Ch. 9 - Cellular Respiration/Fermentation Study Guide
A. Introduction
1. All living things need energy for metabolism.
a. Plants – produce glucose through photosynthesis; break down
glucose during cellular respiration to release energy (ATP).
b. Animals, Fungi, and non-photosynthetic Protists – must consume
food & break the food molecules/organic molecules (GLUCOSE)
down to release energy (ATP). They too carry out the process of
cellular respiration. NOTE: Photosynthetic protists such as Euglena
also metabolize glucose by the process of cellular respiration.
2. When food molecules (a.k.a. organic molecules/carbs, proteins, lipids)
are broken down energy is released & stored in ATP (adenosine
triphosphate).
3. Production of ATP occurs in the MITOCHONDRIA of the eukaryotic cells.
REMEMBER: MITOCHONDRIA ARE THE “POWERHOUSE” OF THE CELLS.
4. Animal, fungi, protists, and plant cells are all eukaryotic cells (have a
nucleus) & all have mitochondria; therefore they ALL produce ATP.
5. How do they produce ATP? By the process of cellular respiration which
occurs in all eukaryotic cells.
B. Anatomy of the Mitochondria
1.
Outer & inner membranes are made of lipids & proteins; has pores that
allow substances to enter & leave the mitochondria.
Inner membrane has folds called “cristae” which increase surface area.
3. Fluid matrix refers to the fluid inside the mitochondria.
4. NOT SHOWN: Mitochondria also contain their own ribosomes & DNA;
mitochondria are able to reproduce on their own. REMEMBER:
mitochondria & chloroplasts are cousins to bacteria because they all
have their own DNA, ribosomes & can reproduce on their own (binary
fission).
2.
C. Cellular Respiration – occurs only if oxygen is present.
1. Have you ever stopped to think about how the foods you consume on a
daily basis are broken down to produce energy? Not only do you eat
food on a regular basis, but you usually drink some type of water-based
beverage with your meal & you breathe in oxygen too.
2. All cells must do work to stay alive and maintain homeostasis.
The energy needed for cell work comes from the bonds of ATP
(adenosine triphosphate). Cells get their ATP by breaking organic
molecules (carbohydrates, lipids, & proteins), a process called cellular
respiration. Although many organic molecules can be broken down,
glucose, the main product of photosynthesis, is the primary fuel
molecule for the cells of living organisms.
3. The energy stored in the foods organisms consume/eat is released
during the process of cellular respiration. Every living organism,
autotrophs and heterotroph, must do cell respiration. In fact, the
metabolic pathways used in the process of cellular respiration are the
same in virtually all eukaryotic organisms, and many prokaryotic
organisms. Remember that organisms that do photosynthesis or
chemosynthesis (make their own food molecules) are called
autotrophs. Heterotrophs obtain their food molecules by eating other
organisms. Animals, fungi, many protists and many bacteria are
heterotrophs. Plants, some protists and some bacteria are autotrophs.
4. Eukaryotic organisms such as protists, fungi, plants, and animals are
aerobic, meaning they need oxygen to survive. The oxygen that you & I
breathe is needed during cellular respiration to break down the organic
food molecules we eat and release energy that can be stored in ATP.
5. Reactants of cellular respiration: glucose, oxygen, water
Products of cellular respiration: carbon dioxide, water, ATP (energy)
6. EQUATION FOR CELLULAR RESPIRATION
glucose + 6 oxygen + 6 water
ENZYMES
C6H12O6 + 6 O2 + 6 H2O
ENZYMES
6 carbon dioxide + 12 water + 40 ATP/energy

6 CO2
+
12 H2O + 40 ATP/energy
NOTE: What do you notice about this equation; why does it seem familiar?
The equation for cellular respiration is the exact opposite of the equation for photosynthesis. The
products of photosynthesis become the reactants for cellular respiration; the products of cellular
respiration (carbon dioxide & water) become the reactants for photosynthesis.
6 CO2
+
6 carbon dioxide +
12 H2O
sunlight/chlorophyll
 C6H12O6 + 6 O2 + 6 H2O
12 water sunlight/chlorophyll
glucose + 6 oxygen + 6 water
D. How Does Cellular Respiration Occur?
As with many metabolic processes, cell respiration has a number of stages.
 Glycolysis – always occurs in the cytoplasm/cytosol of the cell & produces
2 ATP’s (Four molecules of ATP are produced during glycolysis, but 2
molecules are consumed in activating the glucose.); glycolysis is an
anaerobic process and does NOT need oxygen. All living organisms go
through glycolysis; it is the most widespread metabolic process on earth.
First prokaryotes on earth used glycolysis to produce energy because early
atmosphere DID NOT contain oxygen.
The first stage of glucose metabolism, or cell respiration, is a process
called glycolysis, which splits a glucose molecule into two molecules of
pyruvate (a.k.a. pyruvic acid), a 3-carbon molecule (these 6 carbons were
originally in glucose).
If oxygen is available and the organism has the enzymes to do aerobic respiration,
the 2 pyruvate molecules (a.k.a. pyruvic acid) will be broken down in the next
stages of aerobic respiration: Kreb’s Citric Acid Cycle and Electron Transport
Chain.
Krebs Citric Acid Cycle & Electron Transport Chain – occurs in the mitochondria
of the cell & produces 36 ATP’s. Both the Krebs Citric Acid Cycle & Electron
Transport Chain are aerobic processes and need oxygen in order to occur.
The 2 pyruvate molecules leave the cytoplasm and enter the mitochondria. When
they enter the mitochondria they are broken down into 6 carbon dioxide
molecules during the Krebs Citric Acid Cycle. The Electron Transport Chain takes
the hydrogen from glucose and use their energy to form ATP’s. The hydrogens
then combine with the oxygen you breathe to form water.
NOTE: The 40 ATP’s of energy released from a molecule of glucose represents
40% of its stored energy; the other 60% of the energy stored in glucose is
released as heat & helps you maintain a constant body temperature.
E. Fermentation – Cellular Respiration Without Oxygen (Anaerobic Process)
1. Most living organisms must do aerobic cellular respiration to stay
alive and provide their cells with 40 ATP’s of energy.
2. When no oxygen is available (or is in short supply) for aerobic cellular
respiration, or if the organism doesn’t have the enzymes needed for
cellular respiration, eukaryotic organisms, and some (bacteria), will
break down glucose by the process of fermentation and produce 2
ATP’s of energy.
3. Like cellular respiration, fermentation begins with the process of
glycolysis occurring in the cytoplasm of the cell.
4. Two fermentation pathways in eukaryotes:
a. Alcoholic Fermentation – occurs in yeast cells (fungi) & some
bacteria. Used in making bread, beer, & wine.
glucose (6C)  2 pyruvate molecules (3C)  2 ethyl alcohol (2C) + 2CO2 + 2ATP’s
NOTE: The carbon dioxide gas makes bread dough rise & puts the holes in bread.
Baking the dough causes the alcohol to evaporate.
b. Lactic Acid Fermentation – occurs in human/animal muscle cells.
glucose (6C)  2 pyruvate molecules (3C)  2 lactic acid molecules(3C) + 2ATP’s
NOTE: Once the body’s metabolism slows down, oxygen becomes available and
lactic acid changes back to pyruvate (pyruvic acid), allowing continued aerobic
metabolism (respiration) and energy (ATP) for the body.
F. How Are Photosynthesis & Cellular Respiration Related?
PHOTOSYNTHESIS
CELLULAR RESPIRATION
OCCURS IN THESE
ORGANISMS:
PLANTS & SOME PROTISTS
(EUKARYOTES)
SOME CYANOBACTERIA
(PROKARYOTES)
PROTISTS, FUNGI, PLANTS,
ANIMALS
(ALL EUKARYOTIC CELLS)
ORGANELLES IN WHICH
THESE PROCESSES OCCUR
CHLOROPLASTS (PLANTS)
MITOCHONDRIA
REACTANTS NEEDED:
CARBON DIOXIDE & WATER
(INORGANIC MOLECULES)
GLUCOSE, OXYGEN, WATER
PRODUCTS FORMED
GLUCOSE, OXYGEN, WATER
CARBON DIOXIDE, WATER, ATP
(REMEMBER: ATP STORES THE
ENERGY RELEASED FROM THE
BREAKDOWN OF FOOD
MOLECULES)
OTHER REQUIREMENTS
ENERGY FROM SUNLIGHT,
GREEN PIGMENT CHLOROPHYLL
ENZYMES
HOW PRODUCTS ARE
USED BY LIVING THINGS
GLUCOSE-USED IN CELLULAR
RESPIRATION BY ALL LIVING
THINGS
CARBON DIOXIDE-ANIMALS
EXHALE IT INTO THE AIR &
PLANTS USE IT IN
PHOTOSYNTHESIS TO MAKE
GLUCOSE
OXYGEN-RELEASED INTO AIR &
USED TO BREAK DOWN
GLUCOSE IN CELLULAR
RESPIRATION
WATER-RELEASED INTO AIR &
BECOMES PART OF WATER
CYCLE
WATER-USED TO REHYDRATE
CELLS OR RELEASED INTO
AIR/ENVIRONMENT
ATP-STORES ENERGY
RELEASED FROM BREAKING
DOWN GLUCOSE & OTHER
ORGANIC MOLECULES (LIPIDS,
PROTEINS, OTHER
CARBOHYDRATES)
Energy arrives from the sun and is captured by green photosynthetic plants, and stored
in the chemical bonds of glucose. But non-photosynthetic organisms must obtain their
energy by the breakdown of these energy rich storage molecules in order to release the
energy for their use.
Photosynthesis stores this energy in glucose, glycolysis and cellular respiration
release energy. Within plant cells themselves these same processes happen in
chloroplasts and mitochondria.
Provides energy to autotrophs/
plants for PHOTOSYNTHESIS
(in CHLOROPLASTS)
CARBON DIOXIDE &
WATER
OXYGEN & GLUCOSE
Taken in by heterotrophs
(animals, fungi, protists)& plants (autotrophs)
for CELLULAR RESPIRATION
Glycolysis & Cellular Respiration
(in CYTOPLASM)
(in MITOCHONDRIA)
4040
40
ATP’s of
ENERGY
f ffo
Used by cells for METABOLISM
(The 40 ATPs represent 40% of
the energy stored in glucose)
HEAT
(60% of the energy
in glucose is released
as heat energy)
SUMMARY OF REACTIONS IN CELLULAR RESPIRATION & THE NUMBER OF ATPs
THEY PRODUCE
GLUCOSE
(in cytoplasm of cell)
GLYCOLYSIS
(anaerobic)
(in cytoplasm of cell)
splits glucose into
4 ATP’s produced (2 ATPs NET)
2 PYRUVATE MOLECULES
(enter the fluid matrix of the mitochondria)
KREBS CITRIC ACID CYCLE
(aerobic)
(in fluid matrix of mitochondria)
2 ATPs & 6CO2 produced
Hydrogen from glucose are passed to the
ELECTRON TRANSPORT CHAIN
(aerobic)
(inner membrane of mitochondria)
34 ATPs & 12 H2O produced
Hydrogen from glucose combine
with oxygen we breathe to form water
________________________
A total of 40 ATPs of energy for
cells to carry out metabolic activities.