Organisation of the cell and methods to study cells

What is the fundamental unit of life?

All organisms are made of cells

What is the cell?

The simplest collection of matter that can live

What is the importance of cell structure?

Correlates with function

What are the 2 types of Light Microscopes?

Upright and Inverted

What is the Upright Light Microscope?

Objective lens points towards sample from above

What is the Inverted Light Microscope?

Objective lens points from below

What are the types of Light Microscopy?

Brightfield, Optical contrast, Fluorescence

What are the types of Electron Microscopy?

Transmission, Scanning

Describe Unstained Brightfield Microscopy

• Easy

• No colour - Difficult to see structures

• Light passes through - no contrast

Describe Stained Brightfield Microscopy

• Increased detection of subcellular structures

• Can kill cells - harsh chemicals

• Colour

Describe Phase-Constrast Microscopy

• Amplifies variations in density

• Cells alive - no staining

• White outline

What is the benefit of Phase Contrast Microscopy?

Allows observation of transparent living cells

How does Phase Contrast Microscopy work?

• Light passes through diaphragm which focuses a ring of light onto sample

• Causes phase shift to alter light wave path

• Results in improvement of contrast

How does Differential Interference Contrast Microscopy work?

Interference between polarised light, objects appear in relief, casting shadows (3D)

Optical Contrast Differential Interference Contrast Microscopy

Good contrast, looks 3D

Optical Contrast Phase Constrast

White halo around cell

How does Immunocytochemistry work?

• Antigen on cell

• Enzyme/dye bound to antibody - to visualise binding of antibody

• Dye indicates where antigen is

How do Electron Microscopes work?

Electromagnetic lenses focus electron beam

How does the resolution of an Electron Microscope compare to a Light Microscope?

Higher resolution

How are samples viewed in Electron Microscopes?

• Stained w/ heavy metals for contrast

• Vacuum to prevent electron scatter

Scanning Electron Microscopes

Focus electron beam onto surface of specimen, 3D image

Transmission Electron Microscopes

Focus beam through specimen, mainly study internal structure of cells

Cell Fractionation

• Takes cells apart and separates major organelles

• Enables scientists to determine functions of organelles

  • Biochem + cytology help correlate cell function w/ structure

Process of Cell Fractionation

• Pellet rich in nuclei and cellular debris

• Spin at increasing speeds for longer times

• Mitrochondria, Microsomes, Ribosomes

Which organisms consist of prokaryotes?

Only bacteria and archae

How is DNA stored in Eukaryotes?

In nucleus bound by membranous nuclear envelope

How are organelles stored in Eukaryotes?

Membrane bound

Where is the cytoplasm in Eukaryotes?

Region between plasma membrane and nucleus

How are Prokaryotes different than Eukaryotes?

No nucleus, unbound DNA (nucleoid), no membrane-bound organelles, cytoplasm bound by plasma membrane