LIPIDS

Objectives2. Investigate the properties of carbohydrates, lipids, and proteins

2.3 Describe the relationship between fatty acids and fats by providing examples to illustrate when they are useful to a living system

2.6 Indicate the component parts of a fat molecule.

Lipidso Lipids provide concentrated source of chemical

energy for the body. They help in the absorption of vitamins, are the main component of cell membranes, and serve as insulation for the body

o Certain hormones, including sex hormones are lipids as well

o Fats which we eat are made up of three fatty acids bonded to a glycerol molecule which makes up a triglyceride this triglyceride can either be saturate or unsaturated depending on the structure of their chains.

o The length of the chain determine the level of fat digestion and absorption. It also affects how the fat functions with in the body. Chain length also determines saturation

o In a healthy diet lipids should constitute no more then 30% of the energy intake (calories)

Triglyceride

A triglyceride is a lipid composed of glycerol and three fatty acids that are bonded together.

H – C – O – C – – (Carbon hydrogen chain)

H O

O

H

O

H – C – O – C – – (Carbon hydrogen chain)

H – C – O – C – – (Carbon hydrogen chain)

Saturated FatsoSaturated fats are usually solid at room temperature and are chiefly made from animal by-products

oSaturated fats contain no double bonds in their fatty acid chains between the carbon and hydrogen. The carbon is saturated in hydrogen.

oStudies have shown that people who eat a diet rich in saturated fats are often more unhealthy then those who eat a diet rich in unsaturated fats

Unsaturated Fatso Unsaturated fats are liquid at room temperature, for example oils. They are mainly made from plant material.

oUnsaturated fats have double bond between the carbons and hydrogens in their fatty acid chains. This creates kinks in the chains.

oOne double bond creates a monounsaturated fat where as many double bonds create a polyunsaturated fat.

oThe kinks in the fatty acid chains make the lipids less dense which allows them to stay liquid at room temperature.

oThe more double bonds a lipid has the easier it is to metabolize so polyunsaturated fats are considered healthier then monounsaturated fats

Essential Fatty-AcidsoSome fatty acids are referred to as essential fatty acids because our bodies aren’t capable of synthesising them so they must be obtained through diet. oEx. Omega-3 fatty acid are unsaturated and important in maintaining good health and preventing health issues such as heart disease and arthritis. It is found in oily fish, nuts, seeds and leafy greens

Sterols

oSterols have parts that can dissolve in fat like molecules and parts that can dissolve in water. The most widely known human sterol is cholesterol, which serves as a precursor to steroid sex hormones testosterone and estrogen.and fat-soluble vitamin

oSex hormones control the development of male and female characteristics

oCholesterol is a key component of all animal cell membranes.

oVitamins which are fat-soluble including A, D, E and K are formed by other organisms from sterols and are ingested into your system

Trans and Cis Fatty AcidsoTo emulate the desirable cooking properties of saturated fats using healthier unsaturated fats the food industry began the process of partially hydrogenating unsaturated fats. That is, they added hydrogen atoms to vegetable oils to create a product they thought had the best properties of both fatty acids. A common example is margarine.

oHowever this process was not fool proof. When adding the hydrogen they created an enantiomer (the opposite placement of molecules) to the healthy cis-fats; trans fats.

oThese trans fats are relatively straight, much like saturated fats. The different shape of cis and trans fats affects not only their physical properties but also your health. This may be because your body recognizes the trans fats as saturated fats but your body is not able to metabolize the trans fats. It is recommended that you try to avoid foods that contain trans fats

Phospholipidso Phospholipids are a class of lipids that are a major component of all cell membranes

oPhospholipids are used in our bodies in many ways. They help fats transport through our blood stream, as our blood is composed of water lipids will not dissolve. They help material transport in and out of cells. The exact process will be discussed in Unit 2. They aid in the digestion of dietary fats and are used in the liver to make fats

Why do we need fats?oFats provide energy – fat has twice the energy per gram than carbohydrates or proteins

oMajor fuel source when we are at rest – our cells are getting lots of oxygen while resting so we can break down fat

oFuel physical activity – our body signals change in hormones to release adrenaline and decrease insulin so we can use fat for energy instead of glucose

oStores energy for later use – our body stores extra energy in the form of fat for us to use when resting, exercising, and not eating

oEnables the transport of fat soluable vitamins – we need various vitamins for essential metabolic processes that fats transport to area they need to be

Why do we need fats con’toMaintain cell function – it is a critical part of the cell membrane integrity and regulates what substances go into and out of the cell and what binds the cell

oProtect the body – protect organs and provides insulation

oContributes flavor and texture to food – makes food creamy, moist, tender and crispy

oHelps us fell satiated – makes us feel full after eating

Fat ReplacersoJust as with artificial sweeteners scientists have developed fat replacers which act like fat in food. They can be carbohydrate or protein based.

oOne non caloric fat replacer called Olestra interfered with the absorption of nutrients and gave those who ingested it diarrhea and stomach cramps

oCarbohydrate and protein based fat replacers have been shown to be safe with current research

Fat BlockersoFat blockers are substances that prevent the body from absorbing fat.

oThey bind with the fat or prevent the body from creating the enzymes need to break down the fat

oResearch says they are moderately effective but include many side effects such as abdominal pain and flatulence