LECTURE: MEMBRANE TRANSPORT
LECTURE: MEMBRANE TRANSPORT KIRSTIN BROWN
Lecture: MEMBRANE TRANSPORT Outline: 1. Passive Transport o Simple diffusion o Facilitated diffusion 2. Active Transport o Primary active transport o Secondary active transport
Membrane permeability Why do we need membrane transport? o The cell membrane is a __________________
barrier
o Many important molecules cannot cross the
cell membrane without __________________
Small, hydrophobic molecules eg. O2, CO2, N2
Membrane permeable
Small, uncharged polar molecules eg. H2O, urea, glycerol
Membrane mostly permeable – some pass by diffusion or osmosis
Large, uncharged polar molecules eg. Glucose, sucrose
Membrane mostly impermeable – requires transport proteins
Ions eg. Na+, K+, Cl-, Ca2+
Membrane completely impermeable – requires transport proteins
Membrane permeability Why do we need membrane transport? o Some molecules need to move against the
concentration gradient o This requires: __________________
Outside
Inside
Passive Transport Molecules moving with the concentration gradient o No energy required
o Two types: ➢ Simple diffusion ➢ Facilitated diffusion
Passive Transport Simple diffusion o No transport protein required
o Membrane is permeable to molecules
Simple diffusion
Passive Transport Facilitated diffusion o Requires transport protein
o Molecules can move through: ➢ Protein channels ➢ Carrier proteins
Simple diffusion
Channelmediated
Carriermediated
Facilitated diffusion No energy requried
Active Transport Molecules move against the concentration gradient o Requires energy
o Two types: ➢ Primary active transport ➢ Secondary active transport
Carriermediated
Simple diffusion
Channelmediated
Carriermediated
Facilitated diffusion No energy requried
ENERGY Active transport
Active Transport Primary active transport o Energy for moving molecules against the
concentration gradient come from: __________
o Can be used to generate an: ________________ ➢ The electrochemical gradient can be
used as an energy source for secondary active transport
o Example: Na+/K+ pump High [Na+] More (+) Opens to the outside
3 Na+ OUT
2 K+ bind
ENERGY 3
Na+
Opens to the inside
bind
ATP
2 K+ IN
Low [Na+] Less (+)
Active Transport Secondary active transport o Energy for moving molecules against the
concentration gradient come from: ___________________________
o Example: Glucose/Na+ transport o Movement of Na+ ________ the concentration
gradient provides energy for glucose to move ____________ the concentration gradient Na+
Primary
glucose
High [Na+] More (+) 3 Na+ OUT
2 K+ IN Low [Na+] Less (+)
Secondary
ATP
Active Transport Secondary active transport o Two types: ➢ Symport: ➢ Antiport:
Na+
Primary
glucose
High [Na+] More (+) 3 Na+ OUT
2 K+ IN Low [Na+]
Secondary
ATP
Summary Membrane Transport
Summary Simple Diffusion
Type of transport Energy requirement Membrane protein Direction of transport
Facilitated Diffusion
Primary Active Transport
Secondary Active Transport
Summary By which method would you predict that these molecules would enter the cell? a)
Oxygen: ________________________________
b)
Sodium: ________________________________
c)
Water:__________________________________
d)
Glucose: _______________________________
Summary The level of glucose inside vs. outside the cell is at equilibrium. Draw the curves for what would happen if the cell transports glucose as follows: a)
Transported OUT by active transport
b)
Transported OUT by facilitated diffusion
c)
Transported IN by facilitated diffusion
d)
Transported IN by active transport
e)
Crosses membrane by simple diffusion
Lecture: MEMBRANE TRANSPORT Outline: 1. Passive Transport o Simple diffusion o Facilitated diffusion 2. Active Transport o Primary active transport o Secondary active transport
Membrane permeability Why do we need membrane transport? o The cell membrane is a __________________
barrier
o Many important molecules cannot cross the
cell membrane without __________________
Small, hydrophobic molecules eg. O2, CO2, N2
Membrane permeable
Small, uncharged polar molecules eg. H2O, urea, glycerol
Membrane mostly permeable – some pass by diffusion or osmosis
Large, uncharged polar molecules eg. Glucose, sucrose
Membrane mostly impermeable – requires transport proteins
Ions eg. Na+, K+, Cl-, Ca2+
Membrane completely impermeable – requires transport proteins
Membrane permeability Why do we need membrane transport? o Some molecules need to move against the
concentration gradient o This requires: __________________
Outside
Inside
Passive Transport Molecules moving with the concentration gradient o No energy required
o Two types: ➢ Simple diffusion ➢ Facilitated diffusion
Passive Transport Simple diffusion o No transport protein required
o Membrane is permeable to molecules
Simple diffusion
Passive Transport Facilitated diffusion o Requires transport protein
o Molecules can move through: ➢ Protein channels ➢ Carrier proteins
Simple diffusion
Channelmediated
Carriermediated
Facilitated diffusion No energy requried
Active Transport Molecules move against the concentration gradient o Requires energy
o Two types: ➢ Primary active transport ➢ Secondary active transport
Carriermediated
Simple diffusion
Channelmediated
Carriermediated
Facilitated diffusion No energy requried
ENERGY Active transport
Active Transport Primary active transport o Energy for moving molecules against the
concentration gradient come from: __________
o Can be used to generate an: ________________ ➢ The electrochemical gradient can be
used as an energy source for secondary active transport
o Example: Na+/K+ pump High [Na+] More (+) Opens to the outside
3 Na+ OUT
2 K+ bind
ENERGY 3
Na+
Opens to the inside
bind
ATP
2 K+ IN
Low [Na+] Less (+)
Active Transport Secondary active transport o Energy for moving molecules against the
concentration gradient come from: ___________________________
o Example: Glucose/Na+ transport o Movement of Na+ ________ the concentration
gradient provides energy for glucose to move ____________ the concentration gradient Na+
Primary
glucose
High [Na+] More (+) 3 Na+ OUT
2 K+ IN Low [Na+] Less (+)
Secondary
ATP
Active Transport Secondary active transport o Two types: ➢ Symport: ➢ Antiport:
Na+
Primary
glucose
High [Na+] More (+) 3 Na+ OUT
2 K+ IN Low [Na+]
Secondary
ATP
Summary Membrane Transport
Summary Simple Diffusion
Type of transport Energy requirement Membrane protein Direction of transport
Facilitated Diffusion
Primary Active Transport
Secondary Active Transport
Summary By which method would you predict that these molecules would enter the cell? a)
Oxygen: ________________________________
b)
Sodium: ________________________________
c)
Water:__________________________________
d)
Glucose: _______________________________
Summary The level of glucose inside vs. outside the cell is at equilibrium. Draw the curves for what would happen if the cell transports glucose as follows: a)
Transported OUT by active transport
b)
Transported OUT by facilitated diffusion
c)
Transported IN by facilitated diffusion
d)
Transported IN by active transport
e)
Crosses membrane by simple diffusion
