Lesson Notes By Weeks and Term v4 - SHS 2
CELL STRUCTURE AND FUNCTIONS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
CELL STRUCTURE AND FUNCTIONS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Biology
Class: SHS 2
Term: 1st Term
Week: 18
Grade code: 2.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 2.1.2.CS.1
Indicator code: 2.2.2.LI.3
Theme: LIFE IN THE FUNDAMENTAL UNIT
Subtheme: CELL STRUCTURE AND FUNCTIONS
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
This lesson explores the two most important molecules in life: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid). We will investigate why children often resemble their parents, why a maize seed always grows into a maize plant, and how our bodies know how to build everything from our hair to our hearts. These molecules are the "blueprint" and the "workers" that control everything a cell does. Understanding their structure is key to understanding their vital roles.
A. The Building Blocks: Nucleotides
Both DNA and RNA are polymers, meaning they are large molecules made up of repeating smaller units. The repeating unit is called a nucleotide. Think of it like a single brick used to build a large house.
Every nucleotide has three parts: A Phosphate Group: A molecule containing phosphorus and oxygen. A Pentose Sugar: A sugar molecule with 5 carbon atoms. A Nitrogenous Base: A molecule containing nitrogen. B. DNA (Deoxyribonucleic Acid): The Master Blueprint
DNA is the molecule that contains the genetic instructions for the development, functioning, growth, and reproduction of all known organisms. It is the "master plan" or "recipe book" stored safely in the nucleus of the cell. Structure of DNA: Sugar: The sugar in DNA is Deoxyribose. Bases: DNA has four nitrogenous bases: Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Structure: DNA is a double helix. Imagine a ladder that has been twisted. The two long sides of the "ladder" are made of alternating sugar and phosphate molecules. This is called the sugar-phosphate backbone. The "rungs" of the ladder are made of pairs of nitrogenous bases. Complementary Base Pairing: The bases always pair in a specific way, held together by weak hydrogen bonds: Adenine (A) always pairs with Thymine (T). (A-T) Guanine (G) always pairs with Cytosine (C). (G-C) This strict rule is crucial for copying DNA accurately. Relevance (Function) of DNA: