Test 3 Flashcards
What are the 5 main functions of cell membrane?
1) Boundary and permeability barrier
2) organization and localization of function
3) Transport processes
4) signal detection
5) cell to cell communication
What is the function of boundary and permeability barrier?
To keep desirable things IN and undesirable things OUT
What prevents polar or charged molecules from crossing the membrane without help?
Hydrophobic interior
What is the membrane made of?
phospholipid bilayer with the tails pointing inside
What is the function of Organization and localization?
intracellular membranes compartmentalize various functions within organelles
-each organelle has particular proteins associated with its membrane that have specific functions
What is the function of Transport Process?
proteins found in each membrane can selectively transport solutes across the membrane
-selectively designed for what is suppose to come in and out
What is the function of signal detecting?
proteins found in the cell membrane detect electrical and chemical signals from outside the cell
What happens in cancer that pertains to signal detecting?
cells grow out of control and only happens if signaling pathways are messed up in which they stay on the entire time
What is the function of cell adhesion and communication?
Tight Junctions, Gap Junctions, Adhesive Junctions, membranes are made of proteins
What is more than half of the membrane composed of?
Protein
What is less than half of the membrane composed of?
Lipids
What are the three main classes of membrane lipids?
Phospholipids
Glycolipids
Cholesterol
What is Tay-Sachs disease?
body can’t break down gangliosides= accumulate in brain and nerves= impaired function, paralysis, severe mental deterioration, death
What does not contain cholesterol?
prokaryotes or mitochondria
True or False. Lipids are distributed equally in a membrane?
False, Glycolipids are exclusively in outer layer while PE, PI, PS are more prominent in the inner layer
Why can’t lipids flip flop?
due to the hydrophilic and hydrophobic layers. The hydrophilic head won’t go through hydrophobic areas
What are the 3 Movements/ explain that phospholipid molecules can do within membranes
Rotation (rotate in same spot) Lateral Diffusion (Moves within same layer) Transverse diffusion "flip-flop" ( lipid moves from one layer to other, but this can't be done on its own)
What lipid can be as high as 50% in the membrane?
cholesterol
The rigid structure of cholesterol causes membranes to what at higher temperatures?
Less fluid
Cholesterol also keeps fatty acid chains from packing how?
too tight
At lower temperatures, the structure of cholesterol gives the membrane what?
more fluid
Less cholesterol will pack between lipids in higher temperatures why?
because lipids will expand
More cholesterol will pack between lipids in lower temperatures why?
When lipids, which are packed tight, need more expansion
What does cholesterol reduce?
permeability of membranes to small molecules
What type of bond forms between phospholipid and cholesterol in membrane?
hydrogen bonds
What are lipid rafts?
areas in a membrane that are thicker and less fluid than the rest of the membrane
What are lipid rafts high in?
cholesterol, glycolipids and saturated fatty acids
Why do unsaturated fatty acids have more fluid?
because they are bent and allow for more space and more fluid. The saturated fats are straight and pack tighter together with less fluid
What molecules are easily permeable through membrane?
Hydrophobic molecules (O2, CO2, N2, benzene)
What molecules can get across as long as they are not charged?
H2O, urea, glycerol
charged molecules can’t get through hydrophobic interior
What is able to get across the membrane sometimes?
large uncharged polar molecules, glucose, sucrose
What is not able to get through the membrane unless with help?
Ions, H+, Na+, HCO3-, K+, Ca2+, Cl-, Mg2+
What types of molecules NEED to get in and out of membrane bound organelles?
Water, Oxygen/CO2, Sugars, Amino Acids, Ions, ATP
What are the holes in nucleus called/ what is the structure?
Nuclear pores that are filled with proteins and are highly regulated and controlled
How does a cell get molecules that are water-soluble (hydrophilic) ACROSS a membrane?
various proteins
What are the four protein processes?
Simple diffusion
Facilitated diffusion (carrier proteins)
Active transport
Facilitated diffusion (channel proteins)
What is Simple diffusion?
when molecules are small enough and uncharged and are able to cross without help
What is Facilitated diffusion through a carrier protein?
Carrier protein binds and carries the molecule and then releases
Does facilitated diffusion require energy?
If it is going with the gradient, then no. If going against, yes
What is Facilitated diffusion through a channel protein?
like pores that are very selective and specific to what can get across
What is Active transport?
Requires ATP, pump that pumps molecules across
What is the definition of simple diffusion?
Unassisted movement of a molecule from an area of HIGH concentration to an area of LOW concentration
Only works for small, nonpolar molecules (like gases)
Diffusion is movement towards what?
an equilibrium
What is hypertonic?
high solute concentration
What is hypotonic?
Low solute concentration
What is osmosis?
movement of water from hypotonic to hypertonic solution
What are the 2 types of proteins involved in transport?
carrier and channels
What are the two types of transport?
passive and active
What is passive transport?
solute is moving with the gradient. (high to low)
no energy is required
What is active transport?
solute is moving against the gradient (low to high)
requires energy
Carrier proteins are often called what?
transporters or permeases
What is the mechanism of carrier proteins?
1) Bind
2) conformational change
3) release molecule(s)
4) return to original conformation
What is symport?
when molecules flow through the same direction
What is antiport?
When molecules flow through in opposite directions
Do channel proteins undergo a conformation change upon binding a solute?
No, they simply form a channel
What is the channel proteins lined with?
hydrophilic amino acids
What is the size of channel proteins?
typically the size of the molecules
How fast do channel proteins pass molecules?
1,000,000 ions/second
How are channel proteins very selective?
only allow 1 type of ion to pass through
What is endergonic in nature?
active transport
What is active transport?
against the gradient “UPHILL”
What are active transport proteins often called?
pumps
Active transport can be what two things?
direct or indirect
What is direct active transport?
transport is coupled directly to ATP hydrolysis energy is used to drive pump
What is Indirect active transport?
transport of 1 molecule uphill is coupled with the transport of 1 molecule downhill (pulley system)
How do differences in ACTG account for observable and behavioral differences?
These bases code for different proteins that are made unique to each other and these proteins are what distinguish our features and do functions
DNA contains what which provides the info to make proteins?
genes
What is the cell cycle of mitosis?
1) DNA replication
2) Cell division
What is the structure of DNA
Nucleic acid structure that is in double helix formation