B2.1 Flashcards
what are amphipathic membranes
Molecules that have both hydrophilic and hydrophobic parts
examples of other amphipathic molecules
Other amphipathic molecules besides phospholipids are some of the proteins like integral proteins
example of simple diffusion across membranes
movement of oxygen and carbon dioxide molecules between phospholipids
Both oxygen and carbon dioxide are small and uncharged molecules
Diffusion of these gases move from a high concentration area to a low concentration area
Oxygen and carbon dioxide can diffuse across the plasma membrane to carry out gas exchange in between the cell and the surrounding environment. This can also be carried out in the alveoli of the lungs and gill filament of different animals. Plant cells can also have diffusion of these gases for photosynthesis and respiration
integral proteins
a kind of membrane protein that is anchored in the plasma membrane with amphipathic nature. It has both a hydrophilic (interacting with the phosphate groups of the membrane) and a hydrophobic (interacting with the hydrophobic tails of the membrane)
Structure of Phospholipids
Consist of a polar hydrophilic head composed of a glycerol and a phosphate molecule
Consist of two non-polar hydrophobic tails composed of fatty acid (hydrocarbon) chains
Because phospholipids contain both _hydrophilic (water-loving) and lipophilic (fat-loving) regions, they are classed as amphipathic.
Arrangement of the Phospholipid Bilayer
Phospholipids spontaneously arrange into a bilayer
The hydrophobic tail regions face inwards and are shielded from the surrounding aqueous fluids, while the two hydrophilic head regions associate with the cytoplasm and extracellular fluids respectively
types of proteins
hormone-binding
enzymatic
cell adhesion
cell-to-cell communication
channel forming
pumps for active transport
hormone-binding
these proteins have specific shapes exposed to the exterior that fits the shape of specific hormones. the attachment between the protein and the hormone causes a change in the shape of the protein, which results in a message being relayed to the interior of the cell
enzymatic
these proteins occur on either the interior or the exterior membrane surface. they are often grouped together so that a sequence of metabolic reactions, called. metabolic pathway, is catalyzed
cell adhesion
this protein type allows temporary or permanent connections called junctions between cells. there are two types of junctions, gap junctions and tight junctions
cell-to-cell communication
most of these proteins have carbohydrate molecules attached. They provide an identification label so that organisms can distinguish between self and non-self material
channel forming
some proteins span the membrane, providing passageways for substances to be transported through
pumps for active transport
in active transport, proteins shuttle a substance from one side of the membrane to another by changing shape. This process requires the expenditure of energy in the form of adenosine triphosphate (ATP)
channel proteins
channel proteins exist to transfer large or polar substances, e.g. water
aquaporin
A type of integral proteins to allow water molecules to pass through the plasma membrane
The middle part of this protein allows water to go through but not for charged ions or solutes
cell junctions
tight junctions
desmosomes
gap junctions
tight junctions
impermeable junctions
prevent molecules from passing through intercellular space
e.g. lining of the digestive tract
desmosomes
anchoring junctions bind to adjacent cells like Velcro
form internal tension-reducing network of fibers; plaques on surface of membrane attach to protein filaments
e.g. found in tissues subject to stress like skin; heart muscle
