Cells and Microscopes

topic 1

Why are cells typically small in size?

• To ensure maximum surface area

• The more surface area, the better cells can function

• Functions = chemical communication, nutrient absorption, regulation

What happens as cells get larger?

• Less surface area

• The cell needs to compensate in order to properly function

What is the primary function of microscopy in studying cells?

To magnify objects and reveal details not visible to the naked eye

Who is credited with discovering cells using a microscope in 1665?

Robert Hooke

What does magnification refer to in microscopy?

The ability to make an object appear larger than its actual size

How does resolution work in microscopes?

Smaller resolution values are better for distinguishing separate points in microscopes. larger resolution is better for photos

What is contrast in microscopy?

The ability to distinguish the cell and its parts from the background

Who was associated with the light microscope?

Robert Hooke

How does a light microscope produce an image?

• Light passes through the sample and is absorbed to create a 2D image

• magnified by glass lenses

What key features distinguish electron microscopes from light microscopes?

They use electron beams, electromagnetic lenses, and computers for better resolution, cell details, and detect the image

How does a Transmission Electron Microscope (TEM) work?

A 2D image with lots of detail (not as much as a SEM), where the electron beam passes through the sample and is detected in order to create an image

What is unique about Scanning Electron Microscope (SEM) imaging?

Electrons bounce off the sample's surface for a 3D image with detail, but not internals

Why is staining used to improve contrast in samples?

To selectively highlight certain proteins, genes, or components, making them stand out from the background

How does phase contrast work in microscopy?

Phase shift differences are converted into big brightness differences (not as much detail as DIC)

• dark = dense areas

• light = less dense areas

What is a phase shift when it comes to microscopy?

The concept that different parts of a cell affect light differently used in phase contrast (dense vs. less dense)

• Dense = light slows down more (eg. nucleus)

• Less dense = light slows down less (eg. cytoplasm)

What is differential interference contrast (DIC) when it comes to microscopy?

• polarized light is used and is split into two beams

• the two beams pass through the specimen at slightly diff positions and recombine

• same delay = flat image

• slower delay (1 beam) = contrast

• you see much more detail than within phase contrast

Who is Antonie van Leeuwenhoek known as?

The father of microbiology; first to see live cells and bacteria (microbes) and was able to achieve 200X more magnification than Robert Hooke

What is the challenge when it comes to contrast in microscopy?

Cells are clear/hard to see between the sample and the background since light microscopes pass light through the sample the same way

What are the two solutions to solving the problems regarding contrast in microscopy

1. Staining (colour or fluorescent) specific to respective proteins/genes

2. Phase Shift/Contrast and Differential Interference Contrast (DIC)