2.1 - Cell structure Flashcards
(35 cards)
Describe the structure and function of the cell-surface membrane
- phospholipid bilayer
- proteins: receptors
- cholesterol: controls membrane fluidity
Function: control what enters and leaves the cell
Describe the structure and function of the nucleus
- contains chromosomes, 1 or more nucleoli
- nuclear envelope: controls passage of ions, molecules, RNA, between nucleoplasm and cytoplasm
- nucleolus: assembling ribosomal subunits
- chromatin
- nucleoplasm
Function: genetic info to code for protein synthesis
Describe the structure and function of the mitochondria
- cristae
- mitochondrial matrix: contains respiratory enzymes
- double membrane
Function: producing ATP via aerobic respiration
Describe the structure and function of a chloroplast
- thylakoids
- grana
- lamellae
- stroma
- double membrane
Function: site of photosynthesis
Describe the structure and function of the Golgi apparatus
- apparatus: modifies and packages proteins and lipids
- vesicles: transport these to target cells
- also produces lysosomes
Describe the structure and function of the rough endoplasmic reticulum (RER)
ribosomes on its surface
Function: folds and processes proteins
Describe the structure and function of a ribosome
- small and large subunit
- no membrane
Function: site of protein synthesis
Describe the structure and function of the smooth endoplasmic reticulum (SER)
similar to RER but no ribosomes
Function: makes and processes lipids
Describe the structure and function of the cell wall
plants + algae: cellulose
fungi: chitin
bacteria: peptidoglycan
Function: provide structural support to cell
Describe the structure and function of a lysosome
- vesicle containing digestive enzymes
- bound by a single membrane
Function: breakdown of proteins, polysaccharides, lipids, nucleic acids, old organelles
Describe the structure and function of a vacuole
- surrounded by tonoplast
- cell sap
Function: keep cell rigid and isolate unwanted chemicals
Describe the function of the cytoplasm
site of many metabolic reactions in the cell
List the key differences between a eukaryotic and prokaryotic cell
- prokaryotes are smaller
- prokaryotes have no membrane-bound organelles in cytoplasm, eukaryotes do
- eukaryotes have golgi and mitochondria, prokaryotes don’t
- prokaryotes have smaller 70S ribosomes whereas eukaryotes have larger 80S
- prokaryotes have single circular free-floating DNA molecule, eukaryotes have nucleus
- prokaryotic DNA not associated with proteins, eukaryotic is
- prokaryotes have a murein cell wall, eukaryotes have no cell wall
List features that SOME prokaryotes have, but not all
- 1 or more plasmids
- capsule surrounding cell
- 1 or more flagella
Describe the general structure of a virus and draw a diagram
- genetic material
- capsid (protein coat)
- attachment protein
- (sometimes lipid envelope)
Describe how an optical microscope works, as well as its advantages and disadvantages
- uses light and focuses using lenses
- advantages, sample shown in colour, live specimens can be used
- disadvantage: low resolution compared to other microscopes
Describe how a transmission electron microscope works, as well as its advantages and disadvantages
uses electrons and focuses using magnets
Advantage:
- high resolution due to shorter wavelength of electrons so smaller organelles can be observed
Disadvantages:
- only dead specimens can be used
- sample is shown in black and white
- requires thinner specimens
- requires complex preparation
- produces 2D images
Describe how a scanning electron microscope works, as well as its advantages and disadvantages
- uses electrons
- advantage: produces 3D images
- disadvantage: lower resolution than TEM
Define magnification
how many times larger the image of a specimen observed is than the actual size of the specimen
Define resolution
the minimum distance 2 objects can be distinguished as separate in an image
State the formula to calculate magnification
image size/actual size
Describe the process of cell fractionation and ultracentrifugation
- blend sample in homogeniser to form homogenate
- ensure solution ice-cold, buffered and isotonic
- filter homogenate to remove cell debris
- spin in centrifuge at low speed
- densest organelle forms pellet first
- decant supernatant and re-spin in another test tube at a higher speed
- next densest organelle forms pellet and so on
What are some examples of artefacts?
dust, air bubbles, fingerprints
Explain why the solution used in cell fractionation should be ice-cold, buffered and isotonic
- ice-cold: prevent enzymes damaging organelles
- buffered: keep pH constant so enzymes don’t denature
- isotonic: keeps water potential constant so no water enters or leaves the cell by osmosis, causing shrinkage or lysis
