2 - Basic components of living systems Flashcards
Light microscopes
- lower magnification and resolution than electron microscopes
- uses light
- used to look at whole cells/tissues.
- max magnification x1500
- alive
laser scanning confocal microscopes
- laser beams are used
- resolution is higher than an light microscope.
- used to look at objects at different depths and thick specimens.
Transmission electron microscopes
- beam of electrons transmitted through a specimen.
- x1 000 000
- high resolution 0.5nm
- dead
Scanning electron microscope
- beam of electrons
- resolution 3-10nm
3d images produced. - false coloured
- x500000
- dead
How is a microscope slide prepared?
- dry mount
- wet mount
- smear slides
- squash slides.
what stains are used in light microscopy and why?
- methylene blue
- different cell components take up stains to different degrees.
- the contrast makes the different parts show up.
dry mount microscope slide how?
- use tweezers to put thin specimen on middle of clean slide.
- put a cover slip on top.
wet mount microscope slide how?
- pipette a small amount of water onto the slide
- use tweezers to place specimen on top of water drop.
- place cover slip at an angle.
under light microscope, gram-negative bacteria appear…
red
under light microscope, gram-positive bacteria appear…
blue
How do you use a light microscope?
- clip slide onto the stage
- select lowest powered objective lens
- use coarse adjustment knob for rough focusing
- use fine adjustment knob for finer focusing for a clearer image.
- switch to a higher powered objective lens to see the specimen with a higher magnification.
1 division on the stage micrometre is?
0.1mm
formula linking image size, actual size, magnification?
image size = actual size x magnification.
What is magnification?
how much bigger the image is than the specimen
What is resolution?
The ability to be able to distinguish between two distinct points on an image.
cell surface membrane?
- regulates the movement of substances into and out of cells.
- has receptor molecules which respond to chemicals eg hormones
nucleus
- controls activity of the cell
- where genetic information is stored, replicated, copied into RNA
nucleolus
makes ribosomes
nuclear envelope
protective double layer with nuclear pores.
lysosome
- contain powerful hydrolytic enzymes called lysozymes
- breaks down worn out cell components or digest invading cells.
ribosome
- site of protein synthesis.
rough endoplasmic reticulum
- folds and processes proteins made at the ribosomes.
smooth endoplasmic reticulum
- site of lipid and carbohydrate synthesis
- storage
vesicle
- transports substances in and out of the cell.
- formed by golgi apparatus, endoplasmic reticulum
golgi apparatus
- receives proteins from rough ER
- modifies and processes molecules (e.g new lipids and proteins) and packages them into vesicles.
- makes lysosomes.
mitochondrion
- site of aerobic respiration
- ATP is produced by them.
chloroplast
- site of photosynthesis
- grana
- stroma
centriole
- involved in separation of chromosomes in cell division
cilia
- for locomotion
- waft substances along the cell surface.
- microtubules allow them to move
flagellum
- enables cell mobility
- microtubules contract to make the flagellum move
- propels cells forwards
what us the cytoskeleton composed of?
- microfilaments
- microtubules
- intermediate fibres
cell wall
- gives plant cell structure mechanical support.
- gives plant cells their shape.
- cellulose
what is the importance of the cytoskeleton?
- providing mechanical strength to cells
- aiding transport within cells (microtubules)
- enables cell movement.
Interrelationship between organelles (protein production and secretion)
- DNA in the nucleus contains the gene to make protein.
- This gene is copied by mRNA and is taken out of the nucleus via nuclear pore and to the ribosome.
- protein is synthesised at the ribosome (bound to RER)
- protein passes into cisternae of RER and is packaged into a vesicle.
- vesicle moves to Golgi apparatus and fuses.
- Protein is structurally modified and processed.
- Golgi apparatus repackages the protein in a secretory vesicle.
- secretory vesicle travels along microtubules, and fuses with cell surface membrane.
- contents released by exocytosis.
what is cisternae
rough ER has flattened stacks of membrane bound sacs which forms sheets called cisternae.
Special features of prokaryotic cells?
- 70s ribosomes
- no nucleus
- no membrane bound organelles
- plasmids
- single strand of DNA free in cytoplasm
- cell wall
- sometimes have flagella
- bacteria
- circular DNA
Special features of Eukaryotic cells?
- 80s ribosomes
- DNA enclosed in nucleus
- has membrane bound organelles.
- plant and animal cells
- linear DNA
what type of microscope is needed to see bacterial cells?
electron microscopes.
