Last Time I Gave This Out:
Very Important! Look at Schedule of Classes!
Adipose/Liver-Free Fatty Acid/VLDL cycle
Because the Dixon cycle (my favorite term for this system) is a
cycle, it can start anywhere and end anywhere. In the adipocyte
(fat cell–and we are mainly talking about the white adipose cell),
triglyceride (TAG) in the fat droplet is broken down (See #1) to
free fatty acids (FA), which then diffuse into blood and bind to
albumin, the predominant protein in blood. Albumin carries (via
blood) the free fatty acids (yellow arrows) throughout the
body–especially to heart, bone, and muscle (See #2). The left
over free fatty acids are taken up by liver (See #3), where they
are re-synthesized into TAGs. Apolipoprotein B (ApoB)–a very
large protein made in liver, wraps itself around (like a belt!) a
lipid droplet containing triglyceride (TAG) and cholesterol to form
the lipoprotein called Very Low Density Lipoprotein (VLDL). The
liver hepatocyte secretes VLDL particles into the blood (See #5)
and they permeate throughout the body and deliver fatty acids
(red arrows) to tissues like heart, muscle, and bone marrow. An
enzyme called Lipoprotein Lipase (LPL) is located on the surface
of the endothelium of blood vessels (facing the blood flow) of
many tissues and “catches” the VLDL particles. Lipoprotein
Lipase reaches into the droplet within the VLDL particle and
hydrolyzes the three fatty acids off the TAG molecule.
These fatty acids either diffuse or are transported into cells of the heart,
muscle, and other tissues. Eventually, the remaining fatty acids
in VLDL (in the form of TAG), are returned to adipose cells. In
this way, using two unique and overlapping systems–the albumin
system and the VLDL system, all of the tissues of the body have
access to energy, in the form of fatty acids (the body’s gasoline).
In the final step of the cycle (right bottom corner-See #6) about
50% of the VLDL particles, now largely depleted of TAG, are
converted to Low Density Lipoprotein (LDL) (also known as the
“Bad Cholesterol”), which, after a half-life of 3 days, is then taken
up by the liver using LDL receptors. This returns the remaining
extra cholesterol and other lipids back to the liver.
Note Schedule of Classes!
How much Protein is enough? Do we need much much more than the RDA for Protein when Training?
How much protein is ridiculous?
February 12, 2018 For Exam 1 Questions from Students:
Q: I keep trying to calculate the total kcals for the questions you gave us but keep coming up with the wrong total. everything except for the fat gets times by 4 correct? I keep coming up with 174 instead of 234? What could I be doing wrong?
ANSWER: For question #28 on the practice exam:
Hi, In this question I included alcohol which I didn’t stress this semester. The Atwater number for alcohol is 7! so it is like this:
20 x 7
18 x 4
2 x 9
1 x 4
adds up to 234 Kcal per drink!
Q: Hi professor Dixon, For the health and nutrition exam do we have to know the functions of the individual parts of the G.I. tract? Also, which chemicals of the G.I. tract do we have to know? I know you mentioned two of them in class and said the other one wasn’t necessary but I forget the names of the first two. Thank you,
Answer: You really do not have to know too much on the GI tract. More for glucose than anything. The two I mentioned are Secretin and Gastrin.
Q: Dear Professor Dixon, The last slide covered in class on Friday was RDA for Protein Cont. with totals for pregnancy, etc. Does this mean protein complementation, daily recommendation for adult vegetarians, plant protein, and regulation of fluid balance, etc will not be on the exam. The review notes touch upon soy and toxicity, all past the coverage in lecture. Should we review the slides at home or stop at slide 83 about RDA for the exam? Thank you!
Answer: Yes, we did not get past the RDA for protein so that’s where the exam stops – we will cover nutritional aspects of protein next class. (How the RDA was calculated is very important).
Q: Hello professor, quick question. Approximately how many of the 50 questions on the exam will be based on the Dixon chapters mentioned on the syllabus? Are there any particular chapters we should spend more time on?
ANSWER: Hi, All of the material is from the lectures and the textbook when I specifically point it out. The Dixon chapters just give extra information if you wish to read about it. Almost all of the Dixon chapters are wider discussions of something from the lectures.
Q: I had a question regarding Tolerable Upper Limit Values and how they are determined? Is it using the inverted U-curve? I understand how RDA’s are determined by adding 2 standard deviations to the EAR, is the same done for UL, by adding standard deviations to the RDA?
Answer: Thank you for the question. The UL were determined from extensive individual toxicity reports etc. The committee that sets the RDA debates what the UL should be. There is really no statistical analysis like for the RDA. We have to just take the committee’s recommendation.
Q: Dear Prof. Dixon, I have been looking all over the notes and textbook for how many total kcals of glycogen are stored in humans, but can not find it. I know that in the liver it is 570 kcals and in muscle it is 2000 kcals, maybe the answer is right in front of me and I can not see it, but could you please explain what the answer is? Thank you!
Answer: You are so close – 2000 for muscle and 570 (~600) – Add together = 2600 ( just a very vague average) but the best we have as we can’t cut people up and check!
Stone Grinding versus Mechanical Milling