CH. 4 Cellular Processes
Biology
4A- Cellular Energy
4.1 Energy Relationships
• Explain why energy is required for me
• Define autotroph and heterotroph
• Describe how energy is stored in ATP molecules
Energy and Life?
• The primary need of all cells is energy.
• Only cellular need that is not recyclable in the environment
• Must be in constant supple
Autotrophs and Heterotrophs
Autotrophs
• Organisms that make their
own food
• Plants, Algae, etc.- capture
light energy and produce
their own food.
• Also known as Producers
Heterotrophs
• Organisms that depend on
other organisms for their
energy
• Consumers
• Humans, animals, fungi,
bacteria
ATP: The Energy Currency in Cells
ATP
• ATP molecule made up of
Adenosine (adenine + simple
sugar) and three phosphate
groups
• Key to how ATP stores energy is
found in the bonds between the
three phosphate groups; these
are bound to each other by
unstable, high energy covalent
bonds
ADP
• A phosphate group broken off
from the original three
phosphate attached groups.
ATP: The Energy Currency in Cells
ATP
• ATP ADP + P + Energy
ADP
• ADP + P + Energy  ATP
4.2 Photosynthesis
• Objectives:
• Write a simple equation for photosynthesis
• Explain how light energy is captured for use in
photosynthesis
• Describe the light-dependent phase and the Calvin Cycle
• List the final products of photosynthesis
• Explain how the environment affects photosynthesis
Photosynthesis
• The process of absorbing light and converting it into stored
chemical energy
• Primary photosynthetic organisms: green plants and algae
Chlorophyll and Light
• Chlorophyll- a green pigment, a primary catalyst of
photosynthesis
• Pigments- Special light absorbing molecules
• Chlorophyll a and Chlorophyll b- The two primary pigments
of photosynthesis
• Found in the grana of chloroplasts in photosynthetic eukaryotic
cells
• Chlorophyll a is more abundant and serves as primary catalyst for
photosynthesis
The Process of Photosynthesis
Light Dependent Phase
• First phase, also called “Light
Reactions”
• Step One: Light energy absorbed
by pigments and used to energize
electrons in a chlorophyll a
molecule.
• Step Two: e- Transport Chain
• Step Three: Photolysis- splitting of
water molecule into H+ ions,
electrons, and oxygen
• Step Four: NADP+ picks up 2 e- and
H+ ion to become NADPH
Calvin Cycle
• Light Independent Phase- takes
place in stroma of the
chloroplast
• Step One: CO2 molecule diffuses
from cytoplasm into stroma,
binds to RuBP. Energy stored in
ATP and NADPH is used to
produce PGAL.
• PGAL molecules are used to
make glucose and also more
RuBP
Calvin Cycle in a Nutshell
• Calvin Cycle produces sugar using the atoms from CO2,
energy from ATP, and the electrons and hydrogen ions
provided by NADPH
• See PG’s 82 and 83
4.3 Cellular Respiration
• Cellular Respiration: the breaking down of a food
substance into usable cellular energy in the form of
ATP.
• Glucose is primary food source of cellular energy,
however, lipids, monosaccharides, and even protein
can used.
Aerobic and Anaerobic
Aerobic
• Requiring Oxygen
• C6H12O6 + 6O2  6H2O+ 6CO2 +ATP
Anaerobic
• No Oxygen
Glycolysis
• Go to PG. 87
• The breakdown of glucose into pyruvic acid, H+ ions, and
electrons
• Step One: two molecules of ATP supply activation energy.
Using energy and 2 Phosphates from ATP, glucose is broken
down into 2 molecules of PGAL
• Step Two: Each molecule of PGAL releases electrons and
hydrogen ions to an electron carrier molecule (NAD+). Each
PGAL molecule also has a Phosphate attached to it.
Glycolysis CONT.
• Step Three: Each phosphate group added in Step 1 and 2 is
removed and added to a molecule of ADP, forming 4 ATP
molecules. This reaction produces 2 Pyruvic Acid molecules
Krebs Cycle
• Pyruvic Acid reacts with an enzyme that removes a carbon
from pyruvic acid to produce acetyl coenzyme A (Acetyl
CoA), CO2, Hydrogen ions, ATP, and electrons
Electron Transport Chain
• Majority of ATP produced here.
• Converts 3 molecules of ADP to ATP
• In total, one molecule of glucose produces 32 ATP
Aerobic Respiration Energy Output
• Converts 40% the energy contained in a glucose molecule
into the for of ATP
Alcoholic Fermentation
• In this, the pyruvic acid molecule is changed to a molecule of ethyl
alcohol in a two step process:
• Step One: Pyruvic acid gives off a carbon dioxide molecule, converting
it into a 2 carbon-compound
• Step Two: 2-carbon compound takes the hydrogen ions and electrons
from the carrier molecule NADH to make ethyl alcohol. The use of the
of the hydrogen and the electrons frees the carrier molecule to be
used again in glycolysis
Lactic Acid Fermentation
• Has only one step: Pyruvic acid take the hydrogen and
electrons from the NADH produced during glycolysis, freeing
the carrier molecule to be used again in glycolysis to produce
ATP
Fermentation Energy Output
• Fermentation supplies no ATP energy beyond that obtained from
glycolysis. Cellular fermentation, therefore, produces a net gain of
only 2 ATP molecules per glucose molecule.
4B- Cellular Metabolism and Protein Synthesis
• Objectives:
• Describe the structure and function of the three kinds of
RNA
• Differentiate between introns and exons
• List and describe the steps in translation
Protein Synthesis
The Code of Life
• Code of life: 4 bases (amino acids)• Adenine
• Thymine
• Guanine
• Cytosine
• All the “words” or “instructions” in the DNA are three
letters long (Codons)
Types of RNA
• mRNA- contains the code for a polypeptide chain of amino
acids and carries the code from the DNA in the nucleus to
the ribosomes, in the cytoplasm, where the code is read.
• tRNA- where amino acids are attached. tRNA molecules
are about 80 nucleotides long and are formed in the
nucleus. The chain of nucleotides forms several loops. On
the edge of these loops are anticodons (complimentary
base pairs for specific codons in the mRNA)
•G-C
•A-U
•C-G
Types of RNA
• rRNA- manufactured by the DNA of the nucleus. It
combines with various proteins in the cytoplasm to
form a ribosome.
Translation
• The process of assembling the polypeptide from
information coded in the mRNA
The Manufacture of Messenger RNA
• Exons: sections of mRNA that are actually read as
codons when making the protein.
• Introns: sections of transcribed RNA that do not code
for amino acids and therefore cannot be translated
into proteins. These tend to be cut out of the
sequence.
Anabolism and Catabolism
• Anabolism: process that build molecules and store
energy
• Catabolism: processes that break down molecules
and release energy
Three types of Cellular Digestion
• Intracellular Digestion: Phagocytosis or pinocytosis,
materials are then broken down by enzymes.
• Extracellular Digestion: enzymes released by vesicles
outside of cell to breakdown food substances. The
products are then absorbed through the membrane of
the cell.