Cell Physiology Flashcards
What is diffusion?
Net movement of a subst from where it is in a high concentration to where it is in a lower conc
How is dif across a membr affected by conc grad?
Increased the c.g- faster diffusion
Size of mol
Small mol diffuse faster than larger mol
Temp
Increase temp- increase diffusion as mol have more kinetic en
Thickness
V thin- ideal for rapid dif
S.a of membr
Greater sa- faster diffusion
Facilitated Diffusion
Supported/ fac by proteins
What do Carrier Proteins do?
Take in dif mol I.e glucose
Change shape
Rel mol on other side of membr
They have binding sites that match spec mol and assist movement of these mol across membr
What does (Ion) Channel Protein do?
These channels are formed by proteins with a central pore that enables charged particles (ions) to pass thru
Some are perm open vs others gated
Gated channels can open/close allowing contr of ion movement
Rate of facilitated diffusion is dep on no. Carrier/ channel proteins in membr
What does Active Transport do?
Conc grad- en req high to low conc
Inv protein carrier molecules
Subst to be transp binds to carrier protein
As with carriers in fac dif, carrier changes shape
Rel transp subst on other side of membr
Carriers are spec to partic type of mol/ion
What are the 2 key dif between active transport and fac dif?
1: subst moved against conc grad
2: met en in form of ATP req
What do cells that carry out a lot of active transport?
Large no. mitochondria- supply ATP for a.t
What is cytosis?
Subst transp in and out of cell w/o passing thru membr itself
Why is the process of cytosis imp in transp?
1: Large mol too big for carriers
2: Bulk transp of smaller mol
What is endocytosis?
Cell surf membr invaginates around a subst entering cell from outside to form membr bound sac/ vesicle which then pinches off inside of cell surf membr
When vesicles taken into cell, fluid nature of cell surf membr allows it to reform and close gap created by cytosis
Phagocytosis
Inv transp of s mat into cell e.g. engulfing of bacteria by phagocytes
Pinocytosis
Inv transp of fluid into cell
What is exocytosis?
Movement of subst out of cell
Descr process of exocytosis
Secretory vesicles( poss having budded off from GA) move to and fuse with cell surf membr
Contents of vesicles released outside cell
Creation of gap in cell surf membr is followed by reforming of membr
What is osmosis?
Net movement of water from high water conc (dilute) to low water conc across spm
Hypertonic vs Hypotonic
Stronger sol vs weaker sol
Isotonic
If 2 sol have equal conc= isotonic- no osmosis
What is water potential?
Tendency to take in water across spm
Why is pure water 0kPa?
All water mol free- not forming associations with other water mol
In sol some of water mol not free as they form hydr shells around solutes
Why does solution always have a negative water pot?
Always some water in hydr shells
How does a high conc solution affect water in cell?
The more neg Wp as more water bound up in hydr shells and not free
More likely to take in water by osmosis
What is osmosis in relation to Wp?
Net movement of water through selectively permeable membrane from soltuion of less neg water pot to sol of more neg water potential
What is the solute potential?
The potential of a solution to take in water
What is this affected by?
Affected by space avail within the cell
Descr the turgidity of a cell and its effect on ab to take in water
Turgid cell still has potential to take in water- more conc than pure water b/c turgid may be unable to take in water as there is no space
What is pressure potential?
Effect of pressure on the solution
What in particular inf the ability of turgid plant cell to take in/ lose water by osmosis?
Turgid plant exerts considerable pressure on cell wall
What is equ for water pot of cell?
Wcell= Ws+Wp
How is turgor support created?
Opposing forces of cell membr and cell wall on each other help create turgor support itself
What is flaccidity?
Ceases to turgid- wilts
What is plasmolysis?
Loses water by osmosis- vacuole shrinks to the extent where cell membr pulls away from cell wall (except at points where adj. protoplasts are joined via plasmodesmata)
What is incipient plasmolysis?
the point at which cell membr just begins to lose contact with cell wall
What may cause plasmolysis?
Plants growing in a field that has been given too much fertiliser
Seed from woodland tree being carried to salt marsh and starting to germinate in this env.
What is osmosis in animal cells like?
No cell wall- so nothing to stop expansion of cell membr until it bursts (lysis)- hypoton sol takes place
What happens when animal cell placed in hypotonic sol?
Cell loses water by osmosis, shrinks and shrivels up (crenation)
