Exam 2: January 23-27 Flashcards
what are the functions of the plasma membrane?
1) it’s the boundary around our cell that acts as a discriminating barrier
2) it binds chemical messengers through the proteins on the surface of the cell
3) it sets cell characteristics such as shape and motility
how does the plasma membrane set cell characteristics?
it can set the shape and motility
cells can move themselves sometimes instead of being immobile
it can also be a connection to other cells which is needed to make tissues which turn into organs
also connects cells with the EC matrix
what are the components of the plasma membrane?
1) phospholipids
2) cholesterol
3) proteins
4) glycocalyx
what form does the plasma membrane have?
it’s a fluid mosaic model
you expect it to be constantly moving and made of lots of components
what are phospholipids?
part of the plasma membrane - the main building block of the PM
it has a polar head with 2 non polar tails = amphipathic
polar heads like being associated with intercellular fluid while tails don’t so they group together and bond due to hydrophobic bonding and a bilayer forms spontaneously
what is cholesterol?
part of the plasma membrane
1:1 relationship with the phospholipids
how does cholesterol prevent certain molecules from getting through the PM?
small polar molecules can’t go through the membrane as easily
Na+ get’s bounced easily by the hydrophobic tails because it’s charged however, water isn’t charged but it’s polar and it can slip through the gaps in the membrane but cholesterol fills those gaps
what function does cholesterol serve?
increases stiffness of the PM
allows for controlled bending of phosphomembrane and without cholesterol you couldn’t make a sphere shape
also helpful for vesicle formation!
what is a protein?
1:50 ratio with phospholipids but they’re actually half the mass of the plasma membrane aka they’re really big
what are the two types of proteins?
1) integral
2) peripheral
what are integral proteins?
ALWAYS amphipathic because part of it is in the phospholipid membrane and the other is associated with the interstitial/intercellular fluid
most are transmembrane proteins but not always
cannot be removed from the membrane without destroying the PM
what are the types of integral proteins?
1) channels
2) receptors
what are channels?
a type of protein which allow polar compounds to cross the membrane without having to associate with the non polar region
what are receptors?
a type of protein that is on the surface of the cell and receives signals and can also be anchors
what are peripheral proteins?
predominantly on the intracellular cellular fluid side aka the inside of the cell
can impact the shape and motility of the cell
proteins on the outside are extracellular matrix proteins
what is the glycocalyx?
the branch sugar structures that we find on the extracellular fluid side of our membrane - we don’t see it on the inside
it can be attached to phospholipids and integral proteins
causes a fuzzy appearance – glycocalyx is 3D and you can only focus on one plane at a time so it’s easy to focus in inside of PM but not the outside with a microscope
what are the functions of the glycocalyx?
1) identification
2) mechnical protection
3) limits cell growth
how does the glycocalyx serve as identification?
the glycocalyx on Bronson’s cells are different than mine
how does the glycocalyx serve as mechanical protection?
glycocalyx kind of stick out and look like hairs on our arm and they help us to prevent things from getting to our skin so the glycocalyx gives us mechanical protection for our cells so things can’t get to integral proteins or our phospholipids
how does the glycocalyx limit cell growth?
it limits how close cells can be to each other so it limits cell growth
what are junctions?
direct linkage of cells
what are the types of junctions?
1) gap junctions
2) desmosomes
3) tight junctions
what are gap junctions?
they are direct linkages that are small channels created by proteins called connexons
it’s multiple connexons that help make the gap junction
not that strong
what are gap junctions made by?
proteins called connexons
is there ICF or ECF flow with gap junctions?
ICF flow? Yes! Things can move from cell to cell without leaving either cell - whomever this is also limited because you can’t move huge things through them, only small things
ECF flow? Yes! water can just go around the gap junctions and get around them like it it’s raining and you’re standing under a walkway you’ll still get wet because water can go around the tunnels
what are desmosomes? what are they made up of?
made up by cadherin protein linkages where cadherin linkages are proteins that both cells have
it’s the strongest connection
is there ICF or ECF flow with desmosomes?
ICF flow? No! there’s not peace for anything to move because it’s just proteins linking up and forming a bond
ECF flow? Yes! because just like gap junctions you can go right around it
like two people’s arms stuck together by gum
what are tight junctions? what are they made up of?
they create the sealing of our plasma membrane
they’re made of claudin protein linkages which are also proteins that come from both cells
we’re creating a zipper around the cell, not buttons - multiple cells are connecting all the way around
forces movement through the cell aka transcellular so you have more control since your membrane is selective
you want this in epithelial cells because they’re supposed to be a barrier and you don’t want things to be slipping through them
is there ICF or ECF flow with tight junctions?
ICF flow? No!
ECF flow? No!
why is ATP an energy source for cellular metabolic pathways?
Phosphates are high energy bonds because it’s a covalent bond which is very strong and breaking it releases a lot of energy
aka equation 1: ATP ADP + Pi + energy
you don’t invest ATP, you have to make it
what are the two ways to make ATP?
1) substrate level phosphorylation
2) oxidative phosphorylation
what is substrate level phosphorylation? where does it happen?
bound Pi transferred to ADP to create ATP
ADP + XP ←→ ATP + X
happens in glycolysis and TCA cycle
what is oxidative phosphorylation? what’s an example of it?
you create an energy input that allows us to transfer an unbound Pi to ADP
equation 1
happens in the electron transport chain
what is glycolysis?
breaking down of sugar = catabolism of sugar/carbohydrate
a series of 10 enzymatic reactions
where does glycolysis occur?
it doesn’t require a special compartment to occur it just occurs in the cytosol
what is the net production of glycolysis?
1 glucose gets us 2 ATP plus other products based on the conditions we run glycolysis under
what are the products of glycolysis if under aerobic conditions?
NADH and pyruvate
aerobic means there’s oxygen
what does NADH do?
it’s an intermediary that will help us move energy from one place to another
what are the products of glycolysis if under anaerobic conditions?
lactate and NAD+ are made from pyruvate and NADH
what happens if you’re under anaerobic conditions?
you get lactic acid build up when you’re under anaerobic conditions because you convert pyruvate to lactate so that you can convert pyruvate to lactate and NADH gets converted to NAD+ which is the “empty” dump truck
what is the oxygen dependence of oxygen?
glycolysis is independent of O2 because without oxygen we can still complete the process - it just changes the end point and we get lactate and NAD+ instead of NADH and pyruvate
how is glycolysis regulated?
the job of glycolysis is to make ATP so you don’t need to be running this process all the time
high [ATP] lessens glycolysis
high [ADP] increases glycolysis
what kind of phosphorylation is glycolysis?
substrate level phosphorylation
what are alternate names of the krebs cycle?
citric acid cycle or the tricarboxylic acid cycle or TCA cycle
what’s the relationship between the Krebs cycle and glycolysis?
the Krebs cycle starts with the catabolism of pyruvate aka glycolysis feeds into the Krebs cycle
what happens to the Krebs cycle if pyruvate isn’t available?
derivatives from amino acids and lipids
if we didn’t have enough glucose we could use the breakdown products from proteins (AA) and lipids (fats) to create ATP
where does the Krebs cycle occur?
mitochondria
8 enzymatic reactions
what is the net production of the Krebs cycle? what kind of phosphorylation is used?
2 ATP via substrate level phosphorylation plus CO2, NADH, and FADH2
what critical equation does the Krebs cycle rely on?
critical equation 3 because the Krebs cycle makes CO2 which then has to be dealt with
what is the independence on oxygen of the Krebs cycle?
the Krebs cycle is indirectly dependent on O2 because the krebs cycle will not work under anaerobic conditions
the reason it’s indirect is because there isn’t actually oxygen in the process - some other process that influences this one is what needs oxygen
how is the Krebs cycle regulated?
high [ATP] means less Krebs cycle
higher [ADP] means more Krebs cycle
how much ATP is made between Krebs and glycolysis?
4 ATP
2 from glycolysis and 2 from Krebs
what does the ETC do? where does it happen?
it recycles NADH and FADH2 to make NAD+ and FAD
takes the loaded dump truck and off loads them - what’s in the dump truck is electrons - it’s moving electrons through the proteins in our mitochondria
this occurs in the mitochondria
what’s the net production of the ETC?
28-34 ATP and H2O
dependent on other activities occurring in the mitichondria at the time
recycling the dump trucks gets you back NADHback so you can continue to run in aerobic conditions
what is the dependence on oxygen of the ETC?
directly dependent on O2
the ETC DOES NOT HAPPEN without oxygen because there’s oxygen directly in these steps
what happens to the water product of the ETC when you’re sick?
most of the time we’re making water but sometimes your immune system tweaks the process and you can instead make free radicals – this is why you need to stay hydrated when your sick because you’re making less water
what’s the summary of glycolysis, krebs and ETC?
glycolysis: glucose and other molecules fuel the process to make pyruvate which makes 2 ATP
Krebs: prtuvate from glycolysis makes acetyl CoA which goes through TCA cycle to make 2 ATP
ETC: electrons carrier by NADH and FADH2 through oxidative phosphorylation
what do tight junctions force us to do?
they prevent extracellular fluid movement which forces us to have to go across the plasma membrane barrier = transcellular movement
what is a discriminant barrier?
it’s not an absolute barrier
what is the purpose of the tails in the plasma membrane?
the non polar tails of the phospholipids in the PM limits polar movement across membrane because tails are non polar and are held together by hydrophobic interactions
what passes through the PM easily?
the PM is not a barrier to small non polar compounds
NP come out on the other side because there isn’t space for them to stay in the middle with eh tails
what has difficulty passing through the PM?
the PM is a barrier to any sized polar molecules and large non polar molecules
cholesterol makes it even harder for small polar molecules that could have possibly slipped through because cholesterol fills the gaps between the tails
large non-polar molecules have trouble moving across because it would disrupt the tail pattern and cause problems
what is used to get things across the PM?
proteins!
channels: create a gap like a regular door
transporters/carriers: revolving door
is everything always in constant motion?
Yes!
unless we’re at absolute zero (0K) components are always in random motion
what drives motion?
[X]
[X] = # of X/V
when does diffusion happen?
when [X] different between two areas
diffusion won’t happen if a gradient isn’t present - random motion will still be happening there just won’t be net movement
how does diffusion work?
you diffuse form high to low concentration areas
it will always follow the gradient! diffusion will NEVER happen against its gradient so the cell doesn’t have to put in any energy since the compounds are all moving naturally
what does diffusion depend on?
1) permeability
2) surface area
3) size of [X] gradient
4) distance
how does diffusion depend on permeability?
there’s a direct relationship between diffusion rate and permeability
the higher the permeability the faster the rate
a window with a screen with different gap sizes
how does diffusion depend on surface are?
direct relationship
how much space do we have for this diffusion to happen across?
the smaller the surface area the slower the diffusion rate
like a slightly open window vs. a wide open window
how does diffusion depend on the size of the gradient?
direct relationship
the bigger the gradient the bigger the diffusion rate
the bigger the hill the faster you’ll be able to go down it
how does diffusion depend on distance?
inverse relationship
if you take the two areas and start moving them apart it’ll take longer for diffusion to happen
diffusion has a problem with distance
our lungs and GI track are as thin as possible to make the distance as small as possible – so when distance gets larger, diffusion gets slower which is an inverse relationship
what are examples of things that can move across the PM?
the bilayer is small and non polar so the only things that can diffuse across are small non polar things like O2 and CO2
is the plasma membrane a barrier?
no! because things just diffuse from high to low - it’s like a chain link fence to hold in a mouse
this causes a storage problem!! we do better in making ATP if our cells are oxygenated and we aren’t in anaerobic conditions
but if we store oxygen in the cells then there isn’t enough in the interstitial fluid and the oxygen would flow out of the cell with its gradient
what can we do to make sure the cell is getting as much oxygen as possible?
1) If we want oxygen always going into our cell, we want loads of oxygen outside of our cells so that the gradient is constantly sending oxygen inside our cells
2) another way to keep oxygen in our cells is to bind the oxygen to something that is too big and can’t go across the membrane (like a cone on a pet) – for example we can store oxygen in our skeletal muscles by binding oxygen to myoglobin so we don’t have to go anaerobic and have acid lactic build up
what are channels?
they are solute specific!
sodium and potassium specific channels that other ions can’t move through
channels are diffusion so it’s also with the gradient and has no energy cost
what are the types of channels?
1) leak channels
2) gated channels
3) aquaporins
what are leak channels?
allows things to continually leak and they’re always open
relatively rare category (look like a hotdog bun)
what are gated channels?
only open when triggered – they can be either open or closed - there’s multiple ways that you can set up for how that gate can be open or closed
what are the types of gated channels?
1) chemically gated
2) voltage gated
3) mechanically gated
4) thermally gated
what are chemically gated channels?
binding ligand – when we bind something to a protein we change its shape that gets us from being closed to open
what are voltage gated channels?
electrical distribution change which changes the shape from being closed to open
what are mechanically gated channels?
stretch/deform the protein from closed to open form
this can happen in association with the membrane because it’s fluid mosaic model
what is a thermally gated channel?
heat/cool the protein and converts it from being closed to open
at the right temperature we have the right matching component
what is an aquaporin?
water doesn’t diffuse, it does osmosis
what is osmosis?
the net diffusion of H2O across a membrane
water will move from high to low water concentration
water goes from low solute concentration to high solute concentration
