C2- Cell biology Flashcards
What are the 4 main types of slide preparation?
Wet mount- Specimen submerged in water and cover slip added
Dry mount- Specimen placed onto slide directly and cover slip placed on top
Squash slides- Wet mount prepared and cover slip is used to squash the cells
Smear slides- Edge of a slide is used to create a smooth thin layer of cells over a slide.
What is magnification
the number of times larger an
image is compared with the real size of the object.
What is resolution
the ability to distinguish between
two separate points. If two points cannot be resolved
they will be seen as one point, eg. like car headlights
Light Microscope advantages (5)
Can be used to look at cells and large organelles within cells
Staining cells makes organelles clearer
Preparation quick and simple
Natural colour of material observed
Living tissues can be observed
TEM vs SEM
TEM passes a beam of electrons through the specimen
SEM fires a beam of electrons across the surface, which
are reflected, and then collected
Transition electron microscopy
2D image
Max Magnification = x 500,000
Better resolving power– 0.5nm
Scanning electron microscopy
3D image
Max Magnification =x 100, 000
Less resolving power = 3-10nm
Methylene Blue stain
Positively charged dye attracted to negatively charged molecules
Stains DNA
Differential staining
Used to distinguish between 2 types of organisms, or organelles within an organism
Positively charged stains
Crystal violet
Methylene Blue
Attracted to negatively charged materials in the cytoplasm
Dry mount
used with whole or sectioned specimens
Can see living organisms
Mounts are temporary unless you seal the coverslip
Wet Mount
Specimens suspended in liquids such as oil or water
Cover slip placed at an angle
Greater refraction due to the liquid
-> Greater magnification and resolution
Squash slide
Wet mount first prepared
Gently press down on cover slip
Good for softer samples such as roots
Smear slide
Edge of a slide is used to smear a sample creating a thin even coating
Cover slip then placed
Negatively Charged Dyes
Congo Red
Nigrosin
Repelled by negatively charged cytosol
-> Stays outside cells, makes them stand out
Differential staining
Aids distinguishing between organisms or organelles
Gram stain technique
Acid fast technique
Prepared slide types (4)
1- Fixing= formaldehyde used to preserve
2- Sectioning= Dehydrate, wax and then slice with a microtome
3- Staining
4- permanent mounting
Cytoplasm- Structure
Contains Enzymes
Fluid = Cytosol
Cytoplasm- Function (3)
Where chemical reactions for cells take place
Holds membrane bound compartments (organelles)
Metabolism
-> Catabolism+ Anabolism. Break down and building of molecules
Nucleus- Structure (4)
Dark patches= Chromatin
Double membrane= nuclear envelope
Nuclear pores -> RNA can leave though as DNA too large
Nucleolus inside
Nucleus- Function (4)
Contains genetic material
Chromatin= histones (proteins) forms complex with DNA. Coils and then condenses into chromosomes
Contains instructions to make proteins
When cells divide chromatin condenses to visible chromosomes
Nucleolus (4)
- Inside Nucleus
-Composed of proteins + RNA
-Produces ribosomes
- RNA used to produce ribosomal DNA (rRNA) combined with proteins to make ribosomes
Mitochondria- Structure (4)
- 2 membranes separated by a fluid filled space
- Inner membrane folded to cristae. The inner fluid is the Matrix
- Membrane holds respiration energy
-Own DNA (mtDNA) and own enzymes
Mitochondria- Function
Where ATP is produced during respiration
Vesicles
Single membrane with fluid inside
used to transport materials inside cells
Lyosomes
Specialised vesicles that contain hydrolytic enzymes
Break down waste material in cells such as old organelles
Play a role in apoptosis
Break down pathogens ingested by phagocytotic cells
Flagella
whiplike
longer (than cilia)
For cell movement
Extensions form cell surface
cillia
Hair like
Numerous
Extensions form cell surface
Present in sensory organs
Involved in creating currents
Endoplasmic rectilium
structure
flattened membrane bound sacs (cisternae) which are continuous with outer membrane
Endoplasmic rectilium
Function
smooth= involved in making lipids
rough= transport proteins made on attached ribosomes
Ribosomes
Structure
Very small organelles in cytoplasm and on RER
2 Subunits- large and small
Manufactured in the nucleolus from RNA and proteins
Ribosome
Function
Site of protein synthesis
–> Acts as an assembly line to use MRNA to make proteins
Golgi apparatus
Structure
Stack of membrane bound flattened sacs
Similar structure to the Smooth ER
Golgi apparatus
Function
Receives proteins from ER
Modifies them (post office)
–> e.g. adds sugar
Protein production
5 key steps
1- Proteins are synthesised on ribosomes on RER
2- Pass into cisternae and are packaged into transport vesicles
3- vesicles move to golgi apparatus via function of the cytoskeleton
4-Vesicles fuse with Cis face of golgi apparatus. Proteins then enter. Proteins are structurally modified. Then leave in vesicles from the trans face
5- Secretory vesicles carry proteins to membrane and then fuse. Released via exocytosis. Some vesicles form lysosomes
Centrioles
small protein tubes of microtubules
Form fibres in cell division called spindles which go on to separate chromosomes
Cytoskeleton
Present throughout cytoplasm
responsible for the shape and stability of a cell
holds organelles in place and controls movement
Cytoskeleton
Microfilaments
Contractile fibres
–> contain actin
Responsible for cell movement
Cytoskeleton
Microtubules
scaffolding proteins for the shape of the cell
spindle fibres
–> pull apart chromosomes in cell division
cytoskeleton
intermediate fibres
mechanical strength
How to calibrate eyepiece graticule
SMU/ EMU x100
SMU=, stage micrometer
EMU= Eyepiece micrometer
Graticule
stage vs eyepeice
Stage= true lengths
eyepiece= regular divisions that must be calibrated
Biological drawing
low power lens
No individual cells should be drawn
Biological drawing
5 key points
pencil only
scale bar
magnification
title
no shading
Exocytosis
Process by which materials are removed from or transported out of cells
( vesicles fuse with cell membrane and release proteins)
Vesicle vs Pernament Vacuole
Both are membrane bound sacs that function in storage and transport
Permanent vacuole doesn’t fuse with membranes
Plant vacuoles have enzymes that break down macromolecules
–> like lysosomes
Compartmentalisation
The separation of the cell interior in distinct compartments with specific local conditions that allow simultaneous occurrence of diverse metabolic reactions and processes
Endosymbiosis
An organism that lives within the body or cells of another organism
(opposite of parasitosis)
Theory for ribosomes and mitochondria
Prokaryotes
plasmids replicate independent of main chromosomes
cell wall made of peptidoglycan
mesosome= inner extensions of cell membrane, site of respiration
smaller ribosomes
–> 70s not 80s
Prokaryotic ribosomes
70s not 80s
s= where they settle in a centrifugal tube
Prokaryotic flagella
Do not have a 9+2 arrangement
Smaller
Movement from chemiosmosis not ATP
“watermill”
Chloroplasts
structure
2 membranes separated by a fluid filled space
stack of thylakoids is a granum
chlorophyll molecules present on the membranes
Chloroplasts
Function
Site of photosynthesis
Light energy is used to derive carbohydrate molecules form carbon dioxide
Permanent vacuole
Structure
Bound by a membrane called the tonoplast
Vacuole contains cell sap
–> solution of sugars, amino acids, salts, waste chemicals
Permanent Vacuole
function
Food stores
accumulate waste products
maintains turgidity
Cell wall (plants)
Structure
Cellulose cell walls
Cell wall (plants)
Function
!!!Different in bacteria and fungi
protects cell from mechanical damage
maintains rigidity under turgor
–> water diffusion in/out of cell
Freely permeable
Barrier to pathogens
Organelles not membrane bound
Cytoskeleton
villi/ flagellum
ribosomes
