Chapter Two: Life's Chemistry and the Importance of Water Flashcards
Each element has a unique number of ______
protons
Different isotopes have different numbers of ______
neutrons
How do radioisotopes behave?
They are unstable and spontaneously breakdown, giving off energy
Atoms with _____ outer shells are stable
full
What do atoms do to maximize stability?
They react (bond) with other atoms to obtain full outer shells
Why are noble/inert gases non-reactive
their shell is full
When does a covalent bond form
when the electron orbitals of the two atoms overlap in an energetically favorable manner
When does unequal sharing of electrons occur?
when the two atoms are different elements and they have differences in electronegativities
What happens to the electrons in a polar bond?
electrons are pulled closer to the nucleus of the more electronegative atom; because of this the more electronegative atom will be slightly negatively charged and the other will be slightly positively charged
What is a nonpolar bond?
electrons are shared equally
Electronegativity of Oxygen
3.5
Electronegativity of Hydrogen
2.1
Properties of the covalent bonds of water
Both are polar and have a slight negative on the oxygen and slight positive on the hydrogen
When do covalent bonds form and when do ionic bonds form, based on electronegativities?
smaller difference in electronegativity: polar covalent bond
larger difference in electronegativity: ionic bond formation
If the electronegativity of atoms differs by 0.4 or less…
Covalent with equal sharing forms
If the electronegativity of atoms differs by 0.4 to 2.0…
Covalent with unequal sharing forms
If the electronegativity of atoms differs by more than 2.0…
Ionic bond forms
What is an ionic bond?
The transfer of electron(s) from one atom to another
When can a complete transfer of an electron occur
When the electronegativity difference is greater than 2.0
Cations
positively charged ions
Anions
negatively charged ions
What are ionic bonds formed by?
electrical attraction of anions and cations
Ionic compounds tend to form _____ in which there is a regular arrangement of ______ and _____
crystals; anions; cations
Where can hydrogen bonds form?
Between two water molecules, water and a polar molecule, or two separate parts of a big molecule
Van der Waals interactions
Attractions between oppositely charged atoms in nonpolar molecules. Movement of electrons results in small temporary dipoles
When does Van der Waals result in significant force?
When there are many interactions
What does Anabolism do?
Converts subunits to macromolecules
What does catabolism do?
Convert macromolecules to subunits
What is a subunit?
sugars, amino acids, fatty acids, nucleotides
What is a macromolecule?
carbohydrates, proteins, fats, nucleic acids
What are energy transformations linked to in cells?
chemical transformations
Does catabolic or anabolic reactions need energy input? releases energy?
Anabolic needs energy input, catabolic releases energy
What is metabolism?
The sum total of all chemical reactions occurring in a biological system at a given time
What is energy?
The capacity to do work
What is potential energy?
energy stored as chemical bonds, concentration gradient, charge imbalance, etc.
What is kinetic energy?
the energy of movement
Define 1st Law of Thermodynamics
Energy is neither created nor destroyed
Define 2nd Law of Thermodynamics
When energy is converted from one form to another, some of that energy becomes unavailable to do work
What is entropy?
Some energy is converted to a nonusable form associated with disorder or randomness
Will a change that decreases entropy occur spontaneously?
No – only can occur if energy is added to the system
In a closed system, the amount of usable` energy _______ with every transformation
decreases
Equation for enthalpy
Enthalpy (H) = free energy (G) + entropy (S)
What energy can be used for cellular work?
Free Energy (G)
∆G Equation
∆G = H-TS = Gproducts - Greactants
When G is negative, free energy is ________ and the reaction is _____ . When G is positive, free energy is _____ and the reaction is ____.
released, exergonic;
consumed, endergonic;
Chemical reaction
when atoms combine or change their bonding partners
What is activation energy (Ea)
The additional energy required to initiate the reaction
In what type of reactions is Ea required? Why?
Both exergonic and endergonic; Covalent bonds in reactants must be broken
In exergonic reactions, do reactants or products have higher free energy?
reactants
In endergonic reactions, do reactants or products have higher free energy?
products
What is a condensation reaction?
glucose + fructose = sucrose + H20
What is hydrolysis?
complex molecule + h20 = simpler molecules
Does a condensation reaction have positive or negative G?
positive G, meaning it requires energy
Describe exergonic reactions
release free energy, the complexity decreases, the disorder is generated and can occur spontaneously
Describe endergonic reactions
consume free energy, complexity increases, localized decrease in entropy, does not occur spontaneously
anabolic reactions are ______ and catabolic reactions are _____
Endergonic
Exergonic
What is equilibrium?
a point where the forward and reverse reactions proceed at the same rate and ∆G=0
Heterotrophs
start with chemical energy from photosynthetic cohabitants
How do photosynthetic organisms get energy?
capture solar energy and convert it to chemical energy
Is work able to be done at equilibrium?
No
Why are water molecules polar
unequal charge distribution and asymmetric shape
What makes water naturally cohesive?
H bonds
Why does water have a high specific heat?
It has a large number of H bonds
What molecules are soluble in water
hydrophilic molecules (ionic, polar)
How do salts dissolve in water
Anions are surrounded by the hydrogens on a water molecule and cations are surrounded by oxygens
Nonpolar molecules are more attracted to _________ _________ than water
one another
How do you calculate pH
-log(H+)
Does water act as a base or acid?
Water acts as both a weak base and weak acid
What happens when acids dissolve in water?
they release hydrogen ions
What do bases do?
accept H+ ions; decreases proton concentrations
What percent of cells are water?
70%
What is intracellular pH
ranges from 7.0 - 7.4
What do buffers do?
help maintain constant pH by absorbing or releasing H+ ions
What are buffers composed of?
a weak acid and its corresponding base
What is homeostasis
the process of living organisms mainting constant internal conditions
changes in pH can alter _______
cellular structures
Hydroxyl Group
-OH
Aldehyde
-C=OH
Keto
-C=O
I
Carboxyl
=COOH
Amino
R-NH2
What do functional groups do when they attach to larger molecules?
they give their properties to the larger molecules
Sulfhydryl
-SH
