10.2 Free Radicals
Free radicals are frequently mentioned in health talks, advertisements, and magazines. In the human body, oxidation naturally produces free radicals, but excessive amounts caused by internal and external factors can damage cells and lead to serious health problems.
Learning Objectives
- Define free radicals.
- Explain how free radicals are formed through oxidation.
- Identify internal and external factors that produce free radicals in the human body.
- Describe the effects of free radicals on human health and body structures.
Internal and External Sources of Free Radicals and Their Effects on DNA
Free radicals originate from internal processes and external exposures, leading to electron removal and DNA damage.
Short Explanation
Definition of Free Radicals
Free radicals are atoms or molecules that lack one electron. The lack of an electron makes these atoms or molecules unstable, highly reactive, and tend to attack other atoms or molecules.
Formation of Free Radicals
Oxidation is a chemical reaction that occurs when a substance loses electrons in its reaction. The oxidation process occurs naturally inside the body to produce free radicals. This situation triggers a chain reaction that produces more free radicals.
Factors Producing Free Radicals in the Human Body
Internal Factors
Metabolism — occurring in mitochondria.
Inflammation — involving white blood cells.
External Factors
Cigarette smoke, exposure to radiation such as ionising radiation, sunlight with ultraviolet rays, air pollution, and toxic waste.
The Effects of Free Radicals on Human Health
| Effect | Description |
|---|---|
| Damage to DNA | Free radicals damage our DNA structure by removing electrons from molecules that build DNA. This forms carcinogenic substances that may cause mutations and cancer. |
| Diseases | Cause diseases such as cardiovascular disease and infertility. |
| Organ damage | Damage vital organs including the kidneys, liver, and lungs. |
| Premature aging | Cause premature aging conditions such as wrinkles and grey hair. |
Try to Answer First
Answer in your mind, then press “Check Answer”.
What is the definition of a free radical?
Name two internal factors that produce free radicals inside the human body.
How do free radicals cause DNA damage and lead to cancer?
Common Mistakes
- Thinking free radicals have an extra electron instead of lacking an electron.
- Assuming free radicals come exclusively from external pollutants, neglecting natural internal processes like metabolism and inflammation.
- Confusing oxidation with reduction; oxidation involves the loss of electrons, not the gain of electrons.
- Assuming free radicals only cause skin wrinkles, ignoring serious internal impacts like cardiovascular disease, DNA mutations, and organ damage.
Concept Misunderstandings
Free radicals are foreign chemicals that only enter the body from the outside environment.
Free radicals are also produced naturally inside the body as by-products of internal cellular processes such as metabolism in mitochondria and inflammation involving white blood cells.
Free radicals directly add harmful substances into the DNA structure.
Free radicals cause damage by stripping electrons away from the molecules that construct DNA, altering the structure and forming carcinogenic substances.
Summary
- Free radicals are unstable, reactive atoms or molecules that lack one electron.
- Oxidation is a chemical reaction where a substance loses electrons, naturally producing free radicals in a chain reaction.
- Internal factors producing free radicals: metabolism and inflammation.
- External factors producing free radicals: cigarette smoke, ionising radiation, ultraviolet rays, air pollution, and toxic waste.
- Negative health impacts: DNA damage (mutations and cancer), cardiovascular disease, infertility, damage to kidneys, liver, and lungs, as well as premature aging (wrinkles and grey hair).
Short Activity
A. Objective Quiz
1 Which of the following is an internal factor that produces free radicals in the body?
2 What makes a free radical chemically unstable and reactive?
B. Fill in the Blanks
3 Oxidation is a chemical reaction that occurs when a substance loses in its reaction.
4 Free radicals damage DNA structure by removing electrons, forming substances that may cause mutations and cancer.
C. Drag and Drop: Match Each Factor or Health Effect to Its Description
Drag each term to the 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 Factor or Health Effect to Its Description
Write the correct term next to each description.
| Description | Term / Factor |
|---|---|
| 1. An internal process occurring in mitochondria that produces free radicals | |
| 2. An external factor that increases the amount of free radicals in the body | |
| 3. A condition caused by free radicals leading to wrinkles and grey hair | |
| 4. An unstable atom or molecule that lacks one electron |
Answer choices: Metabolism • Cigarette smoke • Premature aging • Free radical
