Chapter 2-Cell Biology

Question 1

The chemical behavior of an atom is determined by the number of electrons in the outermost electron shell. Explain?

Answer 1

An atom with an incomplete (partially full) electron shell is reactive whereas an atom with a full electron shell is inert, or not chemically active.

Question 2

A reactive atom will try to fill the valence shell by interacting with otheratoms. This interaction may result in two atoms forming a chemical bond. What is a chemical bond?

Answer 2

A chemical bond is an attraction that holds two atoms together.

Question 3

What is a molecule?

Answer 3

A molecule is two or more atoms held together by chemical bonds. The smallest unit that retains the physical and chemical properties of a compound.

Question 4

If an atom has an almost empty or an almost full outer electron shell is likely to form an ion. What is an ion?

Answer 4

An ion is a charged atom or molecule. It is charged because it has either lost or gained electrons.
An anion is a negatively charged atom or molecule. It has gained an electron.
A cation is a positively charged atom or molecule. It has lost an electron.

Question 5

What is a covalent bond?

Answer 5

A covalent bond is a bond formed when two atoms share pairs of electrons.

Question 6

What are non polar and polar covalent bonds?

Answer 6

A nonpolar covalent bond is a covalent bond in which the sharing of the electron pair is equal. A polar covalent bond is a covalent bond in which the sharing of the electron pair is unequal.

Question 7

What is electronegativity?

Answer 7

Electronegativity is defined as an atom’s ability to attract and hold electrons. An indication of how much positive charge is in the nucleus. Assigned a numerical value. The higher the #, the more electronegative an atom is.
Atoms with higher electronegativities have a more positively-charged nucleus, and will hold onto the electron pair more strongly than atoms with significantly lower electronegativity.

Question 8

What is an atom?

Answer 8

An atom is the smallest unit of matter that retains the physical and chemical properties of the element.

Question 9

Describe a hydrogen bond.

Answer 9

A Hydrogen bond is formed by the charge attraction when a hydrogen atom which is covalently bonded to one atom is attracted to a second atom.

Question 10

What are carbohydrates?

Answer 10

Carbohydrates are monosaccharides that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio. Have a ring structure with two major purposes: energy or for structural support.

Question 11

What is the energy storage molecule in humans?

Answer 11

Energy storage molecule in humans is glycogen. Used for quick-energy, and is metabolized when blood sugar levels drop. Stored in the skeletal muscle and liver of humans.

Question 12

What is carb-loading?

Answer 12

Carb-loading is the process of increasing the amount of glycogen stored in the body prior to a race or competition.
A two stage process:
Depletion phase: A week or two prior to competition, intense exercise and a no-carb / high protein diet.
Loading phase: A couple of days before competition, no intense exercise, eating as many carbs as you can take in.

Question 13

Water Weight

Answer 13

Blood glucose is metabolized first in the human body. Afterwards, glycogen reserves are metabolized. Finally, fat is burned.
Glycogen is polar, which means it dissolves in water. Each ounce of glycogen has as many as four ounces of water attached to it.
Fat is extremely nonpolar. It has no water attached to it.

Question 14

What are lipids?

Answer 14

Lipids consist of nonpolar hydrocarbon chains and rings.
Usually hydrophobic (insoluble in water).

Question 15

Saturated vs. Unsaturated fats

Answer 15

Saturated fats are solid at body temperature. They have no C=C bonds. They are saturated with hydrogens. (Lard, grease, fat)
Unsaturated fats are liquid at body temperature. They have at least one C=C bond. (olive oil, vegetable oil)

Question 16

What are phospolipids?

Answer 16

Phospholipids are two fatty acids + phosphate group attached to glycerol backbone. is a dominant component of cell membranes. Contains hydrophilic (polar) and hydrophobic (nonpolar) regions.

Question 17

What are steroids?

Answer 17

Steroids have a three 6 carbon rings + one 5 carbon ring, are mostly nonpolar and many function as hormones.

Question 18

What are proteins?

Answer 18

Proteins are composed of multiple amino acids (amino acid polymers). the sequence of amino acids is determined by DNA through processes of transcription and translation.

Question 19

What are amino acids?

Answer 19

Amino acids are composed of an amino group, a carboxyl group, and a functional group or R group.There are 20 R groups and therefore 20 different amino acids.The R groups give amino acids different properties (eg., polar, nonpolar).

Question 20

Describe protein structure.

Answer 20

Secondary, tertiary, and quaternary structure contribute to 3D shape of protein. Protein 3D structure is diverse. 3D structure of protein determines function. Because bonds between amino acids and peptides can be weak, proteins can be denatured (broken apart) by heat, changes in pH, etc.

Question 21

What are nucleotides?

Answer 21

nucleotides are composed of a five-carbon sugar, one or more phosphate groups, and a nitrogenous base
Nitrogenous bases fall into two categories:
Pyrimidine: one carbon ring (eg., cytosine (C) and Thymine (T) in DNA)
Purine: two carbon rings (eg., guanine (G) and adenine (A) in DNA)

Question 22

What are the three functional types of nucleotides?

Answer 22

The three functional types of nucleotides are: 
Cellular energy exchange (eg, adenosine triphosphate or ATP).
Intracellular signaling (eg, cyclic AMP).
Storage and expression of genetic information.  These are polymers of nucleotides called nucleic acids (eg, DNA and RNA)

Question 23

What is a gene?

Answer 23

A gene is a length of DNA that codes for a specific protein

Question 24

How do you convert DNA into proteins?

Answer 24

Converting DNA into proteins.
Transcription: DNA  RNA, occurs in nucleus
Translation: RNA  protein, occurs in cytoplasm

Question 25

Describe the process of transcription?

Answer 25

1. RNA polymerase binds to promoter
2. RNA polymerase then unzips DNA,
   separates double helix
3. Free ribonucleotides bind complementary bases on DNA sense strand.
4. RNA polymerase moves down DNA and a new RNA molecule is synthesized. Producing the pre-mRNA product.

Question 26

Genes and the human genome project

Answer 26

The Human Genome Project revealed that most of the DNA of humans does not encode mRNAs or any other RNAs. Appear to serve no purpose whatsoever in our life cycle.
Accounts for an astonishing ~98.5 % of human chromosomal DNA.
These non-coding regions are similar in humans, but not identical. Accounts for your DNA fingerprint. Called mini-satellite sequences.

Question 27

How is RNA turned into mRNA?

Answer 27

Pre-mRNA – mRNA
Introns are removed
CAP is added to 5’ end of pre-mRNA
Poly-A tail is added to 3’ end of pre-mRNA

Question 28

What are the three types of RNA?

Answer 28

mRNA (messenger RNA): carries genetic code out of nucleus
rRNA (ribosomal RNA): forms RNA component of ribosome, allows protein assembly
tRNA (transfer RNA): allows protein assembly

Question 29

Describe the process of translation?

Answer 29

1. Initiation: tRNA, ribosome, and mRNA
   come together. Codon on mRNA pairs with Anti-codon on
   tRNA. Always starts with AUG (methionine)
2. Peptide bond forms between amino acids.
3. tRNA at P site is released. tRNA at a site moves into P site. Another tRNA moves into now empty A site.
4. Peptide bond forms between amino acids.

Question 30

What is post-translational processing?

Answer 30

Post-translational processing is the cleavage of amino acids. Addition of other chemical groups (eg, addition of carbohydrates through glycosylation. Many post-translational modifications occur in the ER and Golgi apparatus

Question 31

What is the genome and the proteome?

Answer 31

The genome is all the genes in a particular individual or all the genes of a particular species.
Researchers believe humans have ~25,000 genes.
The proteome is all the proteins that are produced from the genome.
More than 150,000 proteins are produced in the human body.

Question 32

How can a gene code for more than one protein?

Answer 32

mRNA is altered after transcription. Proteins are made of many polypeptide chains. Protein modification occurs by: Adding a lipid or carbohydrate, Adding a phosphate group, or Cutting into small units.