Photosynthesis End of Section Questions
Chapter 4 Section 1
1. How are ATP and ADP related?
ADP is a lower energy-carrying molecule that only has two phosphates, when a third
phosphate is added it becomes ATP which is a charged energy carrier.
2. What types of molecules are broken down to make ATP? Which are most
often broken down to make ATP?
Carbohydrates, Proteins, and Lipids can be broken down to make ATP. Lipids are
most often broken down because they provide the most amount of energy.
3. How are some organisms able to survive without sunlight and
photosynthesis?
They use the process of chemosynthesis (using chemicals instead of light) to make
carbon-based macromolecules.
4. Describe how you do not get energy directly from the food that you eat.
The energy needs to be broken down first before the body can use it. Remember
chicken protein broken down into amino acids then built back up into human
protein.
5. How are the energy needs of plant cells similar to those of animal cells? How
are they different?
Plants need ATP too but they get it through a process called photosynthesis. Animals
must consume other organisms.
6. Add a water molecule to ATP to break down ATP into ADP.
H2O + ATP -> ADP + P
Chapter 4 Section 2
1. What are the roles of chloroplasts and chlorophyll in photosynthesis?
Chloroplasts are the organelle in which photosynthesis occurs. Chlorophyll is a
pigment contained in the chloroplast that captures the energy from the sunlight.
2. Describe the stages of photosynthesis. Use the terms thylakoid, lightdependent reactions, and light-independent reactions in your answer.
The first stage of photosynthesis is the light dependent reactions that take place in
the thylakoids. Energy is absorbed from sunlight and transferred through the
thylakoid membrane. The energy is used in the light-independent reactions to
produce sugars.
3. Suppose you wanted to develop a light to help increase plant growth. What
characteristics should the light have? Why?
The light should emit the optimal wavelengths, such as blue and red, to be absorbed
by the pigments in plants.
4. Explain why photosynthesis is important for building the structure of plant
cells.
In plants, the cell wall is responsible for structure and support. Cell walls are made
from cellulose, which is a carbohydrate that is built up from sugars produced during
photosynthesis.
5. Overall, do you think photosynthesis is endothermic or exothermic? Explain.
It is endothermic; it absorbs energy to produce sugars.
Chapter 4 Section 3
1. How do the two photosystems work together to capture energy from
sunlight?
Photosystem II absorbs energy and energizes electrons. The electrons are passed
along to photosystem I, which absorb more energy and adds it to the electrons.
2. Explain the relationship between the light dependent and the light
independent reactions.
The light dependent reactions absorb energy from sunlight and transfer the energy
to the light independent reactions that produce sugars.
3. Explain how the Calvin Cycle is a bridge between carbon in the atmosphere
and carbon based molecules in the food you eat.
Carbon dioxide is removed from the atmosphere by plants for photosynthesis. The
carbon is incorporated into sugars and other carbon based molecules that are eaten
by other organisms.
4. Explain why the chemical equation for photosynthesis (below) is a highly
simplified representation of the process. How is the equation accurate? How
is it inaccurate?
6CO2 + 6H2O -> C6H12O6 + 6O2
The equation shows the general reactants and products of the process. However, it
does not show intermediate steps. For example, carbon dioxide and water do not
actually react with each other.
5. Explain how both passive transport and active transport are necessary for
photosynthesis to occur?
Active transport moves hydrogen ions against the concentration gradient in
photosystem II. Passive transport occurs when hydrogen ions diffuse/flow through
the channel bound to ATP synthase.