Cells And Celll Structure Flashcards
Define resolution
Minimum distance between 2 objects where they can still be viewed as seperate
What’re the features of light microscopes
A beam of light is condensed to make images
- lower resolution due to higher wavelength
-lower magnification
-coloured images
-can view living samples
What’re the features of electron microscopes
-beam of electron condensation condensed by electromagnets
-higher resolution and magnification
-black and white 3d images
-sample must be in vacuum so electrons aren’t absorbed by air
What’re the features transmission electron microscopes
- thin specimen
- electron beam passes through specimen
- some parts absorb electrons and then appear as dark
What’re the features of scanning electron microscopes
-specimens not as thin
-electrons scattered onto surface and produce 3D images
What’re the limitations of electron microscopes
-whole system must be in a vacuum and therefor living specimens can’t be observed
-a complex staining process is required and even then the image is only in black and white
- specimen must be extremely thin
- image could contain artefacts (things that result from the way specimen is prepared)
What’s cell fractionation
When cells are broken up and organelles are separated out
Why is tissue placed in cold isotopic buffered solutions
Cold- reduce enzyme activity that could break down organelles
Isotonic - prevent organelles from gaining or losing water by osmosis (no shrink or burst)
Buffered solution- maintain constant pH
What’s homogenation
Cells are broken by homogeniser (blender) which releases organelles from cells. Homogenate fluid released as a result of fluid being filtered.
What’s ultracentrifugation
Filtered fragments separated in ultracentrifuge machine where you spin homogenate tube at high speeds and heaviests organelles turn into sediment and supernatant is the left over homogenate fluid.
Describe the structure and function of the nuclear envelope
Double membrane surrounding nuclear,close to endoplasmic reticulum,allows entry and exit of materials
Describe the structure and function of the nuclear pores and nucleoplasm
Nuclear pores- allow passing of large molecules
Nucleoplasm- granular jelly like material which makes up most of the nucleus
What does the nucleolus do
Manufactures ribosomal RNA and assembles ribosomes
What’re the 3 overall functions of the nucleus
- produce mRNA and tRNA
-retain genetic material in chromosomes - make up ribosomes
Why do mitochondrion have an inner membrane
To control entry and exit to material
What are cristae
Extensions of the inner membrane which are folded to increase surface area and allow attachment of enzymes and proteins.
What does the matrix contain and what is its function
Contains lipids proteins ribosomes and enzymes,allow mitochondria to make its own proteins.
What’s the function of the chloroplast and what does it contain
Photosynthesis, chloroplast envelope,grana,granal membrane and stroma
What’s a grana
Stacks of thylakoids where chlorophyll is stores,some thylakoid have extensions to join with others in the adjacent grana where light absorption takes place.
What’s the stroma
Fluid filled where synthesis of sugar takes place
How is the chloroplast adapted to its functions (3)
Granal membrane provides large SA for attachment of chlorophyll,electron carriers and enzymes
-stroma fluid has all enzymes needed to synthesize sugar for photosynthesis
-contains dna and ribosomes to manufacture needed proteins for photosynthesis
Wha are the tubules and sacs on the membrane of the ER called
Cisternae
What’s the structure and function of the rough endoplasmic reticulum
A series of flattened sacs enclosed by a membrane with ribosomes on the surface,it forms and processes proteins made on the ribosomes
Describe the structure and function of the smooth endoplasmic reticulum
A system of membrane bound sacs,it produces and processes lipids
