2.2 Transport of Substances Across CM Flashcards
What is passive transport
- Spontaneous movement of particles across semi-permeable membrane from area of high concentration to area of low concentration
Is energy required for passive transport
No
What is concentration gradient
diff concentration b/w two regions
- molecules tend to travel down or along the concentration gradient
What are the types of passive transport
- diffusion
- facilitated diffusion
- osmosis
What drives diffusion
Brownian movement
What is diffusion
net movement of particles from an area of higher concentration to an area of lower concentration
- net diffusion continues until dynamic equilibrium is reached
What molecules can dissolve in the core of the phospholipid bilayer and diffuse most easily through cell membrane
Small non-polar, uncharged molecules (oxygen, carbon dioxide)
What is facilitated diffusion
diffusion through CM with the aid of a membrane protein
What is a channel protein
made of 1 or more helixes that form open pores in membrane
- allows ions, charged molecules, polar molecules with certain size and charge to cross CM
- may be gated, only opening in response to hormones, electric charge. etc
What is the carrier protein
- selectively binds to non-charged molecule (glucose, aa) to be transported
- undergoes conformational change to release the molecule on the other side of CM
- low rates of diffusion b/c can only bind to a few molecules at a time
What is osmosis
diffusion of water across a semi-permeable membrane
What are the protein channels in osmosis
aquaporins
How does water diffuse
slowly as it is polar
Hypertonic
high concentration of solute/low H2O concentration
Isotonic
equal solute concentration/equal water concentration
- net movement is zero
Hypotonic
low concentration of solute/high H2O concentration
Active transport
movement of substances from area of lower concentration to an area of higher concentration
- moving against/up the concentration gradient
- energy is required in the form of ATP
- may involve the use of membrane carrier proteins
What does atp stand for
adenosine triphosphate
What happens when phosphate bond is broken
- atp forms into adp and inorganic phosphate
- energy is released
- energy can be used to power cell processes such as movement, reproduction, protein synthesis, trannport etc
Primary Active Transport
ATP is used directly by carrier proteins to move substances (ions, aa, acids, vitamins…) across CM
- molecule attaches to active site of carrier protein on one side of membrane
- ATP is broken down to ADP and phosphate
- energy released causes carrier protein to change shape
- molecules is released on other side of membrane
- molecule is not changed
Secondary Active Transport
- Doesn’t use ATP to fuel transport
- Instead, uses electrochemical gradient generated by primary active transport to fuel the transport of other molecules or ions across the CM
- Involves a symport carrier protein which carries out co-transport
Secondary Active Transport of Sucrose in Plants
plants use sat to move sucrose into the sieve tube elements
- when plants use an H+/sucrose symporter: proton are moving down their concentration gradient, while sucrose are moving up their concentration gradient
What are Membrane Assisted or Bulk Transport used to transport
- large amounts of material across CM
- particles that are too large or too polar to pass through CM via passive transport or molecular active transport
What does membrane assisted require
energy in the form of ATP
what are the two forms of bulk transport
endocytosis and exocitosis
what substances do endocytosis tranport
pinocytosis (liquid)
phagocytosis (solids)
receptor-assisted endocytosis (specific molecules)
what does exocytosis transport out of cell
hormones, enzymes, proteins, waste, nutrients
Which way does phagocytosis extend
out to “swallow” particle
Which way does pinocytosis extend
in to “swallow” particle and form vesicle
How does exocytosis occur
vesicle, budded from endoplasmic reticulum or golgi app, migrates to CM
- membrane of vesicle fuses with CM
- contents of vesicle released outside of cell
