Methods of Transport Flashcards
Passive transport
Movement of substances across a membrane without using energy
Diffusion
Movement of solutes within a cell from high to low concentration
Molecular movement
Always happening when a substance is above absolute zero
The drive behind diffusion
Entropy
Entropy
One region is more concentrated on one side of the membrane, has localized energy
Entropy energy
Entropy increases as the energy speeds until the concentrations are equal (highest)
Rate of diffusion
Dependent on concentration difference, a big difference leads to fast diffusion, and a slow difference leads to slower diffusion
Simple diffusion
Movement of molecules across a concentration gradient without transporters
Rate of simple diffusion
Depends on molecular size and lipid soluability
Molecules that can pass through simple diffusion
Nonpolar molecules, steriod hormones, amphipatic drugs and some uncharged polar molecules
Molecules that can’t pass through simple diffusion
Charged molecules such as Cl-. Na+ PO43-
Facilitated diffusion
Diffusion with the aid of a transporter, used by a polar and charged molecules
Facilitated diffusion uses
Channel and carrier proteins
Channel proteins
Provide a hydrophilic pathway in the membrane shielding the hydrophobic core, allowing molecules to pass. There are specific channels for specific molecules
Water diffusion
Executed by aquaporins
Aquaporins
Transport proteins in diverse organisms. Narrow and allows a billion molecules per second.
Aquaporins preventing ions technique
Has a positive core which deflects positive ions from entering
Gated channels
Can open, close and in between. Important for ions including Na+, K+, Ca+, Cl-
How do gated channels open and close
The can use voltage, which physically alters the proteins shape
Gated channels example
Nerve conduction (gated voltage), and CRFT in cystic fibrosis
Carrier proteins
Binds to a specific solute and carries it though the membrane. Uniport transport, Has a high rate of substrate specificity
Unitransport
Only one molecule can be taken at a time
Substrate specificity
Regulating the in and out of molecules in the cell.
Facilitated vs simple diffusion graphs
Facilitated is steep but reaches a plateau as all of the substrates are being used. Simple diffusion is a steady line
Osmosis
The passive transport of water across a semipermeable membrane from a solution of low ion concentration to high ion concentration
Why osmosis
Because the ions cannot leave so water comes in to establish the proper balance
Types of osmosis
In can be simple diffusion or facilitated through aquaporins
Hypotonic soloution
Lower concentration than the cells concentration. The cell swells and can burst in animal cells. Cell walls prevent bursting.
Hypertonic solution
Higher concentration than the cells concentration. Water leaves the cell and it shrinks in both plant and animal cells
In animal cells
Solutes go in and out of the cell, so it becomes isotonic, requires more energy because of constant ion pumping
Active membrane transport
Goes against the concentration gradient. Requires energy that is often ATP.
Active transport example
Concentrated sugars and amino acids inside the cell and ions outside the cell.
3 functions of active transport
Uptake of essential nutrients
Removal of secretory or waste
Maintenance of essential intracellular concentrations
Membrane potential
Electrical difference across the plasma membrane due to voltage created from active transport
Primary active transport
1 protein transports and hydrolyzed ATP to use
Secondary active transport
Indirectly driven by ATP, uses concentration gradients made from primary active transport to their advantage
Primary active transport pumps
Transport positively charged ions essential for life
Proton pomp (hydrogen pump)
Pushes H+ from the cytoplasm to the cells exterior, generates membrane potentials
Proton pump function
Bonds with the third phosphate in ATP temperarly removing it, creating energy
Proton pump purpose in lysosomes and vacules
To keep the pH low so the enzymes can thrive
Calcium pump
In almost all eukaryotes. Pushes Ca2+ from the cytoplasm to the cells exterior and from the cytosol to the ER
Uses of the calcium pump
Secretion, microtubule formation, muscle contractions
Sodium potassium pump (Na+/K+ pump)
In the plasma membrane. 3 sodium’s are pushed out of the cell for every two potassium brought in, leads to positivity outside the cell and negativity inside the cell
Voltage
An electrical potential difference
Membrane potential
Voltage across a membrane, - means more - inside the cell than out, the basis for ATP production
Electrochemical gradient
Stores energy used for other transport mechanisms
Secondary ATP pump example
High outside Na+ gradient in most animal cells from sodium potassium pump. Transfer of solute is coupled with the transfer of ions
Secondary ATP pump 2 processes
Symport and antiport
Symport and example
Uses cotransport. Glucose and amino acids
Cotransport
Solute moves though the channel in the same direction as the driving ion
Antiport and example
Uses exchange diffusion. Cl- and red blood cells, bicarbonate and membrane channels
Exchange diffusion
Driving ion moves in 1 direction providing energy for active transport of a molecule the other way
Endo and exocytosis
Largest active transport molecule is an amino acid or monosaccharide. Both need ATP
Exocytosis
Removal of molecules from the cell. Used by all eukaryotic cells
Endocytosis
Carry protein, molecule parts, or molecules into the cytoplasm.
How exocytosis works
Vesicles move through the cytoplasm to the plasma membrane, the membrane fuse and the product is released.
How endocytosis works
A depression forms and then pinches off to form an endocytic vesicle.
2 pathways of endocytosis
Bulk phase and receptor mediated
Bulk phase (pinocytosis)
Water is taken in with the molecule. Nothing binds to any surface receptors
Receptor mediated endocytosis
Molecules bond to receptor proteins on the cells surface, then it pinches off.
Coated pit
A depression with full receptor sites
Clathrin
The network of bonded proteins on the cytoplasmic side . Once a vesicle, the clathrinid membrane dissolves and fuses with a lysosome. The lysosome will dissolve the membrane or the product uses a transport protein to get out
Phagocytosis
The process of cells taking in large chunks of cells or molecules
steps of phagocytosis
- surface receptors bind to the molecule
- Cytoplasmic lobes extend to create a pit and join together
- The cytoplasm covers the product and digests it using the same process and receptor mediated endocytosis
Membrane surface area
Endo and exocytosis make sure it is the proper size
