transfer sequences

7 of each, in alternating fashion

4 start transfer sequences and 3 stop transfer sequences

7 start transfer sequences

2. The role of GTP hydrolysis by the Signal Recognition Particle during cotranslational translocation to the ER is

to release the SRP after docking to the translocon so translation can resume.

to open the gate/pore of the translocon into the ER.

to arrest translation so that synthesis does not finish before the peptide is delivered to the translocon.

to allow binding to the ribosome.

3. The cisternal maturation model is just one model that describes how objects might move through the Golgi. Some of the statements below describing the cisternal maturation model are correct and some are incorrect. Select all the incorrect descriptions.

There's no need for retrograde movement

Vesicles bud off from the Trans Golgi Network toward the plasma membrane

Vesicular tubules move materials from the cis to medial Golgi networks.

There are no vesicles moving in the anterograde direction

4. Select all statements that are correct concerning electron transport and ATP synthesis during photosynthesis in chloroplasts.

Each photosystem (I and II) pump protons.

Protons are pumped into the lumen of the thylakoid.

The bulb of the synthase projects into the stroma

Photosystem I is reduced directly by Photosystem II

5. Select all that are true about ATP synthesis with an F_oF₁ synthase complex.

Each ADP+Pi is transferred from one beta subunit in Open conformation to a second beta subunit in Loose conformation and finally to the 3rd beta subunit in the T conformation

As the gamma subunit rotates to each beta subunit, it forces them to the open state.

As the gamma subunit rotates to a particular beta subunit, the unit before it changes conformation to Tight and the one ahead of it changes to Loose

As the gamma subunit rotates to a particular beta subunit, the unit before it changes conformation to Loose and the one ahead of it changes to Tight

All 3 beta subunits are always in a different conformation (open, loose, or tight)

6. The number of ATPs per NADH generated by the electron transport system is higher than the number generated per FADH2 because __________.

		electrons from FADH₂ are not oxidized all the way to water
		NADH is converted to NAD⁺, which increases the charge gradient for ATP synthesis
		FADH₂ has a lower (less negative) redox potential than NADH does
		FADH₂ has a higher (more negative) redox potential than NADH does

1) The parasympathetic nervous system generally promotesdigestion. Innervation is via the vagus nerve. Ach binds tomuscarinic receptors. True or False?

2) Which of the following statements is correct?

a) The liver receives oxygenated blood from the hepatic arteryand deoxygenated blood from the hepatic portal vein. Branches ofboth veins carry blood into liver sinusoids. Hepatocytes absorboxygen, most of the nutrients, and some toxins. Needed substancesare secreted back into the blood. Blood then drains into thecentral vein and into a hepatic vein.

b) The liver receives deoxygenated blood from the hepatic arteryand oxygenated blood from the hepatic portal vein. Branches of bothveins carry blood into liver sinusoids. Hepatocytes absorb oxygen,most of the nutrients, and some toxins. Needed substances aresecreted back into the blood. Blood then drains into the centralvein and into a hepatic vein.

c) The liver receives oxygenated blood from the hepatic arteryand deoxygenated blood from the hepatic portal vein. Branches ofboth veins carry blood into liver central vein. Hepatocytes absorboxygen, most of the nutrients, and some toxins. Needed substancesare secreted back into the blood. Blood then drains into thesinusoids and into a hepatic vein.

d) The liver receives oxygenated blood from the hepatic arteryand deoxygenated blood from the hepatic portal vein. Branches ofboth veins carry blood into liver sinusoids. Kupffer cells absorboxygen, most of the nutrients, and some toxins. Needed substancesare secreted back into the blood. Blood then drains into thecentral vein and into a hepatic artery.

3) Regulation of secretion of saliva involves:

a) Parasympathetic and sympathetic stimulation

b)Action of the inferior and superior salivatory nuclei in themedulla

c)Activity of the myenteric plexus

d)Activity of the submucosal plexus

4) Bile formed in the liver is transported to the gall bladderfor storage through which pathway? (Some steps may be omitted)

a)Bile duct, right and left hepatic ducts, common hepatic duct,cystic duct

b)Common hepatic duct, right and left hepatic ducts, bile duct,cystic duct

c) Right and left hepatic ducts, bile ducts, common hepaticduct, cystic duct

d) Bile ducts, common hepatic duct, cystic duct, right and lefthepatic ducts

5)Which of the following statements is incorrect?

a)Sodium ions are transported out of absorptive cells bybasolateral sodium pumps.

b) Negatively charged ions follow sodium or are moved out byactive transport.

c)Most water soluble vitamins are absorbed by activetransport.

d) Water absorption in the GI tract involves osmosis

6) Insulin is needed for carbohydrate metabolism because it

a)is required for the breakdown of complex carbohydrates

b)transports glucose in the bloodstream.

c)acts as a glucose receptor molecule on the cell surface.

d) is part of an active transport mechanism required for entryof glucose into cells

e)increases the insertion of a particular type of glucosetransport protein into the cell membrane

burgundygnat457

Normal adult hemoglobin is called Hemoglobin A (Hb A). Ninety-eight percent of adult hemoglobin is Hb A and 2% is Hb A2. There are other forms of hemoglobin. For example, the developing fetus has a different kind of hemoglobin than most normal adults. Fetal hemoglobin (Hb F) is synthesized beginning at the third month of gestation and continues up through birth. After the neonate is born, hemoglobin F synthesis declines (because synthesis of the (chain declines) and hemoglobin A is synthesized. By the time the baby is six months old, 98% of its hemoglobin is Hemoglobin A. There is also a mutant form of hemoglobin called Hemoglobin S, which is found in persons with the disease sickle cell anemia. The disease sickle cell anemia is one of the major health problems facing the African-American community. The World Health Organization estimates that 250,000 babies world wide are born with sickle cell anemia. Currently there is no cure. A person afflicted with sickle cell anemia has inherited a defective gene from each parent. The defective gene is the one coding for the Î²-chain. The amino acid at position 6 on each Î² chain has been mutated from a glutamate to a valine. Normal Î± chains have a decreased affinity for the mutated Î² chains; thus assembly of the HbS tetramer is more difficult. Red blood cells containing HbS form a sickle shape because the Hb S molecules polymerize. Hb S molecules are more likely to polymerize when in the deoxygenated T form than in the oxygenated R form. The polymerized Hb deforms the normal discoid shape of the red blood cells, producing a sickle-shaped cell. The sickle shaped red blood cells become trapped in capillaries and organs, depriving the victim of adequate oxygen supply and causing chronic pain and organ damage.

Glover, R. E., Ivy, E. D., Orringer, E. P., Maeda, H., and Mason, R. (1999) Molecular Pharmacology 55, pp. 1006-1010.

Huang, J., Hadimani, S. B., Rupon, J. W., Ballas, S. K., Kim-Shapiro, D. B., and S. Bruce King (2002) Biochemistry 41, pp. 2466-2474.

S. Bruce King (2003) J.Clin. Invest., 111, pp. 171-172.

1) Why do you think Hb S has higher tendency to polymerize compared to Hb A?