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Fatty Acids

chia — Wed, 29 Apr 2009 18:38:26 +0000

In food, fats are in the form of triglycerides (1 glycerol + 3 fatty acid chains). There are a few types of fatty acids:

Saturated , where the fatty acid chain has no double bonds (think of the hydrocarbon chain being saturated with hydrogens. Animal products such as lard, butter, whole milk, eggs and meat are high in saturated fat.
Monounsaturated fatty acids have 1 double bond. Examples of foods high in monounsaturated fat include avacado and nuts.
Polyunsaturated fatty acids have multiple double bonds.

Saturated fats have a higher melting point and are normally solid at room temperature (butter, animal fat, palm oil, coconut oil…), while unsaturated fats are liquid (e.g. olive oil, sunflower oil, fish oil…).

While fats are often thought of as unhealthy, some fat is actually necessary for good health. We need fatty acids to make and repair cell membranes, aid absorption of fat-soluble vitamins (A, D, E & K), produce hormones and provide protection and insulation of organs.

Certains types of fats must be eaten as they cannot be synthesized by the body, but are needed for metabolic functioning . These are the Essential Fatty Acids. The 2 families of EFAs are omega-3 fatty acids and omega-6 fatty acids. Fish, seeds and nuts are the best sources of EFAs.

Trans fat is unsaturated fat made by partial-hydrogenation of vegetable oils (for example, to produce margarine). Hydrogenation increases the melting point of the unsaturated fat which makes the oil solid, extends its shelf-life and is also useful for baking. However, this process sometimes causes the conversion of cis-double bonds of the fatty acid chain into trans-double bonds. Such a molecular structure is not normally found in high amounts in natural fats. Our bodies therefore do not process trans fats efficiently and this leads to health problems, especially cardiovascular heart disease (CHD).

MayoClinic – Trans fat: Avoid this cholesterol double whammy

Amino acids

Disaccharides

chia — Wed, 28 Jan 2009 19:32:42 +0000

Disaccharides are formed when 2 monosaccharides are linked together by a glycosidic linkage.

Maltose used for beer brewing is glucose + glucose.
Lactose, found in milk, is glucose + galactose.
Sucrose, table sugar, is actually glucose + fructose.

Plants (including fruits and vegetables) usually carry carbohydrates from their leaves to other parts in the form of sucrose.

When we eat sucrose, it is quickly broken down into glucose and fructose, causing a rapid rise in blood glucose levels (not good for diabetics!) Polysaccharides (starch) is broken down much more slowly, so it helps us maintain steady blood glucose levels (and keeps us feeling fuller for longer!).

Polysaccharides

chia — Wed, 28 Jan 2009 19:08:47 +0000

Polysaccharides are polymers of sugars, where hundreds or thousands of monosaccharides are joined together by glycosidic linkages.

A glycosidic linkage is a covalent bond that is formed between two monosaccharides by a dehydration reaction — the removal of a water molecule (H + OH).

Polysaccharides are used for:

1. Storage

In plant cells, excess glucose made by photosynthesis is turned into starch.

In animal cells, excess glucose eaten is stored as glycogen.

We (and animals!) can get our source of sugars by eating starch. We have enzymes that can break down plant starch and turn it into glucose for energy.

2. Structural material

Plant cells have tough cell walls that contain cellulose. Like starch, cellulose is also a polymer of glucose. The difference is that it uses a different form of glucose — beta-glucose. When linked into a chain by beta-1,4-glycosidic linkages, beta-glucose forms a straight chain that can form hydrogen bonds with a neighboring chain. This makes it really strong!

Humans don’t have enzymes that can hydrolyze (break) these beta-linkages, which is why we can’t digest cellulose (dietary fiber). Cows, however, have bacteria in their stomachs that can do this, so they can use the nutrients of the cellulose they eat.

Certain animals (arthropods: insects, spiders, crustaceans…) also use a structural polysaccharide, chitin, to form their exoskeleton.

Glycogen

chia — Wed, 28 Jan 2009 18:36:05 +0000

Glycogen is a polysaccharide consisting of glucose. It is a branched polymer — that means it is not linear/straight but has long chains of glucose coming off the sides of another glucose chain.

Animal cells store glucose in the form of glycogen. After eating, glucose levels in the blood increase, causing insulin to be released. Glucose is then taken up by muscle and liver cells, and converted into glycogen granules (glycogenesis).

When energy is needed (exercise), or when blood sugar levels are low (between meals/fasting), glycogen is broken back down into glucose for use, or released back into the blood.

Glucose

chia — Thu, 08 Jan 2009 20:57:39 +0000

Glucose is a simple sugar, a monosaccharide, that has the molecular formula C6 H12 O6. Other forms of monosaccharides are such as fructose and galactose.

Glucose is used by our bodies as fuel for energy; they are the major starting points for cellular respiration which produces ATP.

When glucose levels in the blood are high, they are converted into glycogen in the liver and muscles (glycogenesis), and also stored as fat in adipose tissue. Insulin controls the levels of glucose in the body to maintain homeostasis.

Diabetes mellitus is a metabolic disease which occurs when glucose levels in the blood are too high due to ineffective insulin action or low insulin production.

Amino acids

chia — Mon, 05 Jan 2009 23:38:42 +0000

Amino acids are the building blocks of proteins. Our bodies need amino acids in order to make new cells and enzymes. Out of the 20 types of amino acids that exist, we can make 10. The other 10 must come from our diet.

An amino acid has an amino group (NH2) and a carboxyl group (COOH), and a side chain (R group) that makes one amino acid type different from another.

A chain of amino acids is called a polypeptide. To link up amino acids, an amino group from one amino acid reacts with a carboxyl group of another amino acid, and they are joined by removal of a water molecule (called a dehydration reaction) to form a peptide bond. Amino acids can be further added to the sides of the chain to form a long polypeptide.