Cell Membrane Flashcards
the cell membrane model that says the plasma membrane is neither rigid nor static in structure but is highly flexible and can change its shape and composition through time.
fluid mosaic model
made of two layers of
lipids that have hydrophilic
heads and hydrophobic tails.
- Most abundant lipids in membranes
- widely accepted
phospholipid
if phospholipids have hydrophilic heads and hydrophobic tails, what is it called?
amphiphatic
how many heads and tails does a phospholipid have
1 head, 2 tails
The ______ of a phospholipid is made of an alcohol and phosphate (PO4) group, while the ______ are chains of fatty acids. (hydrocarbon, CH3, CH2)
head, tails
This head is connected to a _________ with two hydrophobic tails called fatty acids.
glycerol
The cell membrane consists of a diversity of ________, __________, and __________
lipids, carbohydrates, proteins
fatty acids that have single bonds (palmitic acid)
saturated fatty acids
(true or false) The individual lipid molecules
are able to move in their own monolayer.
true
fatty acids that have double bonds (linoleic acid)
unsaturated fatty acids
movement of individual lipids in the cell membrane
- lateral - going from one place to another laterally (most abundant)
- rotation - the movement of lipid on its own axis
- flip flop - moving from one side to the side (not lateral, rarely occurs)
- flexion - more like a result of a movement, so that a lipid can move freely
other than cholesterol, what helps in maintaining the membrane’s fluidity
the presence of double bonds
it is an essential component of animal cell plasma membranes. it modulates the bilayer structure of biological membranes in multiple ways. It changes the fluidity, thickness, compressibility, water penetration, and intrinsic curvature of lipid bilayers.
cholesterol
at warm temperature, the membrane ________, hence the cholesterol _________
expands, restrains movement
at cool temperature, the membrane ________, hence the cholesterol ______________
compresses, maintains its fluidity by preventing tight packing
“good” cholesterol, absorbs cholesterol and carries it back to the liver. The liver then flushes it from the body. High levels of this cholesterol can lower your risk for heart disease and stroke.
high-density lipoprotein
cholesterol is only present in _______
animals
sometimes called “bad” cholesterol, makes up most of your body’s cholesterol. High levels of this cholesterol raise your risk for heart disease and stroke.
low-density lipoprotein
synthesized by plants only, helps maintain its temperature, helps in lowering LDL in the blood
phytosterol
believed to have very similar functions to those of sterols in the membranes of animals and plants in that they can intercalate into phospholipid bilayers and modulate the fluidity of membranes by interacting with their complex lipid components. (in bacteria)
hopanoid
a function of the membrane that means it can:
- keep desirable substances in the cell and also keep undesirable substances out. (acid in the stomach)
- Hydrophobic core prevents the transport of ions and polar molecules (it selects what goes in and out)
- define the boundaries
- act as permeability barriers
can a small and non-polar molecule pass through the cell membrane? (O2, CO2, steroid hormones, N2)
yes
can a small polar molecule pass through the cell membrane? (H2O, ethanol, glycero;)
yes but slow
can a large non-polar molecule pass through the cell membrane? (Carbon Rings)
yes but slow
can a large polar molecule pass through the cell membrane? (Glucose, Ions, amino acids, glucose nucleosides)
no, needs transmembrane proteins
Molecules that require energy expenditure
for them to be transported across the membrane
polar molecules, large molecules (glucose, amino acids, nucleic acids, proteins)
Molecules that are free to move across the membrane
lipids, alcohol, small molecules (oxygen, nitrogen, CO2, water)
The plasma membrane forms the physical barrier between the cytoplasm and extracellular space, allowing for _______________ necessary for life to occur
(thylakoid in the chloroplast that is in charge of light-dependent reaction of photosynthesis)
(energy transduction - one type of energy is converted into another type)
biochemical reaction
Cells in multicellular organisms are in ________ with other cells
In plants, this is done through __________
(example: bladder, for urine, membrane maintains elasticity?)
contact, plasmodesmata/gap junctions
apoplastic pathway in plants
water is transported from root hair to xylem through the cell wall of intervening cells.
symplastic pathway in plants
water moves across the symplast, which consists of the cytoplasm and plasmodesmata (minute connections between the cytoplasm of adjacent cells).
cell membrane contains the protein molecules that act as _______ to detect extracellular signals
receptors
a protein receptor that keeps you awake
caffeine
a protein receptor that makes you sleep
adenosine
the cell membrane has ________________ - proteins that transport substances across biological membranes.
- can either be channel or carrier protein
- water - aquaporin
transport proteins
a _______________ has a channel through which a water molecule or a specific molecule can pass
channel protein
a _______________ alternates between two shapes, moving a solute across the membrane during the shape change
carrier protein
membrane proteins
transport, adhesion, recognition, receptor
______________ fasten adjacent cells together in animal tissues.
adhesion proteins
_____________ proteins help in recognition when
the body is being invaded by pathogens so that
the necessary immune response may be
triggered. (glycoprotein, glycolipid)
recognition
_____________have certain shapes that allow only specific molecules to bind to them. they transmit information to the cell by sensing the presence or absence of their cognate ligands, a process that often involves complex, multi-step pathways.
receptor proteins
integral membrane proteins found in all living organisms from bacteria to humans. they are mainly involved in the transmembrane diffusion of water as well as various small solutes in a bidirectional manner are widely distributed in various human tissues
they transport water across cell membranes in response to osmotic gradients created by active solute transport.
aquaporin
a type of membrane protein that is permanently attached to the biological membrane. they reside within the bilayer membranes that surround cells and organelles, playing critical roles in the movement of molecules across them and the transduction of energy and signals.
function:
- channeling or transporting molecules across the membrane. Others as cell receptors.
integral membrane protein
membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins or penetrate the peripheral regions of the lipid bilayer.
- allows cells to coordinate and communicate using networks of proteins and reactions.
peripheral membrane protein
the third major component of plasma membranes. In general, they are found on the outside surface of cells and are bound either to (peripheral) proteins (forming glycoproteins) or to lipids (forming glycolipids).
these carbohydrates form distinctive cellular markers, sort of like molecular ID badges, that allow cells to recognize each other. These markers are very important in the immune system, allowing immune cells to differentiate between body cells, which they shouldn’t attack, and foreign cells or tissues, which they should. (for recognition)
carbohydrates
The phospholipid bilayer is ____________________ because it only allows certain substances into cells while keeping others out. The size and the chemical nature of the molecules are important determiners of the permeability of the membrane to certain substances.
selectively permeable
