Membrane Movement Flashcards
Main component of membrane
phospholipid bilayer
Hydrophilic head
Hydrophobic tail
Cell membrane function
- Physical Isolation
- Regulation of exchange with the environment (what molecules can or can’t move in)
- Communication between the cell and the environment (nervous system, endocrine system)
- Support and structure (like skin, connect to cytoskeletal system)
What is the four ring structure found in a cell membrane?
Cholesterol (also a lipid)
What does cholesterol do in the membrane?
- fill the gap between two phospholipids
- Make it more flexible or more rigid
Why does the birth control patch work?
Because it is a cholesterol based molecule (steroid hormone) and therefore can go through the lipid bilayer
Membrane proteins
- Transporters: help molecules that need to go through cell membrane
-important for long distance - Structural:
-connect to the cytoskeleton system
- make cell change the structure and move - Receptors: can pick up signals and trigger response
-cascade effect - Enzymes: Helps reactions move forward
Movement across membrane depends on?
lipid solubility: if molecules are lipid soluble it can easily go through membrane
Size: small molecules go through membrane easily
Uncharged/polar: non charged molecules can easily go through and non polar
What energy does passive transport use?
Concentration gradient
What helps glucose go through the membrane?
Glucose carrier through facilitated diffusion.
Which are the two glucose carriers?
-GLUT2
-GLUT4: insulin triggers more of this glucose carrier to lower blood sugar levels
Facilitated diffusion brings glucose into the cell down its concentration gradient.
Carriers go through conformational change
What is G6P?
glucose can be converted into G6P so that glucose can keep coming in and diffusion doesn’t reach equilibrium.
Do carriers get saturated?
yes
Do channels get saturated?
NO
What affects diffusion rate?
- Temperature- higher temp, faster
- Size- smaller, faster
- distance- shorter, faster
- Surface area- larger surface area, more diffusion
Channel carrier
Open channels create a water-filled pore
Do ion channels stay open?
No, if you leave the channel open for too long the ions will keep moving in and can create charge (not good) most are kept closed.
Types of channels
- voltage gated: cells voltage change and gate opens
- Mechanically gated: mechanical force to open
- Ligand gated: something binds to channel and it opens
What energy does active transport use?
ATP (works against concentration gradient)
Characteristics of mediated transport
- Specificity: binding sites are specific (ex. Na+ and K+)
- Competition: have limited seats so you will have competition with molecules)
- Saturation: how many molecules can be transported per time
Secondary active transport (indirect active transport)
- active transporter of X molecule moves from [low] to [high] to set up gradient for X
- X binds to secondary active transporter for Y against gradient
- pump stops working –> transport stops
no ATP
Symporter
Move in the same direction
Antiporter
move in opposite direction
