General Biology 2 Flashcards
defines the borders of the
cell and keep the cell
functional
- selectively permeable
- 5-10 nm thin
PLASMA MEMBRANE
act both as
receivers of extracellular inputs and as
activators of intracellular processes;
attachment site
Proteins - Integral (Receptors)
mosaic of components/fluid character
Fluid Mosaic Model
consist of Glycerol, 2
Fatty Acids and Phosphate-linked head
group
Phospholipid
composed of 4 fused
Carbon Rings found alongside the
phospholipid
Cholesterol
are present only on the
exterior surface of the plasma membrane.
Carbohydrates
→If attached to proteins
GLYCOPROTEINS
→If attached to lipids
GLYCOLIPIDS
forms H Bonds
with water and other polar
molecules on both exterior and
interior of the cellq
HYDROPHILIC
non-polar and
prefer non-polar environment.
HYDROPHOBIC
integrated completely into
the membrane structure
A.Integral Proteins
found on the exterior and interior surfaces of membranes; attached
either to Integral proteins or to
Phospholipids
- serve as enzymes, as structural attachments for the fibers of the
cytoskeleton and as recognition sites - “cell-specific” proteins
Peripheral Proteins
Always found on the exterior surface of
the cells and are bound to either
proteins (Glycoproteins) or to lipids
(Glycolipids).
In chains, 2-60 monosaccharide units
and can be either straight or branched
- Specialized sites/features to be
recognized
CARBOHYDRATES
“sugar coating”; hydrophilic and
attracts larger amounts of water to the surface of
the cell
GLYCOCALYX
- nature of Phospholipids
- unsaturated Fatty Acids kinks
making elbow rooms which is the
reason for its fluidity
Membrane Fluidity
A few molecules move freely
–Water, Carbon dioxide, Ammonia, Oxygen
describes fluid nature
of a lipid bilayer with proteins
–Fluid mosaic model
they allow some substances to pass
through but not others
SELECTIVELY PERMEABLE
material with a low
molecular weight can easily slip
through the hydrophobic lipid core of
the membrane.
→Lipid-soluble
can
pass through the plasma membranes in
the digestive tract and other tissues.
Vits. A, D, E K (fat soluble)
- passive process of transport
- substance moves from higher concentration to lower concentration until the concentration is equal across a space; e.g. Perfume
- no energy needed
- there will be different rates of diffusion of the different substances in the medium
according to their concentration gradient.
DIFFUSION
the greater the
difference in concentration, the more
rapid the diffusion. The closer the
distribution of the materials gets to
equilibrium, the slower the rate of
diffusion.
Concentration Gradient
heavier molecules move slowly; reverse is
true for lighter materials.`
Mass of the molecules diffusing
higher temperature increase
the energy and therefore the movement of the
molecules, increasing the rate of diffusion.
Temperature
as the density of a solvent
increases, the rate of diffusion decreases.
Solvent Density
non-polar or lipid-soluble
materials pass through plasma membranes
more easily than polar materials, allowing a
faster rate of diffusion.
Solubility
increased surface
area increases the rate of diffusion,
whereas a thicker membrane reduces
it.
Surface area and thickness of the
plasma membrane
the greater the
distance that a substance must travel,
the slower the rate of diffusion.
Distance travelled
→Transports only water across a membrane
→ special case of diffusion
OSMOSIS
The movement of water into and out of a cell is known
as
osmosis.
When the number of water molecules inside and
outside the cell is the same, _____ is
reached.
equilibrium (balance)
solute
concentration is equal to that of the inside cell.
ISOTONIC SOLUTION/ENVIRONMENT
→Describes how an extracellular solution can
change the volume of a cell by affecting
osmosis.
TONICITY
describes the total solute
concentration of the solution
OSMOLARITY
the extracellular fluid has
lower osmolarity than the fluid inside the cell.
→ Water enters the cell
Hypotonic Solution
the extracellular fluid has
higher osmolarity than the fluid inside the cell.
→Water leaves the cell
Hypertonic Solution
the extracellular fluid has the
same osmolarity as the cell.
→ No net movement of water into or out of the cell
Isotonic Solution
→Materials diffuse across the plasma membrane
with the help of
membrane proteins
→The material being transported is first attached to
a _____ receptors on the exterior
surface of the plasma membrane.
protein or glycoprotein
The substances
are then passed to specific ____ that
facilitate their passage.
integral proteins
Others are _____ which bind with the
substance and aid its diffusion through the
membrane
carrier proteins
an integral protein which is also referred to as Transport Proteins
- they function as either channels for the material or carriers
Channels
hydrophilic; open and close as they
respond to stimuli.
- some channel proteins open or close when a specific substance, other than the substance to be transported, binds to the channel
e.g. Aquaporins – channel proteins that allow water to pass through the membrane at a very high rate
Channel Protein
binds a substance
and triggers a change of its own
shape, moving the bound molecule
from the outside of the cell to its
interior.
- specific for a single substance.
- e.g. Glucose filtration in the kidneys (diabetic)
Carrier Proteins
facilitate diffusion at a rate of tens
of millions of molecules per
second,
Channel proteins
work at a rate of a thousand to a
million molecules per second.
carrier proteins
→moving of solutes across a membrane, up the concentration
gradient
→requires the expenditure of energy; it utilizes ATP (energy
currency of the cell)
→the movement across the membranes is unidirectional
ACTIVE TRANSPORT
IMPORTANCE
- It enables the transport of nutrients to the cell even when their
concentration on the inside is already higher. - It makes possible the removal of waste
materials from the cell despite their higher
concentration outside the cell. - It enables the cell to maintain the
concentration of essential ions such as K+, Na+, Ca2+, and H+
.
→Large molecules, such as proteins and polysaccharides
cross the membranes in bulk through the processes of
exocytosis and endocytosis.
BULK TRANSPORT
the process of removing materials from
the cell through the vesicles that fuse with the plasma membrane, releasing their contents outside the cell
→ example: secretion of digestive enzymes through the vesicles from the Golgi Apparatus.
the process of removing materials from
the cell through the vesicles that fuse with the plasma
membrane, releasing their contents outside the cell
→ example: secretion of digestive enzymes through the
vesicles from the Golgi Apparatus.
the reverse of exocytosis wherein cells
engulf materials; the engulfed substance then enters the
cytoplasm while enclosed in a vesicle.
ENDOCYTOSIS
“cellular eating”; the plasma membrane
wraps around the solid material and engulfs it. Example: how
the Amoeba captures food and how white blood cells engulf
bacteria
Phagocytosis
“cellular drinking”; the plasma membrane
wraps around the dissolved materials and forms a vesicle that
contains the engulfed materials. Example: the human egg
cell’s uptake of nutrients from its surroundings
Pinocytosis
