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Objective 2
Biology
Cell and Cell Structures
Cells are: smallest biological unit
that can sustain life.
Two different types of Cells
Prokaryotes
pronounced (pro-carry-oats)
Pro = before
Karyo = kernel or seed
“Before the Nucleus”
Prokaryotic cells are
one where the genetic
material is not
contained in a nucleus.
The DNA is just floating in the cell in
a ring called a Plasmid.
Best Example
– E-coli bacteria in your gut
EuKaryotes pronounced (you-carry-oats)
Eu = true
Karyo = kernel or seed
“True Nucleus”
Eukaryotes have genetic
material stored in the nucleus.
They are:
•generally bigger
•have organelles
•may live in multi-cellular units
Best example - You
Diffusion:
Things moving
from high
concentration to
low
concentration.
Things will diffuse until they reach Equilibrium
Osmosis:
Water moving across a membrane to equalize
another molecule’s concentration.
Example:
A substance (solute) is placed in a
beaker that is divided by a semipermeable membrane.
When a molecule can’t move
across a membrane to equalize
concentration, Water will!
Water will move to equalize the
concentration.
DNA = DeoxyriboNucleic Acid
What is it made from?
Nucleotides:
Phosphate group
Ribose (5 carbon) sugar
Nitrogen Base
Groups of Nucleotides
Purines
Adenine
Guanine
Pyrimidines
A
G
T
C
Thymine
Cytosine
Pairing Rule
1. Adenine always bonds with Thymine
2. Guanine always bonds with Cytosine
How do they link up?
One Nucleotide links with the
next one in the chain by a
COVALENT bond between
the ribose and the next
nucleotides phosphate
The opposite side goes in the other
direction, linking across the
nitrogen base by HYDROGEN
bonds
How do cells make new copies of DNA for new cells?
Replication:
1. When DNA needs to be copied,
it unwinds in the nucleus
2. An enzyme, DNA Helicase,
starts to “unzip” the DNA
making a replication fork.
3. As DNA is unzipped, another
enzyme, DNA Polymerase,
begins to add nucleotides to
the now exposed bases of the
old strand.
4. The two new DNA strands
recoil.
DNA making DNA
DNA makes RNA,…….. But How?
Transcription: DNA making RNA
1. DNA unwinds and unzips.
2. The RNA Polymerase
attaches to a Initiation site.
3. The RNA Polymerase
begins to move only on one
(1) of the strands adding
RNA nucleotides
4. When reaching a
termination site, the RNA
Polymerase releases the
DNA and goes to make
more RNA
Transcription occurs in the nucleus, but the
Messenger RNA (mRNA) leaves the nucleus.
It attaches to a
Ribosome which
begins to read the
mRNA
It reads three (3) letter
words called Codons
Example: An mRNA that attaches to the Ribosome
A
c
u
a
a
a
g
c
g
u
a
u
g
c
a
It reads ACU, then it moves down and reads AAA and so on…
The process of reading the
mRNA code and making
Proteins is called:
Translation
The Ribosome doesn’t
just read the mRNA, it
calls for Amino Acids for
each Codon it reads.
The codon “U G C” calls for
the amino Acid Cysteine.
U
G
C
Hey! I need
a Cysteine!!
A little help
here?
Help comes from
another type of
RNA:
tRNA
U
G
C
A
C
G
Transfer RNAs have a
group of three bases
called the “anticodon”
that is the compliment of
the mRNA
Each TRNA carries a
different Amino Acid:
ACG carries Cysteine
Cysteine
The Ribosome
moves down the
mRNA and calls
for the next
Amino Acid
The first tRNA
goes away when
the second amino
acid is attached
to the first with a
Peptide bond
Then the ribosome
moves to the next
Codon
U
G
C
A
C
G
Cysteine
A
U
C
G
G
C
Threonine
Cell Division
Cells divide for two reasons.
1. To create copies Mitosis
2. To create sex cells -
Meiosis
Mitosis
4 stages:
1. Prophase:
The Centrioles begin to move apart.
Chromosomes thicken
The Nuclear membrane disappears
2. Metaphase:
The centrioles are at the “poles” of the cell
The chromosomes line up in the middle
of the nucleus
3. Anaphase:
The Chromosomes are pulled toward the
centrioles by spindle fibers
4. Telophase:
The nucleus begins to reform and the
cell begins cytokinesis
Meiosis:
The process of creating haploid
sex cells called Gametes
Gamete - sperm or egg
Has two “phases” of
“Mitosis-like stages”
For humans, it takes a
cell with 46
chromosomes and
makes cells with 23.
Let’s look at some Genetic traits
DOMINANT
Black color This dog’s genetics could be two ways
We show the genetics like this:
“B” from one parent, “B” from the other parent
OR
“B” from one parent, “b” from the other parent
“BB” is Homozygous for the trait.
“Bb” is Heterozygous for the trait.
Recessive
lighter color This dog’s genetics CAN ONLY be
shown one way:
“b” from one parent, “b” from the other parent
Recessive traits are ALWAYS
homozygous; thus it would be “bb”
OK, now for a problem:
If I have a
heterozygous black
male and a golden
femalewhat
that ismate,
the chances
of having golden
Bb
puppies in the litter? 50% black
X
bb
100%
golden
50% golden
You either multiply it out or make a Punnett square
Or
b
b
B
Bb
Bb
b
bb
bb
50%
EVOLUTION
Darwin’s Theory - Natural Selection
Those organisms that are best “fit” to the
environment will survive the environment.
Adaptation – a characteristic that an organism
has that allows it to survive.
Extinction – all members of a population dying
out due to not having beneficial
adaptations.
What Evidence is there for Natural
selection?
1. The Fossil Record
Fossils found at lower
layers of rock are
more simple than
those found at upper
layers.
2. Homologous Structures.
Structures from one creature are similar to the
structures from other creatures.
3. Vestigial Organs
Organs that are found in you that have no purpose
in the body, but are found and used in other
organisms.
1. You have an appendix.
2. Snakes have hipbones. 
3. Whales have
hipbones too.
4. Missing Links
There are missing links in the fossil record that
show that the species that are in the earth today.
Rhodocetus – Whale-like species
with limbs.
Archaeopteryx – ancient bird-like
reptile with wings, and
feathers. But it has teeth
and claws on the
forelimbs.
Sometimes change is directional
Directional Selection:
This happens when one of the “extremes” is favored
in an environment over the other extreme or the old
average.
Stabilizing Selection:
Then the average is favored over either of the
extremes in a population.
Disruptive Selection:
This situation happens when either extreme is favored
over the average.
Virus and Bacteria
Virus:
Non-living
Parasitic
Biological Particle
Viruses do not “live”
because they can not
reproduce outside a
“host” cell.
Host: - any organism that is used by a virus
or bacteria to complete it’s lifecycle
Bacteria!!!!
Prokaryotic cells
Living cells!
Bacteria come in three shapes.
Spirilla – corkscrew
shaped
Bacilli – rod
shaped
Cocci - spherical
shaped
Classification
Carolus Linnaeus created a system that allowed scientist
all over the world to name the species
that were discovered
Kingdom – broadest classification King
Phylum – separates into major groups
within the Kingdom (plural – phyla)
Phillip
Class – breaks phyla into smaller groups
Came
Order – more specific
Family – very similar characteristics
Genus – a reproductive grouping
Species – most specific
Over
For
Good
Soup
How are animals put into the taxonomic
categories?
They used to be put in by looks
(physical Characteristics).
That can
cause
problems!
Black Bear
Koala (not bear)
Phylogeny - the study of evolutionary
relationships
Cladogram
- a way to visually show relationships
between organisms.
Two examples
Now organisms are organized
by similarities in their DNA.
Types of Kingdoms
1. Animalia
- heterotrophic
multi-cellular
no cell walls
(there are 6 different kingdoms)
2. Plantae
-Autotrophic
multi-cellular
with cell walls
3 Fungi
- Heterotrophic
multi-cellular
with cell wall
4 Protista
-Heterotrophic or autotrophic
single cellular Eukaryotic
with or without cell walls
5. Bacteria
- heterotrophic or autotrophic
single cellular
prokaryotic
with cell walls
6. Archaebacteria
-Heterotrophic or autotrophic
single cellular
prokaryotic
with cell walls
live in extreme environments