Chapter 2: The Chemical Context of Life Flashcards
What does matter consist of?
chemical elements in pure form and in combinations called compounds
What does an element’s properties depend on
the structure of its atoms
What does the formation and function of molecules depend on?
chemical bonding between atoms
What do chemical reactions do?
make and break chemical bonds
What gives water properties that help make life possible on Earth
Hydrogen bonding
What are organisms composed of?
matter
What is matter?
anything that takes up space and has mass
What is an element?
a substance that cannot be broken down to other substances by chemical reactions
How many elements occur in nature?
92
What is a compound?
a substance consisting of two or more elements combined in a fixed ratio
What elements are needed to live a healthy life and reproduce?
Essential elements
How many essential elements do humans need?
25
How many elements do plants need?
17
What elements are required by an organism in only mine quantities?
Trace elements
T/F: Fe is only required in humans
False - it is required in all forms of life
What is iron used to make in humans?
hemoglobin in blood
What is I used by
the thyroid gland
What is Iodine deficiency called?
goiter
What compound accounts for the high percentage of oxygen in the human body?
water
What is an atom?
The smallest unit of matter that still retains the properties of that element
What are the 3 parts an atom is composed of?
neutrons, protons, and electrons
What is the charge of a neutron
neutral
What is a charge of a proton?
positive
What is the charge of an electron?
negative
What is the mass of a neutron in daltons?
1
What is the mass of a proton in daltons?
1
What is the mass of an electron in daltons?
1/2000 (but we consider it to be 0)
Where is the neutron?
the atomic nucleus
Where is the proton?
atomic nucleus
Where is the electron?
orbitals around the nucleus
What is the atomic number?
the number of protons which is unique to each element?
What is the mass number?
the number of protons and neutrons found in the nucleus
What is equal since an atom is electrically neutral?
The number of protons and the number of electrons
What are isotopes?
atoms of the same element that have the same number of protons but different numbers of neutrons (different weights)
What is a radioactive isotope?
an isotope that decays spontaneously releasing particles and energy
What is half-life?
the time required for 50% of the atom of any radioactive material to decay
What is energy?
the capacity to cause change–for instance, by doing work
What is potential energy?
the energy that matter possesses because of its location or structure
What does matter have a tendency to do?
move to the lowest possible state of potential energy
What are valence electrons?
the number of electrons in the outermost shell
What does the chemical behavior of an atom depend on?
the number of valence electrons
What happens when an electron is moved away from the nucleus?
NRG is absorbed
What happens when an electron is moved toward the nucleus?
NRG is released
Why is neon unreactive?
Because its valence shell is already filled, therefore it is inert
How many electrons can be placed in the first orbital?
2
How many electrons can be placed in the second orbital?
8
How many electrons can be placed in the third orbital?
8
Why do Fluorine and Chlorine exhibit similar chemical behavior?
Because they have the same number of valence electrons
What are chemical bonds
attractions caused by interactions that either share or transfer valence electrons
What type of bond shares one pair of electrons?
A single bond
What type of bond shares two pairs of electrons?
Double
What us electronegativity?
the attractions of a particular atom for the electrons of the covalent bond
What bond if formed when two atoms have the same electronegativity?
non-polar covalent bond
What bond is formed when two atoms do not share the electrons equally?
polar covalent bond
When does ionic bonding occur?
when there is a transfer or stealing of electrons from one atom to another
What happens any time an atom loses or gains electrons?
it becomes charged and is considered an ion
What is a cation?
a positively charged atom
What is an anion?
a negatively charged atom
What are ionic compounds?
compounds formed by ionic bonds
What is another word for ionic compounds?
salts
What are covalent and ionic bonds found within the molecule considered?
intramolecular bonds
What are bonds that exist between different molecules called?
intermolecular bonds
hat is a hydrogen bond?
a non-covalent attraction between a hydrogen and an electronegative atom such as oxygen or nitrogen
What are van Der Waals interactions
weak temporary regions of positive and negative charges that occur when atoms and molecules are very close together
What do van Der Waals interactions allow molecules to do?
come together and respond to each other in some way and then separate
Why is molecular shape crucial in biology?
it determines how biological molecules recognize and respond to one another with specificity
Why do opiates and endorphins have similar effects in the brain?
opiates have similar shapes to Endorphins and mimic them by binding to endorphin receptors in the brain
What are chemical reactions?
the making and breaking of chemical bonds, leading to changes in the composition of matter
What are reactants?
starting materials
What are resulting materials?
products
All chemical reactions are ________
reversible
What happens when a chemical reaction is reversed?
the products of the forward reaction become reactants of the reverse reaction
What is chemical equilibrium
the point at which the rate of the forward reaction equals the rate of the reverse reaction
What is water the only common substance to do?
exist in the natural environment in all three physical states of matter solids, liquids, and gasses
What makes a polar molecule?
unequal sharing of electrons, meaning that its overall charge in unevenly distributed
What makes water a polar molecule?
its V-like shape and unequal sharing of electrons
What charge does the oxygen region of the water molecule have?
negative
What charge does the hydrogen region of the water molecule have?
positive
What are water’s four properties that contribute to the fitness of the Earth?
cohesive behavior, ability to moderate temperature, expansion upon freezing, versatility as a solvent
What is adhesion?
the clinging of one substance to another
What is cohesion in water?
all of the hydrogen bonds that collectively hold together the water molecules
What is transpiration?
when cohesion of the water molecules and the adhesion to the cell walls of the xylem work together to transport water to the leaves in tall plants against the pull of gravity
What is surface tension?
a measure of how difficult it is to stretch or break the surface of a liquid
Why is surface tension unusually high in water?
the high number of hydrogen bonds
How does water moderate air temperatures?
by absorbing heat from air that is warmer and releasing the stored heat to the air that is cooler
What is the water moderating air temperatures called?
the lake effect
What is kinetic energy
the energy of moment
What is thermal energy?
the kinetic energy associated with the random movement of atoms or molecules
What does temperature represent?
the average kinetic energy of the molecules in a body of matter
What is heat?
thermal energy in transfer from one body of matter to another
What is a calorie?
the amount of heat it takes to raise the temperature of 1 g of water by 1 degree C
Where does the ability of water to stabilize temperature stem from?
its relatively high specific heat
What is specific heat?
the amount of heat that must be absorbed or lost by that substance to change its temperature by 1 degree C
What can specific heat be thought of as?
a measure of how well a substance resists changing its temperature when it absorbs or releases heat
What is vaporization or evaporation
the transformation from a liquid to a gas
What does evaporative cooling do?
helps stabilize temps, and provides a mechanism for organisms to keep from overheating
Water is less dense as a ______ than it is a ______
solid; liquid
When is water at its greatest density?
at 4 degrees C
What happens below 4 degrees Celsius?
the hydrogen bonds keep the water molecules far enough apart to make it 10% less dense than liquid water
How can freezing of water crack boulders?
water seeps between cracks and then its structure expands when forming ice which fractures the rock
What is a solution?
a liquid that is a completely homogeneous mixture of two or more substances
What is a solvent?
the dissolving agent
What is a solute?
the substance being dissolved
What is an aqueous solution?
a solution in which the solvent is dissolved in water
What is water a very good solvent for?
ionic and polar compounds
Whaat is a hydrophilic molecule?
a molecule that has an affinity for water (water-loving)
What is a hydrophobic molecule?
a molecule that repels water (water fearing)
What is an acid
a substance that increases the H+ concentration in a solution
What is a base
a substance that reduces the concentration in a solution
How can a base reduce the H+ concentration in a solution?
directly by accepting hydrogen ions from the solution, and indirectly by donating hydroxide ions to the solution (OH-)
What is the difference between a strong acid and a weak acid (strong base and weak base)?
A weak acid’s reaction is reversible, a strong acid’s is not (fully dissociate)
What is the internal pH of living organisms?
7
Why is any change in pH dangerous?
because chemical processes are very sensitive to the concentration of hydrogen and hydroxide ions
What are buffers?
substances that protect biological fluids from changes in pH
Are buffers commonly weak acids/bases or strong acids/bases
Weak acids or bases
Why does pH decrease as the H+ concentration increase?
because the pH of a solution is defined as the negative logarithm of the hydrogen concentration
