BIOB111_CHBIO - Tutorial activity for Session 12 General topic for week 6 Session 12 Lipids Useful Links: 1. Animations on Cholesterol (its synthesis, lifestyle factors, LDL) http://www.wiley.com/college/boyer/0470003790/animations/cholesterol/cholesterol.htm http://courses.washington.edu/conj/bess/cholesterol/liver.html 2. Lipoproteins (define chylomicrons, VLDL, LDL and HDL cholesterol): http://www.wiley.com/college/pratt/0471393878/student/animations/lipoproteins/index.html 3. Lipids: Basic concepts: http://www.ausetute.com.au/lipids.html General tutorial questions: 1. Matching Questions 1. Prostaglandins 2. Lipids 3. Linolenic acid 4. Oils 5. HDL a) Synthesised from arachidonic acid some of them are mediators of inflammation b) Type of lipoprotein that transports cholesterol back to the liver from the cells; composed primarily of protein, good for health. c) Lipids that are liquid at room temp d) Family of compounds that includes triglycerides, phospholipids, and sterols insoluble in water e) An essential fatty acid which cannot be synthesised by humans Last Updated on 6-Feb-14 Page 1 of 9
2. What are the differences between a triacylglycerol and a phospholipid? (Hint: compare the components that make up each structure) 3. Fatty acids that are saturated: a) Have an even number of carbon atoms b) Have single carbon-carbon bonds connecting all carbon atoms c) Have an odd number of carbon atoms d) Have double carbon-carbon bonds connecting some of the carbon atoms 4. A lipid is any substance of biochemical origin that is: a) Insoluble in non-polar solvents but soluble in water b) Insoluble in both water and non-polar solvents c) Insoluble in water but soluble in non-polar solvents d) Soluble in both water and non-polar solvents 5. Which of the following fatty acids is both monounsaturated and an omega-6 fatty acid? a) CH3 (CH2)18 COOH b) CH3 (CH2)7 CH=CH (CH2)7 COOH c) CH3 (CH2)4 CH=CH (CH2)2 (CH2)6 COOH d) CH3 CH2 (CH=CH CH2)4 (CH2)2 COOH 6. The products of the hydrolysis of a triacylglycerol (TAG) are three fatty acids and one: a) Long chain alcohol b) Glycerol c) Phosphoric acid d) Amino alcohol 7. The most abundant steroid in the human body is: a) Progesterone b) Testosterone c) Estradoil Last Updated on 6-Feb-14 Page 2 of 9
d) Cholesterol 8. Which of the following is a distinguishing characteristic between fats and oils? a) Their physical state at room temperature b) The presence or absence of the alcohol functional in their structures c) The type of linkage between fatty acids and the alcohol present d) The presence or absence of the ether functional group in their structures Conceptual multiple choice questions: 9. Concept: Saturated fatty acids Context: Commonly consumed fats and oils contain the dietary lipid triacylglycerol (TAG). Each TAG unit contains one glycerol which is connected to three individual fatty acids via ester linkages. The fatty acids themselves are composed of a long chain of carbons and hydrogen, as well as a carboxylic acid group at one end. Question: Which of the following accurately describes saturated fatty acids? a) Single carbon-carbon bonds are present in saturated fatty acids, thus the fatty acids contain less than the maximum number of hydrogen atoms attached to the carbon atoms b) One or more double carbon-carbon bonds are present in saturated fatty acids, thus the fatty acids contain less than the maximum number of hydrogen atoms attached to the carbon atoms c) Single carbon-carbon bonds are present in saturated fatty acids, thus the fatty acids contain the maximum number of hydrogen atoms attached to the carbon atoms d) One or more double carbon-carbon bonds are present in saturated fatty acids, thus the fatty acids contain the maximum number of hydrogen atoms attached to the carbon atoms 10. Concept: Unsaturated fatty acids Context: Commonly consumed fats and oils contain the dietary lipid triacylglycerol (TAG). Each TAG unit contains one glycerol which is connected to three individual fatty acids via ester linkages. The fatty acids themselves are composed of a long chain of carbons and hydrogen, as well as a carboxylic acid group at one end. Last Updated on 6-Feb-14 Page 3 of 9
Question: Which of the following accurately describes unsaturated fatty acids? a) Single carbon-carbon bonds are present in unsaturated fatty acids, thus the fatty acids contain less than the maximum number of hydrogen atoms attached to the carbon atoms b) One or more double carbon-carbon bonds are present in unsaturated fatty acids, thus the fatty acids contain less than the maximum number of hydrogen atoms attached to the carbon atoms c) Single carbon-carbon bonds are present in unsaturated fatty acids, thus the fatty acids contain the maximum number of hydrogen atoms attached to the carbon atoms d) One or more double carbon-carbon bonds are present in unsaturated fatty acids, thus the fatty acids contain the maximum number of hydrogen atoms attached to the carbon atoms 11. Concept: Melting points of fats and oils Context: Each TAG contains three fatty acids which can either be saturated forming straight chains or unsaturated fatty acids which are bent. The shape of the fatty acids determine how well individual TAG s can stack on top of each other, which impacts on the melting point of the TAG. Question: Which of the following best describes the melting points of fats & oils? a) The bent fatty acids in fats stack on top of each other easily, forming liquid oils with higher melting points than fats b) The straight chain fatty acids in fats stack on top of each other with difficulty, forming solid fats with higher melting points than oils c) The straight chain fatty acids in fats stack on top of each other easily, forming solid fats with higher melting points than oils d) The bent fatty acids in fats stack on top of each other with difficulty, forming liquid oils with higher melting points than fats 12. Concept: Micelles Context: Through reacting with a strong base such as NaOH, a fatty acid is converted into a fatty acid salt. When many fatty acid salts come together they orient to form micelles (soap) that have distinct, polar and non-polar regions. The fatty acid salt has one region Last Updated on 6-Feb-14 Page 4 of 9
that is polar, the head composed of the carboxyl group and Na +, and also a region that is non-polar, made up of a long chain of carbons and hydrogens. Question: Which of the following best describes the action of a micelle when removing an oil stain from a cloth? a) The inner non-polar region of each micelle, made up of many non-polar tails, binds and removes a small amount of the oil stain from the cloth b) The outer polar region of each micelle, made up of many polar heads, binds and removes a small amount of the oil stain from the cloth c) The inner non-polar region and the outer polar region of each micelle, binds and removes a small amount of the oil stain from the cloth d) Neither the inner non-polar region nor the outer polar region of the micelle binds to the oil stain, but the oil stain is removed regardless in the presence of the micelles 13. Concept: Conversion between poly/monounsaturated and saturated fatty acids Context: Hydrogenation and dehydrogenation reactions result in the hydrocarbon compound gaining and losing two hydrogen atoms, respectively. Question: Which of the following accurately explains how a monounsaturated fatty acid is converted into a saturated fatty acid? a) A double carbon-carbon bond is added to the compound via a dehydrogenation reaction, where two hydrogen atoms are removed and replaced by a double carbon-carbon bond b) The double carbon-carbon bond is removed from the compound via a dehydrogenation reaction, where two hydrogen atoms are removed allowing the removal of the double carbon-carbon bond c) The double carbon-carbon bond is removed from the compound via a hydrogenation reaction, where two hydrogen atoms replace the double carbon-carbon bond Last Updated on 6-Feb-14 Page 5 of 9
d) A double carbon-carbon bond is added to the compound via a hydrogenation reaction, where two hydrogen atoms are added allowing a double carbon-carbon bond to form 14. Concept: Conversion between poly/monounsaturated and saturated fatty acids Context: Hydrogenation and dehydrogenation reactions result in the hydrocarbon compound gaining and losing two hydrogen atoms, respectively. Question: Which of the following accurately explains how a saturated fatty acid is converted into a monounsaturated fatty acid? a) The double carbon-carbon bond is removed from the compound via a dehydrogenation reaction, where two hydrogen atoms are removed allowing the removal of the double carbon-carbon bond b) A double carbon-carbon bond is added to the compound via a dehydrogenation reaction, where two hydrogen atoms are removed and replaced by a double carbon-carbon bond c) The double carbon-carbon bond is removed from the compound via a hydrogenation reaction, where two hydrogen atoms replace the double carbon-carbon bond d) A double carbon-carbon bond is added to the compound via a hydrogenation reaction, where two hydrogen atoms are added allowing a double carbon-carbon bond to form 15. Concept: Conversion between poly/monounsaturated and saturated fatty acids Context: Hydrogenation and dehydrogenation reactions result in the hydrocarbon compound gaining and losing two hydrogen atoms, respectively. Question: Which of the following accurately explains how a monounsaturated fatty acid is converted into a polyunsaturated fatty acid? a) The double carbon-carbon bond is removed from the compound via a dehydrogenation reaction, where two hydrogen atoms are removed allowing the removal of the double carbon-carbon bond b) The double carbon-carbon bond is removed from the compound via a hydrogenation reaction, where two hydrogen atoms replace the double carbon-carbon bond Last Updated on 6-Feb-14 Page 6 of 9
c) A double carbon-carbon bond is added to the compound via a dehydrogenation reaction, where two hydrogen atoms are removed and replaced by a double carbon-carbon bond d) A double carbon-carbon bond is added to the compound via a hydrogenation reaction, where two hydrogen atoms are added allowing a double carbon-carbon bond to form 16. Concept: HDL and LDL cholesterol Context: Cholesterol is a lipid (non-polar) that requires lipoproteins to carry it around the body (polar). LDL carries cholesterol from the liver to other parts of the body, whereas HDL cholesterol carries cholesterol from other parts of the body back to the liver. Everyday our liver synthesises a significant amount of cholesterol from fatty acids. Cholesterol is an important component of cell membranes, it is required to generate bile and it is the precursor for creating steroid hormones. Question: Which of HDL and LDL are considered good and bad cholesterol and why? a) LDL is considered to be the bad cholesterol as it can damage the valves of the heart, whereas HDL is considered to be good cholesterol as it assists in restoring the health of the arteries b) HDL is considered to be the bad cholesterol as it can lead to the formation of plaques that contribute to cardiovascular disease, whereas LDL is considered to be good cholesterol as it takes cholesterol back to the liver c) HDL is considered to be the bad cholesterol as it can damage the valves of the heart, whereas LDL is considered to be good cholesterol as it assists in restoring the health of the arteries d) LDL is considered to be the bad cholesterol as it can lead to the formation of plaques that contribute to cardiovascular disease, whereas HDL is considered to be good cholesterol as it takes cholesterol back to the liver 17. Concept: Phospholipid bilayer Context: Many phospholipids come together to form a phospholipid bilayer, also known as the cell membrane. Each phospholipid is composed of two fatty acids (non-polar tail) that connect to a glycerol, with glycerol also attached to a phosphate that is connected to an alcohol (polar head). Last Updated on 6-Feb-14 Page 7 of 9
Question: How are the non-polar tails of the phospholipids arranged within the phospholipid bilayer (cell membrane)? a) The non-polar tails of a phospholipid directly contact the polar heads within other phospholipids b) The non-polar tails of a phospholipid directly contact the polar heads and non-polar tails within other phospholipids c) The non-polar tails of a phospholipid do not directly contact the polar heads or the non-polar tails within other phospholipids d) The non-polar tails of a phospholipid directly contact the non-polar tails within other phospholipids 18. Concept: Phospholipid bilayer (plasma membrane) Context: Many phospholipids come together to form a phospholipid bilayer, also known as the cell membrane. Each phospholipid is composed of two fatty acids (non-polar tail) that connect to a glycerol, with glycerol also attached to a phosphate that is connected to an alcohol (polar head). Question: How are the polar heads of the phospholipids arranged within the phospholipid bilayer (cell membrane)? a) The polar head of a phospholipid directly contacts the polar heads of other phospholipids in the same layer of the lipid bilayer Last Updated on 6-Feb-14 Page 8 of 9
b) The polar head of a phospholipid directly contacts the non-polar tails of other phospholipids in the same layer of the lipid bilayer c) The polar head of a phospholipid directly contacts the non-polar tails and polar heads of other phospholipids in the same layer of the lipid bilayer d) The polar head of a phospholipid does not directly contact the non-polar tails or the polar heads of other phospholipids in the same layer of the lipid bilayer 19. Concept: Properties of the phospholipid bilayer (plasma membrane) Context: Each cell contains a plasma membrane (aka the phospholipid bilayer) that acts as a barrier between what is inside and what is outside the cell. H 2O (water) is the main component of the solutions that are both inside and outside the cell. Question: Which part(s) of the lipid bilayer are responsible for stabilising the membrane in the H 2O rich environment? a) The polar heads (within the phospholipids) in both layers of the bilayer come into contact with H 2O b) Neither of the layers of polar heads within the bilayer come into contact with H 2O c) Only the polar heads (within the phospholipids) closest to the inside of the cell come into contact with H 2O d) Only the polar heads (within the phospholipids) closest to the outside of the cell come into contact with H 2O Last Updated on 6-Feb-14 Page 9 of 9