Lipids: Structure, Function & Types

Fundamentals of Science - Level 6 Certificate in Food Science and Technology

• Session 2 covers nucleic acid structure, lipids and glucose, carbohydrates, and homeostasis.
• Learning objectives include nucleic acid structure and function definition, lipids and carbohydrates descriptions, and impact of proteins, carbohydrates and lipids as part of nutrition

Module Contents

• Biology includes Cell Structure and Function, Proteins and Analysis, Nucleic Acids, Lipids, Carbohydrates, Nutrition, Enzymes, Quantitative Analysis, Spectro & Lambda Max, and Weights, Measures, and Preparation.
• Chemistry includes Periodic Table, Chemical Bonds, Acids and Bases, and Elemental Analysis.

Function of Lipids

• Fats are biomolecules
• Involved in Cholesterol and Fats and Obesity
• Consists of Fatty Acids with subdivisions Saturated vs unsaturated fatty acids, hydrogenation, cis and trans fats.
• Also includes Triglycerides – structure and the diet and Fats and the cells - Phospholipids.
• Lipids are a diverse group of molecules.
• Fatty acids are precursors for more complex lipids
• Triglycerides act as a storage form of fat energy
• Phospholipids are found in cell membranes to create a barrier for the cell and control the flow of material
• Sterols consist of cholesterol and steroids
• Fat soluble vitamins are A, D, E, and K.

Basic Units of Lipids

• Fatty acids have a carboxyl group and a hydrocarbon chain
• Chain can vary, leading to different types of fatty acids, they consist of a long chain of carbon atoms linked together by covalent bonds (sharing)
• Fatty Acids: The number of carbon atoms will always be even
• Contains carbon atoms most commonly C16 and C18
• Is uncommon to contain less than 14 and more than 20
• Saturated fats contain No Carbon double bonds
• Unsaturated fats have 1 or more Carbon double bonds.
• Monounsaturated will contain a 1 Carbon double bond
• Polyunsaturated will contain >2 Carbon double bond

Saturated vs Unsaturated

• Saturated fatty acids are animal products
• Saturated fats storage is solid at room temperature
• Unsaturated fatty acids are from plant products
• Unsaturated fats storage is liquid at room temperature
• Atherosclerosis is the clogging of arteries due to saturated fatty acids
• Due to the double bonds of polyunsaturated fats, they do not pack well due to their irregular shape

Unsaturated fats: Cis and Trans Fats

• Cis fats are the typical form of unsaturated fats
• Contains C=C double bonds
• These bonds can come in two forms, namely cis and trans

Hydrogenation of Fats

• Unsaturated fats that are altered by reaction with hydrogen (in presence of a catalyst)
• Result is that it breaks all the double bonds and is now fully saturated
• Vegetable oils used to produce saturated fats (solid)
• Process is completed in industry due to more desirable physical properties
• Melts at a desirable temperature (30–40 °C)
• Involves long storage time
• This is opposite to polyunsaturated oils (rancid when reacted with O2 in air)
• Trans fats are considered bad
• Cis fats are considered good - unsaturated
• Trans fats are unhealthy because the enzymes responsible for metabolising them are expecting 'cis fats' which disrupts the metabolic chain
• Trans fats occur as products created during hydrogenation as contaminants, created by an unwanted side reaction
• Trans fats are a by product of partial hydrogenation
• Partial hydrogenation increases the risk of coronary heart disease
• Trans fats sources include common commercial baked foods, microwave popcorn, and fried foods
• Trans fats have been mitigated by banning by the FDA (US)

Triglycerides

• Formed when a glycerol molecule reacts with three fatty acid molecules
• Main function is in energy storage, either fat or oil form
• A neutral Fat Molecule is nonpolar and uncharged
• Has hydrophobic properties that dislike water
• Insoluble, but soluble, in organic solvent
• Glycerol is an alcohol that contains 3 carbons that are all attached to OH (hydroxyl group).
• Together, a reaction between COOH (fatty acid) and OH from the glycerol
• The reaction results in the removal of a water molecule
• This removal process forms an ester bond
• In the body, glycerol reacts with three fatty acids through ester linkages to form triglycerides.
• Triglycerides are naturally found in food
• In the body, saturated fats can be found in animal products in solid form
• Unsaturated fats can be found in plants as liquid form

Function of triglycerides

• Provides cellular energy for the body
• Stored inside fat droplets in the adipose tissues as fuel storage for use during starvation
• Fatty tissue provides protection from trauma to organs and provides insulation to maintain body temperature.

Fats in the diet

• A small amount of fat is good for you
• Too much saturated fat can increase your risk of developing circulatory diseases
• Replacing the saturated fat with unsaturated fact helps keep your heart healthy and manage your weight
• 1g fat = 9kcal

Digestion of fats

• Most fat digestion takes place in the small intestine via pancreatic enzymes and bile salts
• Pancreatic lipase acts as the main enzyme in triglyceride hydrolysis
• Hydrolysis results in breaking triglyceride into monoglycerols and free fatty acids
• Fats are then absorbed by enterocytes

Role of fats in the Cell

• Phospholipids are another lipids with a hydrophilic head containing a phosphate group and a hydrophobic tail from fatty acids
• Phospholipids are lipids with a lipid bilayer membrane
• This basic cellular structure acts as a barrier to protect the cell.

Cholesterol

• A lipid made by the body
• Can be found in every body cell
• Cholesterol forms a key component of the plasma membrane which helps stabilize membrane structure against temperature effects
• The body needs cholesterol for hormones, it acts as a precursor to steroid hormones with the like of testosterone, estrogen, progesterone and cortisol
• Provitamin D is a derivative of cholesterol, it is converted to vitamin D in the skin by UV light

Atherosclerosis

• A disease in which plaque builds up inside your arteries
• Arteries are blood vessels that carry oxygen-rich blood to your heart and other parts of your body
• Plaque is made up of fat, cholesterol, calcium and other substances found in the blood
• Over time, plaque hardens and narrows your arteries
• Limits the flow of oxygen rich blood to your organs and other parts of your body
• Arthrosclerosis can lead to serious problems, including heart attack, stroke or even death

Links between fat and obesity

• Obesity occurs when extra calories are stored in the body as fat
• Fat cells, or adipocytes, expand in number and size filing with trigyclercides
• Obesity is associated with visceral fat, often called 'belly fat'
• The recommended daily allowance for men 30g of saturated fat per day and for women 20g of saturated fat per day

Location of fatty tissue

• Location of fatty tissue determines its metabolic profile
• Visceral fat is located underneath the abdominal wall and around the heart, lungs, kidneys, and below the abdominal muscle
• Recently discovered to be a significant producer of signaling chemicals (hormone)
• Involves other hormones that are involved in inflammatory responses, linked to obesity and Type 2 diabetes
• Sub-cutaneous fat is located beneath the skin but not around the vital organs, keeps us warm and provides padding so protects from injury

Summary of Lipids

• Different types of fats include Saturated, monounsaturated and polyunsaturated.
• Includes Saturated and unsaturated sources.
• Role of trans fats with benefits of a low fat diet/ fat in the diet
• Know Recommended daily allowance

Revision Questions:

• What are the two types of unsaturated fats?
• What is the process of hydrogenation and what is its application in industry?
• What are trans fats?
• What are the functions of fats?
• What is the structure of a triglycerides?
• How are lipids digested?
• What is atherosclerosis?
• What is the difference between visceral and subcutaneous fats?
• What is the role of fat in obesity and how can it be monitored to prevent?

Explore lipid structure, function, and types, including fatty acids (saturated, unsaturated, cis, and trans), triglycerides, and phospholipids. Learn about the role of lipids in the diet, cells, and their impact on health, including cholesterol and obesity.