BS 120: Lipids Flashcards
What are lipids?
Lipids are:
- heterogenous class of naturally-occurring compounts
- relatively insoluble in water
- freely soluble in nonpolar organic solvents like: ether, chloroform, & benzene
Some lipids are…
amphipathic as they possess both hydrophilic & hydrophobic regions iwthin the same molecule.
How is the amphipathic characteristic of some lipids relevant?
It allows them to form essential structures like cell membranes.
- this characteristic is crucial for maintaining their cellular functions
What makes lipids unique?
Unlike polysaccharides, proteins, & nucleic acids, lipids are NOT POLYMERS.
What are other unique properties of lipids?
- no distinguishible functional group or structural feature.
- lipids at room temperature are liquid, called oil
- lipids are called fats when solid
What is the chemcical composition of lipids?
most but not all lipids are compounds formed by an alcohol and fatty acid(s) covalently bonded in an ester linkage
What are examples of lipids?
- fats
- oils
- waxes
- and more
What are the physiological functions of lipids and which lipids perform each function?
- they are structural components of biomembranes, regulating the membrane permeability [phospholipids & cholestrol]
- function as cell-signalling molecules and metabollic regulators [steroid hormones & prostaglandins]
- act as surfactants, detergents, & emulsifying agents [amphipathic lipids like bile salts]
- help in absorption of fat-soluble vitamins (A, D, E, & K absorption)
- precursor of vitamin D and many steroid hormones
- lipoproteins act as transporting lipids
What are the visceral functions of lipids and which lipids perform each function?
- they act as energy-storing molecules [9Kcal/g in triglycerides]
- act as electric insulators in neurons [myelin sheath]
- a subcutaneous thermal insulator against loss of body heat [subcutaneous fat]
- protect internal organs by providing a cushioning effect [pads of fat]
- supply the essential fatty acids that cannot be synthesized in the body [consumed lipids]
What are the 2 main classes of lipids?
- Saponifiable lipids
- Non-saponifiable lipids
What is the difference between saponifiable and non-saponifiable lipids?
Saponifiable lipids can undergo hydrolysis when in the presence of bases, acids, or enzymes. This is due to the 1 or more commonly many ester bonds that are formed due to the fact that these lipids are a combination of alcohol and fatty acids.
Non-saponifiable lipids cannot be disintegrated into smaller molecules through hydrolysis.
What are examples of saponifiable lipids?
They can either be:
1. Simple lipids
2. Complex lipids
examples of simples lipids (lipids that only contain a fatty acid & alcohol) include: triglycerides & waxes
examples of complex lipids (lipids that contain other components as well) include: phospholipids & sphingolipids
so together: triglycerides, waxes, phospholipids, & sphingolipids are all saponifiable lipids; lipids that can undergo hydrolysis
What are examples of non-saponifiable lipids?
non-saponifiable lipids, aka non-esters (since they lack ester bonds) include:
- free cholestrol
- steroids
- bile acids
- prostaglandins
What are the 2 types of lipids?
- simple
- complex
What are simple lipids?
esters of fatty acids with various alcohols
What are the 2 types of simple lipids?
with definition
- triacyl-glycerides (triglycerides): esters of fatty acids with glycerol. ex. oils/fats
- waxes: esters of fatty acids with monohydric alcohols with a high molecular weight .
What sets wax apart from triclyceride simple lipids?
Waxes are made from monohydric alcohols with high molecular weight, which means they only have one ester bond as the alcohol only contains one hydroxyl group. This is different because the glycerol alcohol in triglycerides contains 3 hydroxyl groups, allowing for 3 ester bonds with 3 chains of fatty acids for every glycerol molecule.
What are complex lipids?
esters of fatty acids containing functional groups additional to the alcohol and fatty acid.
What are the 2 types of complex lipids?
- Phospholipids
- Glycolipids (glycosphingolipids)
What are phospholipids?
Lipids containing a phorphoric acid residue.
- frequently have nitrogen-containing bases & other substituents.
What are examples of phospholipids?
- Glycerophospholipids, where the alcohol is glycerol
- Sphingolipids, where the alcohol is sphingosine
What is sphingosine?
Scientific name: 2-amino-4-trans-octadecene-1,3-diol
an 18-carbon amino alcohol with an unsaturated hydrocarbon chain.
What does sphingosine do?
It is a primary part of sphingolipids
- sphingolipids are a class of cell membrane lipids that includes sphingomyelin, an important phospholipid.
What are glycolipids?
aka glycosphingolipids, these are lipids that contain fatty acids, sphingosine, & carbohydrate.
What are examples of glycolipids?
- there are other complex lipids: such as sulfolipids & aminolipids
- lipoproteins may also be considered glycolipids
Define simple lipids:
esters of fatty acids with alcohols, and can be sub-divided into triacyl-glyceride & waxes.
Characteristics of triacylglycerol
- neutral fat
- most abundant lipid in the body
- an ester composed of 1 glycerol and 3 fatty acids
- solid at room temperature are known as fats
- some are liquids at room temperature and are known as oils
- storage form of lipids
- source of energy
What are neutral fats or oils?
- lipids are a broad group of biomolecules that include fats, oils, waxes, phospholipids, and steroids
- fats are a type of lipids that are also called triglycerides. They are composed of glycerol and three fatty acid molecules
What do the physical properties of triglycerides depend on?
It depends on the fatty acid components
What happens to the melting point of fatty acids?
It increases as the number of carbons in it hydrocarbon chains increases and as the number of double bonds decreases.
What are the properties of oils?
they triglycerides rich in unsaturated fatty acids
- generally liquid at room.
unsaturated = liquid
What are the properties of fats?
they triglycerides rich in saturated fatty acids
- generally semisolids/solids at room temp
saturated = fat
What are examples of triglycerides?
- olive oil
- butter
What is olive oil?
- it is composed of oleic acid, a mono-unsaturated fatty acid.
- liquid at room temp.
- has a melting point of about 13*C
Why is olive oil considered a healthy oil?
Because it may lower the risk of cardiovascular disease & inflammation
What is butter?
- mainly composed of palmitic acid and stearic acid, both saturated fatty acids.
- it is solid at room temperature
- melting point of about 35*C
