Lesson Notes By Weeks and Term v4 - SHS 3
CELL STRUCTURE AND FUNCTIONS
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CELL STRUCTURE AND FUNCTIONS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Biology
Class: SHS 3
Term: 1st Term
Week: 10
Grade code: 3.2.1.LI.2
Strand code: 2
Sub-strand code: 1
Content standard code: 3.2.1.CS.2
Indicator code: 3.2.1.LI.2
Theme: LIFE IN THE FUNDAMENTAL UNIT
Subtheme: CELL STRUCTURE AND FUNCTIONS
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This lesson explores the fascinating world of human blood groups and the Rhesus factor. We often hear about blood types like 'O positive' or 'A negative' during hospital visits, blood donation drives organised by the National Blood Service, Ghana, or in emergency situations after an accident on the Accra-Kumasi road. But what do these classifications really mean? They are determined by specific molecules on the surface of our red blood cells. Understanding our own blood group is not just a piece of trivia; it is a critical piece of medical information that can save lives during blood transfusions and ensure the health of a mother and her unborn child.
This section breaks down the essential scientific principles governing blood groups. A. The Building Blocks: Antigens and Antibodies
To understand blood groups, we must first understand two key players: antigens and antibodies. Antigens: These are protein or carbohydrate molecules found on the surface of our red blood cells. Think of them as a "name tag" or a "jersey" that identifies the cell. The type of antigen you have determines your blood group. Antibodies: These are proteins found in the blood plasma. They are part of the body's immune system. Think of them as "security guards" that patrol the blood, looking for foreign invaders. If an antibody finds a foreign antigen that it doesn't recognise, it will attack and cause the foreign cells to clump together (a process called agglutination). This clumping is dangerous and can block blood vessels, leading to organ damage or death.
The Rule: Your body produces antibodies against the antigens you *do not* have. B. The ABO Blood Group System
This is the most well-known system for classifying blood. It is based on the presence or absence of two antigens: Antigen A and Antigen B.