5.4 Fats
Fats are an essential class of food and a vital component of a balanced diet in human nutrition. As organic carbon compounds composed of carbon, hydrogen, and oxygen, fats exist in solid and liquid forms and serve as major sources of fatty acids and energy.
Learning Objectives
- State the definition, elemental composition, and states of fats.
- Identify animal and plant sources of fats and oils.
- Compare and contrast saturated fats and unsaturated fats in terms of their similarities and differences.
- Explain the physiological importance of cholesterol in the human body.
- Describe the health effects of excessive fat and cholesterol intake, including gallstones, jaundice, atherosclerosis, hypertension, stroke, and heart attack.
- State preventative steps to avoid health problems caused by excessive cholesterol in the blood.
Comparison of Saturated and Unsaturated Fats & Mechanism of Atherosclerosis
Distinguish the structural and physical properties of saturated versus unsaturated fats and visualise how cholesterol plaques narrow the artery lumen in atherosclerosis.
Short Explanation
Definition
Fat is a type of organic carbon compound containing the elements carbon, hydrogen, and oxygen.
Fats are organic molecules made of carbon, hydrogen, and oxygen that do not dissolve in water. Solid fats typically come from animals and have molecules that already hold the maximum possible number of hydrogen atoms; therefore, no more hydrogen can be added to them, making them "saturated" and giving them higher melting points. Liquid fats (oils) usually come from plants, have lower melting points, and their molecules can still bond with additional hydrogen atoms, classifying them as "unsaturated".
Physical States of Fats
Solid fats exist as solids at room temperature and usually originate from animal sources, such as chicken, cow, goat, fish, butter, meat, and milk. Liquid fats (oils) exist as liquids at room temperature and normally originate from plant sources, such as palm oil, coconut oil, soya bean oil, and groundnut.
Similarities Between Saturated and Unsaturated Fats
Both are organic compounds containing carbon, hydrogen, and oxygen. Both do not dissolve in water. Both are important sources of fatty acids in the body.
Cholesterol in the Human Body
Saturated fats from animal sources, such as cheese, eggs, butter, and meat, contain high levels of cholesterol. Cholesterol is important for building cell membranes, synthesising bile, synthesising sex hormones, and producing vitamin D in skin that is exposed to sunlight.
Health Effects of Excessive Fat and Cholesterol Intake
Eating food containing excess fats, especially saturated fats, raises the cholesterol level in the blood. Excessive cholesterol in the blood can form gallstones that block the bile duct. A blocked bile duct causes jaundice.
Cholesterol accumulates and deposits on the inner artery walls, causing the artery lumen to narrow. This narrowing disrupts or blocks blood flow, leading to a condition called atherosclerosis. Atherosclerosis can cause hypertension, stroke, and fatal heart attack.
Preventive Measures
Reduce the intake of saturated fats in nutrition. Consume unsaturated fats, which can lower cholesterol levels in the blood.
Try to Answer First
Answer in your mind, then press “Check Answer”.
What are fats?
State two differences between saturated fats and unsaturated fats.
Name three health problems caused by excessive fat intake.
Common Mistakes
- Thinking that all fats are solid or that plant oils are not classified as fats. Liquid oils are liquid forms of fats.
- Assuming cholesterol is entirely harmful. Cholesterol has vital biological functions in building cell membranes, synthesising sex hormones, making bile, and producing vitamin D.
- Reversing hydrogen capacity. Saturated fats already possess the maximum number of hydrogen atoms, so addition of hydrogen is not possible.
Concept Misunderstandings
Unsaturated fats raise blood cholesterol just like saturated fats.
Saturated fats elevate blood cholesterol levels, whereas consuming unsaturated fats can lower blood cholesterol levels.
Jaundice is caused directly by heart failure.
Jaundice occurs when gallstones formed from excess cholesterol block the bile duct.
Summary
- Fats are organic carbon compounds composed of carbon, hydrogen, and oxygen that are insoluble in water and provide fatty acids.
- Saturated fats come from animals, are solid at room temperature, have high melting points, contain the maximum number of hydrogen atoms, and cannot accept more hydrogen.
- Unsaturated fats come from plants, are liquid at room temperature (oils), have low melting points, do not have the maximum number of hydrogen atoms, and can accept additional hydrogen atoms.
- Cholesterol is essential for cell membrane structure, bile synthesis, sex hormone synthesis, and vitamin D synthesis under sunlight.
- Excessive saturated fat intake causes high cholesterol, leading to gallstones and jaundice, as well as arterial plaque deposits (atherosclerosis), which can trigger hypertension, stroke, and fatal heart attacks.
Short Activity
A. Objective Quiz
1 Which of the following is a characteristic of unsaturated fats?
2 What condition occurs when excess cholesterol accumulates and narrows the lumen of arteries?
B. Fill in the Blanks
3 Excessive cholesterol in the blood can form gallstones which block the bile duct and cause .
4 Saturated fats originate from and have a high melting point.
C. Drag and Drop: Match Each Fat or Health Property to Its Description
Drag each property or term to its correct description. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.
C. Match Each Fat or Health Property to Its Description
Write the correct property or term next to each description.
| Description | Property / Term |
|---|---|
| 1. Contains maximum number of hydrogen atoms and is solid at room temperature | |
| 2. Originates from plants and addition of hydrogen atoms to molecule is possible | |
| 3. Narrowing of the artery lumen due to cholesterol accumulation that can lead to heart attacks | |
| 4. Synthesises bile and sex hormones, builds cell membranes, and produces vitamin D |
Answer choices: Saturated fat • Unsaturated fat • Atherosclerosis • Cholesterol
