Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Describe the structure and functions of major organelles.
• Explain the differences between prokaryotic and eukaryotic cells.
• Differentiate between plant and animal cells.
• Explain cellular organization into tissues, organs, and systems.
• Draw and label diagrams of plant and animal cells.

Lesson summary

This week, we delve deeper into the fundamental building blocks of all living organisms: cells. Understanding cells is crucial because they are the basis of everything from the smallest bacteria to the largest animals and plants. All life processes, from obtaining energy to fighting off disease, happen at the cellular level. Here in South Africa, a good understanding of cells is vital for tackling health challenges like HIV/AIDS, tuberculosis, and the understanding of how vaccines work.

Furthermore, understanding plant cells helps us to improve crop production to ensure food security.

Lesson notes

2.1 The Cell Theory The cell theory is the cornerstone of biology.

It states: All living organisms are composed of one or more cells. The cell is the basic structural and functional unit of all living organisms. All cells arise from pre-existing cells. 2.2 Prokaryotic vs. Eukaryotic Cells The most fundamental distinction in cells is between prokaryotic and eukaryotic cells.

Prokaryotic Cells: These are simple cells that lack a nucleus and other membrane-bound organelles. Their DNA is located in the cytoplasm in a region called the nucleoid. Bacteria and Archaea are prokaryotes.

Example: Escherichia coli (E. coli), a bacterium found in the human gut.

Eukaryotic Cells: These are more complex cells that have a nucleus (where the DNA is stored) and other membrane-bound organelles, such as mitochondria, endoplasmic reticulum, and Golgi apparatus. Plants, animals, fungi, and protists are eukaryotes.

Example: A human skin cell or a cell from a maize plant.

Key Differences Summarized: | Feature | Prokaryotic Cell | Eukaryotic Cell | | ------------------ | -------------------- | ---------------------- | | Nucleus | Absent | Present | | Membrane-bound Organelles | Absent | Present | | DNA | Circular, in nucleoid | Linear, in nucleus | | Size | Smaller (0.1-5 µm) | Larger (10-100 µm) | | Complexity | Simpler | More complex | | Examples | Bacteria, Archaea | Plants, animals, fungi | 2.3 Cell Structures and Organelles 2.3.1 Cell Membrane: Function: A selectively permeable barrier that controls what enters and exits the cell. It protects the cell and maintains its internal environment.

Structure: Composed of a phospholipid bilayer with embedded proteins. Imagine a "sandwich" of fats (lipids) with protein "chunks" stuck within it.

Real-life Analogy: Like the border control of South Africa, deciding what goods (molecules) can come in and out of the country (cell). 2.3.2 Cytoplasm: Function: The gel-like substance within the cell where organelles are located. It is the site of many metabolic reactions.

Composition: Primarily water, but also contains salts, sugars, and other organic molecules. 2.3.3 Nucleus: Function: The control center of the cell; it contains the DNA (genetic material) and controls all cellular activities.

Structure: Surrounded by a double membrane called the nuclear envelope. Contains the nucleolus, where ribosomes are made.

Real-life Analogy: Like the Parliament in Cape Town, making all the important decisions for the country (cell). 2.3.4 Endoplasmic Reticulum (ER): Function: A network of membranes involved in protein and lipid synthesis.

Types: Rough ER: Has ribosomes attached; involved in protein synthesis and modification.

Smooth ER: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage.

Real-life Analogy: Like factories in Durban producing different products. 2.3.5 Golgi Apparatus: Function: Modifies, sorts, and packages proteins and lipids for transport to other parts of the cell or for secretion outside the cell.

Structure: Stack of flattened, membrane-bound sacs called cisternae.

Real-life Analogy: Like the South African Post Office, packaging and sending things to different locations. 2.3.6 Mitochondria: Function: The "powerhouse" of the cell; responsible for cellular respiration, which produces energy (ATP).

Structure: Double membrane structure with an inner membrane folded into cristae, which increase the surface area for ATP production.

Real-life Analogy: Like Eskom generating electricity for the country (cell). 2.3.7 Ribosomes: Function: Site of protein synthesis.

Structure: Small structures composed of RNA and protein. Can be free in the cytoplasm or attached to the E

R. Real-life Analogy: Like construction workers building houses (proteins) from blueprints (DNA). 2.3.8 Lysosomes: Function: Contain enzymes that break down cellular waste and debris.

Structure: Membrane-bound vesicles containing digestive enzymes.

Real-life Analogy: Like waste management companies cleaning up the city (cell). 2.3.9 Vacuoles: Function: Storage of water, nutrients, and waste products. Plant cells typically have a large central vacuole that helps maintain cell turgor (rigidity).

Structure: Membrane-bound sacs.

Real-life Analogy (Plant): Like a water reservoir, providing water for the city (cell). 2.3.10 Chloroplasts (Plant Cells Only): Function: Site of photosynthesis, where light energy is converted into chemical energy (glucose).

Structure: Double membrane structure containing chlorophyll, the pigment that captures light energy.

Real-life Analogy: Like a solar panel, capturing sunlight to generate energy. 2.3.11 Cell Wall (Plant Cells Only): Function: Provides support and protection for the plant cell.

Structure: Rigid structure composed of cellulose.

Real-life Analogy: Like the walls of a house, providing structure and protection.