5.2 The plasma membrane and cell wall Flashcards
What make up the plasma membrane?
phospholipids and embedded proteins
What is the plasma membrane?
A fundamental, defining feature of all cells. The boundary that defines the space of the cell, separates internal contents from the surrounding environment.
What is a cell wall?
external to the plasma membrane, helps maintain the structure of the cell and protects. made up of carbohydrates and proteins
How does the cell maintain homeostasis?
the plasma membrane is semi permeable (lets certain molecules in, lets others in under certain conditions, or prevents molecules) requires a lot of energy
How is the plasma membrane selectively permeable?
results from a combination of lipids and embedded proteins.
- hydrophobic interior prevents ions and charged or polar molecules from diffusing freely.
- some macromolecules and proteins are too big to cross PM
which molecules can freely. one across the plasma membrane?
gases, lipids and small polar molecules.
what is the purpose of protein transporters in the membrane?
allow the export and import of molecules including ions, and neutrons that cannot cross the cell membrane on their own.
what is the simplest form of movement in and out of the cell and how does it work?
Passive transport and it works by diffusion
how does diffusion work?
a network of movement of a substance through a concentration gradient of high to low.
what is the process when a molecule moves by diffusion through a membrane protein and bypasses the lipid bilayer
facilitated diffusion
What is the difference between facilitated and simple diffusion?
facilitated diffusion
-the molecule moves through a membrane transporter
simple diffusion (requires no help)
-molecule moves directly through lipid bilayer
What are the two types of membrane transporters?
channel and carrier
what is a channel protein
provides an opening between inside and outside cell.
some are gated (open in response to a signal)
what is a carrier protein
binds to and transports specific molecules.
what is the purpose of aquaporins?
specific protein channels that allow water to move more readily across the PM by facilitated diffusion.
- right shape
- polar attracts polar
what is the definition of osmosis?
the net movement of a solvent, such as water across a selectively permeable membrane toward the side of higher solute concentration
What is active transport?
The uphill (low to high) movement of substances across the plasma membrane, required ATP energy
how does the sodium potassium pump work?
actively moves 3 sodium out of cell and 1 potassium into the cell
what is primary active transport?
active transport that uses the energy of ATP directly (sodium potassium pump)
what is an antiporter?
when molecules are moved in and out of the cell along a protein electrochemical gradient in opposite direction.
what are the 3 steps in secondary active transport?
- protons pumped across membrane by primary active transport
- protein pump generates electrochemical gradient (higher concentration of protons outside the cell, lower concentration of protons inside the cell)
- antiporter uses proton electrochemical gradient to move different molecules out of cell against conc. grad.
How does a pump generate a concentration gradient?
actively pumping protons (H+) out of the cell.
What is an electrochemical gradient
a gradient that has both charged and chemical. components (protons crossing membrane)
When is active transport secondary
when the movement of protons in from high to low and movement of coupled molecules is from low to high. the movement of coupled molecule is derived from protons and not ATP directly the process is then secondary.
What is secondary active transport
uses potential energy of an electrochemical gradient to drive the movement of molecules.
what is the definition for hypotonic, hypertonic and isotonic?
hypotonic- lower solute concentration then that inside the cell
hypertonic- higher solute concentration then that inside the cell
isotonic- same solute concentration then that in the cell
what is a vacuole?
a cell structure that absorbed water and contributes to turgor pressure (plant cells)
