bio exam #1: chap. 2-5

What is an element?

a substance that cannot be broken down into other substances by chemical reactions

How many naturally occurring elements are there?

92

Compound

a substance consisting of two or more elements in a fixed ratio

What makes up 96% of human body mass?

oxygen, carbon, hydrogen, and nitrogen

Trace elements

elements required by an organism in relatively minute quantities

atom

the smallest unit of matter that still retains the properties of an element

What are the 3 "large" subatomic particles?

Protons: positive charge Neutrons: neutral charge Electrons: negative charge

Atomic number

the number of protons in the nucleus of an atom

Atomic mass

the sum of protons and neutrons in the nucleus

Isotopes

have nuclei with the same number of protons but different numbers of neutrons

Radioisotopes

unstable isotopes that decay spontaneously and give off potentially damaging electromagnetic radiation and subatomic particles. ex) using radioactive glucose to detect cancer cells

Half-life

the rate of decay of a radioisotope (vary from seconds or days to billions of years)

Energy

the capacity to cause change by doing work

Potential energy:

the energy that matter has because of its location or structure

What is the electron's state of potential energy?

electron shell

What electron shell has the HIGHEST potential energy?

third outermost shell

What electron shell has the LOWEST potential energy?

first innermost shell

If an electron moves closer to the nucleus potential energy is

lost

If an electron moves away from the nucleus energy is

absorbed

Elements with no more than 3 electron shells (max number each can occupy)

1st shell: max of 2 electrons 2nd shell: max of 8 electrons 3rd shell: max of 8 electrons

When are electron shells most stable?

when they're full

What is an atom's chemical behavior determined by?

the distribution of electrons in its electron shells (valence electrons)

When are elements chemically inert (no chemical reactivity)?

when it's valence shell is full

What is an orbital?

the three-dimensional space where an electron is found 90% of the time

Electronegativity

an atom's attraction for the electrons in a chemical bond

Polar covalent bonds

valence electrons are not shared equally by bonded atoms since one atom is more electronegative than the other(H2O)

Nonpolar covalent bonds

valence electrons shared equally by bonded atoms that are equally electronegative (H2)

Ionic bonds

bonds resulting from the loss and gain of electrons by bonded atoms; strong but weaker than covalent bonds. (NaCl) (hint: + and - charges)

Hydrogen bonds

weak bond formed between a hydrogen atom in a polar compound and an electronegative atom in another polar compound (2 H2O molecules bonded together) (hint: dashed line)

Van der Waals Force

very weak bonds resulting from transient shifting of charges created by the constant movement of electrons

Covalent bond

the sharing of a pair of valence electrons by two atoms.

Molecule

two or more atoms held together by covalent bonds

Ion

An atom or group of atoms that has a positive (cation) or negative (anion) charge. (Result of ionic bonds, opposite charges hold the bond together)

Ionic compounds

compounds formed by ionic bonds (salts)

Chemical equilibrium

when the forward and reverse reaction rates are equal

What is Wilson's disease?

excessive accumulation of copper in liver, brain, kidney, cornea; inherited disorder of copper metabolism (too much of a trace element)

What charge does oxygen have in H2O?

slightly negative

What charge does hydrogen have in H2O?

slightly positive

What allows water molecules to form hydrogen bonds with each other?

water's polarity

Cohesion

chemical attraction between particles of the same substance (hydrogen bonds)

Adhesion

chemical attraction between particles of different substances (hydrogen bonds)

How many hydrogen bonds can one water molecule make?

4

Surface tension

a measure of how difficult it is to stretch or break the surface of a liquid

Kinetic energy

energy of motion

Specific heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C.

The greater the specific heat of a substance, the greater it

resists changing temperature when it absorbs or releases heat

What causes water to have a high specific heat?

hydrogen bonding

Water absorbs heat when

hydrogen bonds are broken

Water releases heat when

hydrogen bonds are formed

Evaporative cooling

as a liquid evaporates, its remaining surface cools

When does water reach its greatest density?

when frozen at 4 degrees Celsius (less dense than liquid water: ice floats on liquid water)

Solution

a liquid that is a completely homogeneous mixture of substances

Solvent

the dissolving agent of a solution (water)

Solute

a substance that is dissolved in a solution.

Aqueous solution

a solution in which water is the solvent

Why is water the universal solvent?

water's polarity allows the molecule to form hydrogen bonds easier

What can water dissolve?

ionic compounds and nonionic polar molecules

Hydrophilic substance

one that has an affinity for water (water loving/polar covalent bonds)

Hydrophobic substance

one that does not have an affinity for water (scared of water/nonpolar covalent bonds)

Molecular mass

the sum of all atomic masses of all atoms in a molecule

Molarity (M)

the number of moles of solute per liter of aqueous solution

hydronium ion (H3O+)

the positive ion formed when a water molecule gains a hydrogen ion

hydroxide ion (OH-)

a negative ion made of oxygen and hydrogen

What can drastically change the chemistry of a cell?

changes in the concentrations of H+ and OH- ions

Acid

any substance that increases the H+ concentration of a solution

Base

any substance that reduces the H+ concentration of a solution

Strong acids and bases

dissociate completely in water

pH of 7

neutral (H+ = OH-)

pH less than 7

acidic solution (H+ > OH-)

pH greater than 7

basic or alkaline solution (OH- > H+ )

What is the pH of most biological fluids?

6-8, mostly neutral.

Buffers

substances that minimize changes in concentrations of H+ and OH- in a solution

What do most buffered solutions contain?

a weak acid and it's corresponding base which combine reversibly with H+ ions

All known organisms on earth consist primarily of

carbon based compounds

Tetravalent

4 electrons in valence shell, Ex. carbon

Organic chemistry

the study of compounds containing carbon

Most organic compounds contain

carbon and hydrogen

Methane (CH4)

Ethane (C2H6)

Ethene (C2H4)

Carbon skeletons

can vary in length, size, shape branching, double bonds, and rings (each corner of a ring is a carbon)

Hydrocarbons

compounds composed of only carbon and hydrogen (ex. fats)

Hydrocarbons can undergo reactions that ________________________.

release large amounts of energy

What are the major components of fossil fuels?

hydrocarbons

Skeletal formulas

are stick representations of carbon skeletons of organic compounds in which carbon atoms of the skeleton are assumed to be bonded to hydrogen atoms, unless otherwise noted

Isomers

compounds with the same molecular formula but different structures and properties

Structural isomers

have different covalent arrangements of their atoms

Cis-trans isomers

have the same covalent bonds but differ in spatial arrangements (arise from double bonded carbons)

Enantiomers

isomers that are mirror images of each other

differing effects of enantiomers demonstrate that organisms are

sensitive to even subtle variations in molecules

Functional groups

parts of organic molecules that are involved in chemical reactions

What replaces one or more hydrogens bonded to the carbon skeleton of a hydrocarbon?

functional groups

hydroxyl group (-OH)

Polar due to electronegative oxygen. Forms hydrogen bonds with water. Compound name: Alcohol

Carbonyl group (C=O)

Sugars with ketone groups are called ketoses; those with aldehydes are called aldoses. Compound name: Ketone (center carbon) or aldehyde(end carbon)

Carboxyl group (-COOH)

acts as an acid (can donate H+) because the covalent bond between oxygen and hydrogen is so polar

Amino group (-NH2)

acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms) compound name: amine

sulfhydryl group (-SH)

Two —SH groups can react, forming a "cross-link" that helps stabilize protein structure. Compound name: Thiol

Phosphate group (PO₄³⁻)

contributes negative charge. When attached, confers on a molecule the ability to react with water, releasing energy. Compound name: Organic phosphate

Methyl group (-CH3) (only NONPOLAR group)

Affects the expression of genes. Affects the shape and function of sex hormones. Compound name: Methylated compound

The sex hormones estrogen and testosterone differ only in the presence of certain

functional groups