2.1 - Cell structure Flashcards
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)
- has 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
making and processing lipids
Describe the structure and function of the cell wall
- cellulose in plants + algae, chitin in fungi, peptidoglycan in bacteria
Function: provide structural support to cell
Describe the structure and function of a lysosome
- vesicles 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 do
- 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
- live specimens can be used
- adv: sample shown in colour
- disadv: 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
Adv: - high resolution due to shorter wavelength of electrons so smaller organelles can be observed
Disadv:
- 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
- adv: produces 3D images
- disadv: 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, which could cause shrinkage or lysis
Order that organelles form a pellet in ultracentrifugation
- nuclei
- chloroplasts (if using plant tissue)
- mitochondria
- lysosomes
- ER
- ribosomes
Describe the structure and function of centrioles
- hollow cylinders containing ring of microtubules
Function: produce spindle fibres for cell division
Describe the structure and function of capsule
- protective, slimy layer
Function: helps cell to retain moisture and adhere to surfaces
Describe the structure of a plasmid
circular DNA
Describe the structure of a flagellum
tail-like structure which rotates to move the cell
Describe the structure of pili
hair-like structures which attach to other bacterial cells
Name structures prokaryotes contain that eukaryotes don’t
- cell wall
- capsule
- plasmid
- flagellum
- pili
Name differences between DNA in chloroplasts and nucleus
chloroplasts: DNA not associated with histones
nucleus: DNA associated with histones
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells
- DNA in nucleus is code
- ribosomes produce protein
- mitochondria produce ATP for protein synthesis
- golgi package/modify proteins
- vesicles transport proteins
Name an organelle found in both a chloroplast and a prokaryotic cell
ribosome
Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical microscope
- add drop of H2O to slide
- obtain thin section of tissue and place on slide
- stain with I2
- lower cover slip using mounted needle
