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The Living Environment
The study of organisms and their
interactions with the environment.
Topics
• Unit 1:
• Unit 2:
• Unit 3:
• Unit 4:
• Unit 5:
Ecology
The Cell
Genetics
History of Biological Diversity
The Human Body
Unit 2: The Cell




Chemistry in Biology
Cellular Structure and Function
Cellular Energy
Cellular Reproduction
The Building Blocks of Life

All organisms are made up of carbon-based
molecules. Specifically molecules called
hydrocarbons. (...they contain C and H)
 Macromolecules
are large molecules that are
formed by joining smaller organic molecules
together. There are four major categories of
biological macromolecules:




Carbohydrates: store energy and provide structural
support.
Lipids: store energy and provide barriers
Proteins: transport substances, speed reactions, provide
structural support, and make hormones
Nucleic Acids: store and communicate genetic
information
Carbohydrates



The diagram to the right
is glucose molecule.
Carbohydrates are
compounds composed of
carbon, hydrogen, and
oxygen. CH2O
Carbohydrates can be
simple sugars,
monosaccharides, or
complex sugars,
polysaccharides.
Carbohydrates





Glucose is a simple sugar or monosaccharide. Glucose
plays a central role as an energy source for organisms.
Sucrose, such as table sugar and lactose, is a
disaccharide. They also serve as an energy source for
organisms.
Glycogen is a polysaccharide found as long chains of
glucose molecules in the liver and skeletal muscle to be
used as stored energy.
Cellulose is also a polysaccharide which is used to give
structural support in the cell walls of plant cells.
Chitin is another polysaccharide and is the main
component in the hard outer shell of shrimp, lobster,
and many insects.
Carbohydrates
Lipids



The diagram to the right
is a phospholipid.
Lipids are composed of
fatty acids, glycerol, and
other components.
Phospholipids act as
barriers because of their
hydrophilic, “waterloving” heads and their
hydrophobic, “waterfearing” tails.
Proteins



Proteins are made of small
carbon compounds called
amino acids. There are 20
different amino acids.
There are four
conformations of proteins.
Cells contain about 10,000
different proteins that
transport substances
within the cell and
between cells, speed up
reactions, communicate
signals, and control cell
growth.
Proteins as Enzymes



Catalysts are substances
which increase the speed
of a chemical reaction.
Enzymes are biological
catalysts, composed of
amino acids, that will
speed up the rate of
reactions such as
photosynthesis and
digestion.
Reactants of a chemical
reaction are called
substrates.
Proteins as Enzymes
When a substrate binds
to the active site of an
enzymatic protein a
reaction occurs forming
the products.
 Specific enzymes are
designed to function only
with specific substrates
for specific reactions. The
two fit like a lock and
key.
 If a drug is introduced
that chemically “fits” into
the active site of an
enzyme, the enzymatic
reaction can be blocked.
How Enzymes Work

Proteins as Enzymes


The effectiveness of
an enzyme on the
rate of the reaction
can be affected by
factors such as pH
and temperature.
Enzymes are typically
named after the
molecule with which
they will interact but
end in –ase or –in.
For example,
amylase, lipase,
pepsin, and trypsin
are all enzymes.
Nucleic Acids



Nucleic acids are made
up of smaller repeating
subunits called
nucleotides.
There are six major
nucleotides all of which
contain a phosphate,
nitrogenous base, and a
ribose sugar.
The main function of
nucleic acids is to store
and transmit genetic
information such as DNA
and RNA.
Nucleic Acids

Adenosine
triphosphate
or ATP is a
storehouse of
chemical
energy used
by cells.
Summary of Macromolecules
Carbohydrates Lipids
Proteins
Nucleic Acids
Sugars/starches
Fats/oils/
steroids
Amino acids
Nucleotides
Short
Long
term
energy storage
Provides
structural
support
term Transports
energy
substances
storage Enzymes
Structural
Provides a
support
barrier Make
hormones
Communication
Store
and
communicate
genetic info
Storehouse
chemical
energy
of
Describe what you see in the following slide.
Describe what you see in the following slide.
The Cell


First discovered in 1665
by Robert Hooke who
built one of the first light
microscopes and viewed
dead cork cells. He is
credited for calling them
cellulae which eventually
became the word cell.
Not long after Hooke,
Anton van Leeuwenhoek
designed a microscope
and viewed living
organisms in pond water,
milk, and other
substances.
The Cell Theory

Developed in the mid 1800’s by German
and Prussian scientists it states:
 1.
All living organisms are composed of
one or more cells.
 2. Cells are the basic unit of structure and
organization of all living things. “basic unit
of life” – cells perform life functions.
 3. Cells arise only from previously existing
cells, with cells passing copies of their
genetic material on to their daughter cells.
The Cell
Plant cell using light microscope
The Cell
Plant cell using electron microscope
Describe what you see in the following
slides.
Types of Cells
Prokaryote
Visualizing Cells
Eukaryote
The Plasma Membrane


The main function of
the plasma
membrane is to
maintain the cell’s
homeostasis.
A cell’s homeostasis is
controlled by the
plasma membrane
due to its selective
permeability.
The Plasma Membrane
The Fluid Mosaic Model
The Plasma Membrane



Composed of a phospholipid bilayer, the plasma
membrane can maintain its structure due to the
polar heads and non-polar tails of the lipids.
Cholesterol molecules between the lipids keep
them from sticking together and help the
membrane maintain its fluidity.
Carbohydrate chains identify the cell and help
the cell identify incoming chemical signals.
The Phospholipid Bilayer
The Plasma Membrane



Transport Proteins: move needed substances or
waste materials through the plasma membrane.
Receptor Proteins: transmit signals to the inside
of the cell.
Support Proteins: anchor the plasma membrane
to the cytoskeleton and give the cell its shape.
The Plasma Membrane
The Fluid Mosaic Model


The phospholipids can move sideways within the
membrane as well as the proteins. This constant motion
of molecules sliding past one another creates a fluidity of
the membrane.
Because there are different substances in the
membrane, a pattern, or mosaic, is created on its
surface.
The Cytoplasm



Cytoplasm is the semifluid substance that fills
the inside of all cells.
It is composed mostly of
water.
In prokaryotes, chemical
processes occur directly
in the cytoplasm. In
eukaryotes these
processes occur in
organelles.
The Cytoskeleton


The cytoskeleton is a
supporting network of
long, thin protein fibers
that form a framework for
the cell.
It is composed of
microtubules and
microfilaments that
support the cell and allow
movement of substances
within the cell.
Cell Structures
Cell Structures
The Nucleus



The nucleus is the cell’s
control center.
It contains most of the cell’s
DNA which is used to make
proteins for cell growth,
function, and reproduction.
The nucleus is surrounded by
a double membrane called
the nuclear envelope. It has
pores to allow substances to
move in and out of the
nucleus.
The Nucleus continued…


Within the nucleus is the
site of ribosome
production called the
nucleolus.
As ribosomes are
produced they move out
of the nucleus and either
attach to endoplasmic
reticulum or are free
floating in the cytoplasm.
The Ribosome
Ribosomes


Ribosomes are composed of RNA and protein,
and are NOT membrane bound organelles.
The function of ribosomes is to synthesize
PROTEINS!
Endoplasmic Reticulum



ER is composed of folded
membrane and sacs and
is a site for protein and
lipid synthesis.
Rough ER is covered by
ribosomes that produce
proteins.
Smooth ER lacks
ribosomes and is a site for
polysaccharide and
phospholipid synthesis.
Golgi Apparatus




Golgi Apparatus, or Golgi
Body, is a flattened stack
of folded membranes.
Its function is to modify,
sort, and package
proteins into sacs called
vesicles.
These vesicles can then
be shipped outside of the
cell.
Sometimes referred to as
the cell’s post office.
Vacuoles


A membrane bound sac
used to temporarily
store food, water,
enzymes, and
sometimes waste.
Plant cells require very
large central vacuoles
for storing water.
Mitochondria



Mitochondria have an
outer membrane and a
folded inner membrane
that forms many cristae.
Cristae provide a large
surface area for breaking
down sugar molecules.
Mitochondria are known
as the “powerhouse” of
the cell.
Mitochondria



Mitochondria are found in all
eukaryotes and are
responsible for cellular
respiration.
Mitochondria release the
energy from nutrients
obtained by the cell.
They have their own DNA
called mDNA. Because of this
fact, they are believed to
have once been single celled
organisms themselves.
Chloroplasts



Chloroplasts are found
only in photosynthetic
cells such as plant cells.
They have an outer and
inner lipid membrane and
contain stacks of
thylakoids.
In many ways they are
similar to mitochondria
but DO NOT perform the
same function.
Chloroplasts



Chloroplasts are responsible
for using sunlight to
produce chemical energy
through a process called
photosynthesis.
Chloroplasts contain a
green pigment that traps
sunlight called chlorophyll.
They also have their own
DNA and are believed to
have once been a single
celled organism known as
cyanobacteria, possibly the
first life forms on Earth.
Lysosomes



Lysosomes are
membrane bound vesicles
that digest excess or
worn out organelles and
food particles.
They will also digest
bacteria and viruses that
have entered the cell.
Lysosomes function to
keep the inside of the cell
clean.
Centrioles



Centrioles are groups of
microtubules that
function during cell
division.
They produce the spindle
fibers that separate
chromosomes during
mitosis and meiosis.
Usually found in pairs
called centrosome.
Cell Wall


The cell wall is a thick,
rigid, mesh composed of
cellulose and structural
proteins.
It surrounds the cell
membrane of plant cells
and provides protection
and structural support for
the cell.
Cilia and Flagella




Cilia and flagella are both
composed of
microtubules.
They are used for
locomotion and/or
feeding in different types
of cells.
Cilia are usually very
numerous although there
are typically only one or
two flagella if they are
present.
Not all cells have cilia or
flagella.
Cellular Transport


Cellular Transport moves substances
within the cell and moves substances into
and out of the cell.
Cellular Transport is primarily carried out
by the plasma membrane and the
cytoskeleton, specifically the cell’s
microtubules.
Passive Transport: Diffusion


Diffusion is the
net movement
of particles
down the
concentration
gradient.
Particles always
move from an
area of high
concentration
to an area of
low
concentration
until an
equilibrium has
been reached.
Diffusion...continued
• Once the
concentrations are
equal, particles will
continue to move
randomly but will
maintain a dynamic
equilibrium.
• Factors affecting
the rate of diffusion
are concentration,
temperature, and
pressure.
Diffusion across the plasma membrane


Facilitated diffusion uses transport proteins to
move ions and small molecules across the
plasma membrane.
Figure (a) is a channel protein and figure (b) is a
carrier protein.
Osmosis...


...the diffusion of water across a selectively
permeable membrane.
Regulating the movement of water across the
plasma membrane is an important factor in
maintaining homeostasis within the cell.
Cells in solution...



When a cell is in an isotonic solution, the
concentration of water and solutes outside the cell
is equal to the concentration inside the
cell...effectively creating a dynamic equilibrium.
When a cell is in a hypotonic solution, the
concentration of water is greater outside the cell
than inside...causing water to rush into the cell and
causing it to swell and possibly burst. (cellular
lysing)
When a cell is in a hypertonic solution, the
concentration of water is greater inside the cell than
outside...causing water to rush out of the cell,
resulting in the cell shriveling.
Cells in solution...
Osmosis in Various Solutions
Passive Transport vs. Active Transport


Passive transport, such as diffusion and
osmosis, does not require the use of any
energy to move the substance because
substances naturally flow with the
concentration gradient.
Active transport is necessary when
substances must move against the
concentration gradient, that is, from areas
of low concentration to areas of higher
concentration.

Therefore, active transport typically requires
the use of an energy source, usually ATP.
Passive Transport vs. Active Transport


Figure (a) is a channel protein used for passive
transport because it does not require the use of
energy to change its conformation.
Figure (b) is a carrier protein used for active
transport which does require the use of energy
because the protein must change its
conformation.
Passive Transport
Active Transport



In order to maintain homeostasis, cells often
need to remove substances or absorb
substances against their concentration
gradients.
Moving substances from lower concentrations to
higher concentrations across the plasma
membrane requires energy.
Active transport occurs with the aid of carrier
proteins, sometimes called pumps.
Active Transport
Sodium/Potassium ATPase Pump


The pump uses energy
in the form of ATP to
transport sodium out of
the cell, while moving
potassium into the cell.
This pump moves ions
against their
concentration gradient
and is therefore an
example of active
transport.
Sodium Potassium
Pump
Transport of Large Particles


Endocytosis is the
process by which a cell
surrounds a substance in
the outside environment,
enclosing the substance
in a portion of the plasma
membrane.
The membrane then
pinches off, creating a
vacuole containing the
substance within the cell.


Exocytosis is the
secretion of materials at
the plasma membrane.
Cells use exocytosis to
expel waste and secrete
substances with the use
of vesicles produced by
the Golgi apparatus.
Endocytosis and Exocytosis
Cellular Energy


All of the chemical reactions that take
place within a cell are referred to as the
cell’s metabolism.
A common example of metabolism that
takes place within your body is the body’s
ability to breakdown food into nutrients
and utilize the carbohydrates and fats as a
source of energy.
Cellular Energy


Photosynthesis and Cellular Respiration
are examples of metabolic pathways,
whereby chemical reactions take place
that result in energy transfer.
Photosynthesis occurring in autotrophs
and Cellular Respiration occurring in
heterotrophs, results in a natural cycle
known as the Carbon-dioxide/Oxygen
cycle.
ATP: The Unit of Cellular Energy



Adenosine Tri-Phosphate
is a biological molecule
that provides chemical
energy.
ATP is composed of an
adenine base, ribose
sugar, and three
phosphate groups.
ATP releases energy
when the bond between
the second and third
phosphate groups is
broken; producing ADP
+ Energy
PHOTOSYNTHESIS


Photosynthesis occurs
in all autotrophic
organisms including
plants, algae, and some
bacteria.
Photosynthesis is the
chemical process of
using carbon-dioxide
and water, in the
presence of sunlight, to
produce glucose and
oxygen.
PHOTOSYNTHESIS


Photosynthesis occurs
inside organelles called
chloroplasts, which
contain a green
pigment called
chlorophyll.
Other photosynthetic
pigments, such as ßcarotene, result in
other colors such as
the orange-yellow color
of carrots and sweet
potatoes.
PHOTOSYNTHESIS

Photosynthesis typically occurs in two
phases:
 Phase
I: Light Reactions – light is captured
and the energy is temporarily stored as
NADPH and ATP.
 Phase
II: The Calvin Cycle – NADPH and
ATP produced from the light reactions are
converted to and stored as glucose.
PHOTOSYNTHESIS Reaction
6CO2 + 6H2O
sunlight
Carbon-dioxide + Water
Photosynthesis
C6H12O6 + 6O2
sunlight
Glucose + Oxygen
Cellular Respiration


Cellular respiration
occurs in both
autotrophs and
heterotrophs.
Cellular respiration is
the chemical process
of releasing energy
from glucose and
using that energy to
make ATP.
Cellular Respiration


Cellular respiration
occurs within
organelles called
mitochondria, found
in all Eukaryotes.
Similar to
photosynthesis,
cellular respiration
occurs in two stages.
Cellular Respiration


The first stage of cellular respiration is
called glycolysis which is an anaerobic
process, and therefore does not require
oxygen.
The second stage of cellular respiration is
an aerobic process and includes the Krebs
cycle. This stage does require the use of
oxygen.
Cellular Respiration Reaction
C6H12O6 + 6O2
Glucose + Oxygen
6CO2 + 6H2O
+
ATP
Carbon-dioxide + Water + ENERGY
Photosynthesis & Cellular Respiration
Reactions Compared

Photosynthesis Reaction
6CO2 + 6H2O

sunlight
C6H12O6 + 6O2
Cellular Respiration Reaction
C6H12O6 + 6O2
6CO2 + 6H2O
+
ATP
The Cell Cycle / Cellular Reproduction



The Cell Cycle is
essentially the life cycle
of a cell.
The Cell Cycle includes
three phases:
Interphase, Mitosis, and
Cytokinesis.
Interphase is divided
into 3 subphases: G1, S,
and G2.
The Cell Cycle
The Cell Cycle




Interphase is the first and
longest phase of the cell
cycle.
During G1 (Gap1), the cell
grows and performs normal
functions.
During S (synthesis), DNA in
the nucleus is replicated.
During G2 (Gap2), the cell
prepares for Mitosis.
During Interphase S...


DNA in the nucleus
replicates itself forming
sister chromatids.
Pairs of identical sister
chromatids are
connected at the center
with a centromere
forming an X shaped
chromosome during
prophase of mitosis.
Mitosis


Mitosis is the stage of
the cell cycle during
which the cell’s nucleus
and nuclear material
divide.
Mitosis occurs in four
substages: Prophase,
Metaphase, Anaphase,
and Telophase.
Prophase
During Prophase...




Nuclear envelope disintegrates.
Nucleolus disappears.
Chromatin (DNA strand) condenses
forming X-shaped chromosomes of
identical pairs of sister chromatids.
Centrioles move toward opposite sides of
the cell and produce the mitotic spindle
fibers.
Metaphase
During Metaphase...


Chromosomes align along the cell’s
equator forming the metaphase plate.
Spindle fibers attach to each chromosome
at the centromere.
Anaphase
During Anaphase...


Sister chromatids are pulled apart at the
centromeres as the spindle fibers contract.
Chromosomes move toward opposite
poles of the cell.
Telophase
During Telophase...





Chromosomes reach opposite poles of the
cell.
Mitotic spindle fibers disappear.
Nuclear envelope reforms.
Nucleolus reappears.
Chromosomes decondense back into
Chromatin (DNA strand).
Cytokinesis


In animal cells: microfilaments pinch inward at the cell’s
equator until the cell divides in two.
In plant cells: a cell plate forms where the metaphase
plate had formed earlier and then a new cell wall forms
on either side, dividing the cell in two.
Mitosis
Mitosis continued...
Various Stages of Mitosis Occurring
in an Onion Root Tip
Results of Mitosis



Essentially, Mitosis is a
form of asexual cell
reproduction.
A single parent cell makes
a copy of its genetic
information, then splits
into two new cells called
daughter cells.
Daughter cells formed as
a result of mitosis are
identical to each other
and to the parent cell.
The Cell Cycle & Mitosis
What are the roles of Mitosis?

Growth and Development

Replacement of damaged/dead cells
Abnormal Cell Cycle: Cancer



Cancer is the
uncontrolled growth
and division of cells.
Cancer is typically the
result of a change in
the DNA that controls
the production of
proteins that regulate
the cell cycle.
Substances known to
cause cancer are called
carcinogens.
Apoptosis: Programmed Cell Death



Apoptosis occurs to
normal cells when they
receive the signal, usually
in the form of genetic
code, to commit suicide.
The cell will shrink, the
nucleus will collapse, and
the cell and all organelles
will lyse.
Apoptosis typically occurs
in developing fetuses as
well as in cells with
damaged DNA.
Stem cells


Stem cells are unspecialized cells that can
develop into specialized cells under the right
conditions.
Stem cells have the potential to replace any
damaged cell(s) anywhere in the body.
Meiosis



Meiosis is a specialized type of
cell division that results in the
production of gametes, or sex
cells.
Meiosis only occurs within the
reproductive organs of
organisms that reproduce
sexually.
Because the cells produced by
meiosis are only used for
reproduction, they contain ½
the number of chromosomes
as the original cell.
Meiosis


In order to maintain the
same number of
chromosomes from parent
to offspring, sex cells can
only have ½ the number of
chromosomes as typical
body cells.
For example: Human body
cells (somatic cells) each
contain 46 chromosomes,
but human gametes (sex
cells) only contain 23
chromosomes in each cell.
How Meiosis Works
Meiosis
Meiosis involves two
consecutive cell divisions
called meiosis I and
meiosis II.
 By the end of meiosis I,
two new cells are produced
each containing the same
number of chromosomes as
the parent cell, but with
genetic variation.
 By the end of meiosis II,
four cells have been
produced, each containing
½ the number of
chromosomes as the
original cell, each with
genetic variation.
Stages of Meiosis

Meiosis
During prophase of
meiosis I, homologous
chromosomes pair
together forming a tetrad.
 Once paired, crossing
over occurs, resulting in
recombinant
chromosomes that allows
genetic variation among
offspring of the same
parents.
 In males, each of the four
daughter cells will
become a sperm cell. In
females, only one
daughter cell will survive
to become an egg cell.
Unique Features of Meiosis

Comparison of Meiosis and Mitosis