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 electrons 6 protons 6 neutrons 6 electrons 6 protons 8 neutrons 6 electrons 6 protons 7 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 (H 2 0) – 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 Bonds Covalent bond: formed when electrons are __________________ between atoms Strongest type of bond Single bond→2 electron shared Double bond →______ electrons shared Triple 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 H 2 O Water is neutral Molecule 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 Bonds Hydrogen 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

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 pH Chemical Processes only work within a specific pH range Organism could die if subjected to major pH changes Organisms need to maintain Homeostasis Homeostasis: process in which organisms maintain a stable internal environment

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