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416 Cards in this Set

  • Front
  • Back
Six levels of organization
chemical
cellular
tissue
organ
organ system
organismal
The five parts of the chemical level of organization
subatomic particles
atom
molecule
macromolecule
organelle
**The cell represents the ___ level of organization in the human body.
second
The cell is the smallest ___ unit we know of.
living
To understand the cell is to understand the ___.
body
**___ has been the rate-limiting step in determining what we know about cells.
technology
T/F: We cannot see, hear or touch cells.
true
Broad categories of techniques used in cell biology
microscopy
cell culture
methods that separate part of
the cell
manipulation of DNA
___ can solidify observations obtained through other techniques.
microscopy
Electron microscopes enlarge up to ___ times.
1 million
___ may be the single most valuable tool used in studying cells.
cell culture
In cell cultures, cultures of a ___ can be maintained.
single cell
Examples of processes that can be studied in a cell culture
cell division
cell movement
membrane function
By ___, cellular organelles can be isolated and studied, e.g., macromolecules making up the cell can be separated by weight, electrical charge
separating components of the cell (cell fractionation)
___ is various techniques in which a mixture of dissolved components are separated while moving through a porous matrix.
chromatography (a technique for separating components of the cell)
The central theme in ___ is the use of bacteria and viruses and their natural enzymes.
DNA manipulation
Used in DNA manipulation of bacteria to cut DNA at specific sites
restriction endonucleases
Used in DNA manipulation of viruses to build DNA from RNA
reverse transcriptase
Manipulating DNA allows some intriguing possibilities, such as reconstructing (recombining) DNA to observe the ___ of key segments.
function
We can cut DNA into specific segments and then produce ___ of that segment (used in genetic testing).
large quantities
___ = cleave human DNA with restriction nuclease, get millions of genomic DNA fragments; DNA fragments are inserted into plasmids; these plasmids can be introduced into bacteria
DNA recombination (recombinant DNA molecules are now part of those plasmids)
The building block of all organisms
the cell
All organisms are composed of one or more ___.
cells
Cells can only arise by division from a ___.
preexisting cell
The cell is the smallest ___ unit we know of.
living
T/F: Cells may subsist outside of their organism of origin
true (e.g., cell culture)
First example of isolating cells (early 50's), still using this cell line today
HeLa cells
Properties of cells:
1. very ___, very ___
2. contain our genetic ___
3. can ___ themselves
4. acquire and utilize ___
5. carry out ___ reactions
6. engage in ___ activities
7. self-___
1. complex, organized
2. blueprint (DNA)
3. reproduce
4. energy
5. chemical
6. mechanical
7. regulate
T/F: Every cell contains the entire genetic blueprint of the organism
true
Every cell on earth stores its genetic blueprint as ___.
DNA
Cells acquire and utilize energy in order to maintain ___.
cellular organization
___ serves as directions for reproducing and running the organism.
DNA
T/F: Cells can repair themselves and can even kill themselves
true
Two basic classes of cells
prokaryotic
eukaryotic
The two basic classes of cells are distinguished on the basis of ___ and ___.
size
internal structures (organelles)
Generally, ___ cells are larger and more complex.
eukaryotic
Class of cell without a (membrane-bound) nucleus
prokaryote
Class of cell with a (membrane-bound) nucleus
eukaryote
___ contain much more genetic information because they have a membrane-bound nucleus.
eukaryotes
Example of a prokaryotic cell
bacterium
___ lack organelles (ER, mitochondria, etc.)
prokaryotes
Plant and animal cells = ___ cells
eukaryotic
There are around ___ cells in the human body.
75 trillion
There are about ___ different cell types in the human body.
250
The various cell types differ greatly in terms of ___, ___, and ___.
shape
size
function
A cell that stores nutrients
fat
___ lay down extracellular matrix.
fibroblasts
Examples of cells that move organs and body parts
fibroblasts
erythrocytes
epithelial
skeletal muscle
smooth muscle
Cell that fights disease
macrophage
Cell that gathers information and controls body functions
nerve
Cell of reproduction
sperm
Cells performing a common function aggregate to form ___.
tissues
Four tissue types
epithelial
connective
muscle
nervous
Although tissues will contain many cell types, each tissue will usually be composed of a ___ cell type.
predominant
RBCs are an example of ___ tissue.
connective
The three main parts of the eukaryotic cell
plasma membrane
cytoplasm
nucleus
Boundary of the eukaryotic cell
plasma membrane
The ___ of the eukaryotic cell contains various organelles.
cytoplasm
The ___ of the eukaryotic cell contains chromosomal DNA.
nucleus
Much of what we know about the cell has been obtained from a limited number of ___.
representative organisms
Advantages of learning about a cell from representative organisms
consistency
efficiency
experimental ease
Disadvantage of learning about a cell from representative organisms
certain findings could be organism-specific
The ___ cell has been crucial in learning about manipulating DNA.
E. coli
The nude mouse has been useful in research because ___
no thymus, therefore no T cells, and therefore doesn't reject lots of stuff
Cells are almost always ___ in size.
microscopic
Bacterial (prokaryotic) cells are typically ___ micrometers in length; eukaryotic cells are typically ___ micrometers.
1 - 5
10 - 30
The science concerned with the atomic composition of substances and their interactions
chemistry
___ considers the composition of substances and how they change.
chemistry
The properties of cells and organelles derive directly from the ___.
activities of their constituent molecules
Atoms can be subdivided into ___, ___, and ___ (but not through normal reactions).
neutrons
electrons
protons
___ are the simplest form of matter to have unique chemical properties.
atoms
T/F: Subatomic particles are not unique.
true
A proton from a carbon atom is ___ to a proton from an oxygen atom. However, ___ are unique.
identical
atoms (e.g., gold is different from silver, etc.)
**The uniqueness of atoms is based on the ___ of neutrons, electrons and protons they contain.
number
Atoms contain a ___ consisting of ___ and ___.
central nucleus
protons
neutrons
Because protons have a positive charge and neutrons have no charge (neutral), an atom's nucleus is ___ charged.
positively
Protons and neutrons have about the same ___.
mass
___ are tiny particles which orbit the nucleus.
electrons
Electrons have a negative charge which ___ the positive charge of protons.
equals
Atoms have an equal number of protons and electrons, but the number of ___ may vary.
neutrons
Electrons have ___ the mass of protons/neutrons.
1/2000th
Each form of an atom is known as an ___.
element
Each element has unique ___ and ___ properties.
physical
chemical
**___ are the smallest forms of matter that possess unique physical and chemical properties.
elements (atoms)
___ properties are detected with senses or measurement (e.g., color, texture, boiling/freezing points)
physical
___ differences of elements pertain to bonding behavior (iron rusts, gasoline combusts, animals digest, etc.).
chemical
**The uniqueness of any given element is solely due to this one factor
different elements contain different numbers of neutrons, electrons and protons
The ___ of an atom refers to the number of protons in its nucleus.
atomic number
The atomic number of an atom refers to the number of ___.
protons in its nucleus
The number of protons always equals the number of ___.
electrons
T/F: Since the number of protons always equals the number of electrons, the atomic number will also tell us the number of electrons in the atom.
true
The ___ of an atom refers to the total number of protons and neutrons in its nucleus.
mass number
The mass number of an atom refers to the ___.
total number of protons and neutrons in its nucleus
There are about ___ elements that have a normal physiological role in the body.
24
There are about ___ natural elements.
92
The four most important elements in the human body
oxygen
carbon
hydrogen
nitrogen
Electrons are organized concentrically around the nucleus in ___.
electron shells (or energy levels)
Most atoms combine with other atoms to form ___.
molecules
Two basic types of molecules
molecules of an element
molecules of a compound
Two or more atoms of the same element combine; cannot be broken down by chemical means
element (e.g., O + O = O2; H + H = H2)
Two or more different kinds of elements combine
compound (e.g., H2 + O = H2O)
In a ___, individual atoms lose their properties and assume its own properties (e.g., NaCl)
compound
A ___ is a relationship between electrons of interacting (reacting) atoms
chemical bond
T/F: Electrons are organized around the nucleus of an atom in concentric shells
true
There are ___ possible energy (concentric) shells that can organize around a nucleus.
seven
T/F: The first energy shell must be filled before the second, the second before the third, etc.
true
It is electrons in the ___ shell of one atom that will react with the electrons in the ___ shell of another atom.
outermost
outermost
**A chemical reaction will occur when the ___ is incomplete.
outer shell
In ___ bonding, outer shell electrons are shared between reacting atoms.
covalent
In covalent bonding, outer shell electrons are ___ between reacting atoms.
shared
Outer shell electrons are shared between reacting atoms in ___ bonding.
covalent
In covalent bonding, the bonding between both atoms will fill the ___ of each atom.
outer electron shell
The benefit of covalent bonding for both atoms is that they will be ___.
stable
An ionic bond occurs following a ___ between atoms.
transfer of electrons
An ___ bond occurs following a transfer of electrons between atoms.
ionic
In ionic bonding, one atom ___ an electron and one atom ___ an electron.
loses
gains
In ionic bonding, the ___ atom loses an electron; the ___ atom gains an electron.
donor
acceptor
The donor atom that loses an electron in ionic bonding is now a(an) ___ charged ion.
positively
The acceptor atom that gains an electron is now a(an) ___ charged ion.
negatively
A positively charged ion is a(an) ___.
cation
A negatively charged ion is a(an)___.
anion
The cation and anion will attract each other because of ___ charges.
opposite
**The ___ bond results from the opposite-charge attraction between cation and anion.
ionic
Compounds, such as NaCl, dissociate in water to produce ions, which are called ___.
electrolytes
Important ions in the body involved in such things as nerve conduction, muscle contraction, enzyme function
electrolytes
The weakest of the three types of bonds
hydrogen
___ bonds are more like attractions and are not as strong as covalent and ionic bonds.
hydrogen
___ bonds form between slightly positive hydrogen atoms and other atoms, which are slightly negative.
hydrogen
___ is an excellent example of hydrogen bonds at work.
water
Water is a ___ molecule.
polar
A ___ occurs whenever chemical bonds are formed, broken, or rearranged.
chemical reaction
Chemical reactions can be written as ___.
equations (reactants --> product)
T/F: Many chemical reactions are reversible.
true
Most chemical reactions will exhibit a ___ (e.g., of synthesis, decomposition or exchange reaction)
pattern
Reaction which results in the formation of a larger, more complex molecule
synthesis
Type of reaction: A + B --> AB
synthesis
Reaction in which a molecule is broken down
decomposition
Type of reaction: AB --> A + B
decomposition
Reaction in which reactant molecules exchange 'partners'
exchange
Type of reaction: AB + CD --> AD + CB
exchange
One particular type of chemical reaction that is critical in living systems, the basis for which is a loss or gain of electrons in the reactants
redox reaction
A process by which a molecule loses one or more electrons and releases energy
oxidation
In oxidation when a molecule loses an electron, there will always be another molecule to accept that electron, usually ___.
oxygen
A process in which a molecule gains one or more electrons and gains energy
reduction
**The oxidation of one molecule is always accompanied by the ___ of another.
reduction
**The ___ of one molecule is always accompanied by the reduction of another.
oxidation
LEO the lion says GER
lose electron = oxidation
gain electron = reduction
Oxidation-reduction reactions
redox
Redox reactions are ___ reactions.
decomposition
___ reactions are the basis for obtaining energy from food.
redox (i.e. decomposition)
The food we eat is broken down (digested) into small molecules which are then ___.
oxidized
Glucose is ___ to provide energy.
oxidized
The study of the chemistry of living organisms
biochemistry
The two classes of chemicals in the body
organic
inorganic
The main inorganic compounds in the body
water
salts
many acids and bases
Compounds which contain carbon, are covalently bonded; many are large
organic
Organic compounds contain ___ and are ___ bonded.
carbon
covalently
The most important and abundant inorganic compound in living material
water
___ is the major constituent of our bodily fluids.
water
Humans are more than half ___.
water
Five properties of water
1. high heat capacity
2. high heat of vaporization
3. polar solvent properties
4. reactivity
5. cushioning
The high heat capacity of water is good for ___.
absorbing heat from muscular activity
The polar solvent properties of water are important because ___ must happen in solution.
biochemical reactions
___ uses heat from muscular activity.
evaporation (sweat)
Ionic compounds containing cations other than H+ and anions other than OH- (hydroxyl ion)
salts
Common salts in the body
NaCl (sodium chloride)
Ca2Co3 (calcium carbonate)
KCl (potassium chloride)
Salts dissociate into their ___ constituents in water.
ionic
Ions such as Ca++, Na+, Cl-, etc. are also known as ___.
electrolytes
Like salts, ___ and ___ are ionic compounds which dissociate in water.
acids
bases
An ionic compound that releases a proton, or hydrogen ion (H+)
acid (sour taste)
An ionic compound that accepts a hydrogen ion (H+)
base (tastes bitter)
Many ___ are ionic compounds that dissociate to release OH- (NaOH --> Na+ + OH-). The hydroxyl ion then accepts H+ to form ___.
bases
water
Another definition of salt: any compound that results from the chemical interaction of ___.
an acid and a base
Chemical interaction of an acid and a base
neutralization reaction
A classic ___ reaction:
HCl + NaOH --> NaCl + H2O
(acid + base --> salt + water)
neutralization
The pH scale was originally devised to measure the acidity of ___.
beer
pH is a measure of the ___ concentration of a solution.
hydrogen ion (i.e., acidity)
The greater the H+ concentration of a solution, the ___ the acidity.
higher
The lower the H+ concentration of a solution, the ___ the acidity.
lower
pH is a ___ logarithm
negative
lower acidity = ___ alkalinity
higher
The greater the H+ concentration, the ___ the pH value.
lower
The lower the H+ concentration, the ___ the pH value.
higher
Two exceptions to the rule that inorganic compounds don't contain carbon
CO
CO2
___ is the defining element of life.
carbon
Carbon is so essential to life because of its ___.
structure
Carbon never ___ or ___ electrons; it ___ them.
gains
loses
shares
Because carbon never gains or loses electrons (it shares them), it can form multiple ___ bonds with other atoms and other carbons.
covalent
Carbon is the basis of what four main categories of macromolecules
carbohydrates
lipids
proteins
nucleic acids
**Carbohydates, lipids, proteins, and nucleic acids are all composed of at least some variation of ___, ___, and ___.
hydrogen
oxygen
carbon
T/F: Carbohydrates are hydrophobic
false (they are hydrophilic)
Water loving
hydrophilic
general chemical formula of carbohydrates
(CH2O)n
Most familiar carbohydrates are ___ and ___.
sugars
starches
Carbohydrates are classified according to size: ___, ___ and ___.
monosaccharide (one sugar)
disaccharide (two sugars)
polysaccharide (many sugars)
three functions of carbohydrates
source of fuel
structure
signaling
T/F: Lipids are hydrophilic organic compounds
false (they are hydrophobic)
fear of water
hydrophobic
T/F: Lipids do not dissolve in water
true
Lipids have a high ratio of ___ to ___.
hydrogen
oxygen
Three different types of lipids in the body
triglycerides (fats)
phospholipids (cell membranes)
steroids (formed from cholesterol)
Function of triglycerides (fats)
energy storage
Function of phospholipids
cell membranes
Steroids are formed from ___ and play a role in ____.
cholesterol
hormones
All amino acids contain a central ___ atom, an ___ group and a ___ group.
carbon
amine
carboxyl
Number of common types of amino acids
20
T/F: All 20 common types of amino acids are identical except for the R group
true
There are ___ essential amino acids.
eight
Amino acids can __ or ___ a hydrogen atom.
accept
donate
Proteins are made up of ___.
chains of amino acids
___ have the most varied functions of any molecule in the body.
proteins
___ are the basic structural material of the body.
proteins
___ accelerate chemical reactions (catalysts).
proteins
___ are used in communication within and between cells.
proteins
Three functions of proteins
1. basic structural material of the body
2. accelerate chemical reactions (catalysts)
3. used in communication within and between cells
The structure of a protein will be determined by its constituent ___.
amino acids
**For proteins to function properly, a ___ is required.
precise structure
Secondary structure of protein is described by ___.
the three-dimensional structure (conformation) of sections of the polypeptide backbone (think beta sheet)
Primary structure of a protein is described by the ___.
amino acid sequence of a polypeptide (think chain)
Tertiary structure of protein is described by the ___.
conformation of the entire polypeptide
Quaternary structure of a protein is described by the arrangement of its ___.
subunits
The four structural levels of a protein
primary
secondary
tertiary
quaternary
Enzymes are proteins that act as ___.
biological catalysts
Catalysts ___ reactions, but they ___ create reactions.
speed up
do not
Enzymes ___ the activation energy required to make a reaction occur.
lower
Enzymes are/are not changed by the reaction
are not
nucleic acids
DNA
RNA
Nucleic acids are so named because they are acids found in the ___ of cells.
nucleus
DNA = ___
deoxyribonucleic acid
RNA = ___
ribonucleic acid
**DNA and RNA are derived from the sugar ___.
ribose
**In DNA the sugar is called ___ since it is missing one oxygen.
deoxyribose
The nucleic acids are made up of ___.
nucleotides
The ___ molecule is referred to as a double-helix.
DNA
DNA, a double-helix molecule, is essentially a ___ of nucleotides.
double chain
The nucleotides of DNA are arranged in such a way as to create a ___ structure.
helical
The DNA double-helix contains a person's ___.
genetic code
The two fundamental roles of DNA
1. replicates itself before a cell divides
2. contains the blueprint required to make every protein in the body
DNA ___ itself before a cell divides.
replicates
DNA contains the blueprint required to make every ___ in the body.
protein
Our bodies break down food into its smallest components to release energy, which is captured in the bonds of the molecule ___.
ATP
ATP uses the energy captured from the breakdown of food to drive ___.
cellular processes
The membrane that encompasses the cell
plasma membrane (cell membrane)
Protects, segregates the inside from the outside of the body
skin
T/F: Life would not be possible without membranes
true
___ enclose and sequester.
membranes
The plasma membrane is crucial to establishing vital differences between the ___ and the ___.
cytosol
extracellular environment
the fluid inside the cell
cytosol
The cell (plasma) membrane is only about ___ wide.
5-10 nm
In electron micrographs all membranes share a common ___ appearance.
tri-laminar
Membranes are ___, ___ sheets. Thus membranes ___ areas.
continuous
unbroken
enclose
Compartmentalization of areas by membranes allows for ___.
specialization
The membrane provides an architectural foundation, or ___, for the cell.
scaffolding
The scaffolding provided by the cell membrane enables the ___ of mechanical signals between intra- and extra-celular structures and a means for ___ to take place.
transmission
biochemical reactions
If you tug on any one "stick," you'll affect another part; the tug reverberates.
tensegrity
___ prevent the unrestricted movement of molecules from cytosol to extracellular space (and vice-versa).
membranes
Membranes are a ___ barrier.
selectively permeable
Passage across the cell membrane is ___; thus the internal environment of the cell is also ___.
controlled
controlled
Cell membranes respond to external stimuli via structures on/in the membrane called ___.
receptors
the capacity to transform one type of energy into another
transduction
___ have the capacity to transform one type of energy into another (transduction).
membranes
In eukaryotes, transduction takes place in ___.
cytoplasmic membranes
In eukaryotes, transduction takes place in the cytoplasmic membranes by/in ___ and ___.
chloroplasts
mitochondria
The concept of a ___ was proposed in 1925 using red blood cells.
lipid bilayer
The lipid bilayer is composed of ___.
phospholipids
Phospholipids provide two biochemically distinct groups: ___ and ___.
hydrophilic polar heads
hydrophobic lipid tails
In phospholipids, the ___ interacts with the cytoplasm or extracellular fluid (water).
hydrophilic polar heads
Water and lipid ___ each other.
repel
Hydrophobic interactions are energy ___.
favorable
In hydrophobic interactions of water and lipids, non-polar molecules are forced into ___.
aggregates (the tails group together and polar heads face outward)
Membranes contain ___ in addition to lipids.
proteins
The term "___" derives from the fact that the membrane is not a solid and movement in the membrane is possible, and that the plasma membrane is composed of many different types of molecules.
fluid mosaic model
**The membrane is not a solid; it is a ___.
fluid
T/F: Movement in the plasma membrane is possible.
true
The plasma membrane is composed of many different types of molecules - it is a ___.
mosaic
The plasma membrane is held together by ___ interactions.
hydrophobic
The two main roles of lipids in the plasma membrane
1. structural backbone
2. barrier to (most) polar molecules
The three macromolecules of the plasma membrane
lipids
proteins
carbohydrates
containing both hydrophilic and hydrophobic regions
amphipathic
All lipids in the cell membrane are ___ (i.e., contain both hydrophilic and hydrophobic regions)
amphipathic
The three main categories of membrane lipids
phosphoglycerides
sphingolipids
cholesterol
T/F: Different cell membranes (and other membranes) have different lipid components; some may contain hundreds of chemically distinct lipids.
true
The lipid profile of the membrane has important effects on the biological properties of the membrane, i.e., the ___ of the membrane and the ___ of membrane proteins.
physical state
function
T/F: The hydrophobic hydrocarbon tails of the membrane never interact with water.
true
T/F: The cell membrane has no free edge; it is continuous.
true
The implications of membrane continuity: formation of ___ in the cell.
networks
The lipid bilayer provides the necessary flexibility to allow ___ (fluidity of the membrane)
deformation
___ of the membrane is crucial during locomotion or cell division.
deformability
The lipid bilayer is thought to facilitate membrane ___ and ___.
fusion (e.g., fertilization)
budding
T/F: The lipid bilayer has the ability to self-assemble.
true
Membrane ___ can be demonstrated in vitro when phospholipids dispersed in aqueous solution will assemble into spherical vesicles (liposomes).
self-assembly
Liposomes have been used in various studies, such as vehicles for ___.
drug delivery
Plasma membranes of eukaryotic cells contain carbohydrates - between ___ and ___% by weight.
2
10
Most carbohydrate (about 90%) in the plasma membrane of eukaryotic cells is covalently linked to ___.
proteins (glycoproteins)
About 10% of the carbohydrate in the plasma membrane is covalently linked to ___.
lipids (glycolipids)
All carbohydrate chains face ___ into extracellular space.
outward
Carbohydrate chains in the plasma cell membrane serve as ___.
markers (recognition tags)
The two main purposes for glycoprotein carbohydrate chains
1. extracellular interactions
2. intracellular protein trafficking
T/F: Glycolipids' function is little known, yet it is likely important.
true
T/F: Cells interact with their environment; cells must recognize each other and be able to work together.
true
Two examples of cells working together and recognizing each other
1. immune system (e.g., blood typing)
2. fusion of sperm and egg
Carbohydrate chains ensure that newly synthesized proteins reach the appropriate ___.
destination
___ give the membrane its functional characteristics; ___ give the physical structure.
proteins
lipid
The amount and type of ___ in a membrane is highly variable.
protein
Myelin sheath has about ___% protein by mass; mitochondrial membrane has about ___% protein by mass.
25
75
Three distinct ways proteins are associated with the cell membrane
integral proteins
peripheral proteins
lipid-anchored proteins
How a protein interacts with the lipid bilayer will reflect the ___ of the protein.
function
Integral membrane proteins are also called ___ proteins.
transmembrane (i.e., span entire membrane)
T/F: Transmembrane proteins span the entire bilayer and may span the bilayer more than once.
true
Facts about integral proteins and their attachment:
1. They are ___ (have polar and non-polar regions).
2. The hydrophobic portions of the protein interact with the ___.
3. The protein is sealed into the lipid bilayer by ___ interactions.
1. amphipathic
2. inner bilayer
3. van der Walls
In van der Walls interactions that seal an integral protein into the lipid bilayer of the cell membrane, the relative ___ of the bilayer is maintained.
impermeability
Van der Waals forces refer to the momentary/weak ___.
attraction of atoms to each other
T/F: Macromolecules with complementary surfaces can establish multiple van der Waals interactions.
true
Three functions transmembrane proteins perform on either side of the bilayer
1. receptors
2. channels or transporters
3. involved in energy transduction
___ proteins are located entirely outside of the lipid bilayer.
peripheral
T/F: Peripheral proteins are found on either side of the lipid bilayer.
true
Peripheral proteins associate via ___ interactions.
non-covalent
Peripheral proteins often form a membrane ___.
skeleton (e.g., spectrin in RBC)
The peripheral protein skeleton ___ the membrane and provides an ___ for integral proteins.
supports
attachment point
T/F: Peripheral proteins have a dynamic relationship with the membrane.
true
Lipid-anchored proteins:
1. located ___ the lipid bilayer
2. found on both ___ and ___ sides
3. are ___ bonded to a lipid
1. outside
2. cytosolic, extracellular
3. covalently
Membrane fluidity implies that ___ and ___ molecules may move about in the membrane.
lipid
protein
Membrane fluidity/movement generally occurs in the ___ plane.
horizontal
Membranes are fluid because their constituent molecules interact via ___ bonds.
non-covalent
___ interactions are key in membrane fluidity.
hydrophobic
Lipid movement is generally restricted to ___ of the bilayer.
one leaflet
T/F: With respect to lipid movement in the membrane, flip-flopping is possible but energetically unfavorable.
true
T/F: Within a leaflet of the bilayer, lipid movement is very slow.
false (it's very rapid)
A single lipid may cross a bacterial membrane in ___, whereas a flip-flop could take ___.
1 second
days
T/F: Within the bilayer, movement is generally restricted.
false (it's generally unrestricted)
Although movement is generally unrestricted within the bilayer, parts of the membrane may be ___.
compartmentalized (fenced in)
The "fence" that compartmentalizes parts of the membrane may consist of ___.
integral proteins
T/F: Compartments in a membrane speed up lipid travel.
false (they slow travel)
Two general patterns of protein movement observed in the membrane
random
non-random (directed)
Patterns of protein movement are likely dependent on the ___.
nature of the protein
Restrictions on membrane protein movement:
1. Some do not move - they are considered ___.
2. Some are crowded by other proteins - they have ___ movement.
3. Compartmentalized proteins have ___ movement.
1. immobilized
2. reduced
3. somewhat restricted
Membrane proteins are inhibited by ___ materials.
extracellular
A technique to show integral protein movement within the membrane in which specific proteins are labeled with a fluorescent dye and a small portion of the cells are irradiated, creating a bleached circle
FRAP (fluorescence recovery after photobleaching)
The cell must precisely regulate the ___ of the membrane in order to carry out specific activities.
fluidity (or the inverse, viscosity)
T/F: Cell processes could simply not occur in too rigid or too fluid a membrane.
true
The fluidity of a membrane is based primarily on ___ and ___.
lipid composition
external temperature
With respect to membrane fluidity, it is important to understand that ___ can mitigate the effects of temperature.
lipid composition
The cell attempts to maintain a given membrane fluidity in the face of changing external conditions (mainly temperature) by appropriately modifying the ___ of the membrane. (cellular homeostasis)
lipid composition
As the body temperature is lowered below the normal body temp (37 degrees C) to a ___ temperature, the tails become more rigid and overall membrane fluidity is lowered.
transition
The temperature below which the movement of membrane molecules is greatly restricted
transition temperature
Transition temperature of the bilayer depends on the ability to pack individual ___ molecules together.
lipid
Tightly packed lipid molecules in the bilayer will have a ___ transition temperature.
higher
The membrane will assume ___ configuration at warmer temperatures.
crystalline gel
Saturated fatty acids are ___ rods; unsaturated fatty acids have ___ at the site of double bonds.
straight flexible rods
kinks
The kinks in unsaturated fatty acids make it more ___ to pack these fatty acids together.
difficult
The ___ the unsaturation of fatty acids, the ___ the transition temperature.
greater
lower
___ lipid hydrocarbon tails lower the transition temperature and reduce the tendency of the tails to interact with each other.
shorter
Three methods of adjusting membrane fluidity (keeping it more fluid)
1. more cis double bonds (i.e., more unsaturated fatty acids)
2. shorter chain length
3. more cholesterol molecules
T/F: Shorter chain length reduces the tendency of tails to interact with each other, so less likely for chains to be packed together
true
T/F: Cholesterol is found in relatively high amounts in eukaryotic cells
true
T/F: Cholesterol molecules keep hydrocarbon tails from interacting (packing together) and results in a lower transition temperature.
true
T/F: The function of each leaf of the lipid bilayer is considerably different
true
___ are microdomains of the membrane composed of specific phospholipids that float within the less "ordered" lipid membrane.
lipid rafts
Lipid rafts are thought to serve as platforms for ___ performing a common task.
proteins
T/F: There is debate as to whether lipid rafts occur in a natural cell environment.
true
The two primary purposes of the plasma (cell) membrane
1. retain cell contents
2. selectively allow passage of substances into and out of the cell
The bilayer must contain ___ permitting controlled passage of molecules.
proteins
T/F: Almost anything can cross a lipid bilayer given time.
true
A molecule's ability to cross the lipid bilayer is based on its ___ and ___.
size
polarity
Which size molecular crosses the lipid bilayer faster - smaller or larger?
smaller
Which molecule crosses the lipid bilayer faster - polar or non-polar?
non-polar (hydrophobic)
Because a lipid bilayer alone would be too restrictive for the passage of many substances, the cell needs ___ to 'circumvent' the bilayer and allow substances to pass through.
membrane proteins
The two ways movement of substances across the cell membrane is accomplished
passively (not requiring energy)
actively (requiring energy)
Three forms of diffusion across the cell membrane (passive movement)
1. simple
2. channel-mediated
3. facilitated
In ___, substances pass directly through the lipid bilayer.
simple diffusion
In ___, substances pass through the lipid bilayer via a channel
channel-mediated diffusion
In ___, substances pass through the lipid bilayer via a carrier.
facilitated diffusion
Active movement of a substance through the lipid bilayer occurs via a ___.
transport protein
In active transport, the transport protein undergoes a ___.
configurational change
Passive movement of a substance across cell membranes is accomplished by ___ and ___.
diffusion
filtration
In ___, molecules move randomly at very high speeds until they are evenly distributed.
diffusion
The net effect of movement through diffusion is that molecules will move from an area of ___ to an area of ___ until equilibrium is achieved.
higher concentration
lower concentration
Molecules are said to move down their ___.
concentration gradient
The diffusion of water is referred to as ___.
osmosis
T/F: Water diffuses rapidly across cell membranes.
true
T/F: Even though the lipid bilayer is hydrophobic, water is able to cross it directly -individual water molecules may slip in between phospholipids.
true
___ are protein channels that permit a more rapid diffusion of water into/out of cells.
aquaporins
Water diffuses through the membrane of certain cells more rapidly than predicted for a simple lipid bilayer due to the presence of ___.
aquaporins
Aquaporins = ___ diffusion
channel-mediated
___ make possible the movement of ions across the membrane.
ion channels
T/F: Lipid membranes are considered highly impermeable to charged molecules (Na+, K+, etc.) even though the rapid movement of ions across the cell membrane is crucial.
true
Ion channels are ___ proteins.
integral (transmembrane)
Ion channels contain a central ___.
aqueous pore
The two main categories of ion channels
open (leak)
gated
Three main types of gated ion channels
1. voltage-gated
2. ligand-gated
3. mechano-gated
___ (ion) channels respond to voltage differences across the membrane.
voltage-gated
___ (ion) channels respond to binding of a specific molecule.
ligand-gated
___ (ion) channels respond to mechanical forces.
mechano-gated
Although ion-gated channels must allow extremely rapid movement of ions through the central pore, the channels must remain ___.
selective
Gated channels selectively allow ions through by use of a ___.
selectivity filter
The selectivity filter for an ion channel permits both ___ and ___ of ion passage.
speed
selectivity
In order to get the ion of choice through an ion channel, the channel ___ the energy barrier.
lowers (energy required to get through fast)
For substances that do not cross the membrane or use a channel, an ___ that facilitates passage is necessary.
integral membrane protein (a facilitative transporter)
___ are often used by polar molecules such as glucose or amino acids to facilitate passage through the membrane.
facilitative transporters
T/F: Facilitative transporters can move solutes in either direction (depends on the concentration gradient).
true
Facilitative transporters assume a particular ___ to accept a specific molecule.
conformation
In facilitated diffusion, once the molecule is bound, the transporters change ___ to allow release of the molecule on the other side of the membrane.
configuration/confirmation
In order for diffusion to occur through a plasma membrane, the membrane must be ___.
semi-permeable
___ is a process in which substances travel down a concentration gradient.
diffusion
___ is used when passive transport is not possible.
active transport
In active transport, substances are being moved ___ the concentration gradient.
against (up)
T/F: Active transport is used for substances too large for channels or carriers (vesicular transport).
true
Active transport requires the energy of ___.
ATP
The sodium-potassium pump is an example of ___.
active transport
The concentration of ___ is much higher outside the cell.
Na+
The concentration of Na+ is much ___ outside the cell than inside.
higher
The concentration of ___ is much higher inside the cell.
K+
The concentration of K+ is much ___ inside the cell.
higher
The normal condition of a higher Na+ concentration outside the cell and a higher K+ concentration inside the cell is necessary for an ___ to take place (i.e., necessary for proper cellular function).
action potential
Cellular ionic concentration gradients would be rapidly lost if not for the action of the ___.
Na+/K+ pump
The Na+/K+ pump burns ___ of our daily calories.
half