Cells Notes

Summary

This video introduces the cell as the smallest unit of life, exploring cell theory and its importance in biology. It explains the differences between prokaryotic and eukaryotic cells, focusing on their structures and functions. The lecture covers topics such as the surface area-to-volume ratio, organelles like mitochondria, chloroplasts, and ribosomes, and the roles of the nucleus and plasma membrane. Additionally, it touches on cell walls, the differences between plant, animal, and bacterial cells, and concludes with a brief discussion of fungi, specifically yeast cells.

Takeaways

• 🔬 Cell theory states that all living things are made up of cells, and new cells come from pre-existing cells.
• 🌱 Cells vary in shape and function; examples include amoebas, plant cells, red blood cells, nerve cells, and bacterial cells.
• 🧫 Cells exchange nutrients and waste through their membrane, and their size is limited by the surface area to volume ratio.
• 🧬 Prokaryotic cells (bacteria and archaea) do not have membrane-bound organelles or a true nucleus, while eukaryotic cells (plants and animals) do.
• 🦠 Prokaryotes are always unicellular, while eukaryotes can be unicellular or multicellular.
• 🌿 Plant cells have structures like cell walls and chloroplasts that animal cells do not.
• 🧪 The plasma membrane controls what enters and leaves the cell, and is composed of hydrophilic heads and hydrophobic tails.
• ⚡ Mitochondria are the powerhouse of the cell, involved in cellular respiration and energy production (ATP).
• 🧱 Ribosomes translate mRNA into proteins, and are found in both prokaryotic and eukaryotic cells.
• 🍞 Yeast is a eukaryotic fungus, not a bacterium or animal, and plays a role in fermentation (like bread rising).

Q & A

What is the cell theory and why is it important?

Cell theory is a fundamental tenet of biology, stating that all living things are made up of cells, cells are the smallest unit of life, and new cells arise from pre-existing cells. It is important because it describes the basic principles of how life functions at the cellular level.

Why are cells considered the smallest units of life?

Cells are considered the smallest units of life because they can perform all the functions necessary for life, including energy conversion, growth, and reproduction. Anything smaller, like parts of a cell, cannot independently sustain life.

How do amoeba move, and what is cytoplasmic streaming?

Amoeba move by extending their plasma membrane to create projections called pseudopodia, into which their cytoplasm flows. This movement process is called cytoplasmic streaming, allowing the amoeba to move and capture food.

What is the significance of surface area to volume ratio in cells?

The surface area to volume ratio limits the size of cells because as a cell grows, its volume increases faster than its surface area, reducing its ability to efficiently exchange nutrients, gases, and waste. Cells need to maintain a high surface area relative to their volume for efficient transport across their membranes.

What are the differences between prokaryotic and eukaryotic cells?

Prokaryotic cells, like bacteria, lack a membrane-bound nucleus and organelles. They are usually unicellular and simpler in structure. Eukaryotic cells, found in plants, animals, and fungi, have a membrane-bound nucleus and organelles, and can be either unicellular or multicellular.

Why do bacteria have no membrane-bound organelles?

Bacteria are prokaryotic, meaning they do not have membrane-bound organelles. Instead, their cellular components, like DNA and ribosomes, float freely in the cytoplasm, with only the plasma membrane enclosing the cell.

What is the function of the plasma membrane in cells?

The plasma membrane controls what enters and exits the cell, maintaining an internal environment that supports cellular processes. It is composed of a phospholipid bilayer with embedded proteins that allow selective transport of substances.

What organelles are involved in protein synthesis and transport?

Protein synthesis begins with ribosomes, either free in the cytoplasm or attached to the rough endoplasmic reticulum (ER). Proteins synthesized on the ER are then transported to the Golgi apparatus, where they are modified, sorted, and sent to their destination.

What is apoptosis and how do lysosomes play a role in it?

Apoptosis is programmed cell death, a process important for development and maintaining cellular health. Lysosomes, which contain digestive enzymes, help break down the cell's components during apoptosis, ensuring the controlled destruction of damaged or unnecessary cells.

How are plant cells different from animal cells?

Plant cells have a rigid cell wall and chloroplasts for photosynthesis, which animal cells lack. They also typically have a large central vacuole for storage, whereas animal cells may have smaller, less prominent vacuoles.