Cells Part 1- Cell Structure And Microscopy Flashcards
Describe how a light microscopes work
Beams of light are condensed to form an image
Focused with a glass lense
What are the advantages and disadvantages of light microscope
Lower mag and reso
Alive, coloured, seen with eye
What is resolution
Minimum distance between 2 points at which can be distinguished from each other
What is magnification
How much bigger than image is than the specimen
What is the wavelength of an electron
0.01 to 0.001 nm
How to transmission electron microscopes work
Beams of electrons pass through the specimen
Parts absorb electrons appear dark
Produces a photo micrograph
What are the advantages and disadvantages of TEM
Smaller objects seen, higher resolution
In vacuum, no living, complex staining technique, extremely thin specimen, artefact, not coloured
How to scanning electron microscopes work
Beams of electrons directed on surface of specimen in a regular pattern
Builds 3D image after analysing pattern scattered electrons that gather in cathode ray tube
How to scanning electron microscopes work
Beams of electrons directed on surface of specimen in a regular pattern
Builds 3D image after analysing pattern scattered electrons that gather in cathode ray tube
What are the advantages and disadvantages of SEM
3D, high resolution, thicker
Vacuum, lower reso then TEM, complex staining, no internal structures seen
What conditions are needed for cell fractionation
Cold- reduce enzyme activity
Isotonic - Same water potential - prevent osmotic damage to organelle
Buffered- prevent denaturing
What are the stages of cell fractionation
1.) Homogenisation- cells are homogenised in a blender to beak them open. The resulting mixture is called cell homogenate (resultant fluid after homogenisation that contains the broken open cells and their components
2.) The homogenate is filtered through a gauze to separate any large cell debris, like connective tissue, from the organelle
3.) Ultracentrifugation- it is centrifuged at various speeds and durations to fractionate the cell components, forming a series of pellets. The heaviest organelles form pellet at the bottom. The supernatant is drained off and spun in a centrifuge at a high speed and the process is repeated
1.Break open cells/tissue and filter
OR
Grind/blend cells/tissue/leaves and filter;
Accept homogenise and filter
2. In cold, same water potential/concentration, pH controlled solution;
Accept for ‘same water potential/ concentration’, isotonic
Accept for ‘pH controlled’, buffered
3. Centrifuge/spin and remove nuclei/cell debris;
4. (Centrifuge/spin) at high(er) speed, chloroplasts settle out;
Why can the same organelle appear differently within the same cell
Cells are a cut/ cross section
Mitochondria are orientated differently
What is an artefact and why should they be minimised
Visible entity that resembles structural detail of specimen
Not a legitimate feature of the specimen
What are the functions of the nucleus
Ribosomal rna- assemble ribosomes
mRNA - protein synthesis
Protect dna and genetic information
Replicate dna for cell division
What is the nuclear membrane for
Outer and inner membrane
Protect and enclose dna
Pores
What is the nucleoplasm for
Controls cell activities
Contains chromatin
What are nuclear pores
Allow sentry of substances
Nucleotides for dna
Exit of mRNA for protein synthesis
What is the nucleolus
Small spherical
Makes rna- ribosomes
Describe and give the function of mitochondria
Repsiration for Krebs cycle
Production of atp
Double membrane
Cristae - folds, increase sa (attachment of enzymes)
Matrix- semi rigid. Site of Krebs cycle
Adaptations of rough Endoplasmic respiration
Ribosome sof surface
Large sa
Pathway to transport proteins throughout cell
Protein synthesis
Adaptations of smooth Endoplasmic reticulum
Synthesises, stores and transports lipids and carbohydrates
No ribosomes
Extension of nuclear membrane (more tubular)
Ribosomes
2 subunits - rna, protein
80s- larger
70s- prokaryotic
Adaptations and function of Golgi body
Made from lipids and proteins
Receives vesicles from ER
Modifies by adding
Produces transport vesicles to move or membrane
Exocytosis- vesicle fuses with cell surface membranes to release contents out of cell
Adaption and functions of lysosomes
Breakdown material ingested by phagocytosis cells- engulf and destroy
Release enzyme
Formed in Golgi body
(Lysosome fusion eight vesicle sand release hydrolytic enzymes)
Adaptation and functions of chloroplast
Site of photosynthesis
Double plasma membrane - isolate reactions
Stoma- fluid filled matrix. Synthesis of sugars
Starch grains
Grana- contains chlorophyll and stacks of thylakoids - light absorption
Adaptation and functions of chloroplast
Site of photosynthesis
Double plasma membrane - isolate reactions
Stoma- fluid filled matrix. Synthesis of sugars
Starch grains
Grana- contains chlorophyll and stacks of thylakoids - light absorption
Function of vacuole
Fluid filled sack
Loneplast- single membrane
Solution of : water, minerals, sugar, salt, amino acids, wastes, pigments
Storage vesicle, waste disposal, protection, growth
Makes the cell turgid
What is in the cell wall of algae
Cellulose
Glycoproteins
What is in the cell wall of fungi
Chitin
Glycon
Glycoproteins
What is a capsule
Late rof slime
Protects cells form other cells
Groups of bacteria to stick together
Give structures that are found in both prokaryotic and eukaryotic cells
Cell membrane
Ribosomes
Cytoplasm
DNA
Compare and contrast a prokaryotic and eukaryotic cell
- Magnification (figures) show A is bigger than B;
- A has a nucleus whereas B has free DNA;
- A has mitochondria whereas & does not;
- A has Golgi body/endoplasmic reticulum whereas B does not;
5.-
A has no cell wall whereas B has a murein/glycoprotein cell wall;
Accept peptidoglycan - A has no capsule whereas B has a capsule;
A has DNA is bound to histones/proteins whereas B has
DNA not associated with histones/proteins
OR
A has linear DNA whereas B has circular DNA: - A has larger ribosomes;
Outline the organelles in the production, transport and release of proteins form eukaryotic cells
- DNA in nucleus is code (for protein);
- Ribosomes/rough endoplasmic reticulum produce (protein);
Accept rER for ‘rough endoplasmic reticulum’ - Mitochondria produce ATP (for protein synthesis);
- Golgi apparatus package/modify:
OR
Carbohydrate added/glycoprotein produced by Golgi apparatus;
Accept body for ‘apparatus - Vesicles transport
OR
Rough endoplasmic reticulum transports; - (Vesicles) fuse with cell(-surface) membrane:
Accept exocytosis at cell membrane
Contrast how optical and TEM work and contrast limitations of use while studying cells
TEM use electrons and optical use light;
TEM allows a greater resolution;
(So with TEM) smaller organelles / named cell structure can be observed
OR
greater detail in organelles / named cell structure can be observed:
TEM view only dead / dehydrated specimens and optical (can) view live specimens;
TEM does not show colour and optical (can):
TEM requires thinner specimens;
TEM requires a more complex/time consuming preparation;
TEM focuses using magnets and optical uses (glass) lenses;
‘clearer’ is not equivalent to ‘detail”
Accept ‘Only optical can view live specimens”
5. Accept ‘Only optical can show colour
Accept ‘TEM requires a more difficult preparation
Ignore references to artefacts
Desire how you count make a temporary mount of a piece of plant tissue to observe the position of starch grains
Add drop of water to (glass) slide;
Obtain thin section (of plant tissue) and place on slide / float on drop of water;
Stain with / add iodine in potassium iodide.
- Allow any appropriate method that avoids trapping air bubbles
Lower cover slip using mounted needle.
What structures do viruses consist of
Lipid envelope, matrix, capsid, Nucleic acid, reverse transcriptase, attachment proteins, mesosomes
What are the similarities and differences between mitosis and binary fission
Both replicate dna, identical daughter cells produce
No nucelus, no nuclear membrane breaks down, no chromosomes, plasmids replicate, no membrane-bound organelles, no spindle fibres
What are kinetochores
Protein complex on centromere, attachment point for spindle microtubules
What are chromatids
Replicate chromosomes / identical copies of chirmsomes
Joined at their centromeres
Following dna replication
