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18 concepts • medium difficulty
Part of TEST
Learn about the pioneering scientists who first observed and described cells.
Have you ever wondered how we learned about the tiny building blocks of life? It all started with some curious scientists and their amazing discoveries! Let's meet the pioneers who first saw cells.
In 1665, Robert Hooke made a big discovery. He looked at a thin slice of cork through his microscope. He saw tiny, empty compartments.
He called these small rooms "cells". These were actually dead cells. He shared his findings in his famous book, Micrographia.
A few years later, Anton von Leeuwenhoek took discovery a step further. He was a Dutch scientist who made his own powerful microscopes.
He was the first person to see living cells! He observed tiny creatures in pond water and called them "animalcules." This was a huge step in understanding life.
Later, in 1831, Robert Brown made another important discovery. He was a Scottish botanist.
He observed a dark, round structure inside plant cells. He named this central part the nucleus. We now know the nucleus is like the control center of the cell.
Understand the key postulates and contributors to the modern cell theory.
Many scientists helped us understand cells better. Their work built the foundation for what we know today.
Matthias Schleidan, a botanist, carefully studied many plants. He observed that all plants are made of different kinds of cells.
Theodor Schwann, a zoologist, then looked at animal cells. He found they have a thin outer layer, which we now call the plasma membrane. He also noticed that plant cells have a cell wall, a feature not found in animal cells. Schwann then suggested that all animals are also made of cells and their products.
Rudolf Virchow added a very important idea to cell theory. He explained that new cells always come from cells that already exist. He famously said, "Omnis cellula-e-cellula", which means "all cells from cells."
These discoveries led to the modern Cell Theory. It has two main ideas, called postulates:
Explore the basic characteristics, examples, and the nucleoid region of prokaryotes.
Prokaryotic cells are very simple and small. They are the oldest type of cell on Earth. These cells do not have a true nucleus or other membrane-bound parts.
Here are some common examples:
Inside a prokaryotic cell, the genetic material is found in a special area. This area is called the nucleoid.
The nucleoid is unique because it does not have a membrane around it. It usually contains just one chromosome. This chromosome is made of double-stranded circular DNA. It holds all the important genetic instructions for the cell.
Test your knowledge on the structure and roles of plasmids in prokaryotic cells.
Understand the three protective layers forming the prokaryotic cell envelope.
Imagine a prokaryotic cell. It has a special outer shield. This shield is a chemically complex protective covering. It keeps the cell safe.
This protective covering has three layers. They are tightly connected. These layers are:
The Glycocalyx is the very first layer. It is on the outside of the cell. This layer helps protect the cell.
It can be found in two forms:
The Cell wall is the layer right after the Glycocalyx. It gives the cell its shape. It also provides strong structural support.
This wall is very important. It stops the bacterium from bursting. It is made of a special material called Peptidoglycan.
Scientists use Gram staining to tell bacteria apart. This method depends on the cell wall.
The Plasma membrane is the innermost layer. It is similar to the plasma membrane in eukaryotic cells.
This membrane is semi-permeable. This means it only lets certain things enter or leave the cell. It acts like a gatekeeper.
Assess your understanding of the prokaryotic cell wall and Gram staining technique.
What is the main job of the cell wall in a prokaryotic cell?