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Ch 2
Chemical Compostion of the Body
47
Physiology
Undergraduate 1
01/27/2009

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Term
Describe th structure of an atom:
Definition
It has a centrally located nucleus, which contains protons (positive charge) and neutrons (no charge).  Outside the positively charged nucleus are electrons (negatively charged) which orbit the nucleus in shells.  Since the number of electrons and protons are equal, the net charge is 0. 
Term
How many electrons can occupy the shells?
Definition
The first shell can contain a maximum of 2, the second, 8.  The third and up can contain even more, and they posess more energy the farther they are from the nucleus.  If the shells are incomplete, or not filled, they are attracted to other electrons to fill the shell to its maximum.
Term
What are valence electrons?
Definition
The electrons in the outermost shell, if complete, that participate in chemical reactions.
Term
Describe the structure of an ion:
Definition
It is an atom or molecule that loses or gains one or more valence electrons and becomes positively or negatively charged.  If it loses electrons, there are more protons than electrons and it becomes positively charged (cation)  If it gains electrons, there are more electrons than protons, and it becomes negatively charged (anion).
Term
Describe the nature of ionic bonds:
Definition
It is when one or more valence electrons of one atom are completely transferred to a second atom.  This is a weak bond, but not the weakest.
Term
Describe the nature of covalent bonds:
Definition
It is when atoms share valence electrons.  It is the strongest bond.
Term
What is a nonpolar covalent bond?
Definition
When electrons in identical atoms are shared equally, such as H2 or O2.  The electrons are shared equally, so there is no charge given off, making it nonpolar.
Term
What is a polar covalent bond?
Definition
In covalent bonds between two different atoms, the electrons may be pulled more toward one atom than the other, giving it a positive and negative "pole".
Term
What are 3 atoms with a strong pull and tend to form polar covalent bonds?
Definition
Oxygen, nitrogen and phosphorous
Term
Describe the nature of a hydrogen bond:
Definition
When hydrogen forms a polar covalent bond with oxygen or nitrogen it gain a slight positive charge at one "pole". It then gains a slight attraction to the electronegative oxygen or nitrogen nearby.  This is the weakest bond out of the 3 bonds (covalent, ionic and hydrogen).
Term
Describe the characteristics of organic molecules:
Definition
Molecules that contain carbon and hydrogen.  Since carbon has 4 electrons in its outer shell, it must covalently bond with 4 more electrons to fill its outer shell with 8 electrons.  This allows carbon to form chains and rings while allowing it to bond with hydrogen and other atoms.
Term
What are some important functional groups of organic molecules, and what do they form?
Definition

Carbonyl group- forms ketones and aldehyde

Hydroxyl group- forms alcohols

Carboxyl group- forms organic acids (lactic and acetic)

Term
Why are ions and polar molecules soluble in water?
Definition
They are hydrophilic ("loves water") Hydrophilic molecules are water soluble because polar water molecules build up and surround certain ions and polar molecules because they give off a charge.  This forms hydration spheres around the ion or polar molecule.  These dissociate in water.
Term
What is the meaning of hydrophobic?
Definition
Hydrophobic ("fears water") molecules are not water soluble because they are primarily formed by nonpolar covalent bonds, which give off few charges and can't form hydration spheres.  These are repelled by water.
Term
Acid:
Definition
A molecule that can release H+ (protons) into a solution.  A proton "donor".
Term
Base:
Definition
A molecule that can combine with H+ (protons) in a solution.  A "proton acceptor".
Term
Explain the pH scale:
Definition
It is a scale that runs from 0-14, which indicates the H+ concentration of a solution.  A solution with a higher H+ concentration than 7 (neutral) is acidic and a lower H+ concentration than 7 is basic.  However- the higher the H+ concentration, the lower the pH.  The lower the H+ concentration, the higher the pH. (pH 2=acid, pH12=basic).
Term
Identify the different types of carbohydrates, and give an example of each:
Definition

Monosaccharide- glucose (simple sugar)

Disaccharide- sucrose (double sugar)

Polysaccharide- starch (many monosaccharides linked together)

Term
What is a carbohydrate?
Definition
Organic molecules that contain carbon, hydrogen and oxygen in the ratio described by its name: carbo (carbon) and hydrate (water, H2O) Its general formula is: CnH2nOn
Term
Identify the different types of lipids, and give an example of each:
Definition

Trigyceride- saturated fat

Ketone bodies- acetoacetic acid

Phospholipid- lecithin

Steroid- progesterone

Prostaglandin- prostaglandin E1

Term
How does a dehydration synthesis reaction occur in a carbohydrate?
Definition
A hydrogen atom (H) is removed from one monosaccharide and a hydroxyl group (OH) is removed from another.  As a covalent bond is formed between the two monosaccharaides, a water (H2O) molecule is produced.
Term
How does a dehydration synthesis reaction occur in a triglyceride?
Definition
3 hydroxyl groups (OH) are removed from the glycerol molecule and 3 hydrogen groups are removed from three fatty acids.  As a covalent bond forms between the glycerol and 3 fatty acids, a trigyceride is formed and 3 water (H2O) molecules are produced.
Term
How does a hydrolysis reaction occur in a carbohydrate?
Definition
It is the reverse of dehydration synthesis- when the covalent bond between two monosaccharides is broken (due to an enzyme) a water molecule provides the atoms required to complete its structure.
Term
How does a hydrolysis reaction occur in a triglyceride?
Definition
It is the reverse of dehydration synthesis- when the covalent bonds between a gycerol and three fatty acids are broken (due to an enzyme) 3 water molecules provide the atoms needed to compete its structure.
Term
peptide bonds:
Definition
After dehydration synthesis, covalent bonds between the hydrogen from the amino end of one amino acid combines with the hydroxyl group of the carboxyl end of another amino acid.
Term
How are peptide bonds formed and broken?
Definition
Peptide bonds are formed by dehydration synthesis and broken by hydrolysis.
Term
Describe the first 2 different orders of protein structure (in order):
Definition

1) primary structure- sequence of amini acids in polypeptide chain

2) secondary structure- conformation of the chain created by hydrogen bonding between amino acids (alpha helix or beta plaeted sheet)

Term
Describe the second 2 orders of protein structure (in order):
Definition

3) Tertiary structure- 3-dimensional structure of a protein; each protein has its own unique tertiary structure

4) Quaternary structure- formation of a protein by the bonding of 2 or more polypeptide chains

Term
What are some different functions of proteins?
Definition
They contribute to structure of different tissues (collagen, keratin), enzymes, antibodies, receptors in cell membranes, carriers for transport of specific molecules across the cell membrane
Term
How does protein structure grant specificity of function?
Definition
Because there are about 20 different kinds of amino acids that can be used to construct a protein, and each amino acid has a different functional group.  This allows for an immense variety of specific functions.
Term
Describe the structure of nucleotides: 
Definition
It is composed of a 5-carbon sugar, a phosphate group attached to one end of the sugar, and a nitrogenous base attached to the other end of the sugar
Term
Distinguish between the structure of DNA and RNA:
Definition

The same, except-

1) RNA contains ribose insterad of deoxyribose

2) RNA contains the base uracil instead of thymine

3) RNA is composed of a single polynucleotide strand instead of a double strand (in DNA)

Term
Explain the law of complimentary base pairing:
Definition
Adenine can only pair with thymine (through two hydrogen bonds) whereas guanine can only pair with cytosine (through three hydrogen bonds)
Term

Describe the structure between the two strands of DNA

Definition
C & G and A & T form hydrogen bonds together, and each complimentary base is covalently bonded to a sugar-phosphate "backbone" which causes it to form a double-stranded DNA molecule. The two strands are like a staircase and the bonded base pairs are like steps.
Term
How does the law of complimentary base pairing occur between the two strands of DNA?
Definition
Even though there are only four bases, of which two can only pair up with two complimentary bases, there are several thousand nucleotides in a gene, leaving an almost infinite number of possible base sequences.
Term
List the components of an atom:
Definition
nucleus, protons, neutrons, electrons
Term
How are the components of an atom organized?
Definition
Centrally located nucleus containing protons and neutrons. Electrons orbit the nucleus in shells (AKA orbitals).
Term
Why are different atoms able to form characteristic numbers of chemical bonds?
Definition
It is determined by the number of electrons needed to fill the outermost shell. ex. hydrogen only needs 1 electron to fill its shell completing it with 2 (the max.) Oxygen needs 4 electrons to fill its second shell with 4, equalling 8 (the max.)
Term

Using chemical equations, explain how bicarbonate ion and carbonic acid function as a buffer pair:

Definition

It is a reversible reaction:HCO3- + H+ <=> H2CO3.

The direction depends on the concentration of molecules on each side.  If H+ rises (more acidity), pH goes down and this would be the reaction: HCO3- + H+ -> H2CO3 (carbonic acid).  If H+ falls (more alkaline), pH goes up and this would be the reaction:

H2CO3 -> H+ + HCO3- (bicarbonate ion).

 

Term
How can carbon atoms bond with each other, and with the atoms of hydrogen, oxygen and nitrogen?
Definition
They form single or double covalent bonds forming a "backbone" which allows them to bond with other atoms to form organinc molecules.  They usually form hyrocarbon chains or rings which attach more reactive functional groups, usually containing oxygen, nitrogen or phosphorous.
Term
Describe the characteristics of a lipid: 
Definition
They are all insoluble in polar solvents (such as water).  They consist of hydrocarbon chains and rings, which are nonpolar, and therefore hydrophobic.
Term
Relate the functions of phospholipids to their structure:
Definition
They have hydrophilic heads and hydrophobic tails, which causes them the nonpolar tails to group together and the polar head to face water.  This alters the interaction of water molecules, decreasing the surface tension of water.  This function makes them surfactants.
Term
Explain the significance of the prostaglandins:
Definition
They are produced by and are active in almost all organs, where they serve a variety of regulatory functions.
Term
Write the general formula for an amino acid:
Definition

 

 

 

Term
How do amino acids differ from one aother?
Definition
They differ by by functional differences in functional groups, indicated in the general formula as "R" meaning "rest of the molecule" or "residue".
Term
What are nucleotides?
Definition
Subunits of nucleic acids.
Term
What are the 3 types of RNA?
Definition

1) rRna- ribosomal RNA (workbench; makes ribosomes)

2) mRNA- messenger RNA- tells how to make a protein

3) tRNA- transfer RNA -taxi

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