Kevin Ahern's BB 350 (Cholesterol & Photosynthesis) 2014 - #35

1. Contact me at [email protected] / Friend me on Facebook (kevin.g.ahern) 2. Download my free biochemistry book at http://biochem.science.oregonstate.ed... 3. Take my free iTunes U course at https://itunes.apple.com/us/course/bi... 4. Check out my free book for pre-meds at http://biochem.science.oregonstate.ed... 5. Lecturio videos for medical students - https://www.lecturio.com/medical-cour... 6. Course video channel at http://www.youtube.com/user/oharow/vi... 7. Check out all of my free workshops at http://oregonstate.edu/dept/biochem/a... 8. Check out my Metabolic Melodies at http://www.davincipress.com/ 9. My courses can be taken for credit (wherever you live) via OSU's ecampus. For details, see http://ecampus.oregonstate.edu/soc/ec... 10. Course materials at http://oregonstate.edu/instruct/bb350 1. The liver is the major organ regulating lipoprotein complexes (VLDLs, IDLs, LDLs). The liver monitors the concentration of complexes. As the concentration increases , the liver slows the release of complexes. As the concentration decreases (indicating increased uptake), the liver releases more. People with deficiencies in the protein on the liver cells have a genetic disease known as familial hypercholsterolemia. 2. LDLs are called "bad cholesterol" because increased levels are correlated with increased risk of atherosclerosis. HDLs, by contrast, are called "good cholesterol" because they help in scavenging cholesterol and LDLs from the bloodstream. 3. Control of levels of LDLs in the bloodstream is the responsibility of LDL receptors on the liver. All cells have LDL receptors and they use them to carry cholesterol (in the LDLs) into cells. In the liver, the amount of LDLs that make it back (after being released as VLDLs) are an indication of how many VLDLs and LDLs the cells used. More LDLs back at the liver indicates less need by cells. If things are working perfectly and the liver is not overloaded, when LDL concentrations rise, the liver will reduce the release of VLDLs. 4. People who do not have functional LDL receptors on the liver have a genetic disease called familial hypercholesterolemia. In this disease, LDL levels rise VERY high and children can die of heart attacks by age 10 if undiagnosed. Highlights Photosynthesis 1. Photosynthesis is a process in plants and some bacteria that use energy from the light of the sun to synthesize glucose using carbon dioxide and water as starting reagents. It accomplishes this in a multistep process that is divided into two phases, called the light reactions (require light) and the dark reactions (don't require light). 2. Photosynthesis occurs in plants in organelles called chloroplasts. The thylakoid disks of the chloroplast are the sites where the light reactions of photosynthesis and the stroma is the location of the dark reactions. 3. Molecules involved in the capture of light energy are known as the chlorophylls. These molecules contain a porphyrin ring (like hemoglobin) with a magnesium ion at the center (instead of the iron molecule found in hemoglobin). 4. In the light reactions of photosynthesis, 1) electrons are removed from water (producing oxygen); 2) ATP is produced by the process of photophosphorylation as electrons pass through the membrane of the thylakoids; and 3) NADPH is produced from NADP+ in the final reduction reaction. NADP+ is therefore the terminal electron carrier in photosynthesis, whereas water is the electron source for the process. 5. There are two photosystems (I and II) that act together to produce the reactions of photosynthesis. Photosystem II is involved in the first set of reactions. Here electrons from the first porphyrin ring complex are excited by light. As these electrons are passed to the electron transport chain of the membrane, the ring extracts electrons from water, creating oxygen. 6. Movement of electrons through the electron transport chain in the thylakoid membrane causes protons to be pumped INTO the thylakoid. This creates a proton gradient (higher proton concentration in the thylakoid than the stroma). Protons in the thylakoid move outside through a proton translocating ATP synthase (PTAS) complex (same general structure as the mushroom-like complex with the same function in mitochondrial membranes). As protons move through the PTAS, ATP is generated from ADP (photophosphorylation). 7. Electrons released from photosystem II eventually reach photosystem I where they are excited by sunlight of a different wavelength. These newly excited electrons are passed ultimately to NADP+, creating NADPH, the final product of the light reactions.