Biochem Chapter 8 Flashcards
Membranes are
semipermeable
What is passive transport
the movement of a substance across a membrane without the need to expend energy (ATP)
What are the types of passive transport
Diffusion, Osmosis, Facilitated Diffusion
What is diffusion
the net movement of molecules from an area of high concentration to an area of low concentration until it reaches dynamic equilibrium
What types of molecules can diffuse across a membrane?
small and uncharged
What types of molecules cannot diffuse across a membrane?
large and charged
The rate of diffusion depends on …
Gradient - the greater the concentration difference the faster the movement
Temperature - the higher the temperature the quicker dynamic equilibrium will be reached
What is osmosis
the net movement of water across a semipermeable membrane driven by a difference in solute concentrations on the two sides of the membrane
How can water move through osmosis?
Freely, or through aquaporins
Tonicity
the relative concentration of solutes dissolved in two solutions separated by a permeable membrane
Hypertonic
Higher external concentration Ex. Salt Water
Hypotonic
Lower external concentration. Ex pure water
Isotonic
Equal concentration
What happens when cells are put into a hypertonic solution?
Water will rush out of the cell and into the solution. Causes the cell to shrivel
What happens when cells are put into a hypotonic
Water will rush into the cell potentially causing it to lyse.
What happens to a cell put in an isotonic solution?
Nothing
Facilitated Diffusion
the transport of ions and polar molecules through a membrane with the help of membrane proteins and without using energy
Types of facilitated diffusion
Channel Proteins and Carrier Proteins
What are channel proteins?
integral membrane proteins that form hydrophilic pathways in the membrane so substances like water and ions can cross. Some remain open at all times and others open and close in response to signals such as hormones, electric charge, and pressure
What are carrier proteins?
They bind to a specific solute (ex. amino acids) and transport them across the lipid bilayer. When performing the transport step, the carrier protein changes shape, allowing the solute to move from one side of the membrane to the other. They are very selective about what they carry
What is active transport?
the movement of substances across membranes against their concentration gradient using pumps. This is an energy-dependent process.
What uses ATP directly to move molecules or ions against their concentration gradient
Primary Active Transport
What is an example of primary active transport?
Sodium/Potassium Pump (Antiport)
Ions/Molecules moving across in opposite directions
Antiport
Primary Active transport creates
electrochemical gradients
Electrochemical Gradients
the difference in charge across a membrane. It generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane
Chemical Gradient
the difference in solute concentration across a membrane. the ion will move across the membrane from high to low concentration through simple diffusion.
Secondary Transport
uses the concentration gradient of an ion, established by a primary pump, as its energy source.
Example of a secondary transport
Hydrogen-Sucrose pump. This is a symport.
Bulk Transport
the movement of large molecules or large quantities of materials into or out of a cell at one time (does require energy)
Forms of Bulk Transport
Exocytosis, Endocytosis
What is exocytosis
the movement of large molecules out of the cell. Vesicles can release their contents into the extracellular environment
What is endocytosis
the form of bulk transport used to bring large amounts of materials into the cell from the extracellular fluid. There are three types, receptor-mediated, phagocytosis, and pinocytosis
What is receptor-mediated cytosis?
receptor proteins on parts of the outside of the cell membrane bind with the specific molecules, and the pit folds inward to form a vesicle. The contents of the vesicle can be digested.
What is phagocytosis?
[eat] occurs only in specialized cells, such as amoeba or bacteria-eating white blood cells (macrophages). It begins when the solid particle comes in contact with the plasma membrane of the cell and the cell membrane sends out finger-like projections called pseudopods that eventually enclose a vesicle. lysosomes may fuse with a phagocytic vesicle to digest the contents
Pinocytosis
[drink] occurs when a cells plasma membrane engulfs a small drop of extracellular fluid
