Membrane Structure And Function Flashcards
Amphipathic
Having both a hydrophilic region and hydrophobic region
How is membrane held together ?
Hydrophobic interactions
What is the most abundant lipid in the plasma membrane
Phospholipids
Phospholipids
Are amphipathic molecules, containing hydrophobic and hydrophilic regions
Peripheral proteins
Are bound to the surface of the membrane
Integral proteins
Penetrate the hydrophobic core
Trans membrane proteins
Integral protein that span the membrane
Major functions of membrane proteins
Transport
Enzymatic activity
Signal transduction
Cell cell recognition
Intercellular joining
Attachment to the cytoskeleton and extracellular matrix
Diffusion
Is the tendency for molecules to spread out evenly into the available space
Where do substances diffuse down their
Concentration gradient
Dynamic equilibrium
As many molecules cross the membrane in one direction as in the other
Passive transport
Is the diffusion of a substance across a membrane with no energy investment
What do membrane structures result in
Selective Permeability
- plasma membranes are selectively permeable, regulating the cell’s molecular traffic
What is the process controlled by the plasma membrane
A cell must exchange materials with its surroundings
Facilitated diffusion
The movement of glucose across the plasma membrane requires the use of a carrier protein.
Transport proteins
Transports proteins speed the passive movement of molecules across the plasma membrane
Allows passage of hydrophilic substances across the membrane
Channel and carrier proteins
Channel proteins
Provide corridors that allow a specific molecule or ion to cross the membrane . Aquaporins are channel proteins because they facilitate the diffusion of water
Carrier proteins
Undergo a subtle change in shape that translocates the solute binding site across the membrane
Ion channels
Facilitates the diffusion of ions
Gated channels
Open or close in response to a stimulus
Active transport
Uses energy to move solutes against their gradients
- allows cells to maintain concentration gradients that differ ,from their surroundings
- exp. sodium potassium pump ( the major electrogenic pump of animal cells)
How many different proteins are there
20
Membrane potential
It is the voltage difference across a membrane
How is voltage created
It is created by differences in the distribution of positive and negative ions across a membrane
Electrochemical gradient
Deives the diffusion of ions across a membrane
Electro genetic pump
It is a transport protein that generates voltage across a membrane
- helps stores energy that can be used for cellular work
Proton pump
The main electrogenic pump of plants, fungi, and bacteria.
They are the heart of the electron transport process. They produce the transmembrane electrochemical gradient that enables ATP Synthase to synthesize ATP
Aquaporins
Transport Protein that facilitates the movement of water across the cell membrane
Osmosis
Is the diffusion of water across a selectively permeable membrane
- water diffuses a membrane from the region of lower solute concentration to the region of higher solute concentration is equal on both sides
Tonicity
Is the ability of a surrounding solution to cause a cell to gain or lose water
Isotonic solution
Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane
Hypertonic solution
Solute concentration is greater than that inside the cell; cell loses water
Hypotonic solution
Solute concentration is less than that inside the cell; cell gains water
Bulk transport
Bulk transport across the plasma membrane occurs by exocytosis and endocytosis
- it requires energy
- large molecules, such as polysaccharides and proteins, cross the membrane in bulk via vesicles
Exocytosis
Transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell
Endocytosis
The cell takes in macromolecules by forming vesicles from the plasma membrane
- Phagocytosis ( cellular eating ) macrophages, used phagocytosis to engulf pathogenic bacteria
- Pinocytosis ( cellular drinking )
- receptor-mediated endocytosis
Co-receptors
Proteins expressed on the surface of immune cells are required for recognition by he HIV virus
