Unit 1: Molecules and Cells Flashcards
polar covalent bonds
when electrons are more attracted to one atom than the other
polar molecule
unequal sharing of electrons in a molecule
cohesion
the linking together of like molecules, often by hydrogen bonds
adhesion
the clinging of one substance to another
surface tension
a measure of how difficult it is to stretch or break a surface of a liquid
kinetic energy
energy of motion
heat
energy in its most random form-amount of heat is a measure of the matter’s total kinetic energy due to the motion of its molecules
temperature
a measure of heat intensity that represents the average kinetic energy of molecules
calorie (cal)
amount of heat it takes to raise the temperature of 1g of water by 1 degree Celsius
kilocalorie (kcal)
amount of heat required to raise the temperature of 1kg of water by 1 degree Celsius
joule (J)
energy unit, 1J=0.239 cal 1 cal=4.184J
specific heat
amount of heat that must be added/lost for 1g of that substance to change temperature by 1 degree Celsius
heat of vaporization
quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state
evaporative cooling
when a liquid evaporates, the surface of the liquid that remains behind cools down
solution
a liquid that is a completely homogeneous mixture of 2 or more substances
solvent
the dissolving agent
solute
substance that is dissolved
aqueous solution
solution in which water is a solvent
hydration sphere
sphere of water molecules around each dissolved ion
hydrophilic
any substance that has an affinity for water
colloid
astable suspension of the fine particles in a liquid
hydrophobic
substances that do not have an affinity for water–nonionic and nonpolar
molecular mass
the sum of the masses of all the atoms in a molecule
mole (mol)
6.02*10^23 –>number of molecules
molarity
the number of moles of solute per liter of solution
hydrogen ion
a single proton with a charge of 1+
hydroxide ion
a water molecule that lost a proton (OH-)
acid
a substance that increases the hydrogen ion concentration of a solution
ex: when HCl is added to H20, HCl–>H+ + Cl-
base
a substance that reduces the hydrogen ion concentration of a solution
pH
negative logarithm (base 10) of the hydrogen ion concentration pH= -log[H+]
buffer
a substance that minimizes changes in the concentrations of H+ and OH-
ocean acidification
when CO2 dissolves in seawater, it reacts with water to form carbonic acid, which lowers ocean pH
acid precipitation
refers to rain, snow, or fog with a pH lower than 5.2
functional groups
a specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and involved in chemical reactions
ketone
if carbon group is within the carbon skeleton
aldehyde
if carbon group is at the end of the carbon skeleton
adenosine triphosphate (ATP)
an adenine containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed
macromolecule
a giant molecule formed by the joining of smaller molecules, usually by a dehydration reaction
polymer
a long macromolecule consisting of many similar or identical building blocks linked by covalent bonds
monomers
repeating units that serve as the building blocks of a polymer
enzymes
specialized macromolecules that speed up chemical reactions
dehydration reaction
when monomers are connected by a reaction in which two molecules are covalently bonded to each other, with the loss of a water molecule
hydrolysis
when polymers are disassembled to monomers by adding water
carbohydrate
sugars and polymers of sugars
monosaccharide
monomer of carbohydrates; molecular formulas usually CH20
disaccharide
two monosaccharides joined
glycosidic linkage
covalent bond formed between two monosaccharides by a dehydration reaction
polysaccharides
polymers with a few hundred to a few thousand monosaccharides joined by a glycosidic linkage
starch
a storage polymer of glucose monomers found in plants
glycogen
a storage polymer of glucose monomers found in animals
cellulose
polysaccharide that’s a major component of the tough walls that enclose plant cells
chitin
carbohydrate used by arthropods to build their exoskeletons
lipids
compounds that mix poorly with water
fat
constructed from two kinds of smaller molecules: glycerol and fatty acids
fatty acid
long carbon skeleton, usually 16-18 carbon atoms in length
triglyceride
3 fatty acid molecules + ester linkage (bond between a hydroxyl group and a carboxyl group) + glycerol
saturated fatty acid
no double bonds between carbons means as many hydrogen can bond to carbon skeleton –> saturated with hydrogen
unsaturated fatty acid
has one or more double bonds with one fewer hydrogen atom on each double-bonded carbon
trans fat
an unsaturated fat, formed artificially during hydrogenation of oils, containing one or more trans double bonds
phospholipids
a lipid made up of glycerol joined to 2 fatty acids and a phosphate group; hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest acts as a polar, hydrophilic head
steroids
lipids characterized by a carbon skeleton consisting of four fused rings
cholesterol
a steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as many hormones
catalysts
chemical agents that selectively speed up chemical reactions without being consumed by the reaction
polypeptide
polymers of amino acids
protein
a biologically functional molecule that consists of one or more polypeptides, each folded and coiled into a specific three-dimensional structure
amino acid
an organic molecule possessing both an amino group and a carboxyl group
peptide bond
covalent bond between two amino acids
primary structure
linked series of amino acids with a unique sequence
secondary structure
coils and folds of amino acids->hydrogen bonds between repeating consitutents
helix
delicate coil held together by hydrogen bonds
pleated sheet
secondary structure of proteins
tertiary structure
when the sheets and coils fold over on each other
hydrophobic interaction
the exclusion of nonpolar substances by water molecules
disulfide bridges
forms when 2 cytosine monomers are brought close together by the folding of a protein
quaternary structure
when 2 or more proteins come together
sickle-cell disease
an inherited biological disorder, caused by the substitution of one amino acid for another amino acid at a specific point in the primary structure of hemoglobin
denaturation
when a protein unravels and loses its original shape and becomes inactive
chaperonin
assists in proper folding of proteins
activation energy
the initial investment of energy for starting a reaction
substrate
the reactant an enzyme acts on
enzyme-substrate complex
when an enzyme binds to its substrate
active site
a pocket or groove on the surface of the enzyme where catalysis occurs
induced fit
as a substrate enters an enzyme’s active site, the enzyme changes shape slightly due to interactions between the substrate’s chemical groups and chemical groups on the side chains of the amino acids that form the active site
cofactors
nonprotein helpers
coenzyme
a cofactor that is organic
competitive inhibitors
inhibitors that resemble the normal substrate molecule and compete for admission into the active site
noncompetitive inhibitors
inhibitors that do not directly compete with the substrate to bind to the enzyme at the active site
allosteric regulation
any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site–either inhibition or stimulation
cooperativity
when a substrate molecule binds to one active site in a multisubunit and triggers a shape change in all the subunits, thereby increasing catalytic activity at the other active sites
feedback inhibition
when ATP allosterically inhibits an enzyme in an ATP-generating pathway
amphipathic
when a molecule has both a hydrophilic region and a hydrophobic region
fluid mosaic model
the membrane is a fluid structure with a “mosaic” of various proteins embedded in or attached to a double layer of phospholipids
selective permeablity
when the membrane allows some substances to cross it more easily than others
integral proteins
proteins that penetrate the hydrophobic interior of the lipid bilayer
peripheral proteins
proteins that are appendages loosely bound to the surface of the membrane, often to exposed parts of integral proteins
glycolipids
carbohydrates covalently bonded to lipids
glycoproteins
carbohydrates covalently bonded to proteins
transport proteins
proteins where hydrophilic substances can avoid contact with the lipid bilayer by passing through them
channel proteins
have a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane
aquaporins
special proteins in the membrane that water molecules pass through
diffusion
the movement of molecules of any substance so that they spread out evenly into the available space
concentration gradient
the region along which the density of a chemical substance increases or decreases
passive transport
the diffusion of a substance across a biological membrane
osmosis
the diffusion of free water across a selectively permeable membrane
tonicity
the ability of a surrounding solution to cause a cell to gain or lose water
isotonic
where the solute concentration is the same and there will be no net change of the amount of water
hypertonic
a solution that has more solutes than another
hypotonic
a solution that has less solutes than another
osmoregulation
the control of solute concentrations and water balance
turgid
very firm
plasmolysis
when a plant cell loses water, it will begin to shrink, bringing in the cell membrane with it
facilitated diffusion
polar molecules and ions diffuse through the membrane with the help of transport proteins that span the membrane
ion channels
channel proteins that transport ions
gated channels
ion channels that open/close in response to a stimulus
active transport
when a solute is pumped against its gradient and expends energy
membrane potential
voltage across a membrane
electrochemical gradient
the combination of forces acting on an ion
electrogenic pump
a transport protein that generates voltage across a membrane
proton pump
main electrogenic pump of plants, bacteria, and fungi
cotransport
when a single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes
endocytosis
the cell takes in biological molecules and particulates matter by forming new vesicle from the plasma membrane
exocytocytosis
the process of secreting certain biological molecules by the fusion of vesicles with the plasma membrane
phagocytosis
when a cell engulfs a particle by wrapping it in a vesicle that becomes a food vacuole
pinocytosis
when the cell “gulps” droplets of extracellular fluid into tiny vesicles
receptor-mediated endocytosis
enables the cell to acquire bulk quantities of specific substances
cytosol
a semifluid, jellylike substance found in cells
cytoplasm
interior of a cell
plasma membrane
the boundary of every cell that functions as a selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell
nucleus
contains most of the genes in the eukaryotic cell
nuclear envelope
encloses the nucleus, separating its contents from the cytoplasm
pore complex
an intricate protein structure that lines each pore and regulates the entry and exit of proteins and RNA
nuclear lamina
a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
chromosomes
structures that carry the genetic information
chromatin
the complex of DNA and proteins making up chromosomes
nucleolus
structure within the nondividing nucleus
ribosomes
complexes made of ribosomal RNA and protein that are the cellular components that carry out protein synthesis
endomembrane system
membranes found in a eukaryotic cell
vesicles
sacs made of membrane
smooth endoplasmic reticulum
produces lipids, stores calcium ions, and detoxifies drugs/poisons
rough endoplasmic reticulum
produces proteins
transport vesicles
vesicles in transit from one part of the cell to another
golgi apparatus
warehouse for receiving, sorting, shipping, and manufacturing
lysosome
a membranous sac of hydrolytic enzymes that an animal cell uses to digest macromolecules
vacuoles
large vesicles derived from the endoplasmic reticulum and golgi apparatus
food vacuoles
formed by phagocytosis and are vesicles that engulf food
contractile vacuoles
pump excess water out of cell
central vacuoles in plants
contains important nutrients, poisons, and pigments
mitochondria
the sites for cellular respiration
chloroplast
the sites for photosynthesis
cell division
reproduction of cells
cell cycle
the life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells
genome
a cell’s genetic information
chromosomes
DNA molecule packages
chromatin
the entire complex of DNA and proteins that is the building material of chromosomes
somatic cells
all body cells except the reproductive cells
gametes
sperm and egg
sister chromatids
joined copies of the original chromosome
centromere
a region containing specific DNA sequences where sister chromatids are attached
mitosis
the division of the genetic material in the nucleus
cytokinesis
the division of the cytoplasm
mitotic phase
mitosis and cytokinesis
interphase
cell growth and DNA replication
G1 phase
growth
S phase
copying of chromosomes
G2 phase
more growth and preparation for division
prophase
chromatin fibers condense and nucleolus disappears
prometaphase
nuclear envelope fragments and microtubules extend and some attach to kinetochores
metaphase
chromosomes meet at the metaphase plate (middle of cell)
anaphase
sister chromatids part and are pulled to opposite ends of the cell
telophase
two daughter nuclei form in the cell and nuclear envelopes start to form and nucleoli appear
mitotic spindle
consists of fibers made of microtubules and associated proteins
centrosome
a subcellular region containing material that functions throughout the cell cycle to organize the cell’s microtubules
aster
a radial array of short microtubules
kinetochore
a structure of proteins associated with specific sections of chromosomal DNA at each centromere
cleavage
cytokinesis in animal cells
cleavage furrow
a shallow groove in the cell surface near the old metaphase plate
cell plate
part of the cell wall starts to form in plant cells that are splitting
binary fission
asexual reproduction of single-celled eukaryotes
origin of replication
specific place on the origin
cell cycle control system
a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
checkpoint
a control point where stop and go signals can regulate the cycle
G0 phase
nondividing state
cyclin
a protein that cyclically fluctuates concentration in the cell
cyclin-dependent kinases (Cdks)
cyclin kinases
MPF
the cyclin-Cdk that was first discovered
growth factor
a protein released by certain cells that stimulates other cells to divide
density-dependent inhibition
the effect of an external physical factor that stops crowded cells from dividing
anchorage dependence
to divide, cells must attached to a substratum
transformation
the process that converts a normal cell to a cancer cell
benign tumor
cancer cells that have too few genetic and cellular changes to survive at another location
malignant tumor
cells whose genetic and cellular changes enable them to spread to new tissues and impair the functions of one or more organs
metastasis
spread of cancer to locations distant from their original site
