Cellular respiration in sperm cells.

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Re: Cellular respiration in sperm cells.

Post by baikuza » Tue Feb 14, 2006 9:57 am

MrMistery wrote:I know that sperm cells use fructose in cellular respiration and not glucose. My question is HOW?

this is quite similar with why we can breakdown sugarfruit?
then why in our blood there are no C5, i.e. fructose, but there is glucose-C6?

did you get what i mean?
the answer is in the digestive processes...

And, if it is so, why dis the living world evolve to use glucose and not fructose? It would much easier to use fructose if this was possible since fructose is the first hexose formed in photosinthesis...

the first is Phospoglyceraldehyde(PGAL) then plant can polymers it to be fat, carbohydrate, and protein. this is in my highschool... actually at 3rd class

and _at_ Dr.Stein...
you look like Dr. Stein as i know before...
you still not change.

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Post by Dr.Stein » Tue Feb 14, 2006 10:00 am

Of course I won't change, this is me, why should I? :P

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Post by MrMistery » Tue Feb 14, 2006 6:39 pm

Who many carbon atoms does Phospoglyceraldehyde have? Because, if you read my post you will see i said fructose is the first hexose to be formed in photosynthesis. And last time i checked PGAL had 3 carbons.. Have a look at a book that has a biochemical approach on photosynthesis...
From phosphogliceric acid, after investing one molecule of NADPH, you get this 3-phosphogliceric aldehide, that is the first sugar, with 3 carbon atoms(remember that it needs to have a carbonil bond to be a sugar, phosphoglyceric acid still has a carboxyl bond so it is an acid). From this compound, fructose-6-phosphate is synthesised. After passing through a series of instable sugars with number of carbon atoms ranging from 3 to 8, there are 2 compunds formed:
1. glucose-6-phosphate- which can be turned into sucrose or used to form normal glucose, who in turn can be used for various types of processes, including synthesis of lipids and proteins
2.glucose-1-phosphate, which, if there is excess glucose, is turned into starch.

Our blood does contain C5, like ribose and dezoxiribose, which are traveling from the digestive tract to various cells. Fructose is a different molecule than glucose, but it is still a hexoze.

My question was not refering to the digestive process, it was reffering to the cellular biochemical process...
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

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Post by baikuza » Wed Feb 15, 2006 7:47 am

G3P is often referred to as 3-phosphoglyceraldehyde (PGAL) with respect to the product of photosynthetic carbon fixation during the Calvin cycle.

During plant photosynthesis, two molecules of glycerate 3-phosphate (GP, but also known as 3-phosphoglycerate (PGA)) are produced by the first step of the light-independent reactions when ribulose 1,5-bisphosphate (RuBP) and carbon dioxide are catalysed by the rubisco enzyme. The GP is converted to PGAL using the energy in ATP and the reducing power of NADPH as part of the Calvin cycle. This returns ADP, Pi, and NADP+ to the light-dependent reactions of photosynthesis for their continued functioning.

PGAL can then be converted to glucose. RuBP is regenerated for the Calvin cycle to continue.

PGAL is generally considered the prime end-product of photosynthesis and it can be used as an immediate food nutrient, combined and rearranged to form monosaccharide sugars, such as glucose, which can be transported to other cells, or packaged for storage as insoluble polysaccharides such as starch.

PGAL is related primarily to autotrophic nutrition.

Balance sheet
6 CO2 + 6 RuBP (+ energy from 12 ATP and 12 NADPH) → 12 PGAL (3-carbon)

10 PGAL (+ energy from 6 ATP) → 6 RuBP (ie starting material regenerated)

2 PGAL → glucose (6-carbon).


Glycolysis pathway.
The color scheme is as follows: enzymes, coenzymes, substrate names, metal ions, inorganic molecules, inhibition and attached phosphate, stimulation

ok, i'm sorry

Fructose (or levulose) is a simple sugar (monosaccharide) found in many foods and one of the three most important blood sugars along with glucose and galactose.

you are right that this is used to skip the reaction. is is more faster than using glucose.

about why not fructose..
just the same as Canalon said
it is not better than glucose if it is exist in human body...-metazoan organism.

Health effects
Fructose depends on glucose to carry it into the blood stream via GLUT-5 and then GLUT-2 (Buchs et al 1998). Absorption of fructose without glucose present is very poor, and excess fructose is carried into the lower intestine where it provides nutrients for the existing flora, which produce gas. It may also cause water retention in the intestine. These effects may lead to bloating, excessive flatulence, loose stools, and even diarrhea depending on the amounts eaten and other factors.

Fructose has by some been hypothesized to cause obesity (Elliott et al 2002), elevated LDL cholesterol and triglycerides, leading to metabolic syndrome. However, supplementation with fructose in the diet in human subjects has not led to increased obesity.

Fructose also chelates minerals in the blood. This effect is especially important with micronutrients such as copper, chromium and zinc. Since these solutes are normally present in small quantities, chelation of small numbers of ions may lead to deficiency diseases, immune system impairment and even insulin resistance, a component of type II diabetes (Higdon).

Fructose is a reducing sugar, as are all monosaccharides. However, it is considered approximately ten times more active (McPherson et al 1988) in the formation of glycations than glucose, so consumption should be limited in order to limit the consequent glycation-related damage to cellular and molecular function. This may be an important contribution to senescence and many age-related chronic diseases (Levi & Werman 1998).


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