Biology87 views·Updated May 27, 2026·4 pages

Comparing Prokaryotic and Eukaryotic Cells

Sophie@soph.g.l

Cells are the building blocks of all living organisms and... Show more

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# Biology notes

What are cells?

Cells are the smallest structural and functional unit of an organism, typically microscopic and consistent

Cells and Cell Theory

Cells are the smallest structural and functional units of organisms. They're typically microscopic, containing cytoplasm and genetic material enclosed in a membrane. According to cell theory, all organisms are composed of cells, cells are the smallest living units, and new cells come from pre-existing cells.

Living organisms perform eight essential functions: nutrition, metabolism, growth/development, sensitivity, excretion, homeostasis, movement, and reproduction. These functions occur at the cellular level and define what it means to be alive.

When working with cells, scientists use standard units of measurement with specific prefixes. These range from very large $giga-, mega-$ to extremely small $micro-, nano-$ measurements, allowing precise description of cellular structures and processes.

💡 The surface area to volume ratio is crucial for cell survival! As cells grow larger, this ratio decreases, making it harder for materials to move in and out efficiently—this is why most cells stay microscopic.

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Types of Cells

There are two major cell types that make up all living organisms: prokaryotes and eukaryotes. Prokaryotic cells are smaller and simpler, lacking a distinct nucleus. Their DNA exists as a loop within the cytoplasm. Bacteria are common examples of prokaryotes and are considered some of Earth's oldest life forms.

Eukaryotic cells are more complex with a distinct nucleus that houses their DNA. Unlike prokaryotes, eukaryotic DNA is wrapped around proteins. These cells contain specialized membrane-bound organelles like mitochondria that perform specific functions. This division of labor increases cellular efficiency. Plants, animals, fungi, and protists all have eukaryotic cells.

The key differences between these cell types include size (eukaryotes are larger), ribosome size (eukaryotes have "eighties" while prokaryotes have "seventies"), and the presence of membrane-bound organelles in eukaryotes. These distinctions reflect different evolutionary paths and survival strategies.

🔬 Think of prokaryotic cells as studio apartments (everything in one space) and eukaryotic cells as houses with many rooms (specialized compartments for different functions)!

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Viewing and Measuring Cells

Scientists use different microscopes to study cells. Compound light microscopes use a series of lenses to magnify objects up to 1500x and have been used for centuries. Electron microscopes provide much higher resolution by using electron beams instead of light, though they can't view living specimens or show true colors.

There are two main types of electron microscopes: Scanning Electron Microscopes (SEM) that create 3D surface images, and Transmission Electron Microscopes (TEM) where electrons pass through the specimen, with denser areas appearing darker. These can magnify thousands of times more than light microscopes.

When measuring cells, scientists use the formula "I AM": Image size = Actual size × Magnification. This can be rearranged to find any variable: Magnification = Image size/Actual size or Actual size = Image size/Magnification. Remember to keep measurements in the same units!

🧮 When calculating cell measurements, always check your units! Using micrometers (μm) for one measurement and millimeters (mm) for another will give you wildly incorrect results.

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Cell Size and Specialization

Cell size is limited by physics and efficiency. Smaller cells have a larger surface area to volume ratio, making them better at transporting materials in and removing waste. This ratio is critical for cell survival and function.

As cells grow larger, they face multiple challenges. The diffusion distance becomes too long, and the surface-to-volume ratio decreases, preventing efficient exchange with the environment. Additionally, larger cells produce more heat and waste in proportion to their volume, potentially causing them to overheat.

To overcome these limitations, cells have developed adaptations. Some cells increase their surface area through protruding extensions or by flattening their shape. These modifications help maintain efficiency even when the cell needs to be larger for specialized functions.

🔍 Your body has over 200 different specialized cell types, each shaped perfectly for its function—from long nerve cells that transmit signals to flat skin cells that protect your body!

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Biology87 views·Updated May 27, 2026·4 pages

Comparing Prokaryotic and Eukaryotic Cells

Sophie@soph.g.l

Cells are the building blocks of all living organisms and the foundation of biology. This topic covers what cells are, their types, and how they function as the basic units of life. Understanding cells helps explain how living things work... Show more

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Cells and Cell Theory

💡 The surface area to volume ratio is crucial for cell survival! As cells grow larger, this ratio decreases, making it harder for materials to move in and out efficiently—this is why most cells stay microscopic.

of 4

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Types of Cells

🔬 Think of prokaryotic cells as studio apartments (everything in one space) and eukaryotic cells as houses with many rooms (specialized compartments for different functions)!

of 4

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Viewing and Measuring Cells

🧮 When calculating cell measurements, always check your units! Using micrometers (μm) for one measurement and millimeters (mm) for another will give you wildly incorrect results.

of 4

Sign up to see the content. It's free!

Access to all documents
Improve your grades
Join milions of students

Cell Size and Specialization

🔍 Your body has over 200 different specialized cell types, each shaped perfectly for its function—from long nerve cells that transmit signals to flat skin cells that protect your body!