Lipids

Question 1

What is the difference between saturated and unsaturated fats?

Answer 1

• saturated fats are fats that have single bonds between carbon atoms in the fatty acid chains, making them solid at room temperature
• unsaturated fats are fats that have one or more double bonds between carbon atoms in the fatty acid chains, making them liquid at room temperature

Question 2

Where is cholesterol made and obtained?

Answer 2

• cholesterol is made in the liver from saturated fats and also obtained in our diet
• it is found in saturated fats such as eggs, meat and dairy products

Question 3

What is cholesterol? What is it essential for? Why do cells require cholesterol?

Answer 3

• cholesterol is a short lipid molecule
• which is essential for good health
• it is a vital component for cell membranes with roles in their organisation and functioning
• cells require a source of cholesterol for cell membrane functioning, sex hormone structure and the synthesis of bile

Question 4

Is cholesterol soluble in water? How is it transported around the body?

Answer 4

• (like all lipids) cholesterol is not soluble in water
• in order for it to be transported in the blood stream, insoluble cholesterol is combined with proteins to form soluble lipoproteins

Question 5

What are saturated fats?

Answer 5

• saturated fats are long and straight hydrocarbon chains
• there are no carbon to carbon double bonds, no more hydrogen can be added to the chain
• saturated hydrocarbon chains can pack together closely
• the strong intermolecular bonds between triglycerides made up of saturated fatty acids result in fats that are solid at room temperature

Question 6

What are unsaturated fats?

Answer 6

• unsaturated fats have double bonds between two of the carbon atoms in each fatty acid
• polyunsaturated fats have a large number of double bonds
• double bond causes a kink in hydrocarbon chain
• this prevents unsaturated hydrocarbon chain to pack closely together
• increase in distance weakens the intermolecular forces between unsaturated triglycerides resulting in oils that are liquid at room temperature

Question 7

What are monounsaturated fats?

Answer 7

• monounsaturated fats have one double bond between two of the carbon atoms in each fatty acid chain

Question 8

What are polyunsaturated fats?

Answer 8

• polyunsaturated fats have a large number of double bonds
• these double bonds create kinks in the hydrocarbon chain

Question 9

How can unsaturated fats be made more solid at room temperature? What are these known as?

Answer 9

• unsaturated fats can be made more solid at room temperature by adding hydrogen to the double bonds making them saturated
• these hydrogenated fats are called trans-fats and are sometimes produced by the food industry and used in processed foods

Question 10

What are triglycerides? What are the monomers? How are they formed?

Answer 10

• they are non-polar, hydrophobic molecules
• the monomers are glycerol and (3) fatty acids
• triglycerides are formed by esterification

Question 11

What is an ester bond?

Answer 11

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Question 12

What is esterification?

Answer 12

• a reaction that produces an ester
• in the formation of a triglyceride a condensation reaction occurs between the carboxyl group of a fatty acid and the hydroxyl group of a glycerol
• this results in an ester bond forming and water is released

Question 13

What is an essential fatty acid?

Question 14

What are lipoproteins? What are the two types of lipoproteins?

Answer 14

• lipoproteins are molecules composed of lipid and protein
• there are two types of lipoproteins; high density lipoprotein (HDL’s) and low density lipoproteins (LDL’s)

Question 15

What are lipids? What are their R group? What do lipids play an important role in?

Answer 15

• lipids are macromolecules that contain carbon, hydrogen and oxygen atoms
• lipids are non-polar and hydrophobic
• lipids play an important role in energy yield, energy storage, insulation and hormonal communication

Question 16

What are LDL’s? What do they contain? What is their role?

Answer 16

• LDL’s (low density lipoproteins) contain saturated fat, cholesterol and protein
• the role = to move cholesterol from liver into blood stream where it remains until required by cells
• they increase blood cholesterol levels when its too low

Question 17

How do LDL’s work? What do high levels of LDL’s lead to?

Answer 17

• LDL’s bind to receptors on cell surface membranes, enabling them to be taken up by the cells that need them and removing cholesterol from the blood
• high levels of LDL’s can lead to blockage of these membrane receptors, causing blood cholesterol to rise

Question 18

What are HDL’s? What do they contain? What is their role?

Answer 18

• HDL’s (high density lipoproteins) contain unsaturated fats, cholesterol and protein
• these molecules transport cholesterol from body tissues to the liver to be recycled or excreted