The study of ____________________ is interdisciplinary because solutions require many different approaches to solve a problem
Living systems have seven characteristics in common
they are composed of one or more cells; are complex and highly ordered; can respond to stimuli; can grow, reproduce, and transmit genetic information to their offsprings; need energy to accomplish work; can maintain relatively constant internal conditions (homeostasis); and are capable of evolutionary adaptation to the environment
____________ is concerned with developing an increasingly accurate description of nature through observation and experimentation
___________ applies general principles to predict specific results
_____________ uses specific observations to construct general specific principles
A _____________ is constructed based on observation, and it must generate experimentally testable predictions; rejected if their predictions cannot be verified by observation or experiment
______________ involve a test in which a variable is manipulated, and a control in which the variable is not manipulated
______________ attempts to understand a complex system by breaking it down into its component parts; limited because parts may act differently when isolated from the larger system
A ________ provides a way of organizing our thinking about a problem; may also suggest experimental approaches
a proposed explanation for some natural phenomenon; a body of concepts that explains facts in an area of study
extends the boundaries of what we know
seeks to use scientific findings in practical areas such as agriculture, medicine, and industry
shows how a scientist develops a hypothesis and sets forth evidence, as well as how a scientific theory grows and gains acceptance
Darwin's theory of evolution
During the voyage of the H.M.S Beagle, _________ had an opportunity to observe worldwide patterns of diversity
Darwin proposed ____________ as a mechanism for evolution
Traits of offspring can be changed by
the basic unit of life and is the foundation for understanding growth and reproduction in all organisms
encoded in genes found in the DNA molecule, is passed on from one generation to the next; the molecular basis of inheritance explains the continuity of life
The ___________ of macromolecules and their complexes is dictated by and dependent on their ________. Similarity of ___________________ from one life form to another may indicate an evolutionary relationship
function; structure; structure and function
Living organisms appear to have had a common origin from which a ___________________ arose by evolutionary change; they can be grouped into three domains comprising six kingdoms based on their differences
diversity of life
The underlying similarities in _______________ and _______________ support the contention that all life evolved from a single science
Cells can sense and respond to environmental changes through proteins located on their ___________________. Differential expression of stored genetic information is the basis for different cell types
Organisms are open systems that need a constant supply of energy to maintain their stable __________________________. Living things are able to self-organize, creating levels of complexity that may exhibit emergent properties.
All matter is composed of
Electrically neutral atoms have the same number of __________ as __________.
Atoms that gain or lose electrons are called
Each atom is defined by its _________________; the number of protons in the nucleus
The sum or the mass of protons and neutrons in an atom
Forms of a single element with different numbers of neutrons, and thus different atomic mass
Isotopes that are unstable
Determine the chemical behavior of atoms; the potential energy of electrons increases as distance from the nucleus increases.
Contain discrete energy levels
The loss of electrons from an atom
The gain of electrons
Electrons can be transferred from one atom to another in
coupled redox reactions
Atoms tend to establish completely full outer energy levels. Elements with filled outermost orbitals are
_______ elements occur naturally in the Earth's crust. ______ of these elements are found in living organisms in grater than trace amounts.
Compounds of carbon
The majority of molecules in living systems are composed of C bound to
H, O, and N
Molecules contain two or more atoms joined by
Contain two or more different elements
Ions with opposite electrical charges form
A molecule formed by a ______________ is stable because it has no net charge; may be single, double, or triple, depending on the number of pairs of electrons shared
________ rule is satisfied, at it has no unpaired electrons
Involve equal sharing of electrons between atoms
Nonpolar covalent bonds
Involve unequal sharing of electrons
Polar covalent bonds
__________ alter bonds
Weak interactions between a partially positive H in one molecule and partially negative O in another molecule; water's structure facilitates
The tendency of water molecules to adhere to one another due to hydrogen bonding. ________ of water is responsible for its surface tension
Water molecules are_______. _______ occurs when molecules adhere to other polar molecules
Action results from water's adhesion to the sides of narrow tubes, combined with its cohension
Water's high specific heat helps maintain
Solid water is less dense than
makes it a good solvent for polar substances and ions
Polar molecules or portions of molecules are attracted to water
Molecules that are nonpolar are repelled by water
Makes nonpolar molecules clump together
Will aggregate to avoid water
Carbon dioxide and water react reversibly to form
The key buffer in the human blood is the
carbonic acid/ bicarbonate pair
The backbone of all biological molecules, can form four covalent bonds and make long chains
Consist of carbon and hydrogen, and their bonds store considerable energy
Small molecular entries that confer specific chemical characteristics when attached to a hydrocarbon
Carbon and hydrogen have similar electronegativity so C--H bonds are not
Oxygen and nitrogen have greater electronegativity, leading to
Molecules with the same formula but different structures
Differ in how groups are attached
Most important biological macromolecules; long chains of monomer units
Biological polymers are formed by elimination of _____ from two monomers. They are broken down by adding water (__________)
The empirical formula of a carbohydrate _______.
Used for energy storage and as structural molecules
_____________ contain three to six or more carbon atoms. Examples are glyceraldehyde (3 carbons), deoxyribose (5 carbons), and glucose (6 carbons)
The general formula for six carbon sugars is ________, and many isomeric forms are possible. Living systems often have enzymes for converting isomers from one to the other
________________ account for differences in molecular properties
______ have the same molecular formulas but different structures
____________________________ include carbohydrates, nucleic acids, proteins, and lipids
___________________ are simple sugars
Sugar isomers have ______________ differences
______________ serve as a transport molecules in plants and provide nutrition in animals
Plants convert _______ into the disaccharide sucrose for transport within their bodies
_______________ provide energy storage and structural components
Glucose is used to make three important polymers: ________ (in animals), and ______ and _________ (in plants)
glycogen; starch; cellulose
A related structural material found in arthropods and many fungi
_____________________ and _________________ are polymers composed of nucleotide monomers
Double helix held together by specific base pairs: adenine with thymine and guanine with cytosine.
The _________________ sequence constitutes the genetic code
___ is a transcript of a DNA strand.
___ is made by copying DNA. This transcript is then used as a template to make proteins
Other nucleotides are vital components of _______________.
____________________ provides energy in cells; NAD- and FAD transport electrons in cellular processes
Adenosine triphosphate (ATP)
Most enzymes are __________. ________ provide defense, transport, motion, and regulation, among many other roles; polymers of amino acids
Amino acids are joined by _______________ to make ___________.
peptide bonds; polypeptides
Proteins have high levels of ______________.
Protein is defined by the following hierarchy:
primary (amino acid sequence), secondary(hydrogen bonding patterns), tertiary (three-dimensional folding), and quaternary (associations between two or more polypeptides)
______ and _______ are additional structural characteristics
Similar structural elements found in dissimilar proteins; can create folds, creases, or barrel shapes
Functional subunits or sites within a tertiary structure
The process of folding relies on___________________; assist in the folding of proteins; example: heat shock proteins
Some diseases may result in ________ folding.
________________ inactivates proteins; an unfolding of tertiary structure, which usually destroys function
Some denatured proteins may recover function when conditioning are returned to normal. This implies that ____________________ strongly influences ____________________.
primary structure; tertiary structure
__________________ refers to separation of quaternary subunits with no changes to their tertiary structure.
Insoluble in water because they have a high proportion of nonpolar C--H bonds
____ consist of complex polymers of fatty acids attached to glyceral; excellent energy-storage molecules
Lipids exist as ______________, three fatty acids connected to a glycerol molecule.
Contain the maximum number of hydrogen atoms
Saturated fatty acids
Contain one or more double bonds between carbon atoms
Unsaturated fatty acids
Excess carbohydrate is converted to fat for
_____________ form membranes; contain two fatty acids and one phosphate attached to glycerol
In __________________________, the phosphate heads are hydrophilic and cluster on the two faces of the membrane, and the hydrophobic tails are in the center
The unifying foundation of cell biology
All organisms are composed of one or more _____. They arise only by division of preexisting _____.
__________ is constrained by the diffusion distance. As it increases, diffusion becomes inefficient
________________ allow visualization of cells and components
______________ gives better resolution than is possible with the naked eye. Staining with chemicals enhances contrast of structures
____ exhibit basic structural structure
All cells have centrally located ___, a semifluid cytoplasm, and an ___________________________________.
DNA; enclosing plasma membrane
_____________ cells have relatively simple organization; contain DNA and ribosomes, but they lack a nucleus, an internal membrane system, and membrane-bounded organelles. A rigid cell wall surrounds the plasma membrane.
____________________ consist of peptidoglycan.
Bacterial cell walls
Composed of carbohydrate cross-linked with short peptides
___________ lack peptidoglycan
Do not contain peptidoglycan, and they have unique plasma membranes
Archaeal cell walls
Some prokaryotes move by means of
Rotate because of proton transfer across the plasma membrane
Cells that have a membrane-bounded nucleus, an endomembrane system, and many different organelles
Acts as the information center; surrounded by an envelope of two phospholipid bilayers; the outer layer is contiguous with the ER
A region of the nucleoplasm where rRNA is transcribed and ribosomes are assembled
In most _______________, DNA is organized into a single circular chromosome
In most ________________, numerous chromosomes are present
The cell's protein synthesis machinery; translate mRNA to produce polypeptides; found in all cell types
Creates channels and passages within the cytoplasm
The endoplasmic reticulum (ER)
A site of protein synthesis; studded with ribosomes, synthesizes and modifies proteins and manufactures membranes
The Rough ER
Has multiple roles; lacks ribosomes; it is involved in carbohydrate and lipid synthesis and detoxificaiton
The smooth ER
Sorts and packages proteins; receives vesicles from the ER, modifies and packages macromolecules, and transports them
The golgi apparatus
Contain digestive enzymes; break down macromolecules and recycle the components of old organelles
A diverse category of organelles
Plants use __________ for storage and water balance
Have a double-membrane structure, contain their own DNA, and can divide independently
Mitochondria and chloroplasts
Mitochondria metabolize sugar to generate ___.
The inner membrane of mitochondria is extensively folded into layers called ______. Proteins on the surface and in the inner membrane carry out metabolism to produce ATP.
__________ use light to generate ATP and sugars
______________ capture light energy via thylakoid membranes arranged in stacks called _________, and use it to synthesis glucose.
Mitochondria and chloroplasts arose by
Proposes that mitochondria and chloroplasts were once prokaryotes engulfed by another cell
The endosymbiont theory
Consists of crisscrossed protein fibers that support the shape of the cell and anchor organelles
Type of fiber that composes the cytoskeleton;
long, thin polymers involved in cellular movement
Actin filaments or microfilaments
Type of fiber that composes the cytoskeleton
hollow structures that move materials within a cell
Type of fiber that composes the cytoskeleton
serve a wide variety of functions
_____________ are microtubule-organizing centers; help assemble the nuclear division apparatus of animal cells
___________ helps move materials within cells.
Molecular motors move vesicles along microtubules. ________ and _______ are two motor proteins.
_________ occurs as actin polymerization forces the cell membrane forward, while myosin pulls the cell body forward
___________ and _______ aid movement
___________ have a 9 + 2 structure and arise from a basal body; _________ are shorter and more numerous than flagella
Eukaryotic flagella; cilia
__________ provide protection and support; composed of cellulose fibers
Plant cell walls
The ______________________, between cell walls, holds adjacent cells together
______________ secrete an extracellular matrix.
_________________ are the main component of extracellular matrix (ECM) of animal cells.
____________ give cells identity.
______________ and ___ proteins on cell surfaces help distinguish self from nonself.
_________________ mediate cell-to-cell adhesion.
Cell junctions include _____ junctions, _________ junctions, and _____________ junctions.
tight; anchoring; communicating
In animals, _________________ allow the passage of small molecules between cells.
In plants, _______________ penetrate the cell wall and connect cells
The _____________________________ shows proteins embedded in a fluid lipid bilayer; proteins float on or in the lipid bilayer
fluid mosaic model
_____________ are sheets of phospholipid bilayers with associated proteins.
______________ regions of a membrane are oriented inward and ____________ regions oriented outward.
_________ consists of four component groups.
In eukaryotic cells, membranes have four components:
a phosopholipid bilayer, transmembrane proteins (integral membrane proteins), an interior protein network, and cell-surface markers
The __________________________, is composed of cytoskeletal filaments and peripheral membrane proteins, which are associated with the membrane but are not an integral part
interior protein network
Membranes contain _____________ and ___________ on the surface that act as cell identity markers
__________________________ has provided structural evidence.
_______________________________ and _______________________________ have confirmed the structure predicted by the fluid mosaic model
Transmission electron microscopy (TEM); scanning electron microscopy (SEM)
______________ are composed of two fatty acids and a phosphate group linked to a three-carbon glycerol molecule
Phospholipids spontaneously form
The phosphate group of a phospholipid is _______ and _____________; the fatty acids are ________ and ___________; and they orient away from the polar head of the phospholipids.
polar and hydrophilic; nonpolar and hydrophobic
The _____________ of the lipid bilayer impedes the passage of water and water-soluble substances
The phospholipid bilayer is
_____________________ of water keeps the membrane in its bilayer configuration; however _____________ and ______________ in the membrane are loosely associated and can diffuse laterally.
Hydrogen bonding; phospholipids and unanchored proteins
_________ can change; depends on the fatty acid composition of the membrane
________________________ tend to make the membrane more fluid because of the "kinks" of double bonds in the fatty acid and tails
Some bacteria have enzymes that alter the fatty acids of the membrane to compensate for ____________________.
__________ and __________________________ perform key functions.
proteins; protein complexes
______________ are integral membrane proteins that carry specific substances through the membrane
_________ often occur on the interior surface of the membrane
__________________________ respond to external chemical messages and change conditions inside the cell;
cell surface receptors
_________________ markers on the surface allow recognition of the body's cells as "self".
___________________ of the membrane proteins relate to function.
Transport can occur by ____________.
_________________ is the passive movement of a substance along a chemical or electrical gradient. Biological membranes pose a barrier to hydrophilic polar molecules, while they allow hydrophobic substances to diffuse freely.
Proteins allow membrane diffusion to be _________.
________ and large ________________________ cannot cross the phospholipid bilayer.
Ions; hydrophilic molecules
_________ is the movement of water across membranes.
_______________ uses energy to move materials against a concentration gradient.
Active transports are classified based on the number of _______ and _____________.
molecules; direction of transport
____________ transport a specific molecule in one direction; __________ transport two molecules in the same direction; __________ transport two molecules in opposite directions
uniporters; symporters; antiporters
The sodium-potassium pump runs directly on _______.
___________ transport uses ATP indirectly; occurs when the energy released by a diffusing molecule is used to transport a different molecule against its concentration gradient in the same direction.
____________________ is similar to coupled transport, but the two molecules move in opposite directions
________________ moves large quantities of substances that cannot pass through the cell membrane
Bulk material enters the cell in ___________.
In ______________, the cell membrane surrounds material and pinches off to form a vesicle. In _____________________________, specific molecules bind to receptors on the cell membrane.
endocytosis; receptor-mediate endocytosis
Material can leave the cell by ________________.
In _________, material in a vesicle is discharged when the vesicle fuses with the membrane.