Lesson Notes By Weeks and Term v4 - SHS 1
MOVEMENT OF SUBSTANCES IN LIVING ORGANISM S
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MOVEMENT OF SUBSTANCES IN LIVING ORGANISM S
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Subject: Biology
Class: SHS 1
Term: 1st Term
Week: 14
Grade code: 1.2.1.LI.2
Strand code: 2
Sub-strand code: 1
Content standard code: 1.2.1.CS.1
Indicator code: 1.2.1.LI.2
Theme: LIFE IN THE FUNDAMENTAL UNIT
Subtheme: MOVEMENT OF SUBSTANCES IN LIVING ORGANISM S
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This lesson focuses on how cells transport very large particles or large quantities of small particles across the cell membrane—a process called bulk transport. While we have previously learned about diffusion and osmosis for small molecules like water and oxygen, our bodies need to move much bigger things. Imagine how your body absorbs large nutrient molecules from the *fufu* and light soup you ate, or how your immune cells attack and "eat" harmful bacteria like those that cause cholera or typhoid. These essential life processes depend on bulk transport. Understanding this helps us appreciate how our bodies stay nourished, defend against diseases, and maintain balance (homeostasis).
Recap: Moving Small Molecules Remember that the cell membrane is selectively permeable. Small molecules can cross it in several ways: Diffusion: Movement from high to low concentration (e.g., oxygen entering blood cells). No energy needed. Osmosis: The special diffusion of water across a membrane. No energy needed. Active Transport: Movement from low to high concentration, which requires energy (ATP) and protein pumps (e.g., mineral salts into root hair cells).
The Challenge: What happens when a cell needs to take in a large food particle, a whole bacterium, or release a large amount of hormones? These are too big to pass through the membrane or a protein pump. This is where bulk transport comes in. What is Bulk Transport? Bulk transport is the movement of large molecules (like proteins, polysaccharides) or entire cells (like bacteria) across the cell membrane. It is an active process, meaning it requires energy in the form of ATP (Adenosine Triphosphate).
Bulk transport is achieved by the cell membrane changing its shape to form small sacs called vesicles. There are two main types of bulk transport: Endocytosis: Moving substances INTO the cell. (`endo` = in; `cyto` = cell) Exocytosis: Moving substances OUT OF the cell. (`exo` = out; `cyto` = cell)
Detailed Explanation of Endocytosis ("Moving In")