Hot answers tagged

47

Sugars in 100% natural fruit juices are chemically the same as in whole fruits. They mainly include glucose, fructose and sucrose: Apple nutrition data (expand the carbohydrate section) Apple juice nutrition data Sugars in whole fruits are "incorporated" into the fruit, which means the digestive system first needs to physically decompose the fruit and then ...


13

As far as I can understand your question, you wish to know why a plant cell consumes ATP to produce glucose when it can directly use the ATP as an energy molecule. ATP is an energy currency and is required in different biochemical pathways. However, it is not a good energy storage molecule. Following are the reasons why production of an energy molecule ...


8

No, but yes. Sucrose is a large polar solute. Because it is polar, it cannot easily pass the hydrophobic core of the membrane. So, if the lipids of the plasma membrane are mostly impermeable to sucrose, how do cells take in sucrose? Plants In biology, membrane-bound proteins are used for efficient transport across the membrane (Brian, 2011 from a review ...


7

Drinking the juice without the fruit can easily lead to over-consumption. It is after all harder to eat four apples than drinking 500ml apple juice. As the liver breaks the fructose through lipogenesis it creates fat and can cause non-alcoholic fatty liver and obesity. Since sugar (fructose/glucose/sucrose et al.) can be absorbed already through the mucus ...


7

In short, sugars are absorbed quicker than proteins and fats because they pass through the stomach quicker and their digestion is simpler. Sugar can be absorbed through the mouth mucosa when applied as a sublingual gel, as discussed here on Biology SE: Is sugar absorbed into the bloodstream through the walls of the mouth?, but probably in much smaller ...


6

Our food mostly gets spoiled by bacteria and / or fungi. There are 2 main reasons for sugar crystals not getting spoiled. 1- Lack of sufficient amount of water to sustain metabolic processes by microbes. 2- Even if sufficient amount of water is present , then due to high osmolality of the fluid formed, will cause plasmolysis or cell shrinkage. Some ...


5

The two structures on the left are correct; the one on the upper left is the alpha-D-fructofuranose form, while the one on the lower left is the beta-D-fructofuranose form. Fructose is a ketohexose (a six-carbon sugar with its carbonyl group present as a ketone group in the molecule's open-chain form); the carbonyl carbon (the 2-carbon, to be precise) is ...


4

Simple sugars such as glucose, fructose and galactose will be absorbed. They are most probably transported by a common carrier, which is why if you present both glucose and galactose, the presence of one will inhibit the absorption rate of the other. Uptake rate also seems to partly depend on the concentration of sodium ions in the buccal cavity. This was ...


4

Jan's answer is great, but I'm just going to quote the paper you reference: The systematic review of the effect of intake of free sugars on body weight included 30 of the 7895 RCTs and 38 of the 9445 cohort studies initially identified as meeting the inclusion criteria. Meta-analysis of the five trials in adults with ad libitum diets (i.e. no strict ...


3

Plants do not produce extra cellulase to break down cellulose for an energy boost when they are grown in dark conditions (that I know of). But remember, cell walls are the structures maintaining turgor pressure in the cells, so breaking them down would be very costly to plant survival. A couple notes: plant cell walls have more components than just cellulose,...


3

The absorption of sugar from the mouth is possible and it was successfully tested for treatment of hypoglycemia. In all mentioned studies, they used D-glucose (dextrose), which is a common natural or added sugar in foods and beverages. 1) Sublingual sugar administration as an alternative to intravenous dextrose administration to correct hypoglycemia among ...


3

These are learning phenomena you describe. I'll try to explain a simple way to think about this. By default, sweet foods are appetitive and, for instance, strongly bitter foods are aversive. However, it is possible to condition yourself to associate a stimulus, no matter how it presents originally, with a different valence (appetitive or aversive). There ...


3

It would depend if the fruit has the ability to sense or capture light. This depends on chlorophyll mostly, found in cellular organelles called chloroplasts. If the fruit is incapable of capturing light, the light can still have an indirect impact by being captures on leaves, since plants circulate nutrients - this is why roots can grow without having access ...


3

The idea that 'dyes and preservatives' cause hyperactivity dates back to this '76 paper by one Dr. Feingold. Despite being disproved neatly in 1978, it's still around. As far as sugar goes, I recommend this review paper covers both the arguments for and against sugar causing hyperactivity, as well as 12 double-blind placebo controlled studies showing sugar ...


3

You need to make a distinction between polymers and monomers (or dimers). Typically, sugars are monomers like glucose, maltose, or fructose. Sucrose (table sugar) is a dimer. These are all carbohydrates (made up of carbon, oxygen, and hydrogen). Polymers of these sugars are also carbohydrates. For example, starch, glycogen, and cellulose. Cellulose, which ...


3

The LD 50 listed on the wikipedia page you link to is 90 mL/kg, which would be about 6 liters for a 68 kg (150 lb) person. This is consistent with at least one report, where someone died from drinking 7 liters of water in 1.5 hours. The mechanism by which water kills people is by lowering the amount of ions (chiefly sodium) in the blood. A condition called ...


2

In a very simplified explanation - the body usually picks the process which is easiest/ fastest which would be to absorb the glucose then the fat would be used for energy as this takes longer to digest and absorb because it is a relatively complex molecule which also requires bile to emulsify it. Starchy/ high glucose products will already be broken down ...


2

The one I found is Ovomucin,though it's not a pure carbohydrate. Ovomucin is a highly glycosylated protein and approximately 33% of ovomucin is made up of carbohydrates. Nutritional Values of Egg White Proteins paragraph of http://ps.oxfordjournals.org/content/92/12/3292.full So you can see it's mostly a protein. Ovomucin is a trypsin inhibitor found in ...


2

Although one might naïvely imagine that the term carbohydrate is used for a molecule containing carbon, hydrogen and oxygen, this is not the case as, if so, it would include compounds like fatty acids. According to the Wikipedia entry it is more restricted, although still somewhat imprecise: A carbohydrate is a biological molecule consisting of carbon (C),...


2

The statement in your question is correct. All sugars are carbohydrates but not all carbohydrates are sugars. In fact, sugars are by definition carbohydrates. Wikipedia defines sugars as : Sugar is the generalized name for sweet, short-chain, soluble carbohydrates, many of which are used in food. They are composed of carbon, hydrogen, and oxygen Not ...


2

Plants do not break down cellulose for energy, although it does store energy. Plants store their energy in the form of starch, which is broken down into glucose for the plant to use for energy. Most plants do not survive once the starch is utilized (but they do not breakdown cellulose). Because cellulose molecules bond strongly to each other, breakdown of ...


1

One of the advantages of lactose in breast milk is that it is digested slower than sucrose and its ingestion results in lower fluctuations of blood glucose levels thus being a stable source of energy. Lactose, a disaccharide of glucose and galactose, is uniquely present in mammalian milk. Human milk provides the infant with about 40% energy as ...


1

Yes it is thought to provide safer milk, less vulnerable to every bacteria that respires and multiplies on sucrose, and which lets the baby grow faster due to higher sugar content. Milk has evolved from pouch mucus, antimicrobal secretions of the immune system, Lysozyme in mucus is a glycoside hydrolase which ruptures bacteria cell walls. So the origins of ...


1

The “positive aspect” or reasons why the surfaces of eukaryotic cells contain sugars are various. Major ones appear to be cell adhesion and cell–cell interaction. In fact, the variation of the sugars in certain cell-surface antigens (blood group antigens and histocompatibility antigens may represent the kind of evolutionary response to infectious agents ...


1

Everything is a poison with the right dosage Here is a fun chart you can use to see what I mean. Even water is poisonous if you drink enough of it. fructose in no more poisonous than glucose. No study has shown fructose to be dangerous when eaten in normal healthy diet. It is poisonous but only in the sense that water is poisonous if you drink to much of ...


1

Sugar is a very casual term used for monosaccharides and oligosaccharides, which normally tastes sweet. The polysaccharides (starch, cellulose etc) usually does not considered as sugar since they are normally tasteless. Monosaccharide, Oligosaccharide and Polysaccharide, all three make the chemical-class carbohydrate. So Polysaccharide is the group of ...


1

A very well-written question, so I'm sorry if my answer is a bit too simple. Perhaps it will attract attention of somebody with a better answer. I think the effect could be mainly caused by the fact that sugary drinks slow down alcohol absorption. So while those who drink just alcohol already know they've had enough, those who have had a couple of energy ...


1

This refers to metabolism of fructose. Many fruits contain high amounts of fructose (hence the name :) in addition to glucose. So does ordinary table sugar (sucrose, which contains equal parts glucose and fructose), and most other sweets you can find --- candy, soft drinks and so on. Dietary fructose is rapidly metabolized, mostly into glucose, glycogen and ...


1

Do you mean fructolysis? Here what I found on the textbook by John L. Tymoczko: Fructose can take one of two pathways to enter the glycolytic pathway.Much of the ingested fructose is metabolized by the liver, using the fructose 1-phosphate pathway. The first step is the phosphorylation of fructose to fructose-1-phosphate by fructokinase. Fructose-1-...


1

The number of fat cells, or adipocytes, in adult bodies remains constant. Therefore, consuming more fat only increases the size of the fat cells not the number. After reaching the age of about 20 years the average number of fat cells is closely related to body mass index. On the other hand, the adipocytes in children increase in number as more fat is ...


Only top voted, non community-wiki answers of a minimum length are eligible