Biology 1B - Cellular Biology Flashcards
what chemical bonds are important for life
ionic - exchanging of electrons
covalent - sharing of electrons
hydrogen bonds - weaker interactions
what is a membrane
phospholipid polymers of fatty acids, glycerol, phosphate and a terminal amine or alcohol group
phospholipids are amphipathic molecules, what does this mean
it means in water they spontaneously form monolayers and bilayers
what are important cellular functions of membranes
to compartmentalise metabolic activities
to protect cellular components
to provide a scaffold for signalling
as a medium for cellular energy generation
this is due to immiscibility of water and membranes
how do membranes generate biological energy
ion (charge) gradients across membranes
how can voltage across cell membranes be measured
using microelectrodes implanted in cells
name some places membranes are found in eukaryotic cells
chloroplasts
Golgi apparatus
mitochondria
vacuole
nucleus
endoplasmic reticulum
what are organelles
membrane delimited compartments in eukaryotic cells
what is the importance of membrane transport
protect metabolic reactions within the cell against the environment
communicate and exchange materials between the cell and environment
transport proteins allow for controlled interaction of cell with environment
describe membrane permeability
high permeability for small hydrophobic molecules and gases
limited permeability for water and hydrophilic molecules
very low permeability for ions ad large solutes
what do transport proteins do
create hydrophilic passage
create a filter
provide possibility for energy coupling
provide possibility for regulation
what is facilitated diffusion
transport proteins increase permeability of substances that already can move through membrane
what two forces drive the movement of molecules across membranes
chemical gradient - concentration gradient
electrical gradient - charge gradient (only for charged molecules)
what are positive and negative ions
cations - positive
anions - negative
what is the charge inside a membrane
negative
what is the electrochemical gradient
the net driving force for movement of a molecule resulting from combination of chemical and electrical gradients
what are the transport proteins for active transport
pumps
co transport systems
what are the transport proteins for passive transport
channels
carriers
what are pumps (transport protein)
- active transport
- use energy coupling - use ATPases, transport is coupled to the hydrolysis of ATP
- conformational change occurs during transport
- pumps establish electrochemical gradients used to drive transport of other molecules
describe how the sodium potassium pump works
1) transporter binds 3Na+ from the inside of the cell
2) phosphorylation occurs and conformation changes
3) now open side exposed to outside of cell, looses affinity for sodium
4) transporter releases 3Na+ to outside and binds to 2K+
5) dephosphorylation occurs and conformation changes
6) releases 2K+ to inside
what are co transport systems
- active transport
- co-transporters couple the downward movement of one ion (driver) to the uphill movement of another solute (substrate)
what are the two types of cotransport systems
symport - driver ion and substrate move in same direction (piggyback principle)
antiport - driver ion and substrate move in opposite directions (revolving door principle)
what are channels
transporter proteins for passive transport
provides an aqueous pore for the passage of ions
what are carriers
transport proteins for passive transport
undergoes conformational change that exposes ion binding sites to different sides of the membrane
how to ion channels exert tight control of the passage
they are selective and have higher permeability for certain ions
they are gated, meaning they can open and close in response to certain stimuli
how can ion channels be measured
using the patch clamp method
uses suction pipette and current amplifier to observe the current when channel is open and closed
