IGCSE Biology - Cell Structure and Organisation (2.1)

Summary

This IGCSE Biology lesson covers the essential concepts of cell structure, focusing on the different types of cells and their functions. It explains the hierarchy of biological organization, from cells to tissues, organs, and systems, and discusses the structures of plant, animal, and bacterial cells. Key topics include the roles of organelles like the nucleus, mitochondria, and chloroplasts, and the process of mitosis. Additionally, specialized cells such as ciliated cells, neurons, and red blood cells are highlighted, providing a comprehensive overview to prepare students for exams.

Takeaways

• 😀 Cells are the basic building blocks of life, and they are grouped into tissues, organs, and organ systems to perform specific functions.
• 😀 The human body contains up to 40 trillion cells, and individual cells have little impact unless they work together in large numbers.
• 😀 Tissues are groups of cells with similar structures that perform a shared function, such as muscle tissue or epithelial tissue.
• 😀 Organs are made up of different tissues working together to carry out specific functions, such as the small intestine which is involved in digestion.
• 😀 Organ systems are groups of organs that perform related functions, like the circulatory system (heart and blood vessels) or the nervous system (brain and spinal cord).
• 😀 An organism is a complete living thing, made up of multiple organ systems, and can survive independently, exhibiting all the properties of life.
• 😀 The cytoplasm, cell membrane, nucleus, mitochondria, and ribosomes are common structures found in both animal and plant cells.
• 😀 Plant cells have unique structures like the cell wall, chloroplasts for photosynthesis, and vacuoles that help maintain structure and firmness.
• 😀 Bacterial cells lack a nucleus and contain a coiled DNA chromosome and plasmids, which are additional genetic material that aids in survival.
• 😀 Mitosis is the process by which new cells are produced, and it involves the replication and division of chromosomes controlled by the nucleus.
• 😀 Specialized cells, like ciliated cells, neurons, red blood cells, sperm and egg cells, root hair cells, and palisade mesophyll cells, perform specific functions that contribute to the overall function of an organism.

Q & A

What are the basic levels of organization in living organisms?

The basic levels of organization in living organisms are cell, tissue, organ, organ system, and organism. Cells are the building blocks of life, and they group together to form tissues, organs, organ systems, and ultimately, the entire organism.

What is the role of tissues in multicellular organisms?

Tissues are groups of similar cells that work together to perform a specific function. For example, muscle tissue contracts to help with movement, and epithelial tissue lines body surfaces like the inside of the mouth or windpipe.

What is the purpose of organ systems?

Organ systems are groups of organs with related functions that work together to perform specific body functions. An example is the circulatory system, which includes the heart and blood vessels that work together to circulate blood throughout the body.

How do plant cells differ from animal cells?

Plant cells have several features that make them unique, including a cell wall made of cellulose, chloroplasts for photosynthesis, and a large central vacuole for maintaining cell structure. Animal cells lack these structures.

What is the function of the cytoplasm in a cell?

The cytoplasm is a jelly-like substance that contains nutrients and organelles. It is the site of most chemical reactions in the cell and helps maintain cell structure.

How do mitochondria contribute to cellular activity?

Mitochondria are organelles that release energy from nutrients, such as glucose, through a process called aerobic respiration. This energy is crucial for cell functions and activities.

What is the function of chloroplasts in plant cells?

Chloroplasts contain chlorophyll, a green pigment that is essential for photosynthesis. They convert light energy into glucose, providing the cell with energy.

What are plasmids in bacterial cells and why are they important?

Plasmids are small, circular DNA structures found in bacterial cells. They carry extra genetic information that helps bacteria survive and adapt to various environments, such as antibiotic resistance.

What is mitosis and how does it contribute to cell division?

Mitosis is the process by which new cells are produced. The chromosomes in the nucleus are replicated, and the cell divides into two, with one cell retaining the ability to divide while the other may become specialized for a specific function.

What are some examples of specialized cells and their functions?

Specialized cells include ciliated cells, which help move mucus in the respiratory system; red blood cells, which transport oxygen using hemoglobin; and sperm cells, which are specialized for reproduction. Each has a specific structure to suit its function.