Define diffusion
Which 4 factors does it depend on?
What are the 2 components of random motion? - answer-diffusion: random/non-directed motion of molecules and small particles in a liquid
factors:
1) driving force (i.e. gradient, temp.)
2) mechanical resistance of the surrounding medium
3) s...
Define diffusion
Which 4 factors does it depend on?
What are the 2 components of random motion? - answer-diffusion: random/non-directed motion of
molecules and small particles in a liquid
factors:
1) driving force (i.e. gradient, temp.)
2) mechanical resistance of the surrounding medium
3) structural properties of the molecule
4) active forces causing non-thermal fluctuations (i.e. contraction/relaxation of cytoskeleton moves
cytoplasm causing active diffusion)
components of random motion:
1) passive/thermal component
2) active/motor-driven component
How does the function of diffusion differ between prokaryotic and eukaryotic cells?
What is the function of diffusion in embryos?
When is diffusion favourable? - answer-prokaryotes: suitable for transportation
eukaryotes:
- suitable for transportation in micro-environments
- provides primary basis for signal transduction network in cytoplasm
embryos: important in development (i.e. morphogenesis to establish embryonic domains)
favourable when: molecules must travel relatively short distances
Time scales in diffusion:
- diffusion is dependant on _________
- why is diffusion sufficient at the synaptic cleft?
- as the distance traveled increases, the time it takes _________ - answer-- diffusion is dependent on
DISTANCE THAT MUST BE TRAVELLED
- synaptic cleft: small distance must be traveled for molecule to have an effect (i.e. diffusion can occur
quickly)
- as distance increases, time also increases
Active Transport:
- Why is active transport needed between different cellular components and living cells?
- What are 2 characteristics of active transport?
[Type here] [Type here] [Type
here]
,- What are the 2 active transport mechanisms seen? - answer-- cellular components/living cells:
associations between them cannot be accomplished by diffusion alone
1) directed motion via molecular motors along biopolymers (i.e. MTs or MFs)
2) useful when movement is required along long distances
------------
1) assembly/disassembly of cytoskeletal filaments
2) molecular motor-directed active motion
Molecular Motors:
- Important for transport of which 3 components within a cell?
- What is required for their function?
- How is movement achieved? - answer-- molecules, particles, organelles
- ATP or GTP hydrolysis
- chemo-mechanical coupling: chemical energy from ATP/GTP is converted into force via
conformational changes in motor proteins
Classes of Molecular Motors:
- What are the 4 classes of molecular motors, and how do they function? - answer-1) polymerization
motors: use actin/MT assembly to help cells generate direct force during movement
2) translational motors: move in a directional step-like fashion along polymerized protein track
3) translocation motors: help thread/pass through a hole (i.e. push/pull actions)
4) rotary motors: embedded in cell membrane and use rotation of mechanical elements to generate
torque
Cytoplasmic Streaming:
- what is it?
- where is this phenomenon observed? (5)
- what is its proposed purpose? - answer-- cytoplasmic streaming: circulation of cellular fluid (i.e.
cyclosis) driven by motor proteins walking along filaments containing organelles
- large cells in: algae, plants, amoebae, nematodes, flies
- purpose: by-product of transportation (i.e. may help overcome slowness of diffusion in large cells)
Cytoplasmic Streaming in Algal cells:
- which 2 components was myosin V found to interact with?
[Type here] [Type here] [Type
here]
, - what do actin filaments serve as?
- what is seen as vesicles move along actin filaments? - answer-- ER and stationary actin bundles
- actin filaments: serve as TRACKS for motor proteins
- as vesicles move, cytoplasm moves with it (i.e. directional/stream-like movement)
MODULE 3 LECTURE 2:
Translational Motors:
- cargo carried at the _____ end, whereas catalysis/hydrolysis of ATP at the ______ end
- what are they associated to?
- _________ motion via step-by-step fashion
- relationship between ATP hydrolysis and stepping motion?
- association to filament depends on __________ not ___________.
- Explain processivity, and which 2 factors influence it - answer-- cargo --> tail end
- ATP hydrolysis --> catalytic motor head
- associated to filamentous polymer (i.e. actin, MTs)
- unidirectional
- ATP hydrolysis is coupled to stepping motion (i.e. to generate movement)
- AFFINITY not covalent interactions
- processivity: number of steps that a single motor can take before it falls off
*depends on:
a) protein type
b) polymer network
What are the 3 translational motors discussed in lecture?
What end do the following proteins move towards:
- dynein
- kinesin
- myosin - answer-1) dynein --> (-) end mostly
2) kinesin --> (+) end mostly
3) myosin --> (+) end mostly
Myosin:
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here]
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