8/13/2019 Life Lecture
1/42
Life
8/13/2019 Life Lecture
2/42
What is necessary for life?
Most life familiar to us: Eukaryotes
First appeared ~ 1.5 - 2 !109years ago
Requirements: DNA, proteins, lipids, carbohydrates,
complex structure, ~ 10
4
- 10
5
genes
FREE LIVINGOr Parasites
8/13/2019 Life Lecture
3/42
Prokaryotes (Bacteria and Archaea)
Requirements: DNA, protein, lipids, carbohydrates,
simpler structure, few thousand genes
FREE LIVING
Or Parasites
First appeared
~ 3 - 4 !109years ago
8/13/2019 Life Lecture
4/42
Viruses DNARNA
Proteins
Viroids, Prions?
Plasmids
RNA
Few hundred bases
Few thousand bases
Protein
Parasites
8/13/2019 Life Lecture
5/42
The tobacco-mosaic virus is made up of a strand of
nucleic acid encased in a rod of one kind of protein.
8/13/2019 Life Lecture
6/42
Minimum Requirements for Life
Proteins and Nucleic Acids for simplest
Or maybe only one.
Lipids and Carbohydrates for any thing
more complex than a virus.
These are all macromolecules.
8/13/2019 Life Lecture
7/42
MacromoleculesProteins made of amino acids (20)
Construction and catalysis (enzymes)
Nucleic acids made of nucleotides
base sugar phosphate
Polymers and Monomers
H, C, N, O (S)
H, C, N, O (P)
8/13/2019 Life Lecture
8/42
Carbohydrates made of sugarsEnergy (food) + structure
[starch] [cellulose]
Lipids (hydrocarbons + carboxyl)
Membranes + Energy
[water-resistant]
H, C, O
H, C, (O)
8/13/2019 Life Lecture
9/42
Sugar
Glucose
hydrocarboncarboxyl
Lipids
Fatty acid is composed of a hydrocarbon
chain with a carboxyl group at one end
8/13/2019 Life Lecture
10/42
Polysaccharides
8/13/2019 Life Lecture
11/42
Proteins
Monomers are amino acids 20 kinds
HH
H
H H
N C C
O
O
a b c
Aminogroup
carboxyl
group
Glycine
Amino group(hook) carboxyl group(eye)
Schematic
Section of Protein
8/13/2019 Life Lecture
12/42
H
H
N
H
C
O
O
eye end hook end Before
After
A Peptide Bond at the Chemical Level
H
H
N
H
C
O
O
eye end hook end
Note that a water molecule must be removed
8/13/2019 Life Lecture
13/42
amino acids
protein
8/13/2019 Life Lecture
14/42
A complex protein:
Involved in oxygenuse Each circle is an
amino acid
8/13/2019 Life Lecture
15/42
Stripped down view
Can you find the
amino end and thecarboxyl end?
Note the heme,
containing iron.
Function depends
on structure, which
depends on folding,
which depends onorder of amino acid
bases
8/13/2019 Life Lecture
16/42
Nucleic Acids (DNA, RNA)
Made of sugars, phosphates, bases
Ribose Sugar
5 C, 5 O, 10 H
Sugar Schematic
Deoxy Ribose
Ribonucleic acid (RNA) uses ribose sugar;
Deoxyribonucleic acid (DNA) uses deoxyribose sugar
8/13/2019 Life Lecture
17/42
phosphate
sugars & phosphates linkedphosphodiester bonds
Segment of side of ladder structure
8/13/2019 Life Lecture
18/42
Nucleic Acids (cont.)
Bases: Carry Genetic Code
Purines
A
G
Adenine
Guanine
Equal numbers of C and N
8/13/2019 Life Lecture
19/42
Pyrimidines
C U T
Cytosine Uracil / Thymine
RNA / DNA
More C than N
8/13/2019 Life Lecture
20/42
Bases in Nucleic acids: Purines and Pyrimidines
8/13/2019 Life Lecture
21/42
Purines
Pyrimidines
Note Uracil
8/13/2019 Life Lecture
22/42
Nucleic Acids (cont.)
Segment of RNA
Segment of DNA
Note that Treplaces U in DNA
8/13/2019 Life Lecture
23/42
Deoxyribose
Phosphate
Deoxyribonucleic Acid (DNA)
At the Chemical Level
8/13/2019 Life Lecture
24/42
8/13/2019 Life Lecture
25/42
Hydrogen Bonds (weak) connect the bases across
the two sides of DNA
8/13/2019 Life Lecture
26/42
Segment of DNA
8/13/2019 Life Lecture
27/42
The two strands of DNA form a double helix,
connected between bases by hydrogen bonds
8/13/2019 Life Lecture
28/42
Further wrapping to make compact chromosome
8/13/2019 Life Lecture
29/42
Information Storage Nucleic acids store information
The information specifies proteins
The information can be replicated
This allows inheritance
8/13/2019 Life Lecture
30/42
Base pairing rules
A - T G - C
- U
" Replication of order (reproduction)
Nucleic Acid - Protein Genetic Code
8/13/2019 Life Lecture
31/42
Codon
3 base sequence specifies an Amino Acid
GeneSequence of codons specifies a Protein
a gene specifies a protein
e.g. tobacco mosaic virus 4 genesbacteria ~ 10
3genes
human cell ~ 25,000genes
(update)
8/13/2019 Life Lecture
32/42
For mRNA Genetic Code
U
C
A
G
Glycine
Glycine
Glycine
Glycine
Aspartic Acid
Aspartic Acid
Glutamic Acid
Glutamic Acid
Alanine
Alanine
Alanine
Alanine
Valine
Valine
Valine
ValineG
U
C
AG
UC
A
G
U
C
A
G
Third
RNA
BASE
Serine
Serine
ArginineArginine
Asparagine
Asparagine
LysineLysine
Threonine
Threonine
ThreonineThreonine
Isoleucine
Isoleucine
IsoleucineStart/MethionineA
ArginineArginine
Arginine
Arginine
HistidineHistidine
Glutamine
Glutamine
ProlineProline
Proline
Proline
LeucineLeucine
Leucine
LeucineC
Cysteine
Cysteine
Stop
Tryptophan
Tyrosine
Tyrosine
Stop
Stop
Serine
Serine
Serine
Serine
Phenylalanine
Phenylalanine
Leucine
LeucineU
GACU
First
RNA
Base
Amino Acids
8/13/2019 Life Lecture
33/42
8/13/2019 Life Lecture
34/42
Structure of a tRNA
8/13/2019 Life Lecture
35/42
8/13/2019 Life Lecture
36/42
Translation
8/13/2019 Life Lecture
37/42
Variations in the Code
1. Wobble Bases
The third base in a codon can sometimes vary.
tRNA mRNA U A or G
G C or U
Comparison to genetic code "no changein amino acids
8/13/2019 Life Lecture
38/42
For mRNA Genetic Code
U
C
A
G
Glycine
Glycine
Glycine
Glycine
Aspartic Acid
Aspartic Acid
Glutamic Acid
Glutamic Acid
Alanine
Alanine
Alanine
Alanine
Valine
Valine
Valine
ValineG
U
C
AG
UC
A
G
U
C
A
G
Third
RNA
BASE
Serine
Serine
ArginineArginine
Asparagine
Asparagine
LysineLysine
Threonine
Threonine
ThreonineThreonine
Isoleucine
Isoleucine
IsoleucineStart/MethionineA
ArginineArginine
Arginine
Arginine
HistidineHistidine
Glutamine
Glutamine
ProlineProline
Proline
Proline
LeucineLeucine
Leucine
LeucineC
Cysteine
Cysteine
Stop
Tryptophan
Tyrosine
Tyrosine
Stop
Stop
Serine
Serine
Serine
Serine
Phenylalanine
Phenylalanine
Leucine
LeucineU
GACU
First
RNA
Base
Amino Acids
8/13/2019 Life Lecture
39/42
2. Some organisms use slightly different codes,with one or more changes in codon translation.
First seen in mitochondrial DNA.
Now known in some nuclear DNA
The code has evolved since the last commonancestor (But not much).
8/13/2019 Life Lecture
40/42
8/13/2019 Life Lecture
41/42
Summary (cont.)
4. Proteins and nucleic acids closely linked atfundamental level. Communicate throughgenetic code. All organisms have almostthe same genetic code. It must have
originated very early in evolution of life.
5. In present day organisms, protein synthesismust be directed by nucleic acids, but
nucleic acid reading or replication requiresenzymes (proteins). Chicken-Egg problem
8/13/2019 Life Lecture
42/42
Some Movies of Processes Animation of transcription (making mRNA)
http://vcell.ndsu.nodak.edu/animations/transcription/movie.htm
Animation of translation (making protein) http://vcell.ndsu.nodak.edu/animations/translation/movie.htm
Both from Virtual Cell Animation collection,Molecular and Cellular Biology Learning
Center