lecture 3 Flashcards
why do we compare ATP hydrolysis to a 20 dollar bill?
-big enough to do something with
-small enough to aviod too much waste (any energy not harnessed by that enzyme in the hydrolysis reaction is just dissipated as heat and entropy
true or false, cytoplasm is an active material
true
give a few theories about the definiiton of cytoplasm
-watery interior of a cell
-material in which organelles are embedded
-region outside of the nucleus
what does the consistency of cytoplasm depend on
depends on who you ask
what are the characteristics of the cytoplasm?
-cytoplasm is crowded
-cytoplasm is a rough-and-tumble place
-cytoplasm is viscous
-cytoplasm is elastic
-cytoplasm is a meshwork
-cytoplasm is an active material
how is cytoplasm crowded?
contains lots of different molecules: ions, water, sugars, amino acids, small molecules, proteins, DNA, RNA, organelles
how crowded is the cytoplasm?
-as crowded as protein crystals, which are ordered packed lattice of proteins that form a solid crystal in a dish
what is the percent protein per weight in protein crystals and in red blood cells?
-protein crystals: 20-60 percent by weight
-red blood cells: 35 percent protein by weight
what do we mean by cytoplasm is a rough-and-tumble place?
proteins constantly colliding with one another, being smashed around by thermal energy
why do molecules move constantly
brownian motion
what is the coefficient D? what does it mean?
characteristic diffusion coefficient (smaller molecules=faster diffusion=larger D)
true or false, Brownian motion explores a lot of space, but you get nowhere on average
true (steps end up cancelling each other out)
what is the structure of proteins distorded by
collisions
is the cytoplasm empty or packed
packed asf
what is inertia?
Resistance of an object to any change in its state of motion
what is viscosity?
a measure of a fluid’s resistance to flow
what is reynold’s number? whats the principle formula (definition)
it represents the relationship between inertia and viscocity
Re=inertial forces/viscous forces
what is negligible in cytoplasm?
inertia
what reynold’s number do cells, organelles, and proteins have? what does this mean
a very low number
this means that their viscous forces are much higher than their inertial forces, which is why from the perspective of a protein in a cell, if it stops moving, it comes to an immediate stop (wont glide cause has no inertia)
low reynolds number=no inertia
Re of bacteria swimming vs human swimming?
bacteria: 10^-4
human: 10^4
how is the cytoplasm elastic?
elasticity: The tendency of an object to return to its original shape after deformation
if i poke cell with needle, it will return back to its shape
why do we say that the cytoplasm is a meshwork?
-actin filaments, organelles, polymers, and other structures define the pore size, therefore restricts movement of some particles (only some can move through)
what is cytoplasm like for an ion?
like salty water, cause they can easily move through little pores around them
what is cytoplasm like for a protein?
jelly (viscous, elastic, crowded)
what is cytoplasm like for a large protein?
glass (too big to move around
the fact that ions, proteins, and big proteins feel different in cytoplasm is explained by what?
the meshwork of the cytoplasm lets certain molecules move freely (small ones like ions), and restricts others (proteins)
what do we mean by the fact that cytoplasm is an active material?
constant energetic churn driving the motion of the molecules and particles inside of it
what does carbon starvation do to a bacteria? why?
turns their cytoplasm into glass, therefore they freeze in space
in absence of metabolic activity, motion of particles inside cell dramatically change
is diffusion active or thermal?
active
what is the difference between the movememnt of particles in cytoplasm and the movement of particles in a test tube?
test tube: movement due to brownian motion, which is a property of thermal energy
cytoplasm: particles moving thanks to diffusion, and energy released by the active dissipation of ATP is powering this. we still have a bit of movement from thermal energy, but most is from active sources
what happened to the cell treated with DNP? why?
IT FROZE
because DNP depletes amount of ATP
what happens to cytoplasm as organisms age?
cytoplasm becomes rigid
