Purpose: Students will compare and contrast and investigate the effects of different types of cholesterol from cholesterol-rich foods on the digestive and cardiovascular systems.

·         Describe the molecular structure of cholesterol

·         Describe cholesterol’s function in the human body

·         Describe the production of cholesterol in the human body

·         Understand cholesterol’s inability to dissolve in blood and its need for substances called lipoproteins to carry it through the blood

·         Describe cholesterol’s breakdown in the digestive tract and its subsequent structure and pathway.

·         Compare and contrast the different types of lipoproteins that transport cholesterol through the blood.

·         Describe what is meant by the terms, “good cholesterol” and “bad cholesterol” and to dissolve the myth, that “Cholesterol is bad for you.”

·         Compare and contrast the different types of fats found in different foods based on their labels.

·         Experimentally test foods for fat content

·         Assess societal influences (media, etc.) on the intake of cholesterol-rich foods by teenagers and adolescents.

Motivation:

Distribute a survey to students asking them to assess their favorite foods from 1-10 (with “1” being their most favorite meal). The survey will encompass a variety of meals and snacks: e.g. A #4 supersized meal at Wendy’s, tuna salad sandwich, bacon & eggs, nuts, berries, potato chips, etc.)

Responses to the “Motivation” will be discussed, with the follow-up question being asked, “Which of these foods is most healthy for you? This will further lead into a discussion of healthy foods and many foods that are healthy and unhealthy contain cholesterol.

Students will then watch a short video and view several pictures on childhood obesity and the presence of cholesterol-rich foods that promote unhealthy dietary practices at: www.authorstream.com/nutrition facts-fast food. Pictures that they will be viewing include

Ask students to write down five thoughts or questions that they have concerning these foods and its effects on the body after viewing the video and pictures. From discussion, they will come to understand that most of these foods that lead to being overweight or obese are cholesterol-rich. Hence, what is cholesterol, that it should cause such damaging effects in the body?

Cholesterol is a waxy, fat-like substance that is needed by the body in small amounts and is already made by the body’s liver but is also found in many foods. We will then consider the molecular ring-like structure of cholesterol and its uses in the body.

•  Cholesterol is a waxy fatty substance that is naturally synthesized by the liver

• It is a member of the steroid family of organic compounds and has a joined ring structure typical of family members

• Except for the polar hydroxyl group that gives cholesterol a hydrophilic quality, cholesterol’s fused ring structure and mostly hydrophobic nature makes it unable to dissolve in water.  Cholesterol is derived from our diet and from its own production in the liver. Needed in the body in small amounts, it is used for maintenance of cell membrane structure and function

• Making bile acids that break down ingested fats

• Production of various steroid hormones

• Synthesis of Vitamin D

After instruction on cholesterol’s molecular structure is provided, divide students into groups of four, with each group being given a chemistry molecular model set to build a cholesterol molecule. Review of which atoms are bonded together and design of its ring structure will be analyzed.

Their responses concerning cholesterol’s structure will allow us to examine its hydrophobic property of being practically insoluble in water. Do oil and water mix? We will also consider the fact that our blood is water-based, being about 40% water. Therefore, cholesterol needs substances to help it to be transported through the blood, substances known as lipoproteins.

Students will view pictures of lipoprotein molecules, its integral parts and then attempt to sketch its structure.

Students will then be instructed on the production of cholesterol in the body. We will briefly discuss that about 20-25% of cholesterol production in the body comes from the liver, with other areas to include the reproductive organs, the intestines and the adrenal glands. The making of cholesterol in the body is related to the amount already present and its current need in the body. There are proteins that sense how much cholesterol is in the body already and can turn off its production whenever necessary.

How are cholesterol-rich foods digested after a meal? To assist in answering this question, have students construct a K-W-L chart and view an animation. Vocabulary words that will be prediscussed and predefined include: chylomicron, atherosclerosis, plaque, lipoprotein, adipose tissue, VLDL, LDL, HDL.

 They will then view the animation: Interactive Concepts in Biochemistry- Interactive Animations: Cholesterol @ http://www.wiley.com/legacy/college/boyer/0470003790/animations/cholesterol/cholesterol.htm

In their K-W-L chart, they will be asked to create a flowchart- showing the path of the cholesterol molecule from being swallowed to being transported in the bloodstream by lipoproteins. Overhead projector and transparencies will be used to review the progress of the cholesterol molecule through different stages of the body.

As well, this animation will also enable then to describe what is meant by the terms, VLDL, LDL, HDL, the differences between them, and the positive and negative characteristics of each.

Further instruction will be provided on the differences among VLDL, LDL and HDL particles in terms of their molecular weight and their density. Low density lipoproteins (LDL) known as “bad cholesterol” are those that transport cholesterol to the walls of arteries to cause the plaques that eventually lead to atherosclerosis and heart disease. HDL is known as “good cholesterol” because it transports cholesterol back to the liver for breakdown instead of going to the walls of arteries that cause heart disease. Students will view the short video, “How cholesterol clogs your arteries-atherosclerosis” @ www.youtube.com/watch?v=fLonH7ZesKs

Have students in groups of four, complete the webquest activity: Hoops for Heart Webquest, @ www.scribd.com. Each group will work on a particular section of the webquest activity and present their finding to the rest of the class while other groups evaluate their findings. Each group will be given a sheet to describe what they have learned from their fellow classmates. I will also provide an assessment to evaluate the completion of each group’s webquest activity as well as each group’s learning from fellow groups in the activity.

Using internet resources, each student in a group of four will be asked to define the words: saturated, unsaturated, monounsaturated, polyunsaturated fats. After review and discussion of these four terms, all students assigned each of these words will be grouped together to complete a collage/poster of the word’s meaning, pictures of foods that contain that specific type of fat, nutrition labels with that type of fat, and assess its “healthiness” or lack thereof. Each collage/poster (saturated, unsaturated, monounsaturated, and polyunsaturated) will be presented and displayed in the classroom.

 Laboratory Activity: Testing different foods for the presence of Lipids (fats)

Materials: test tubes, test tube racks, markers, samples of different foods, oil, Sudan red, water, brown paper bags, cotton swab.

·         Testing for the presence of lipids: Sudan red test

         ·         Demonstrate how to perform this test and refer to student hand-out. Add 2ml of any oil and 2ml of water to a test tube. Then add 2-5 drops of Sudan red to the mix. Shake. Then repeat with a test tube containing only water. Students will see that Sudan red with stain the fat molecules.

• Allow students to test different samples for the presence of lipids. Interesting is to test milk with different fat content. The more fat it contains, the more particles the Sudan red will stain.

• Be careful. Sudan red can stain clothes.

·         Testing for the presence of lipids: Grease spot test

• Have students follow the simple directions on their hand-out. Students draw four squares onto their brown paper bag, then use a cotton swab to put samples of three lipids of their choice and water as a control into the squares. Wipe off excess oil/fat and let sit for few minutes to dry. Once dry, the fats will left a translucent spot behind. This can best be seen when you hold the paper up to a light source.

• Put some sesame or sunflower seeds between two pieces of brown paper and press hard. The seeds are loaded with oil and will leave behind grease spots.

Students will be given a food evaluation sheet to assess the fat content of each of their different samples of foods. More red staining by Sudan and larger grease spots deposited on the brown paper bags means that the food in question contains more fat particles.

 After lab activity is reviewed and discussed, students will culminate the cholesterol unit engaging in a lesson devoted to society’s/ media’s view of these high cholesterol foods- such as those described by picture #3 presented earlier in the unit (Homer Simpson eating a large burger.) How do television, newspapers, internet, portray fast food? Do most people know that there are good and bad forms of cholesterol? Students will read the article, “Myths and Truths about Cholesterol” @ http://www.westonaprice.org/modern-diseases/cardiovascular-disease/1687-myths-a-truths-about-cholesterol.html

What medications, foods are currently advertised on television/newspaper that claim to reduce cholesterol? Students will consult a weekly newspaper and bring in clippings of products that claim to lower cholesterol. They will also describe television commercials advertising products that also make this claim.

National Science Standards: 

As a result of their activities in grades 5-8, all students should develop understanding of

Structure & function in living systems

As a result of activities in grades 5-8, all students should develop understanding of

·         Personal health

·         Populations, resources, and environments

·         Natural hazards

·         Risks and benefits

·         Science and technology in society

As a result of activities in grades 5-8, all students should develop

·         Abilities necessary to do scientific inquiry