Biology - The Chemical Basis of Life

Chemicals that serve as stimuli to other individuals of the same species for varied behavioral responses are ...

Pheromones

Matter is anything that ...

occupies space and has mass

Matter is composed of ...

chemical elements

An element is a substance that ...

can not be broken down into other substances

How many elements occur in nature?

92

How many chemical elements are essential to life?

Around 25

__% of the human body (the bulk) is made up of _____, ______, _______, and _______.

96, carbon, oxygen, hydrogen, nitrogen

Trace elements are _____ to the body even though they are found in _____ quantities.

vital, small

A deficiency in this trace element causes the thyroid gland to grow to an abnormal size (goiter).

Iodine

A deficiency in this trace element causes anemia.

Iron

A deficiency in this trace element causes tooth decay.

Fluoride

True or False: all atoms in an element are similar

True

Formed when 2 or more atoms combine (same or different elements):

molecule

Formed when 2 or more atoms from different elements combine:

compound

NaCl is:

Sodium Chloride

A:

Electron cloud

B:

Nucleus

C:

Electron

D:

Proton

E:

Neutron

F:

Electron shells

The smallest particle of matter is:

Atom

Protons are _____ charged, _____ ______ in the center of the atom

positively, tightly, packed

Neutrons have ___ charge, ______ ______ in the center of the atom.

no, tightly, packed

Electrons are _____ charged, more at the speed of ______, form a ____ around the atom.

negatively, light, cloud

Atomic number =

number of protons in an atom

In a neutral atom, atomic number = number of ______ = number of _____

protons, electrons

All atoms of the same element have the same ____ but different ____.

atomic number, atomic mass

Atomic mass =

number of protons + number of neutrons

1 electron = ______ the mass of a proton

1/2000

Isotopes are atoms of the same ______ with a different atomic _____.

element, mass

Stable isotopes have intact _____

nuclei

Unstable isotopes are _______. Their _____ decays and gives off particles and energy

radioactive, nuclei

Radioactive isotopes work as markers for ...

their nonradioactive counterparts

Radioactive isotopes can work as a treatment for this illness ...

cancer

Radioactive isotopes also help _____ with instruments

diagnosis

Radiation can cause _____.

cancer

Electron arrangement determines the _____ _____ of an atom.

chemical, properties

The farther an electron is from the nucleus, the _____ its energy.

greater

Electron shells are:

electron energy levels

The first shell is full with ____ electrons

2

The second shell is full with ____ electrons

8

The third shell is happy with ___ electrons

8

The fourth shell is satisfied with _____ electrons

18

Electron capacity:

2n^2

Energy levels _-_ are happy with less than the maximum amount of electrons they can hold

3,7

This is the outermost electron shell of an atom:

Valence shell

Electrons in the valence shell are called:

Valence electrons

Valence electrons determine the _____ _____ of an atom

chemical, properties

Atoms with valence shells that are not full tend to do what?

Bond with other atoms and share valence electrons

Both major chemical bonds share two rules: the resulting compound is ____, and the outer orbits are ____.

neutral, full

This bond is attractions between ions of opposite charges:

Ionic bond

The steps to an ionic bond: 1. atoms share ____ until both atoms have _____ electron shells 2. This causes an attraction because the atoms have _____ charges.

electrons, full, opposite

Atom that loses an electron:

cation (positive)

Atom that gains an electron:

anion (negative)

This chemical bond involves atoms sharing electrons:

Covalent bond

Covalent nonpolar molecules share electrons _____

equally

Covalent polar molecules share electrons _____

unequally

These bonds are attractions between oppositely charged parts of polar molecules

Hydrogen bonds

Each water molecule is bonded to ____ other water molecules

4

The 2 strands in a DNA molecule are held together with:

hydrogen bonds

The property by which water molecules stick TO EACH OTHER:

cohesion

Cohesion helps water molecules move from a plant's _____ to its ______

roots, leaves

The property by which water molecules stick TO OTHER SUBSTANCES:

adhesion

The rising of liquids through a small tube with adhesion and cohesion is called:

Capillary Action

How difficult it is to stretch or break the surface of a liquid:

Surface tension

When heat is ______, hydrogen bonds break

absorbed

When hydrogen bonds assemble, heat is ________

released

a small amount of heat only _____ the hydrogen bonds, but a large amount will _____ them.

disrupts, breaks

When a liquid evaporates, only the molecules with ______ kinetic energy are left. This is called ________ ________

less, evaporative, cooling

Evaporative cooling ______ temperature of lakes and ponds, prevents ______ tissue from becoming too warm, and cools down the _____ body by releasing ______.

regulates, plant, human, sweat

Why is ice less dense than water?

Its hydrogen bonds hold the molecules farther apart

Generally, liquids become _____ denser when they cool

more

Water is densest at what temperature? (Celcius)

4

When water reaches this temperature, its molecules spread apart and form a crystal lattice

0

True or False: Ice sinks under water.

False

If ice sank, what would happen?

Aquatic life would be trapped, ponds and lakes would fully freeze

When water turns to ____, it absorbs heat and _____ hydrogen bonds.

vapor, breaks

When vapor turns to ______, it releases heat and ______ hydrogen bonds

water, creates

Anything dissolved in water:

Aqueous solution

Water dissolves what:

ionic compounds and polar molecules

To dissolve molecules, water molecules ____ apart the solvent molecules and _____ them from one another

break, seperate

Sphere of water molecules around each dissolved ion:

hydration shell

These substances like water, are ionic, and are polar:

hydrophilic substances

These substances are scared of water, are non-ionic, and are non-polar:

hydrophobic substances

Hydrogen forms _____ bonds with other elements, while all other group _____ elements form ____ bonds with other elements.

covalent, 1A, ionic

This happens when a small percentage of water molecules break apart into ions in an aqueous solution:

Dissociation of water

What ions are formed in the dissociation of water?

Hydronium ions (H3O+) and Hydroxide ions (OH-)

Synonym for hydronium ions:

Hydrogen ion (H+)

2____ -> ____ + _____

H2O, H3O+, OH-

Acids

A compound that releases H+ ions in a solution

An acidic solution has a higher concentration of _ ions than _ ions.

H+, OH-

Base/Alkaline substance

A compound that accepts H+ ions or releases OH- ions in a solution

A basic solution has a higher concentration of _ ions than _ ions

OH-, H+

The pH of a solution is the negative logarithm of the _____ ions concentration in _____ per ______.

hydrogen, moles, liter

Each pH unit has what change?

10x

What pH level is neutral?

7

Solutions below 7 are:

acidic

Solutions above 7 are:

basic

What do buffers do?

They maintain large fluctuations in pH levels that could damage living tissues