Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Describe the structure and function of plant and animal cell organelles.
• Differentiate between plant and animal cells.
• Explain the role of the cell membrane.
• Understand the three parts of the Cell Theory.

Lesson summary

The cell is the fundamental unit of life. Just like bricks are the building blocks of a house, cells are the building blocks of all living organisms, from the smallest bacteria in our soil to the largest baobab tree in Limpopo. Understanding cells is crucial because it unlocks the secrets of how our bodies function, how diseases develop, and how we can develop solutions to health challenges and improve agricultural yields in South Africa. Think about the food we eat; understanding cells helps us see how plants convert sunlight into energy. Think about diseases like HIV/AIDS; understanding how the virus attacks cells is key to finding treatments.

Lesson notes

2.1 The Cell Theory: The Cell Theory is a fundamental principle in biology.

It has three main tenets: All living organisms are composed of one or more cells: This means whether it's a tiny bacterium found in the mine dumps of Johannesburg or a massive whale swimming off the coast of KwaZulu-Natal, they are all made up of cells. The cell is the basic structural and functional unit of life: Cells are the smallest units that can carry out all the processes necessary for life. Tissues, organs, and organ systems are all built from cells.

All cells arise from pre-existing cells: Cells don't spontaneously appear; they are produced through the division of other cells. This concept is vital for understanding growth, repair, and reproduction. 2.2 Cell Structures (Organelles) and Functions: Both plant and animal cells have several common organelles, but there are also significant differences. Here's a breakdown of the main structures and their functions: | Organelle | Function | Found in | |----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------| | Cell Membrane | Acts as a barrier between the inside and outside of the cell. Controls the movement of substances in and out of the cell (selectively permeable). Made of a phospholipid bilayer with embedded proteins. Imagine it as a gatekeeper of the cell, only allowing certain molecules through. | Both | | Cytoplasm | A gel-like substance within the cell where organelles are located and where many chemical reactions occur. Think of it as the cell's internal fluid environment. | Both | | Nucleus | Controls the cell's activities. Contains the cell's genetic material (DNA) in the form of chromosomes. The nucleus is often called the "brain" of the cell. | Both | | Ribosomes | Sites of protein synthesis. Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum. They are like the cell's factories, producing proteins according to DNA instructions. | Both | | Mitochondria | The "powerhouse" of the cell. Carries out cellular respiration, converting glucose (sugar) into usable energy (ATP). This process is essential for all cellular activities. Think of it as the cell's energy generator. | Both | | Endoplasmic Reticulum (ER) | A network of membranes involved in protein and lipid synthesis and transport.

There are two types: Smooth ER (no ribosomes) and Rough ER (with ribosomes). The ER acts as a highway within the cell, transporting materials. | Both | | Golgi Apparatus | Modifies, sorts, and packages proteins and lipids for secretion or use within the cell. Think of it as the cell's post office, packaging and labeling materials for delivery. | Both | | Lysosomes | Contain enzymes that break down waste materials and cellular debris. They act as the cell's recycling center, breaking down old or damaged parts. | Animal (mostly) | | Vacuoles | Storage sacs for water, nutrients, and waste products. Plant cells typically have a large central vacuole that helps maintain cell turgor pressure. Think of them as storage containers for the cell. | Both, larger in Plants | | Chloroplasts | (Only in plant cells) Site of photosynthesis. Contains chlorophyll, which captures light energy to convert carbon dioxide and water into glucose and oxygen. These are unique to plant cells and are the reason plants are green. | Plant only | | Cell Wall | (Only in plant cells) A rigid outer layer that provides support and protection. Made of cellulose. Think of it as the cell's skeleton, providing structure and shape. | Plant only | 2.3 Plant vs.

Animal Cells: The main differences between plant and animal cells are the presence of a cell wall, chloroplasts, and a large central vacuole in plant cells. Animal cells lack these structures. | Feature | Plant Cell | Animal Cell | |----------------------|----------------------|----------------------| | Cell Wall | Present | Absent | | Chloroplasts | Present | Absent | | Vacuole | Large, central | Small or absent | | Shape | Relatively fixed | Irregular | | Centrioles | Absent | Present | 2.4 Cell Membrane Transport: The cell membrane is selectively permeable, meaning it controls which substances can pass into and out of the cell. This is crucial for maintaining the cell's internal environment and carrying out its functions.

Important processes include: Diffusion: Movement of molecules from an area of high concentration to an area of low concentration. No energy is required. For example, oxygen diffusing from the blood into the cells of your body.

Osmosis: The diffusion of water across a selectively permeable membrane from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration).