{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lecture 9 - BIS 103 09 Pentose Phosphate Pathway FIRST...

Info icon This preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
BIS 103 - 09 - Pentose Phosphate Pathway Oxidative Phase NADPH production Pentose phosphate production ribulose-5-P xylulose-5-P ribose-5-P Non-oxidative Phase Transketolase and thiamine pyrophosphate (TPP) Transaldolase Interconversion of pentose-5-P to F6P and G3P Resynthesis of G6P from F6P and G3P Reducing Power Nucleotides for nucleic acid synthesis FIRST MIDTERM HIGH 195 LOW 40 MEDIAN 147
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
We have discussed the production of ATP with glucose as the major source of metabolic energy. We have also seen how lipids and fatty acids can be a source of stored fuel and used to produce ATP. We will now turn to the generation of another type of metabolic energy - that is, reducing power . The currency of readily available reducing power in the cell is NADPH. The phosphoryl group on C-2 of one of the ribose units of NADPH distinguishes it from NADH (Lecture 2, slide 7).
Image of page 2
8 acetyl-CoA + 7 ATP + 14 NADPH + H + palmitate + CoA + 7 ADP + 7 Pi + 14 NADP + + 7 H 2 O During fatty acid synthesis, you saw that NADPH + H + was required Where does the cell get its NADPH + H + ? One source was the malic enzyme reaction: malate + NADP + pyruvate + CO 2 + NADPH + H + malic enzyme The major source for generating reducing power is the pentose phosphate pathway (PPP). Other reductive biosynthetic pathways also require NADPH.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Remember that NADH is oxidized by the respiratory chain to generate ATP, whereas NADPH serves as an electron donor in reductive biosyntheses. The NAD/NADH linked enzymes oxidize and degrade substrates. The NADP/NADPH enzymes function primarily in reductive and biosynthetic reactions.
Image of page 4
The main functions of the pentose phosphate pathway (PPP) are to produce NADPH + H + and ribose-5-P. NADPH + H + is used in reductive biosynthetic reactions. Tissues that carry out extensive fatty acid synthesis (e.g. liver, adipose tissue, lactating mammary gland) or very extensive synthesis of cholesterol and steroid hormones (liver, adrenal gland, gonads) require NADPH from the PPP.
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
NADPH + H + also is used to counteract the damaging effects of oxygen radicals. Erythrocytes and the cells of lens and cornea are directly exposed to oxygen and the damaging free radicals generated by oxygen. By maintaining a reducing atmosphere (a high ratio of NADPH/NADP + ), they can prevent damages to proteins, lipids and other sensitive molecules.
Image of page 6
Rapidly dividing cells such as those of bone marrow, skin, and intestinal mucosa, use the ribose-5-phosphate to make nucleotides, RNA, DNA, and coenzymes such as ATP, NADH, FAD and CoA. In addition, the pathway operates to metabolize dietary pentose sugars, derived primarily from the digestion of nucleic acids. The role of the PPP is primarily anabolic rather than catabolic. Role of ribose-5-phosphate (R5P)
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHO I HCOH I HOCH I HCOH I HCOH I CH 2 OP CHO I HCOH I HOCH I HCOH I HCOH I CH 2 OH hexokinase ATP ADP glycolysis pentose phosphate pathway (PPP) glucose glucose-6-P
Image of page 8
Glucose Glucose-6-P Pentose Phosphate Pathway NADPH + H + Ribose-5-P Glycolysis The main products of the pentose phosphate pathway are NADPH + H + and ribose-5-P Glucose-6-P is a branch point since glycolysis and the PPP are optional pathways at this point.
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern