Summary
Summary Module 2.1: Cell structure
- Course
- Institution
OCR biology A level, section 1, cell structure. A summary of key concepts ranging from eukaryotes and prokaryotes to microscopes and organelles.
[Show more]
Seller
Follow
katieg1500
Content preview
MICROSCOPY SlidesDry mount = Solid specimen sectioned, cover slip
Microscopes Wet mount = liquid specimen, cover slip at angle
Light microscope Squash slide = wet mount, soft sample, press cover slip
- X200 magnification Smear slide = liquid sample, edge to smear, cover slip
- 200nm resolution
- 400-700nm wavelength Artefacts = structures produced in preparation
- Eyepiece + objective lens (multiplied) - Bubbles (light)
- Cheap, portable, simple prep, no damage, natural - Loss of membrane continuity
colour, living or dead - Organelle distortion
- Empty space in cytoplasm
TEM - Mesosome (inward membrane fold - fixation)
- x500,000-2,000,000 magnification
- 0.5nm resolution Fixing – chemicals to preserve
- Electron beam transmitted through – 3D image Sectioning – dehydrated and into mould
- Thin specimen, denser parts = darker
- Expensive, complex = distortion, black + white, dead Differential staining
- Vacuum = straight electron beam - ↑ contrast as take up stain to different degrees
- Helps identify organelles
SEM - Helps identify different types of cells (distinguish)
- x100,000-500,000 magnification
- 3-10nm resolution + charge = crystal violet + methylene blue (organelles)
- Electron beam across surface - charge = congo red + nigrosine (stain outside cell)
- Reflected electrons collected – 2D image
- Expensive, complex = distortion, black + white, dead Gram stain technique
- Separate bacteria by wall thickness
Laser scanning confocal microscope - Crystal violet, iodine, alcohol wash
- Laser across specimen - g+ bacteria (thick) = blue/purple
- 2D image but 3D if layer focal planes - Safranin dye counterstain
- Non-invasive – eye disease, endoscopic procedures - g- bacteria (thin walls) = red
- Florescence (absorb + reradiate) from dye - g+ bacteria susceptible to penicillin = inhibits cell wall
- Emit ↑ wavelength, filtered through pinhole aperture
- Only use light radiated close to focal plane, light from Acid fast technique
other planes ↓ resolution + blurring - Primary dye = all bacteria red
- Beam splitter (dichroic mirror) reflects laser + - Decolouriser acid = non-acid fast lose red
transmits reflected - Counterstain = non-acid fast turn blue
- Florescent tags for genes to see where travels in cell
Ultrastructure
Nucleus
- Contains DNA
- Controls metabolic activity
- Directs protein synthesis
- Nucleolus contains RNA + proteins = produce ribos
- Double mem nuclear envelope, prevent DNA damage
- Nuclear pores – where RNA molecules leave
I Plasma membrane
M A - Phospholipid bilayer (lipids + proteins)
- Regulate movement of substance (selective perm)
- Receptor molecules
Magnification = times larger the image is than actual
Resolution = ability to distinguish 2 points (detail) Mitochondria
- Limited by diffraction of light, reflections overlap - Matrix = internal enzyme fluid
- Smaller wavelength = higher resolution (electron) - Double membrane, cristae = folded inner membrane
- Mitochondrial DNA + ribosomes = own enzymes
Eyepiece divisions = stage micrometre / graticule divisions - Aerobic respiration – produce energy + ATP
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller katieg1500. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $6.45. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
53068 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now