biology EXAM #1 pt. 2 Flashcards
Biology is a
multidisciplinary science
Living organisms are subject to
basic laws of physics and chemistry
Organisms are composed of
matter
Matter is
Matter is made up of
anything that takes up space and has mass
elements
An element is
a substance that cannot be broken down to other substances by chemical reactions
A compound is a
substance consisting of two or more elements in a fixed ratio
-made of atoms joined by bonds
A compound has characteristics
(emergent properties) different from those of its elements
the number of protons determines the
atom’s identity
an atom’s electron distribution determines
its ability to form bonds.
a compound’s properties depend on its
atoms and how they are bonded together
About _____% of the __ elements are
-20-25% of the 92 elements are essential to life (essential elements)
COHN =
Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
CHNOPS
Most of the remaining elements on Earth
4% consists of calcium (Ca), phosphorus (P), potassium (K), and sulfur (S)
Trace elements :
are those required by an organism in minute quantities: Zn, Fe, Co, Fl, I, Cu, Mn
Some elements can be toxic, for example, :
Some species can become adapted to :
For example,
arsenic
environments containing toxic elements
some plant communities are adapted to serpentine
trace elements : Iodine – essential by ___
Used by :
Its deficiency – causes
-vertebrates
-a hormone produced in the thyroid gland
-abnormal enlargement of the thyroid or goiter.
Each element consists of :
unique atoms
An atom is
the smallest unit of matter that still retains the properties of an element
An atom has a ______ made up of:
-nucleus
-positively charged protons and uncharged neutrons, a surrounding cloud of negatively charged electrons.
Atoms are composed of
These include:
-subatomic particles
-Neutrons (no electrical charge)
Protons (positive charge)
Electrons (negative charge)
Neutrons and protons form :
Electrons form :
_________ are almost identical and are measured in
Electrons are so small they are:
-the atomic nucleus
-a “cloud” of negative charge around the nucleus
-Neutron mass and proton mass and are measured in Daltons
- ignored when calculating the total mass of an atom
Atoms of the various elements differ in
An element’s atomic number =
An element’s mass number =
Atomic mass, the atom’s total mass, can be approximated by
-number of subatomic particles
-the number of protons
-the sum of protons + neutrons in the nucleus
-the mass number
Mass:
Weight:
Amu (atomic mass unit)=
The number of electrons in an electrically neutral atom equals
-amount of matter
-is how strongly the mass is pulled by gravity.
-Dalton = 1.7 X 10-24 gram.
-the number of protons.
Electronic orbitals :
Electrons move within orbitals, three dimensional spaces with specific shapes located within each successive shell
Ions:
Elements with an extra or a minus electron on its outer shell: K+, Na+, Cl-, H+,OH-
Isotopes:
Isotopes are :
Most isotopes are ____, but some are _______, giving off particles and energy:
-Are atoms of an element have the same number of protons but may differ in number of neutrons
-two atoms of an element that differ in number of neutrons
-stable; radioactive.
isotopes of 12C are
13C and 14C (radioactive)
When 14C decays,
This converts :
one of its neutrons is converted to a proton and an electron.
14C to 14N, transforming the atom to a different element
Radioactive isotopes:
applications of radioactive isotopes in biological research:
decay spontaneously, giving off particles and energy
-Dating fossils
-Tracing atoms through metabolic processes
-Diagnosing medical disorders (Pet Scan, MRI scan)
-Autoradiography (used in gel electrophoresis – DNA studies)
A “parent” isotope decays into
In radiometric dating,
Half-life values vary
its “daughter” isotope at a fixed rate, expressed as the half-life
-scientists measure the ratio of different isotopes and calculate how many half-lives have passed since the fossil or rock was formed
-from seconds or days to billions of years
Radioactive isotopes are often used as
Radioactive tracers can be used to
They can also be used in combination
PET scanners can monitor the
diagnostic tools in medicine
track atoms through metabolism
with sophisticated imaging instruments
growth and metabolism of cancers in the body
(PET scan, MRI scan)
Energy is
Potential energy is the energy that
Matter has a natural tendency to move toward
the capacity to cause change
matter possesses because of its location or structure
the lowest possible state of potential energy
The electrons of an atom differ in:
The different states of potential energy that the electrons of an atom can have are called
Changes in potential energy of electrons can occur only
Electrons are found in____ ____ _____, each with a :
their amounts of potential energy based on their distance from the nucleus
-energy levels or electron shells.
-in steps of fixed amounts
- different electron shells; characteristic average distance and energy level
The first shell, closest to the nucleus, has the :
Electrons in outer shells have more
Electrons can change their position only if
-lowest potential energy.
-potential energy.
-they absorb or release a quantity of energy that matches the difference in potential energy between the two levels.
Electrons exist only at____________, which are also called:
An electron can move from one level to another only if
- fixed levels of potential energy
- electron shells.
-the energy it gains or loses is exactly equal to the difference in energy between the two levels.
The chemical behavior of an atom is determined by
The periodic table of the elements shows the:
Inert elements:
Valence electrons are those in
The chemical behavior of an atom is mostly determined by
the distribution of electrons in electron shells
electron distribution for each element
chemical unreactive valence; shell full
the outermost shell, or valence shell
the valence electrons
An orbital is
Each electron shell consists of
No more than __ electrons can occupy a single orbital
Atoms interact in a way that
is the three-dimensional space where an electron is found 90% of the time
a specific number of orbitals
2
completes their valence shells
CHEMICAL BONDING-
The formation and function of molecules depend on chemical bonding between atoms
Atoms with incomplete valence shells can:
These interactions usually result in atoms staying close together, held by :
Types:
- share or transfer valence electrons with certain other atoms
-attractions called chemical bonds
-Covalent
Ionic
Hydrogen
Van Der Waals Interactions
Elements with a full valence shell:
The bonding capacity of an element =
The valence ( or number of ___________) of elements:
are chemically inert
-= valence
-number of unpaired electrons
H is 1
O is 2
N is 3
C is 4
A covalent bond is the
In a covalent bond,:
sharing of a pair of valence electrons by two atoms
two valence electrons are shared on valence shell
The strongest type of bond?
COVALENT BOND
A molecule consists of
two or more atoms held together by covalent bonds
A single covalent bond, or _______, is :
A double covalent bond, or _________, is :
Covalent bonds can form between :
-single bond
-the sharing of one pair of valence electrons
-double bond
-the sharing of two pairs of valence electrons
-atoms of the same element or atoms of different elements
The notation used to represent atoms and bonding is called a
structural formula
H—H represents a; abbreviated:
^^structural formula
single bond
H2
O ═ O represents a
^^structural formula
double bond
Name (molecular formula)
example:
Indicates the elements and the number of atoms of each.
oxygen (O2)
what produces a molecule of water
Single covalent bonds between two atoms of H and one atom of O to
what produces methane:
Four H atoms and one C atoms forming a molecule of methane by means of covalent bonds
atom’s valence is:
A compound is a
-the bonding capacity
-(missing number of electrons in the outer shell)
- combination of two or more different elements
Electronegativity is
The more electronegative an atom, the more:
In a nonpolar covalent bond,:
Carbon and hydrogen have similar ________________, in methane, :
an atom’s attraction for the electrons in a covalent bond
strongly it pulls shared electrons toward itself
- the atoms share the electron equally
-electronegativities; they share electrons more or less equally.
In a polar covalent bond, :
one atom is more electronegative, and the atoms do not share the electron equally
(Oxygen is much more electronegative than hydrogen, it attracts e- more strongly)
Atoms sometimes strip electrons from their:
The two resulting oppositely charged atoms or molecules are called
A positively charged ion is called a
A negatively charged ion is called a
Anions and cations attract each other; this attraction is called
bonding partners
- ions
-cation
-anion
-an ionic bond
IONIC BOND
An example is the transfer of an electron from
After the transfer of an electron, :
A charged atom (or molecule) is called
A salt is a compound formed by
-sodium (Na+) to chlorine (Cl-)
-both atoms have charges
-an ion
-ionic bonding
Compounds formed by ionic bonds are called
Salts, such as sodium chloride (table salt), are often found in nature as
- ionic compounds, or salts
-as crystals
NaCl itself is not a molecule; the formula for an ionic compound indicates
Most salts are :
the ratio of elements in a crystal of the salt
quite stable when dry, but dissociate quite easily in water
Most of the strongest bonds in organisms are :
covalent bonds that form a cell’s molecules
Many large biological molecules are held in their functional form by :
The reversibility of these can be:
-weak bonds
-weak bonds can be an advantage
Weak chemical bonds, such as ___ ___ and ____ ____, are also important in organisms
Weak chemical bonds reinforce :
Example, the _________ bonding:
-gives water specific characteristics:
-Keeps protein molecules :
-ionic bonds and hydrogen bonds
-shapes of large molecules and help molecules adhere to each other
-hydrogen bonding:
cohesion, surface tension, adhesion
folded in their characteristic three-dimensional shapes and DNA double helix held together.
A hydrogen bond forms between molecules when
In living cells, the electronegative partners are:
a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom
usually oxygen or nitrogen atoms
If electrons are not evenly distributed, they may
Molecules or atoms that are very close together can
Van der Waals interactions are attractions between:
Collectively, such interactions can be _______, as between molecules of a gecko’s toe hairs and a wall surface
-accumulate by chance in one part of a molecule
-be attracted by fleeting charge differences
-molecules that are close together as a result of these charges
- strong
A molecule’s shape is usually very important to its:
A molecule’s shape is determined by
In a covalent bond, the s and p orbitals may hybridize, creating
-function
- the positions of its atoms’ valence orbitals
-specific molecular shapes
Molecules have characteristic :
Shape is usually the basis for :
Biological molecules :
Molecules with similar shapes can have :
-size and shape
-the recognition of one biological molecule by another, for the function of molecules
-recognize and respond to one another with specificity (i.e.. Enzymes)
-similar biological effects
Molecular shape determines how:
Opiates, such as _________, and naturally produced __________ have similar effects because
biological molecules recognize and respond to one another
-morphine; endorphins
their shapes are similar and they bind the same receptors in the brain
MOLECULAR MIMICRY
Morphine affects pain reception and emotional state by
-mimicking the brain´s natural endorphins (produces euphoria and releaves pain)
Chemical reactions lead to:
The starting molecules of a chemical reaction are called :
The final molecules of a chemical reaction are called:
new arrangements of atoms
-reactants
-products
Photosynthesis is an:
In photosynthesis, :
- important chemical reaction
-sunlight powers the conversion of CO2 and H20 to glucose (C6H12O6) and O2
6 CO2 + 6 H2O –> C 6 H12O6 + 6 O2.
Some chemical reactions go to completion:
Most chemical reactions are reversible:
Chemical equilibrium is reached when :
At equilibrium the relative concentrations of reactants and products :
All reactants are converted to products
- Products of the forward reaction become reactants for the reverse reaction
-the forward and reverse reaction rates are equal and occur at the same rate
-do not change
Pet Scan
-is an examinatioin that involves the acquisition of images based on the detection of radiatioin from the emision of positron (tiny particles emitted from a radioactive substance) that have been administered to the patient. These images are used to evaluate a variety of diseases.
MRI Scans (magnetic resonance imaging)
-is a new technique, used since the 1980s. Uses magnetic and radio waves so there is no exposure to x-rays or other forms of radiation.
Carbon dating
- radioactive dating which is applicable to matter that was once living and presumed to be in equilibrium with the atmosphere, taking carbon dioxide from the air for photosynthesis.
Autoradiography
- technique that uses x-ray film to visualize molecules or fragments of molecules that have been radioactively labeled. It can be used to analyze the length and number of DNA fragments after they have separated from each other by a method called gel electrophoresis
