CHAPTER 8
CELLULAR ENERGY
• SECTION 8.1 – HOW ORGANISMS
OBTAIN ENERGY
• MAIN IDEA – All living organisms use
energy to carry out all biological
processes.
• QUESTIONS: What is energy?
• Why do living things need energy?
• How do humans obtain energy?
• TRANSFORMATION OF ENERGY
• Chemical reactions and processes in your
cells are continuous, even when you
don’t think you are using any energy.
–Macromolecules are assembled and
broken down, substances are
transported across cell membranes and
genetic instructions are sent.
• All require energy
–Energy is the ability to do work.
• LAWS OF THERMODYNAMICS
st
•1
law of thermodynamics is
the law of conservation of
energy, which states that
energy can be converted from
one form to another, but
cannot be created nor
destroyed.
• AUTOTROPHS AND
HETEROTROPHS
• Autotrophs make their own food
using energy from the sun.
–Convert light energy from the
sun into chemical energy.
• Heterotrophs need to eat food to
obtain energy
• METABOLISM
• Metabolism is all of the chemical
reactions in a cell.
• ATP: THE UNIT OF CELLULAR ENERGY
• Adenosine triphosphate (ATP) is the
most important biological molecule
that provides chemical energy.
• ATP STRUCTURE
• ATP is a multipurpose storehouse of chemical
energy that is used by cells in a variety of
reactions.
–Most abundant energy carrier molecule in
cells & found in all types of organisms.
• ATP is a nucleotide made up of a adenine
base, a ribose sugar, and 3 phosphate groups.
• QUESTION: What macromolecule group does
ATP belong in?
• ATP FUNCTION
• ATP’s function is to release energy when
the bond between the 2nd and 3rd
phosphate groups are broken
–Forms adenosine diphosphate (ADP)
and a free phosphate group
• Energy is released
• SECTION 8.2 – PHOTOSYNTHESIS
• MAIN IDEA – Light energy is trapped and
converted into chemical energy during
photosynthesis.
• QUESTIONS: What is the benefit of
photosynthesis for humans?
• How does photosynthesis benefit plants?
• OVERVIEW OF PHOTOSYNTHESIS
• Photosynthesis is a process where light energy is converted
into chemical energy.
• Chemical equation for photosynthesis is:
light
6CO2 + 6H2O
C6H12O6 + 6O2
• Photosynthesis occurs in 2 phases:
– Phase 1 – light dependent reactions – where light energy
is absorbed and converted into chemical energy in the
form of ATP and NADPH
– Phase 2 – light independent reactions – where the ATP
and NADPH that was made in phase one are used to
make glucose.
• After glucose is produced it can be joined with other
simple sugars to form larger molecules like starches
• Can also make proteins, lipids, and nucleic acids.
• PHASE 1 – LIGHT REACTIONS
• Chloroplasts capture light energy in photosynthesis.
– Mainly found in the cells of leaves.
• Disk-shaped organelles that contain 2 main
compartments essential for photosynthesis.
– Thylakoids – flattened, saclike membranes that are
arranged in stacks called grana
» Light dependent reactions take place within the
thylakoids.
– Stroma are fluid filled spaces outside the grana.
» Light independent reactions in phase 2 take place here.
• Pigments are light absorbing colored molecules that are found in the
thylakoid membranes of the chloroplasts.
– Different colored pigments absorb specific wavelengths of light.
• Chlorophylls
• Carotenoids
• PHASE 2: THE CALVIN CYCLE
• In the Calvin Cycle energy gets
stored in organic molecules like
glucose.
• SECTION 8.3 – CELLULAR RESPIRATION
• MAIN IDEA – Living organisms obtain
energy by breaking down organic
molecules during cellular respiration
• QUESTION: Is air the same as oxygen?
• If it is not the same, how is air different
from oxygen?
• OVERVIEW OF CELLULAR RESPIRATION
• Organisms obtain energy by a process called cellular respiration.
– During cellular respiration electrons are collected from carbon
compounds, like glucose, and use that energy to make ATP.
• ATP is used to provide energy for cells to do work.
• Equation for cellular respiration is the opposite of the equation for
photosynthesis.
• C6H12O6 + 6O2
6CO2 + 6H2O
• Cellular respiration has 2 parts:
– Glycolysis
• Anaerobic process (does not require oxygen)
– Aerobic respiration (Requires oxygen)
• Includes:
– Krebs Cycle
– Electron transport
• GLYCOLYSIS
• Glycolysis is the process where glucose is
broken down in the cytoplasm.
–2 ATP molecules are required to start
the reactions.
–Produces:
• 2 molecules of ATP and 2 molecules
of NADH for each molecule of glucose
that is broken down.
• 2 pyruvate molecules
• KREBS CYCLE
• The 2 pyruvate molecules are transported
to the mitochondria.
• In the mitochondria with the help of
oxygen the pyruvate is broken down into:
–6 CO2
–2 ATP
–8 NADH
–2 FADH2
• ELECTRON TRANSPORT
• Electron transport is the final step in the
breakdown of glucose.
• Electrons move along the mitochondrial
membrane from one protein to another.
• The electron transport produces:
–32 ATP
• In eukaryotes one molecule of glucose
yields 36 ATPS under ideal conditions.
• PHOTOSYNTHESIS AND CELLULAR
RESPIRATION
• Photosynthesis and cellular respiration are 2
important metabolic pathways that cells use
to obtain energy.
• Photosynthesis products are oxygen and
glucose, but these are the reactants for
cellular respiration
• Cellular respiration products are carbon
dioxide and water, but these are the reactants
for photosynthesis