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A-level Biology - 3.1.2 Cells and Cell Structure Part 1

Biology25 CardsCreated about 2 months ago

This deck covers key concepts related to cells and cell structure, including magnification, resolution, and the use of different types of microscopes.

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Key Terms

Term
Definition

÷ Divide to make ____

bigger

× Multiply to make _____

smaller

Describe how you convert cm → mm → μm → nm & vice versa

Define Magnification

How many times bigger the image is than the specimen (object)

Define Resolution

Minimum distance apart that two objects can be in order for them to appear as separate items

State the formula used to work out magnification

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TermDefinition

÷ Divide to make ____

bigger

× Multiply to make _____

smaller

Describe how you convert cm → mm → μm → nm & vice versa

Define Magnification

How many times bigger the image is than the specimen (object)

Define Resolution

Minimum distance apart that two objects can be in order for them to appear as separate items

State the formula used to work out magnification

Describe how optical (light) microscopes work

Light from bulb travels through condenser lens, then specimen, up through objective lens and through eyepiece lens into your eye

State the maximum magnification for an optical microscope

x 1500

State the maximum resolution for an optical microscope

0.2 µm

Name 2 pros of optical (light) microscopes

Easy and cheap to operate Can have living specimens

Name 2 cons of optical (light) microscopes

Low resolution & magnification Can’t see organelles smaller than 0.2 µm (e.g. ribosomes, endoplasmic reticulum and lysosomes) Specimens often need staining to show specific organelles

Why does optical microscopes have a maximum resolution of 0.2 µm?

∵ of the long wavelength of light rays

Name 2 Electron Microscopes

Transmission Electron Microscopes Scanning Electron Microscopes

Describe how transmission electron microscopes work

Use electromagnets to focus a beam of electrons which is then transmitted through the specimen Denser parts of specimen absorb more electrons = makes them look darker on image you end up with

State the maximum resolution for a transmission electron microscope

0.1 nm

State the maximum magnification for a transmission electron microscope

x 10 000 000

Name a pro of transmission electron microscopes

Has highest resolutions & magnification See internal structure of organelles e.g. chloroplasts

Name 4 cons of transmission electron microscopes

Non-living matter only Image in black and white and 2D Preparation may distort structure/give artefacts Vacuum required Elaborate preparation - staining is complex

Describe how scanning electron microscopes work

They scan a beam of electrons across specimen = knocks off electrons from specimens Electrons gathered in cathode ray tube to form image

State the maximum magnification of SEMs

x 30,000

State the maximum resolution of SEMs

20 nm

Name 3 pros of SEMs

Can form complex 3D images of sample Can be used on thick specimens Magnifications & resolutions are higher than light microscopes

Name 3 cons of SEMs

Large and expensive & difficult to operate Specimens has to be mounted in vacuum Specimen has to be dead

What type of cells are like algal cells?

Plant cells = have same organelles (Can be single-celled or multicellular)

What type of cells are like fungal cells?

Plant cells