Download Name: _____ Date: ______ Class:______________

Name: _______________________________________ Date: ____________ Class:___________________
Photosynthesis, Plants, and People
There is one simple chemical reaction that is probably the most important and prolific on all of the planet earth. That
reaction is photosynthesis. The overall chemical reaction for photosynthesis is _____________________ and
_____________________ yields, or is converted into, ____________________ and _____________________. This chemical
reaction makes all of the organic food molecules that are need for every living thing on Earth. The reaction also produces all of
the oxygen that plants and animals need. In eukaryotes, such as plants, the special organelle that carries out photosynthesis is
called the _____________________. These organelles are flat, and coin-shaped, similar to the shape of leaves; both are adapted to
being exposed the most amount of ____________________ possible. These organelles use many kinds of pigments in order to
capture different ____________________ of light energy. Two of the most common are called chlorophyll a and chlorophyll b,
which have similar absorption spectra. These chlorophylls primarily absorb the wavelengths (colors) of ____________________
and ____________________, while they reflect ____________________, making the leaves of most plants have the color that
they have.
Photosynthesis happens in two steps. The first things that happen are called the light-____________________ reactions
because they can only happen if there is sunlight. One of the things that happen using the sun’s energy is the enzyme
____________________ generates ATP, whose energy is used in further steps of photosynthesis. The other process that happens
is ____________________, where water is broken down into H+ ions and O2 gas. The oxygen gas is released by the plant as a
____________________ product; the H+ ions bond to a carrier molecule called ____________________, where the H+ ions are
later used in the next step of photosynthesis. This next step is called the light-____________________ reactions. Here carbon
dioxide is attached together, with the H+ ions, making glucose, a process called ____________________. All of photosynthesis
happens in a special organelle in photosynthetic cells called a ____________________.
Cellular respiration is the chemical reaction that is the opposite of photosynthesis. The purpose of this reaction is to
create the energy that living things need. The overall chemical reaction for cellular respiration is _____________________ and
_____________________ yields, or is converted into, _____________________ and _____________________. All eukaryotes
do this reaction in a specific organelle that is called the _____________________. Both plants and animals do this reaction in this
organelle, because they both need energy to live. Plants can’t get energy for cellular processes directly from photosynthesis;
rather, plants make their own food molecules through ____________________ and then these glucose molecules are broken down
by mitochondria by doing ____________________ to make energy. Animals don’t have chloroplasts doing
____________________, so they have to eat organic molecules, which provide the glucose for cellular respiration. In
photosynthesis, energy must be provided in the form of sunlight; in cellular respiration, energy is given off.
Cellular respiration can have a few different pathways that result in different products. The first step is called glycolysis,
where glucose is broken down into two ____________________ molecules. Then, if ____________________ is present, then the
cell can do aerobic respiration. This happens in the mitochondria and the pyruvate is broken down into ____________________
and ____________________, releasing a great deal of energy. However, if there is no oxygen, then ____________________
respiration happens. Through this process, only a little energy is released. Humans and yeast do processes that result in different
products. Humans break pyruvate into ____________________ and ____________________, whereas yeast break down pyruvate
into ____________________ and ____________________. Whatever the metabolic pathway, the who purpose of cellular
respiration is to make ____________________ for a cell so that it can stay alive. Both plants and animals have to do this; plants
merely make their own glucose for cellular respiration and animals have to eat another living thing to get glucose.
M. R. Lawton 2016
Compare and Contrast In the below Venn diagram, compare and contrast photosynthesis and cellular respiration. Put
at least 3 ideas in each area of the Venn diagram.
Photosynthesis
Cellular Respiration
True or False and Why? If the statement is true, write the word “true.” If it is false, write the word “false,” and then
write a word that would replace the underlined word to make the sentence true.
_________________________ C6H12O6 + H2 O → CO2 + H2O is the chemical reaction for cellular respiration.
_________________________ The chemical formula for glucose is C5H10O4.
_________________________ Animals do not do photosynthesis.
_________________________ Plants do cellular respiration.
_________________________ All life needs energy.
_________________________ Through photosynthesis, plants create monosaccharide molecules from carbon dioxide and water.
_________________________ ATP synthase is an enzyme that makes ATP using energy from sunlight.
_________________________ Photosynthesis creates all of the CO2 that organisms on Earth need for cellular respiration.
_________________________ Photolysis is when CO2 is split during photosynthesis.
_________________________ The energy found in sugar molecules is found in the chemical bonds of the sugar molecule.
_________________________ Only some living things do photosynthesis, but almost all living things do cellular respiration.
_________________________ In the glucose molecules made from photosynthesis, the H atoms come from water.
_________________________ In the glucose molecules made from photosynthesis, the C atoms come from water.
_________________________ In the glucose molecules made from photosynthesis, the O atoms come from carbon dioxide.
_________________________ CO2 + H2O → C6H12O6 + H2O is the chemical reaction of photosynthesis.
_________________________ Aerobic respiration occurs in the absence of oxygen.
_________________________ Fermentation is a chemical reaction carried out by yeast which produces lactic acid and CO2.
_________________________ During cellular respiration, if mitochondria are involved, the products are H2O and O2.
_________________________ Humans doing anaerobic respiration produce ethanol as a product.
_________________________ Aerobic respiration produces the same amount of ATP than anaerobic respiration.
_________________________ ADP has less energy than ATP.
_________________________ The energy-storing molecule in all plants and animals is ATP.
_________________________ For the glucose made during photosynthesis, the H atoms came from water.
_________________________ For the glucose made during photosynthesis, the O atoms came from water.
M. R. Lawton 2016
Working from Models
Use the diagram to the right to answer the below questions.
1. What part of a plant cell does photosynthesis take
place in?
2. What part of a plant cell does cellular respiration take
place in?
3. According to the picture, what is the ultimate source
of energy for all life in the ecosystem?
4. According to the picture, where does a lot of the
energy get lost, or escape from the ecosystem?
5. On the diagram…
a. Write “reactants of photosynthesis” by the
reactants of photosynthesis.
b. Write “products of photosynthesis” by the
products of photosynthesis.
c. Write “reactants of cellular respiration” by
the reactants of cellular respiration.
d. Write “products of cellular respiration” by the
products of cellular respiration.
6. Suppose that the plants were removed from this cycle.
a. What molecules would build up in the environment?
b. What molecules would become used up and run out in the environment?
M. R. Lawton 2016