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Bio181 > Sec 2- Chemical Foundation > Flashcards

Sec 2- Chemical Foundation Flashcards

Unit I- The Basis for Life

1
Q

What is matter?

A

This is anything that occupies space and has mass.

The three states if matter are;
* Gas
* Liquid
* Solid
All matter consist of atoms.
An atom is the fundamental building-block of matter.

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2
Q

What is the structure of atoms?

A

These are composed of subatomic particles.

  • A proton is positively chargeed… # determines element
  • An electron is negatively charged… # determines ion
  • A neutron is electrically neutral… # determines isotope
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3
Q

What are the regions of an atom?

A

Protons and neutron are in the center (nucleus). Electrons whiz around the nucleus in shells/orbitals.

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4
Q

What is an element?

A

A pure substance that consists only of atoms with the same number of protons.

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5
Q

What is the Periodic Table?

A

An organization of the elements.

  • created in 1869 by Dmitri Mendeleev
  • elements are organized by increasing number of protons
  • 118 elements (94-98 occur naturally)
  • element abbreviated by first letter (or two) in English or Latin
  • Ex C for carbon and Ca for calcium
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6
Q

What is the atomic number?

A

This is based on the number of protons in the atomi nucleus.

  • Located above the abbreviation of the element.
  • Determines the element
  • If the atom is neutral, it will also indicate the number of electrons.
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7
Q

What are isotopes?

A

Different forms of an elements that differ in the number of neutrons their atoms carry.

  • Different isotopes have different masses because neutrons are heavy.
  • Neutron= 1 amu
  • Proton= 1 amu
  • Electrons= 0 amu
  • amu= atomic mass unit (or dalton)
  • One amu= 1.7 x 10^-24 g
  • Every form of an element is an isotope
  • Only some are radioactive!
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8
Q

What is mass number?

A

This is the total number of protons and neutrons in the nucleus of an element’s atoms.

  • Located underneath the chemial symbol.
  • The number of neutrons can be determined by subtracting the atomic number form the mass number.
  • The mass number is also sometimes called the atomic mass.
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9
Q

What are radioactive isotopes?

A

Isotope with an unstable nucleus, such as carbon-14.

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10
Q

What is radioactive decay?

A

The process by which atoms of a radioisotope spontaneously emit energy and subatomic particles when their nucleus disintegrates.

The half life of carbon-14 is 5,730 yrs, which makes carbon dating possible.

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11
Q

What are electron shells?

A

Electrons travel around the nucleus in different orbitals (shells; Bohr model).
1st shell can “hold” two electrons
2nd shell can “hold” eight electrons
3rd shell can “hold” eight electrons

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12
Q

What are vacancies?

A

Atoms are “happiest” when they have no vacancies in their outer shell (valence shell).
This is called the octet rule, because besides the innermost shell, it takes eight electrons to fill a shell.
Atoms with vacancies in their outer shells tend to interact with other atoms.
Atoms get rid of vacancies by gaining or losing electrons, or sharing electrons with other atoms.

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13
Q

What are ions?

A

The negative charge of an electron balances the positive charge of a proton in the nucleus.

Changing the number of electrons may fill its outer shell, but changes the charge of the atom.
ion- atom that carries a charge because it has an unequal number of protons and electrons.

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14
Q

How is an ion formed?

A

An atom that gains electrons has a negative and is now called an ion, specificallt an anion.

Ex: Cl^-, F^-, Br^-
The suffix “-ide” is added to anions
Chlorine becomes chloride

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15
Q

How are cations formed?

A

Atoms can also lose elctrons from their valence shell.
They are then positive ions, or cations.

Their valence shell is now also completely full.
Ex: Na^+, Mg^2+, K^+, Ca^2+

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16
Q

What are chemical bonds?

A

Forms when the elctrons of two atoms interact.
Holds the two atoms together.

17
Q

What is the molecule?

A

Group of two or more atoms joined by chemical (covalent) bonds.

Ex: H2O, C6H12O6, H2

18
Q

What are compounds?

A

Type of molecule that has atoms of mroe than one element.

Ex: NaCl, H2O, CH4
H2 and O2 are molecules but NOT compounds.

19
Q

What are ionic bonds?

A

A strong mutual attraction formed between ions of opposite charge.

  • Ionic bonds are formed between oppositely charged ions.
  • Opposites attract
  • For ions to form there had to be a loss and gain of electrons.
  • Specific gain or loss
20
Q

What are covalent bonds?

A

Two atoms sharing a pair of electrons.

  • A covalent bond forms when two atoms hsare one or more pairs of outer-shell (valence) electrons.
  • Covalent bonds are much tronger than ionic bonds.
  • Covalent bonds between aotms form molecules.
  • Sharing instead of gaining or losing.
21
Q

What are polar molecules?

A

Unequal sharing of electrons makes a polar molecules.

  • The electrons of covalent bonds are not always shared equally between the atoms of different elements, like in the example of water.
  • Electrons prefer being around the big, positive nucleus of the oxygen atom instead of the small positive nucleus of the hydrogen atoms.
  • There is a partial positive charge by the hydrogen atoms and a partial negative charge by the oxygen atom.
  • Unequal sharing makes water a polar molecule.
  • But remember that overall, H2O is a neutral molecule.
22
Q

What are Hydrogen Bonds?

A

The polarity of water results in weak electrical attractions between neighboring water molecules. These interactions are called hydrogen bonds.

  • Hydrogen bonds form and break more easily than covalent or ionic bonds - they do not form molecules - they are not chemical bonds.
  • However, the vast number of hydrogen bonds make them a powerful entity in biology.
  • Hydrogen bonds impart unique properties to substances such as water, and hold molecules such as DNA in their characteristic shapes.
23
Q

What are Van Der Waals Interactions?

A

Van Der Waals interactions are weak attractions between molecules or parts of a molecule due to slight fluctuations in electrical densities around the different atoms.

Proteins, for example, have a characteristic 3D shape because of covalent, ionic, hydrogen, and van de Wals forces.

24
Q

How important is water?

A

All living organisms are mostly comprised of water (humansd = 60-70%), and all chemical reactions of life are carried out in water.
Hygrogen bonds between water molecules give water unique properties that make life possible.

25
Q

What are the life-supporting properties of water?

A
  1. Cohesion and adhesion
  2. Capacity to dissolve many substances
  3. Temperature stability (and evaporation)
  4. Ice is less dense than water
  • Water is polar and forms hydrogen bonds!!!
26
Q

What is cohesion and surface tension?

A

Water molecules stick together as a result of hydrgoen bonding. This phenomenon is called cohesion. Cohesion results in surface tension.

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

27
Q

What is adhesion?

A

The polarity of water also makes it stick to surfaces, whcih is called adhesion.

  • Cohesion and adhesion is responsible for capillary action.
  • If a tube has a small enough diameter, water can travel up the tube gainst the downward force of gravity.
  • Adhesion and cohesion are vital for water transport in plants.
28
Q

Water dossolves substances:

A

Polar water molecules hydrgoen-bond to other polar (hydrophilic) substances, and repel nonpolar (hydrophobic) substances.

Hydrophilic (water loving)- A substance that dissolves easily in water.
Hydrophobic (water-fearing)- A substance that resists dissolving in water.
* Water is an excellent solvent
* Solvents are liquids that can dissolve other substances
* A solute is a dissolved substance
* Water molecules surround the atoms of an ionic solid (like salt) and pull them apart, dissolving it.

29
Q

What is temperature stability?

A

Water absorbs more heat (energy) than other liquids befor etemperature rises becaus eof the extensive hydrogen bonding of water.

Temperature-
* Measure of molecular motion
* Temp stability is an important part of homeostasis.

30
Q

What is evaporation?

A

Earth’s giant water supply causes temps. to stay w/in limits that permit life.

Evaporative cooling removes heat from the earth and from organisms.
The heat is used to break hydrogen bonds instead of raising the temperature.

31
Q

Why is it important that ice floats?

A

Since ice floats, ponds, lakes, and even the oceans do not freeze solid.
Marine life could not survive if bodies of water froze solid.

32
Q

What is pH?

A

A measure of the number of hydrogen ions (H^+) in a solution.

  • Water molecules sometimes separate into hydrogen ions (H^+) and hydroxide ions (OH^-).
  • The more hydrogen ions, the lower the pH.
  • Pure water has a neutral pH (pH=7). Number of H^+ ions are = to number of OH^- ions.
33
Q

What is an acid?

A

A substance with more H^+ ions than OH^- ions.

Ex: HCl
pH less than 7

34
Q

What is a base?

A

A substance with less H^+ ions than OH^- ions.

Ex: NaOH
pH greater than 7

35
Q

What are buffers?

A

This keeps solutions in cells and tissues within a consistent range of pH.

  • Most moleculkes of life work only within a narrow range of pH- essential for homeostasis.
  • Buffers are substances that resist pH change
  • They accept H^+ ions when there are too many
  • They donate H^+ ions when there aren’t enough
36
Q

What is blood buffering?

A

The pH of blood needs to stay between 7.35 and 7.45 for life to contine.
CO2 + H2O <–> H2CO3 <–> H^+ +HCO3^-

  • Too much H^+ moves the equation to the left + exhle CO2.
  • Too little H+ moves the equation to the right + keep CO2.

Bio181 (4 decks)

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