Studying cells Flashcards
(11 cards)
What is magnification ?
How much bigger the image is compared to the real structure
What is resolution ?
The ability to see two points as two points
What are the features of a light microscope ?
Uses lenses to focus a beam of light
Low resolution
Can view live specimens
Simple staining and slide preparation
Can see colours
What are the features of an electron microscope ?
Uses electromagnets to focus a beam of electrons
High resolution than light due to smaller wavelengths of electrons
Specimen must be placed in a vacuum and so must be dead
Long prep time
What are the features of a transmission electron microscope ?
Can see internal structures of organelles
Specimen has to be very thin
Image is only 2D
Black and white image only
What are the features of the scanning electron microscope ?
Resolution isn’t as high as tem
3D image
Black and white image only
What are the requirements for doing a scientific drawing
Always in pencil
No outlines
No colouring or shading
Relative sizes should be accurate
A title and the magnification of the image
Label the structures
What is the process of cell fractionation ?
Homogenisation: grind in
Cold- reduces enzyme activity
Isotonic- prevents cell from shrinking or bursting
Buffer- prevents denaturing
Filtration-filter out any large cell debris but organelles don’t pass through
Centrifugation: first low speed to give a pellet of the heaviest organelles e.g nucleus then. Spin at higher speed to give pellets to the shloroplast and mitochondria etc
Ultracentrifugation: spin at very high speeds to separate out molecules depending on their mass
What are the stages of mitosis ?
Prophase- chromosomes condense from chromatin and become visible as 2 chromatids joined at the centromere nucleur envelope and nucleoli disappear
Metaphase-chromosomes line at the equator of the mitotic spindle attached to spindle by centromere
Anaphase- chromosomes split as centromere divides as spindle fibres contract pulled to opposite poles by centromere first
Telophase- chromosomes elongate and uncoil and the nucleur envelope reforms and nucleoli reappear as two nuclei are formed
How does bacteria replicate ?
Circular DNA replicates
Plasmids replicate (can be many times)
The cytoplasm divides and 2 daughter cells are produced each containing one copy of the circular DNA and some of the plasmid copies
How do viruses replicate ?
Attachment proteins attach to host cell receptors
The viral nucleus acid enters the cell
The nucleus acid is replicated inside the cell
The host cell then produces viral proteins
The virus particles are assembled
The host cell bursts releasing the viruses
