Chapter 5 Flashcards
Selective Permeability
allows some substances to cross the cell membrane easier than others
amphipathic
both hydrophilic and hydrophobic regions
what molecule is amphipatic?
phospholipid
fluid mosaic model
membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids
Integral proteins
penetrate the hydrophobic interior of the lipid bilayer
Peripheral proteins
loosely bound to the surface of the membrane
glycolipids
membrane carbohydrates covalently bond to lipids.
glycoproteins
membrane carbohydrates covalently bonded to proteins
transport proteins
allow the passage of hydrophilic substances across the membrane.
aquaporins
channel protein that facilitates the passage of water
diffusion
tendency for molecules to spread out evenly into an available space.
concentration gradient
substances diffuse down or up.
passive transport
diffusion of a substance across the membrane.
osmosis
diffusion of free water across a selectively permeable membrane
tonicity
ability of a surrounding solution to cause a cell to gain or lose water.
isotonic
solute concentration is the same, no net movement of water across the plasma membrane.
The plasma membrane exhibits?
selective permeability
Phospholipids are?
amphipathic
As temperature cools, membranes switch from?
fluid state to solid state.
The temperature at which a membrane solidifies depends on?
the type of lipids it contains
A membrane remins fluid as it cools if it is rich in?
phospholipids with unsaturated hydrocarbon tails
At warm temps cholesterol ______ and at cool temperatures it _________.
restrains movement of phospholipids, maintains fluidity by preventing tight packing.
Variations in lipid composition of cell membranes of many species appear to be?
adaptations to specific environmental conditions
ability to change the lipid compositions in response to temperature change has?
evolved in organisms that live where temperature varys.
Proteins determine most of?
the membrane’s specific functions
Majority of these span the cell membrane
transmembrane proteins
The hydrophobic region of an integral protein consists of?
1 or more stretches of non polar amino acids often coiled into alpha helices
6 Major functions of membrane proteins
-transport
-enzymatic activity
-attachment to cytoskeleton and ECM
-signal transreduction
-cell-cell recognition
-intercellular joining
membranes have distinct ______
inside and outside faces
A cell must regulate ______ across cellular boundaries.
transport of substances
Non polar molecules can ____ in the lipid bilayer and ____.
dissolve, cross it easily
Polar molecules can ______
not pass the membrane easily.
Even ___ does not cross the membrane as good as non polar molecules.
water
channel proteins
transport proteins that has a hydrophilic channel that certain molecules can use as a tunnel.
A transport proteins is specific to ______
the substance it moves.
Dynamic equilibrium
molecules cross the membrane in one direction as in the other
substances move down their own concentration gradient unaffected by?
concentration gradients of other substances
Hypertonic
solute concentration greater than inside cell, cell loses water
Hypotonic
solute concentration is less than inside cell, cell gains water.
osmoregulation
control over solute concentrations and water balance.
turgid
very firm cell
flaccid
limp cell
plasmolysis
In hypertonic environment, plants cells membrane pulls away from the wall.
Plasmolysis is ___ to plant cells.
lethal
facilitated diffusion
transport proteins speed up the passive movement of molecules across the membrane.
ion channels
channel proteins that transport ions
gated channels
open and close in response to stimulus.
active transport
moves substances across membranes against their concentration gradients.
sodium potassium pump
exchanges Na+ for K+ across the plasma membrane of animal cells
passive transport diffuses from?
high to low
active transport diffuses from?
low to high
active transport energy is _____. Passive transport energy is _____.
required, not required
hypertonic or hypotonic environments create ________ for organism.
osmotic problems
The protist paramecium caudatum has a contractile vacuoles that _______.
pumps excess water out of the cell
paramecium caudatum is _____ to its pond water environment.
hypertonic
a plant cells in a ___ swells until the wall opposes uptake; the cell is now _____.
hypotonic solution, turgid
Channel proteins provide ______ that allow specific molecules to ____.
corridors, cross the membrane
ion channels are also known as?
gated channels
carrier proteins undergo a subtle _____ that translocates the solute-binding site across the membrane.
change in shape
active transport allows cells to maintain concentration gradients that differ?
from their surroundings
what kind of energy is required for active transport?
ATP
Example of active transport system
sodium-potassium pump
membrane potential
voltage across a membrane, -50 to -200mV
electrochemical gradient
drives diffusion of ions across a membrane
2 combined forces that make up the electrochemical gradient
-chemical force
-electrical force
electrogenic pump
transport proteins that generates voltage across a membrane
Major electrogenic pump of animal cells
sodium-potassium pump
Proton pump
main electrogenic pump of plants, fungi, and bacteria
cotransport
cells move two different molecules across a membrane at the same time.
plants use the _____ generated by proton pumps to drive active transport of nutrients into the cell.
gradient of hydrogen ions
examples of larger molecules that cross the membrane in bulk by vesicles.
polysaccharides and proteins
bulk transport requires?
energy
exocytosis
transport vesicles migrate to the membrane, fuse with it, then release their contents.
endocytosis
A cell takes in molecules and particulate matter by forming new vesicles
3 types of endocytosis
-phagocytosis
-pinocytosis
-receptor-mediated endocytosis
Phagocytosis
cell engulfs a particle than packages it into a vacuole to be digested
Pinocytosis
cell engulfs fluids along with molecules that can’t pass through the plasma membrane.
Receptor-mediated endocytosis
cell engulfs molecules that can’t get through membrane by binding to cell surface receptors.
In multicellular organisms, ______allows the cells to the body to coordinate their activities
cell to cell communication
gap junctions
junctions in animal cells
plasmodesmata
junctions in plant cells
junctions
directly connect the cytoplasm of adjacent cells
synaptic signaling
neurons communicate at synapses to excite or inhibit the activity of target cells
paracrine signaling
cells release signaling molecules to communicate with other cells
endocrine signaling is also known as?
hormone signaling
endocrine signaling
specialized cells release hormones that travel through circulatory system.
In long distance signaling, plants and animals use?
hormones
3 processes that cells receive signals
-reception
-transduction
-response
reception
detection of the signal
transduction
conversion of signal to a cellular response
transduction uses the _______ pathway
signal transduction
response
cellular activity in response to a signal
ligand
signal molecule
The binding between a ligand and receptor is _____
highly specific
ligand bindings generally cause a _____.
shape change in the receptor.
Many receptors are _____ by a change in shape.
directly activated
2 main types of membrane receptors
-G protein-coupled receptors
-Ligand-gated ion channels
G protein-coupled receptors (GPCR)
plasma membrane receptors that work with the help of a G protein.
ligand-gated ion channel receptor
Acts as a gate for ions when the receptor changes shape.
Where are intracellular receptor proteins found?
cytoplasm or nucleus of target cells
Examples of hydrophobic messangers (3)
-steroid hormones in animals
-thyroid hormones in animals
-nitric oxide in plants and animals
Aldosterone is secreted by cells of the ______ and enter cells _____.
adrenal gland, all over the body
Only ____ contain receptor cells for aldosterone.
kidneys
G-protein
protein that binds GTP together.
