Ch 5 Membranes Flashcards
Tight junctions:
Second type of junction between adjacent cell, preventing material leaking between cells
Cellular membranes play a role in which of the following cell functions?
anchoring the cytoskeleton
protein sorting
cell and nuclear division
cell signaling
What are the three molecular components of cellular membranes?
carbohydrates
proteins
phospholipids
The plasma membrane contains lipids proteins and carbohydrates it is often described
Mosaic model
- Peripheral membrane protein:
Noncovalent associations form with phospholipids or other membrane proteins
- Transmembrane protein:
A segment of amino acids is inserted into the phospholipid bilayer.
- Lipid-anchored protein:
A lipid molecule is covalently attached to an amino acid side chain of the membrane protein
____ are involved in many different cellular functions including cell compartmentalization and the selective uptake of ions and molecules
Biological membranes
The three main types of macromolecules that comprise the plasma membrane are
- Lipids, Carbohydrates, and proteins
Most phospholipids move freely within a semifluid membrane
laterally along the plane of the membrane in two dimensions
The double bonds in unsaturated lipids create ______ in the nonpolar tails, making it more difficult for neighboring lipids to interact.
kinks
membrane fluidity is increased when membrane lipids
shorter nonpolar tails.
Transmembrane protein flip-flop does not occur spontaneously because it would be energetically
unfavorable
all cells are surrounded by a _______ permeable plasma membrane, meaning that the membrane allows the passage of some molecules and ions but not others.
- semi
the reasons why it is more appropriate to describe membranes as semifluid
- phospholipids usually move in two dimensions
- molecules move laterally within the membrane leaflet
What types of transport require a transport protein?
- Facilitated diffusion
- Active transport
the presence of a double bond in a phospholipid tail makes the membrane more fluid because
- it prevents phospholipids from packing tightly
Transmembrane proteins do not flip flop across bilayer leaflets because
hydrophilic protein regions would pass through the hydrophobic bilayer interior.
order the solutes from highest membrane permeability at the top to lowest at the bottom
- oxygen gas
- water
- glucose
- potassium ions
The plasma membrane of a cell is considered to be
- selectively permeable.
A term that describes a situation in which the concentration of a solute is higher on one side of a membrane than the other is
transmembrane gradient
Diffusion
movement of a substance from a region where concentration is high to region where concentration is low
Facilitated diffusion
movement from concentration high to a concentration is low through a passageway provide transport protein
Active transport
Movement from region is concentration low to region concentration is high to aid transport protein and source of energy.
A solution in which the solute concentration on both sides of the membrane is equal is classified as
isotonic
Membrane fluidity is increased when membrane lipids
shorter nonpolar tails.
When the concentration of solutes outside the cell is higher than that intra-cellularly, the solution is said to be __________ relative to the inside of the cell
hypertonic
phospholipid bilayer are an effective barrier to many charged or polar solutes because of their _____ interior region
nonpolar
osmosis, water moves from areas of
lowsoluteconcentration to areas of highsoluteconcentration.
When the solute concentration is higher inside the cell relative to outside the cell, the outside solution is said to be:
hypotonic
a term that describes a situation in which the concentration of a solute is higher on one side of a membrane than other other
transmembrane gradient
Proteins that assist in the movement of substances across membranes can be classified into two types based on how they move solutes across the membrane: _____ and _____
Channels and Transporters
When the concentrations of dissolved particles (solutes) on both sides of the plasma membrane are equal, the two solutions are said to be
isotonic
Unlike transporters, _____ proteins provide an open passageway all the way across the plasma membrane
channel
solution whose solute concentration is higher than the concentration of solutes inside
hyertonic
transporter proteins bind their solutes in a hydrophilic pocket and then undergo a ______ change that switches the exposure of the pocket from one side of membrane to the other
conformational
When the concentration of solutes outside the cell is lower than that intra-cellularly, the solution is said to be _________ relative to the inside of the cell
hypotonic
______ active transport involves a pump that uses energy from ATP to transport solutes against a gradient.
primary
what are the categories of proteins that assist in the movement of molecules and ions across membranes
- transporters
- channels
___active transport involves the use of a pre-existing gradient to drive the active transport of another solute.
Secondary
How do transporters differ from channel proteins?
Transporters must change conformation to allow solutes to cross the membrane.
transporter proteins transport solutes across the membrane via
- conformational change triggered by solute binding
In the 1940s, studies of animal cells suggested that the import of ______ is coupled to the export of ______.
K+ and Na+
Which of the following types of transport involves pumping ions against a gradient using ATP as a source
primary active transport
The sodium/potassium phase transports Na+ and K+ ions against their gradients using the energy from____
ATP
In osmosis, water moves from areas of
lowsoluteconcentration to areas of highsoluteconcentration.
In multicellular organisms, intercellular channels such as gap junctions in animals and plasmodesmata in plants
- allow the movement of substances between adjacent cells.
IN animals functions form channels between cells that allow cells to communicate with one another.
gap
In a plasmodesma, the ______ of one cell is continuous with that of another cell.
plasma membrane
The processes that are coupled across cell membranes
- the export of Na+ ions
- the import at K+ ions
vesicular movement of large molecules into cells is called _____, and vesicular movement of large molecules out of cells is called ______
- endocytosis
- exocytosis
the cells of multicellular organisms also may have ______ that allow the movement of substances between adjacent cells
intercellular channels
he three types of endocytosis are receptor-mediated endocytosis
- phagocytosis
- pinocytosis
- Receptor-Mediated Endocytosis
What do gap junctions do in animals?
Provide passageways for intercellular transport
Cell ______ are specialized structures within multicellular animals that physically adhere cells to each other.
junctions
What organelle in adjacent cells is connected by the central tubules in plasmodesmata?
- smooth endoplasmic reticulum
Select the types of anchoring junctions found in animals.
- hemidesmosomes
- adherens junctions
- focal adhesions
- desmosomes
The primary difference between endocytosis and exocytosis is
the direction of transport.
he two types of anchoring junctions that connect cells to the extracellular matrix are
- hemidesmosomes
- focal
- adhesions
multicellular animals, cells are linked to one another by
cell junctions.
which of the following cell junctions prevent material from passing between adjacent cells of animals?
- tight junctions
The four types of anchoring junctions in humans are
adherens junctions,
desmosomes,
hemidesmosomes,
cell-matrix adhesion complexes.
Which of the following anchoring junctions bind to actin filaments in the cytoskeleton?
- Focal adhesions
- Adherens junctions
Head
site where ATP binds and is hydrolyzed
Hinge
Site bends in response to ATP binding and hydrolysis
Tail
Region attached to other proteins or to other cellular molecules.
