BSCI 170 - Chemistry Is the Basis of Life

What is matter?

anything that takes up space and has mass

What is matter composed of?

elements

Can elements be broken down by a chemical reaction?

no

What does a compound contain?

two or more different elements in a defined ratio

Is sodium chloride (NaCl) a compound?

yes

Is molecular oxygen (O₂) a compound?

no

The chemistry of a compound is normally _________ from the chemistry of the constituent elements

different

How does pure sodium react with water?

it is very reactive

What are some uses of chlorine?

• water purification

• bleach

• sanitation

• chemical weapons

What are the elements that compose 96.3% of the human body?

oxygen, carbon, hydrogen, nitrogen

What are the elements that compose 3.7% of the human body?

calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium

What are the elements that compose 0.01% of the human body called? What are they?

trace elements

• Boron

• Chromium

• Cobalt

• Copper

• Fluorine

• Iodine

• Iron

• Manganese

• Molybdenum

• Selenium

• Silicon

• tin

• Vanadium

• Zinc

All organic molecules have ______.

carbon

Amino acids and proteins have ________.

nitrogen

Iron is found in ________. What is this molecule’s purpose?

hemoglobin, transporting oxygen around the body

Where is iodine found? What condition onsets if there is not enough iodine in the body?

thyroid hormone, goiter is a response to a lack of iodine in the thyroid gland

Each element consist of only one specific kind of ____

atom

What are atoms?

the smallest unit of structure containing all of the chemical and physical properties of an element

What are the big three subatomic particles?

protons, neutrons, electrons

In a simple model of atomic structure…

• electrons are contained within a cloud and not a ring

Do nuclei interact when atoms come together?

no

Where do all interactions between atoms occur between?

electrons only

While all protons are the same, all electrons are…

not the same

Electrons have _______ _________ __ _______

• The closer the electrons are to the nucleus, the ______ their energy

variable amounts of energy, lower

What is energy?

energy is defined as the capacity to do work OR

• energy is the capacity to move something against an opposing force

What are some forms of energy?

wind energy, chemical energy (food we eat, gasoline)

What are the two types of energy?

potential and kinetic energy

What is potential energy?

energy that matter possesses because of its location or structure

What is kinetic energy?

energy associated with the relative motion of objects

What type of energy do electrons have? What is the energy correlated with?

• potential energy

• the amount of potential energy in an electron is correlated with its distance from the nucleus

The closer the electrons are to the nucleus, the _____ their energy

lower

Where are electrons usually found?

within discrete regions of space called orbitals

How many electrons do orbital contain at a maxiumum?

two

What is a “shell”?

all the electrons with approximately the same amount of energy are found in a “shell”

Shells can contain several _______ and several _______ _____.

orbitals, electron pairs

The chemical behavior is determined by the distribution of electrons in the shells

• Shell 1 has room for __ electrons

• Shell 2 has room for __ electrons

• Shell 3 has room for __ electrons

2, 8, 8

Chemical behavior is directly related to the number of electrons in the _____ shell.

• This shell is called the _______ shell

• The electrons in this shell are called _______ electrons

outer, valence, valence

Atoms are _____ ______ when their outer (valence) shells are full

• Much of chemistry, especially biochemistry, centers on atoms trying to interact with, share, release, or steal electrons to _______ _____ _______ ______ and gain stability

most stable, complete their outer shells

What are chemical bonds?

attractions that hold atoms together

What do chemical bonds result from?

interactions between valence electrons of two or more atoms

Covalent bonds are extremely ______ and _____. Why?

strong, stable, result from electron sharing

Why is Hydrogen diatomic?

atoms are most stable when they have a full valence shell

Two electrons shared between two atoms equals a single _________ ______.

covalent bond

________ and _______ covalent bonds are possible when more electrons are shared.

double, triple

What is a molecule?

A molecule is defined as two or more atoms held together by covalent bonds

Do atoms always share electrons equally?

no

What is electronegativity?

a measure of how strongly an atomic nucleus attracts and holds onto electrons

The more electronegative an atom is…

the more strongly it pulls electrons toward its nucleus and holds them there

If a covalent bond is formed between two atoms of the same type, the electrons are shared _______.

equally

Equal sharing occurs between _______ ________ ______.

nonpolar covalent bonds

What are the most electronegative atoms of biological importance?

oxygen, nitrogen

Is there unequal sharing between an Oxygen-Hydrogen bond OR a Nitrogen-Hydrogen bond?

yes

If the electronegativity difference is less than 0.4, then the bond type is:

pure covalent

If the electronegativity difference is between 0.4 and 1.8, then the bond type is:

polar covalent

If the electronegativity difference is greater than 1.8, then the bond type is:

ionic

What do weak bonds result from?

electrostatic attractions between two atoms

What are the types of weak bonds?

hydrogen bonds, ionic bonds, van der Waals interactions

Hydrogen Bonds

• Extremely Important in ________ ________

• Form when a hydrogen _________ ______ to one electronegative atom is _______ __ another nearby electronegative atom

• No life would exist without hydrogen bonds

biological systems, covalently bonded, attracted to

Each individual H bond is _____, but many weak interactions collectively are _______.

weak, strong

What are ionic bonds?

they occur when electronegativity difference may be so large as to literally pull electrons from the outer shell

Salts are compounds formed by _____ _____.

ionic bonds

• NaCl is a _________ and not a ________

  • Defined molecular ratio but no covalent bonds

• NaCl is a ____ and not a ________

  • Na and Cl are held together by ionic bonds

• Ionic bond strength depends on conditions

  • ____: Crystal is very strong; like covalent bonds

  • ____: Crystal falls apart easily

• Cells are effectively ______ solutions.

compound, molecule, salt, molecule, dry, wet, aqueous

What are van der Waals interactions?

• even molecules with nonpolar bonds can have localized regions of partial positive or partial negative charge

• these interact at extremely close range

• the interactions are extremely weak

• the interactions are extremely transient

What are van der Waals interactions critical for determining?

• the 3D shapes of proteins

• the specific interactions between an enzyme and its substrate

• the specific interactions of antigen-antibody interactions

How do geckos use van der Waals interactions?

• each of their toes has hundreds of thousands of microscopic “hairs” (called setae), each with many projections

• each binds to surfaces via van der Waals interactions

• each interaction is weak (and reversible), but together they are strong enough for a gecko to stick to glass upside down