are four substances we refer to as food which can be used to produce energy: carbohydrates,
fats, proteins and alcohol. Alcohol however is not considered a basic nutritional
component of food.
gram of Carbohydrates contains 3.75 calories.
1 gram of fat contains 9 calories.
1 gram of protein contains 4 calories.
1 gram of alcohol contains 7 calories.
(literally hydrates of carbon) are chemical compounds which act as the primary
biological means of storing or consuming energy; other forms being via fat and
protein. Relatively complex carboyhydrates are known as polysaccharides.The simplest
carbohydrates are monosaccharides, which are small straight-chain aldehydes and
ketones with many hydroxyl groups added, usually one on each carbon except the
functional group. Other carbohydrates are composed of monosaccharide units, and
break down under hydrolysis. These may be classified as disaccharides, oligosaccharides,
or polysaccharides, depending on whether they have two, several, or many monosaccharide
or saccharides (Greek sakcharon, "sugar") are simple molecules that are straight-chain
aldehydes or ketones with many hydroxyl groups added, usually one on each carbon
atom that is not part of the aldehyde or ketone functional group. Carbohydrates
are the most abundant biological molecules, and fill numerous roles in living
things, such as the storage and transport of energy (starch, glycogen) and structural
components (cellulose in plants, chitin in animals). Additionally, carbohydrates
and their derivatives play major roles in the functioning of the immune system,
fertilization, pathogenesis, blood clotting, and development.
basic carbohydrate units are called monosaccharides, such as glucose, galactose,
and fructose. The general chemical formula of an unmodified monosaccharide is
(C·H2O)n, where n is any number of three or greater. All carbohydrates have a
hydrogen to oxygen ratio of 2:1.Monosaccharides can be linked together in almost
limitless ways. Two joined monosaccharides are called disaccharides, such as sucrose
and lactose. Carbohydrates containing between about three to six monosaccharide
units are termed oligosaccharides; anything larger than this is a polysaccharide.
Polysaccharides, such as starch, glycogen, or cellulose, can reach many thousands
of units in length.
biochemistry, fat is a generic term for a class of lipids. Fats are produced by
organic processes in animals and plants. All fats are insoluble in water and have
a density significantly below that of water (i.e. they float on water.) Fats that
are liquid at room temperature are often referred to as oil. Most fats are composed
primarily of triglycerides; some monoglycerides and diglycerides are mixed in,
produced by incomplete esterification. These are extracted and used as an ingredient.
with a lot of saturated fats tend to be solid at room temperature, while products
containing unsaturated fats, which include monounsaturated fats and polyunsaturated
fats, tend to be liquid at room temperature. Predominantly saturated fats (solid
at room temperature) include all animal fats (e.g. milk fat, lard, tallow), as
well as palm oil, coconut oil, cocoa fat and hydrogenated vegetable oil (shortening).
All other vegetable fats, such as those coming from olive, peanut, maize (corn
oil), cottonseed, sunflower, safflower, and soybean, are predominantly unsaturated
and remain liquid at room temperature. However, both vegetable and animal fats
contain saturated and unsaturated fats. Some oils (such as olive oil) contain
in majority monounsaturated fats, while others present quite a high percentage
of polyunsaturated fats (sunflower, rape).
protein is a complex, high molecular weight organic compound that consists of
amino acids joined by peptide bonds. Protein is essential to the structure and
function of all living cells and viruses. Many proteins are enzymes or subunits
of enzymes. Other proteins play structural or mechanical roles, such as those
that form the struts and joints of the "cytoskeleton." Proteins are
also nutrient sources for organisms that do not produce their own energy from
sunlight. Proteins differ from carbohydrates chiefly in that they contain much
nitrogen and a little bit of sulfur, besides carbon, oxygen and hydrogen. Proteins
are a primary constituent of living things.
carnivores protein is one of the largest component of the diet. The metabolism
of proteins by the body releases ammonia, an extremely toxic substance. It is
then converted in the liver into urea, a much less toxic chemical, which is excreted
in urine. Some animals convert it into uric acid instead.
nutrition in humans
In terms of human nutritional needs, proteins come in
two forms: complete proteins contain all eight of the amino acids that humans
cannot produce themselves, while incomplete proteins lack or contain only a very
small proportion of one or more. Humans' bodies can make use of all the amino
acids they extract from food for synthesizing new proteins, but the inessential
ones themselves need not be supplied by the diet, because our cells can make them
ourselves. When protein is listed on a nutrition label it only refers to the amount
of complete proteins in the food, though the food may be very strong in a subset
of the essential amino acids. Animal-derived foods contain all of those amino
acids, while plants are typically stronger in some acids than others. Complete
proteins can be made in an all vegan diet by eating a sufficient variety of foods
and by getting enough calories. It was once thought that in order to get the complete
proteins vegans needed to do protein combining by getting all amino acids in the
same meal (the most common example is eating beans with rice) but nutritionists
now know that the benefits of protein combining can be achieved over the longer
period of the day. Ovo-lacto vegetarians usually do not have this problem, since
egg's white and cow's milk contain all essential amino acids. Peanuts, soy milk,
nuts, seeds, green peas, Legumes, the alga spirulina and some grains are some
of the richest sources of plant protein.
eight essential amino acids must be part of one diet in order to survive and are
needed in a fixed ratio. A shortage on any one of these amino acids will constrain
the body's ability to make the proteins it needs to function.
foods contain different ratios of the essential amino acids. By mixing foods that
are rich in some amino acids with foods that are rich in others, one can acquire
all the needed amino acids in sufficient quantities. Omnivores typically eat a
sufficient variety of foods that this is not an issue, however, vegetarians and
especially vegans should be careful to eat appropriate combinations of foods (e.g.
nuts and green vegetables) so as to get all the essential amino acids in sufficient
quantities that the body may produce all the proteins that it needs.
deficiency can lead to symptoms such as fatigue, insulin resistance, hair loss,
loss of hair pigment (hair that should be black becomes reddish), loss of muscle
mass (proteins repair muscle tissue), low body temperature, and hormonal irregularities.
Severe protein deficiency is fatal.
protein can cause problems as well, such as causing the immune system to overreact,
liver dysfunction from increased toxic residues, possibly bone loss due to increased
acidity in the blood, and foundering (foot problems) in horses.
can often figure in allergies and allergic reactions to certain foods. This is
because the structure of each form of protein is slightly different, and some
may trigger a response from the immune system while others are perfectly safe.
Many people are allergic to casein, the protein in milk; gluten, the protein in
wheat and other grains; the particular proteins found in peanuts; or those in
shellfish or other seafoods. It is extremely unusual for the same person to adversely
react to more than two different types of proteins.