Carbohydrates: contents in brief
What are carbohydrates?
Carbohydrates, together with lipids, proteins and nucleic acids, are one of the four major classes of biologically essential organic molecules found in all living organisms.
Carbohydrates, all coming from the process of photosynthesis, represent the major part of organic substance on Earth, are the most abundant organic components in the major part of fruits, vegetables, legumes and cereal grains, carry out many functions in all living organisms and are the major energy source in a Mediterranean-type diet. Finally, they provide flavor and texture in many processed foods.
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Chemical classification of carbohydrates
Carbohydrates, also called Carbs, are defined as aldehydic or ketonic compounds with a some number of oxydrilic groups (so polyhydroxy aldehydes or ketones as well).
Many of them, but not all, have general formula (CH2O)n (only molecules with n>4 are considered carbohydrates); some, in addition to carbon (C), oxygen (O) and hydrogen (H), include nitrogen or sulfur.
On the basis of the number of forming units, three major classes of carbohydrates can be defined: monosaccharides, oligosaccharides and polysaccharides.
- Monosaccharides or simply sugars are formed by only one polyhydroxy aldehydeidic or ketonic unit.
The most abundant monosaccharide is D-glucose, also called dextrose.
- Oligosaccharides are formed by short chains of monosaccharidic units (from 2 to 20) linked one to the next by chemical bounds, called glycosidic bounds.
The most abundant oligosaccharides are disaccharides, formed by two monosaccharides, and especially in the human diet the most important are sucrose (common table sugar), lactose and maltose. Within cells many oligosaccharides formed by three or more units do not find themselves as free molecules but linked to other ones, lipids or proteins, to form glycoconjugates.
- Polysaccharides are polymers consisting of 20 to 107 monosaccharidic units; they differ each other for the monosaccharides recurring in the structure, for the length and the degree of branching of chains or for the type of links between units.
Whereas in the plant kingdom several types of polysaccharides are present, in vertebrates there are only a small number.
Polysaccharides are defined
omopolysaccharides if they contain only one type of monosaccharide as starch, glycogen and chitin;
eteropolysaccharides, instead, contain two or more different kinds (e.g. hyaluronic acid).
Note: the term “saccharide” derives from the greek word “sakcharon”, which means sugar.
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Physiological classification of carbohydrates
On the basis of their degree of polymerization, they can be classified as:
- simple: mono- and disaccharides (also known as “sugars”) and tri- and tetrasaccharides (oligosaccharides);
- complex: the polysaccharides.
A further classification lays the foundations on the possibility of being used directly for energy purpose, so:
- available, as glucose, fructose, galactose between monosaccharides, sucrose, lactose, maltose and maltodextrin between oligosaccharides, and starch and glycogen between polysaccharides;
- not available, as xylose (monosaccharide), lactulose (see lactose) and raffinose (respectively di- and trisaccharide), fiber (cellulose, hemicellulose, lignin, pectins etc.) and resistant or not digestible starch (polysaccharides). The members of this class, also if ingested, are not digestible nor absorbable and will be fermented by intestinal flora with release of short chain fatty acids and so yielding some energy.
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Functions of carbohydrates
- They are used as material for energy storage and production.
Starch and glycogen, respectively in plants and animals, are stored carbohydrates from which glucose can be mobilized for energy production. Glucose can supply energy both fueling ATP synthesis (ATP, the cell’s energy currency, has inside a phosphorylated sugar) and in the form of reducing power as NADPH.
It should be noted that glucose, used as energy source, “burns” without yielding metabolic wastes, being turned in CO2 and water, and of course releasing energy.
Monosaccharides supply 3.74 kcal/g, disaccharides 3.95 kcal/g, while starch 4.18 kcal/g; on average it is approached to 4 kcal/g.
- They exert a protein-saving action: if present in adequate amount in daily nourishment, the body does not utilize proteins for energy purpose, an anti-economic and “polluting” fuel because it will need to eliminate nitrogen (ammonia) and sulfur present in some aminoacids.
- Their presence is necessary for the normal lipid metabolism. More than 100 years ago Pasteur said: “Fats burn in the fire of carbohydrates“. This idea continues to receive confirmations from the recent scientific studies. Moreover, excess carbohydrates may be converted in fatty acids and triglycerides (processes that occur mostly in the liver).
- Glucose is indispensable for the maintenance of the integrity of nervous tissue (some central nervous system areas are able to use only glucose for energy production) and red blood cells.
- Two sugars, ribose and deoxyribose, are part of the bearing structure, respectively of the RNA and DNA and obviously find themselves in the nucleotide structure as well.
- They take part in detoxifying processes. For example, at hepatic level glucuronic acid, synthesized from glucose, combines with endogenous substances, as hormones, bilirubin etc., and exogenous substances, as chemical or bacterial toxins or drugs, making them atoxic, increasing their solubility and allowing their elimination.
- They are also found linked to many proteins and lipids. Within cells they act as signals that determine the metabolic fate or the intracellular localization of the molecules which are bound. On the cellular surface their presence is necessary for identification processes between cells that are involved e.g. in the recognition between spermatozoon and oocyte during fertilization, in the return of lymphocytes in the lymph nodes of provenance or still in the leukocyte adhesion to the lips of the lesion of a blood vessel.
- Two homopolysaccharides, cellulose (the most abundant polysaccharide in nature) and chitin (probably, next to cellulose, the second most abundant polysaccharide in nature), serve as structural elements, respectively, in plant cell walls and exoskeletons of nearly a million species of arthropods (e.g. insects, lobsters, and crabs).
- Heteropolysaccharides provide extracellular support for organisms of all kingdoms: in bacteria, the rigid layer of the cell wall is composed in part of a heteropolysaccharide contained two alternating monosaccharide units while in animals the extracellular space is occupied by several types of heteropolysaccharides, which form a matrix with numerous functions, as hold individual cells together and provide protection, support, and shape to cells, tissues, and organs.
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Stipanuk M.H.. “Biochemical and physiological aspects of human nutrition” W.B. Saunders Company-An imprint of Elsevier Science, 2000
You see a new word that absolutely means nothing to you. The word seems interesting enough so as a wise student you decide to look it up in the dictionary. After researching the term online, you find a proper definition that seems logical enough. Great, you have learned a new word!
However, sometimes a term cannot be described in a sentence or two. This word is so complex and deep that it requires hundreds or even thousands of words to explain it.
Table Of Contents
What is a Definition Essay?
A definition essay can be tricky to write. This type of paper requires you to write a partially personal and also formal explanation of . Considering the fact that this is an essay, you can not pick a term that is describable in a few words. It has to be a complex term that has significant background and origin in history, as well as a term that people can relate to in some way or form. For example, the word "love". It is seemingly impossible to explain this concept in a sentence or two, so we must create an entire essay about it to give it an accurate UNIVERSAL representation!
Types of Definitions commonly used in Definition Essay
- Analysis: Break the subject into parts and define each part individually.
- Classification: What classes does the subject belong to?
- Comparison: Unusual things may be defined by showing its likeness to the common or its contrast from it.
- Details: What are the characteristics and other distinguishing features that describe the idea of the paper?
- Negation: Mention what it is not in order to clear the ground for what it is.
- Origins and Causes: What is the origin of the theme? What is the background information? What is the history of the idea?
- Results, Effects, and Uses: Describe the after effect and uses of the subject.
- What makes someone a Hero
- What is Success?
- Describe Love.
- Explain the definition of Beauty.
- What is Happiness?
- How can one define Respect?
- What is the definition of Loyalty?
- What is Courage?
- Describe Heroism.
- What is Friendship?
These are just some common examples of definition essay questions and topics that are commonly asked on tests and coursework assignments. There are an infinite number of words that can be defined in the span of an essay. The goal here is to pick one that as a student you feel comfortable explaining and portraying. It is time to become a word artist!
A definition essay outline will vary in length based on the term one is describing. As stated previously, some terms are fairly logical and more or less "easy to understand". There are some terms, however, that require deep research and analysis in order to be able and formulate an accurate representation of its meaning! Regardless Every Definition Essay should be written in the classic Intro-Body(s)-Conclusion format.
Steps to take Pre-Writing
Before you even begin writing, obviously a word has to be chosen for the essay to be based around. Here are a few tips to consider before choosing your !
- Choosing a Proper Term:
- As stated previously, it is impossible to write a hefty custom essay on a simple word. That is why it is important to be meticulous during the decision process. Choosing something like a noun is most likely not going to work out. For example, if you chose the term "pencil", there is really not much depth that you as the writer can get into. Sticking in the same sphere, choosing something like "writing" is much more subjective and gives you as the writer some room for implementing different ideas!
- The Word Should be Multi-Dimensional
- Think about it like this: there are certain words in every language that have multiple interpretations; some people will perceive them differently than others!
- Avoid using terms that are universal in every language; an example would be like "hello" or "telephone". Though there are ways you can stretch information on these terms, it is better to pick a juicy one from the start!
- Term Familiarity
- It will be practically impossible to write about a term that has no correlation with your life. You should choose a word that you know well and that also has undiscovered boxes in your life. Ideally, in any research assignment you ever get, there will be some personality knowledgeable gain!
- Do some historical research!
- Considering that humans have been lingual for centuries, there is a 100% chance that your term has a significant past. Check out the Oxford Dictionary's explanation in order to get yourself a point of relevance!
As with any other essay, you are using this part to start informing your writers about the contents of your paper. In a definition essay, the introduction serves two main goals; first, you must give a "standard" definition of the term, and then give the thesis definition!
- Standard Definition: The initial section of the introduction should state the dictionary version. This is important for the readers to have a starting point in regards to the term so as to clarify any possible questions. Also, this is especially important because the standard definition will slightly vary from the thesis one, which allows for multi-dimensionality!
Similar to the classic thesis statement, the thesis definition is your fully completed version of what the term actually means. This is a hybrid of the standard definition, while also mixing in your personal experiences and explanation style! Do not try and describe too much in this section, as you want to split up the bulk of it for the rest of the essay! Make sure that you don’t use passive phrases involving the word when defining your term. The phrases like and are especially ponderous.
The body paragraphs are the part of the essay that really breaks down the term into its core parts. You are taking every variation of the definition and its history and breaking it down into organized sections. An example of good body paragraph structure:
- Body Paragraph 1: History and Origin
- Body Paragraph 2: Full dictionary explanation and use.
- Body Paragraph 3: Personal definition created from experience.
The conclusion is fairly simple and to the point. The main goal here is to summarize the main points of your argument. Rephrase the main parts of the definition and make sure you summed up everything you planned on saying. The last thing that should be mentioned is how this term has impacted you. Usually, before even writing the essay, there is a reason a specific term is picked and part of the reason has to do with personal experience.
Mention how the definition you were talking about affected you.
If the term you define plays a specific part in your life and experiences, your final concluding comments are a great place to concisely mention the role it plays.
Definition Essay Examples
Essay Writing Advice From Our Professional Team
Jackson Super Writer, from EssayPro
When writing a definition essay, a common mistake is choosing a term that is way too broad for the given assignment. When you’ve chosen a term, try to narrow it down so it is easier to define and find examples for. As the article articulates, the term’s origin is very important to the word’s meaning itself. For example, the word “crush” comes from a variety of similar words in nordic languages. It wouldn’t be a bad idea to list every single one of those words as examples. As with word “crush”, a word can have multiple meanings. You can crush a bag of chips and you can have a crush on someone. Whatever definition your essay has, make sure to define it in a unique way. Be creative and approach it from a new angle. As the article states, it isn’t a bad idea to put in examples from your own life of how that specific word has impacted you. This will definitely make it more interesting for the reader.
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Sometimes it can be hard to find a term we know well that also has a multi-dimensional definition. This is a common problem for college students and one that is commonly solved by buying an essay online! EssayPro, the best essay writing service on the web, has dedicated paper writers that know all the tips and tricks necessary to write an effective definition essay, leaving you and your professor satisfied!
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