Unit 3 Study of chemical processes

in living organisms

Atoms

The basic unit of _______________Nucleus: center of atom; contains protons

and _________________ Proton: positive charge Neutron: NO charge

Electron: _________charge Orbits the nucleus

_______________ Electrons:

Found in the outer most orbital

Are the electrons that form ___________ with other atoms

Atoms are neutral

Stable Atoms have a ___________ charge

Equal number of ________________ and electrons

+++++ equals - - - - -

The charges cancel each other out

Element________________: A pure substance that

consists entirely of one type of atom.Represented by one or two letter symbol

EX: C = Carbon Na = Sodium

Atomic ____________ = # protons in element # protons = # electrons

Atomic ___________ = protons plus neutrons

ISOTOPES: Atoms of the same element BUT have a different

number of neutrons.

For Ex: CARBON usually has 6 protons & 6 neutrons

• An Isotope of Carbon would have 6 protons & 7 neutrons

• The atomic # stays the same!!!! It is the same number as the number of protons

• So regular carbon & carbon’s isotope would have an atomic # of 6.

Isotopes

Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

6 electrons6 protons6 neutrons

6 electrons6 protons8 neutrons

6 electrons6 protons7 neutrons

________________ Elements

Have unstable nuclei that breaks down at a constant rate over time

Radiation given off can be dangerous, but useful in science and medicine.

Examples: Geologists using C14 to date rocks; cancer treatments, killing bacteria in food; tracers to follow through an organism

Compounds* formed by chemically combining ______ or

more elements

Examples: water (H20) – most abundance compound in living things and ________ ________(NaCl)

The physical and chemical properties of a compound are usually very different from the elements they were formed from

Chemical Bonds

1. Ionic Bonds

2. ___________________ Bonds (strongest bond)

3. Hydrogen Bonds

4. Van der Waals Forces (weakest bond)

Chemical Bonds Ionic Bonds: formed when 1 or more electrons are

____________________ from one atom to another – creating ions with opposite charges

___________: atom with a positive or negative charge

* due to the LOSS or GAIN of an

electron Na+ Cl-

Attraction between the charged ions form ionic bond

Ionic Bonding between Na and Cl:

Creating Ions:

Positive ions have __________ an electron

Ex: Na+

Negative ions have __________ an electron

Ex: Cl-

Covalent BondsCovalent bond: formed when electrons are

__________________ between atoms

Strongest type of bond

Single bond→2 electron sharedDouble bond →______ electrons sharedTriple bond →6 electrons shared

Covalent Bond between Oxygens:

Single, Double & Triple Bonds:

__________________ Force

A slight attraction that develops between the oppositely charged regions of nearby molecules. A very _______________ bond

Van der Waals forces is what enables a gecko to climb up walls

Properties of Water H2OWater is neutralMolecule is bent at a 104.5° angle

___________________: uneven distribution of electrons between the O and H atoms

Hydrogen end of molecule has a positive charge. Oxygen end of molecule has a _______________

charge.

Hydrogen BondsHydrogen Bonds: bonds formed between

__________________ molecules. The negative end of one molecule is attracted to the positive end of another

H bonds hold water together

and

hold the inner parts of __________ together

Hydrogen bonds between water molecules:

Hydrogen bonds in DNA:

Properties of Water cont.

Cohesion: attraction between molecules of the _________________ substance EX: water droplets = water molecules

sticking

together

Adhesion: attraction between molecules of _____________________ substances EX: water moving up a straw = water molecules

sticking to side of straw

Water properties continued:

Heat capacity is the capability of water to absorb heat without undergoing an increase in temperature. Water has a ________________ heat capacity.

Buoyancy – things less ________________ than water will float – when ice freezes, it is less dense than liquid water.

Properties of water continued:

Water __________________ things –

EX. 90% of blood plasma is water – blood transports oxygen & nutrients

• Things dissolve or ___________________ in water

EX. Nutrients dissolve in soil

• Water has a pH of 7 – it is neutral

Properties of water continued:

Surface Tension of Water - the surface of water sticks together by _________________ & allows it to behave as an elastic sheet.

Allows insects like the water strider to walk on water

Surface Tension Example:

pH Scale

pH scale: indicates the concentration of ________+ ions in a solution

pH Scale Ranges from 0 - 14

pH Scale

Acids

Acids: higher concentration of H+ ions than water

pH value below 7 (_______ - 6.9)

Strong acids pH 1 to 3

EX: lemon juice, stomach acid, polluted rainfall, vinegar

Bases

Bases: higher concentrations of _________ - ions than water

pH value above 7 (7.1 - _______)

Strong bases pH 11 to 14

EX: blood, milk, soap, bleach, sea water

____________________________:Cells can only tolerate small changes in

pHChemical Processes only work within a

specific pH rangeOrganism could die if subjected to major

pH changesOrganisms need to maintain

HomeostasisHomeostasis: process in which organisms

maintain a stable internal environment

Buffers….

Buffers: a substance that binds with H+ ions to _________________ changes in pH