Lipids Overview

Question 1

White Adipose Tissue (WAT)

Answer 1

• Far from being inert, white adipose tissue (WAT) is a complex, metabolically active endocrine tissue
• Functions include: The secretion of hormones, growth factors, enzymes and cytokines; the protection of organs; a form of energy storage; and to provide insulation to protect against temperature extremes.

Question 2

Lipids in the Body

Answer 2

Lipids exist in the body in various forms with each form having a different structure and function. Lipids include:

• Individual fatty acids.
• Triglycerides.
• Phospholipids in every cell membrane.
• Cholesterol and steroid based compounds ( e.g. oestrogen).
• Sphingolipids found in nerve cell membranes, e.g. myelin.
• Glycolipids involved in cell identity (like a cell ‘passport’).
• Cerebrosides glycosphingolipids found in the brain.
• Fat soluble vitamins A, D, E, K.

Question 3

Phospholipid

Answer 3

phosphate + fatty acids

Question 4

Glycolipid

Answer 4

carbohydate + lipid

Question 5

Cerebroside

Answer 5

waxy lipid + sugar

Question 6

Sphingolipid

Answer 6

long chain amino alcohol + fatty acid + sugar

Question 7

Function of Lipids

Answer 7

• Energy (ATP) production - each gram of fat supplies the body with about nine calories.
• Storage of energy reserves - fats are a more efficient form of storage energy than carbohydrates or proteins, so the body stores any excess energy as fat.
• Cell membrane structure - phospholipids and cholesterol stabilise cell membranes, whilst allowing a degree of fluidity which is crucial to the function of every cell.
• Thermal insulation in subcutaneous tissue and protection around organs.
• Steroid hormones - progestogens, androgens, glucocorticoids, mineralocorticoids and oestrogens are derived from cholesterol.
• Formation of eicosanoids - signalling molecules involved in a range of processes such as blood coagulation and inflammation.
• Growth and development - the brain is rich in arachidonic acid (AA) and docosahexaenoic acid (DHA).
• Constituents of nervous tissue structure (sphingomyelin).
• Aid to cell signalling processes.
• Required for the absorption of fat soluble vitamins.

Question 8

Fatty Acids

Answer 8

Fatty acids are hydrocarbon chains with an acid group at one end and a methyl group at the other.

• Short chain fatty acids (up to 5 Cs) and medium chain fatty acids (6-12 Cs) travel directly to the liver where they can be used to create energy or ketones. Medium chain triglycerides (MCTs) can be used as a source of energy before exercise (e.g. 1 tbsp).
• Long chain fatty acids (14-22 Cs) and very long chain fatty acids (> 22 Cs) are used to build cell membranes.

Question 9

Short
Chain Fatty Acids

Answer 9

Short chain fatty acids (SCFAs) have fewer than six carbon atoms.
• SCFAs are produced when dietary fibre is fermented in the colon.
• Acetate, propionate and butyrate are the most common SCFAs.
• Butyrate is particularly important for colon health because it is the primary energy source for colonocytes. It supports the intestinal tight junctions .
• SCFAs are speculated to have a role in the microbiota gut brain axis crosstalk.
• Butyrate is thought to have an anti-inflammatory effect on the colon.

Question 10

Omega System

Answer 10

• The omega system uses the number of carbon atoms, the number of double bonds, and the number of carbons from the omega end to the first carbon in the double bond.
• The omega 6 fatty acid, arachidonic acid , is referred to as 20:4 w6.

20 = no. of carbons

4= no. of double bonds

6= no. of carbons to first double bond

Question 11

Hydrogenation

Answer 11

• Unsaturated fats can be saturated by the addition of hydrogen as in hydrogenation when oils are made into solid spreads.
• Hydrogenation turns the natural fatty acid into unnatural forms (i.e. trans fats ) which are damaging to health

Question 12

Saturated fatty acids:

Answer 12

Contain no C-C double bonds. All the carbons are completely saturated with hydrogen bonds. Solid at room temperature.

Question 13

Unsaturated fatty acids

Answer 13

Contain one or more double bonds between carbons. Liquid at room temperature.

Question 14

Monounsaturated fatty acids

Answer 14

Have one double bond in the chain.

Question 15

Polyunsaturated fatty acids

Answer 15

Have several double bonds.

The more double bonds there are in a fatty acid, the less stable it is, increasing susceptibility to oxidation.

Question 16

Unnatural Trans Fats

Answer 16

Unnatural trans fatty acids are produced by high temperatures and hydrogenation.
• They are found in margarine, processed foods and refined vegetable oils.
• Trans fats stiffen cell membranes, making them prone to oxidation. This also alters their protective action and permeability, impeding normal cell function.
• Trans fats alter blood triglyceride and cholesterol profiles and are linked to an increased risk of cardiovascular disease, insulin resistance and cancer.

Question 17

Cis and Trans Fatty Acids

Answer 17

At each double bond, two possible isomeric forms exist.
– Cis configuration = the H atoms are on the same side of the double bond. The majority of natural fats are cis.
– Trans configuration = the H atoms are on separate sides of the double bond.
• Conjugated linoleic acid (CLA) is a natural trans fat found in grass fed meat and dairy products. Studies
indicate CLA helps increase lean muscle mass and decrease body fat.