Nutrition - Digestion

Digestion has 2 very important uses: Digestion and the absorption of nutrients. The body has to break down large food molecules into smaller amounts which make them more manageable. The job of the digestive system is done though chemical and mechanical digestion.

Enzymes help to speed up the digestive process by breaking down unabsorbable, large macronutrient molecules. Many parts of the digestive system produce these enzymes.

The GI tract (gastrointestinal tract) is where the digestion and absorption of all the nutrients take place.
The GI tract runs through from the mouth to the anus and comes in the form of a hollow tube. The mouth, pharynx, oesophagus, stomach, small and large intestines, anus are what makes up the GI tract. All of these parts have a direct use.

Mouth, salivary amylase, carbs
Stomach, pepsin, proteins
Small intestine, lipase, fats
Small intestine, pancreatic amylase
Small intestine, trypsin, proteins

Carbs result in the end product of glucose, proteins result in the end product of amino acids and fats result in the end product of free fatty acids and glycerol.

Starting with the mouth - mastication is the mechanical chewing, saliva helps to dampen food and protects the teeth against rotting and also contains an enzyme, salivary amylase which begins to break down the larger carb molecoles.

The oesophagus contains peristalsis which helps the food to travel down and into the stomach.

The stomach has gastric juices that hold enzymes and acid, the hydrochloric acid also kills bacteria and pepsin helps to break down the proteins into peptides.

The pancreas has pancreatic juices that contain enzymes, lipase that helps to break fat and into fatty acids, amylase that turns carbs into glucose and trypsin that turns the proteins into amino acids.

Next is the liver although food doesn't enter the liver. It does however produce bile acids which emulsifies fats or mixes them with water.

The gall bladder is a storage place for the bile acids.

The small intestine is the key site of digestion and absorption, the pancreas and the gall bladder empty into the 1st section and duodenum villi helps to absorb the nutrients into blood.

The large intestine has colon that helps to absorb any of the water that's still there that also applies to vitamins and minerals, the bacteria then produces some vitamins and helps to fight any infection that occurs in the intestine, the rectum also stores faeces.

Lastly, the anus is the opening for the elimination of waste!

Next up: Food labelling!

Nutrition - Fats/Lipids - structure of Lipids and Triglycerides

So 1st of all, what are the physiological functions of lipids?

Many things... it provides protection for the internal organs, assists in regulation of enzymes, constitutes the majority of the central nervous system and the spinal cord, the formation of all cell membranes, formation of the myelin sheath within the nervous system, the transportation, storage and utilisation of fat soluble vitamins A, D, E and K, a fuel source during lower intensity work loads, storage of energy within adipose tissue, insulation through subcutaneous adipose tissue and lastly the synthesis of steroid hormones.

Lipids that are solid at room temperature are called fats whilst lipids that are liquid at room temperature are called oils.

There are chains/rings of carbon atoms that join together with other atoms which a lot of dietary lipids consist of. These are most commonly oxygen and hydrogen. Smaller units of fats are called fatty acids. Double strength bonds are present, these change the shape of the molecule and allow the lipids to become versatile.

3 fatty acids are attached to a carbohydrate backbone which is called glycerol. Fatty acids are broken off during digestion and used as needed. This happens when fatty acids occur naturally as triglycerides.

Tomorrow I'll move onto the rest about fats/lipids!