5. Cell Organelles Flashcards
Why are cells typically very small?
- Greater SA:Vol -> enables food and waste to be imported + exported efficiently.
- Small structures have greater integrity.
What are the major classes of cells and what are their differences? How do they reproduce?
Prokaryotic (bacteria) - singled celled, no nucleus, no membrane bound organelles. Reproduce by binary fission.
Eukaryotic - single nucleus, membrane bound organelles. Reproduce mostly by sexual or asexual budding.
What are the kingdoms of eukaryotic life?
- Plantae
- Animalia
- Protista (single celled)
- Fungi
LIST organelles do ANIMAL cells have that plants cells don’t
List: lysosomes, flagella, centrioles.
LIST organelles do PLANT cells have that animal cells don’t?
List: tough cell wall, plasmodesmata, central vacuoles, chloroplasts, amyloplasts.
LIST techniques for studying cells
Light microscopy (can use a stain), super-resolution microscopy, electron microscopy, X-ray crystallography, synchrotron.
What are limitations of light microscopy?
- Limit of diffraction. (Abbe’s limit)
2. Need contrast to see difference between two objects (solved by staining)
What kind of stains are there for light microscopy?
Methylene blue - stains nuclei of animal cells
Eosin - stains cell walls, cytoplasmic material and extracellular structures red or pink.
Some stains fluoresce when excited by UV.
What is super-resolution microscopy?
Employs ‘selectively depleted’ fluorescence and multiple lenses to capture 2D and 3D images at greater than 0.2um detail.
What is electron microscopy?
Uses a stream of electrons to create extremely high magnification images. Must be viewed under vacuum (sampels are dead), and have to be coated in heavy metal. Two kinds: SEM and TEM.
What is difference between SEM and TEM?
Scanning EM - samples reflect electron beam back to detector. Good 3D shape of sample.
Transmission EM - electron beam passes through sample -> best resolution.
How does X-ray crystallography work?
Works by scattering X-rays are regions of electron density within sample. The more electrons = more scattering. Proteins/cell components are isolated, purified then crystallised before X-Ray diffraction.
How do you study organelles?
Isolate it. If sturdy, use tissue grinder.
Cell press - uses sudden change in pressure to cause cells to pop under own internal pressure.
List membrane bound organelles (7 items)
- Nucleus
- Nucleoid
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Lysosome
- Vacuole
List non-membrane bound organelles (4 items)
- Ribosome
- Cytoskeleton
- Flagella
- Centriole
What is the nucleus?
Stores genetic information and where ribosomes are assembled. Porous and continuous with ER.
What is nucleoid?
In prokaryotes. Poorly defined region in centre where single circular chromosomes of bacteria are kept.
What is mitochondria?
Organelle that provides eukaryotes ATP via aerobic respiration. Has outer and inner membrane, separated by intermembrane space. Inner membrane has mitochondrial matrix. Own DNA from maternal line.
What is ER?
ER: Folds of membrane bilayer - one of the sites of protein synthesis. Rough ER = close to nucleus, . Continuous to RER = Smooth ER - site of many enzyme reactions and reservoir for Ca2+.
What is Golgi apparatus?
Downstream of ER, also protein modification and trafficking. 3 types: cis (closest to nucleus), medial, trans (further from nucleus).
What is lysosome?
Helps breakdown large molecules like protein and polysaccharide. Has digestive enzymes and low pH. Repairs plasma membrane.
What is vacuole?
Large central sac of plant and fungal cells. Storage of harmful substances or water products. Often acidic pH.
What is ribosome?
Organelle. Read mRNA to make polypeptides. 2 subunits.
What is cytoskeleton?
Network of protein tubes that give cell structure. 3 kinds: microtubules, intermediate filaments and micro- or actin filaments.
