Download Photosynthesis SG Answers

Biology 10
Unit 4: Cellular Processes (Ch. 8 & 9)
Ch. 8 - Photosynthesis
1.
List 3 reasons why cells require energy.
Metabolic activities, fuel things like the sodium-potassium pump, move materials, build new molecules, and
respond to environmental changes
2. List a few sources/forms of energy that humans use on a daily basis. What is the cellular form of energy called?
Abbreviated?
Gasoline, electricity, wood burning fuel, etc… Cellular form of energy = ATP (adenosine tri-phosphate)
3. Briefly describe how the ATP molecule stores and releases energy for the cell to use.
The energy in the ATP molecule is stored in the bond energy between the 2nd and 3rd phosphate. When the bond
is broken a small amount of heat energy is lost and our cells are able to harness that energy and put it to use.
4. List three activities that your body cells use ATP energy for.
To carry out active transport, synthesis of proteins or other molecules, and responding to chemical signals
(hormones) that are sent to specific cells.
5. How much ATP energy is usually stored in your body cells? Why don’t your cells store a lot of energy in the form
of ATP?
Only enough ATP to last a few seconds is available at any one point. ATP cannot store energy for a long period
of time.
6. What is the big difference between an “autotroph” and a “heterotroph”?
Autotrophs make their own food using sunlight and chlorophyll and heterotrophs have to obtain their food from
the environment.
7. What role do pigments play in the process of photosynthesis?
Absorb the sunlight to excite electrons which drives the reactions of photosynthesis.
8. How do the “chloroplasts” inside of plant cells actually store the light energy that is captured?
Chloroplasts store the energy of light in the electron carrier molecule called NADPH and also in ATP. Since they
cannot hold the energy very long, the energy must be turned into another form of chemical energy, glucose.
9. How are the high energy electrons contained and transported once they are energized by the sunlight?
They are added to an electron carrier NADP+ and a H+ to make NADPH
10. Define “photosynthesis” and write out the full equation for the process.
Photosynthesis is the process by which sunlight is capture by the green plants, bacteria, microorganisms of
EARTH and turned into the chemical energy GLUCOSE.
6CO2 + 6H2O  C6H12O6 + 6O2
11. Briefly summarize what happens in the “Light Dependent” reaction of photosynthesis. Make sure you describe
the reactants and products of the reaction.
The blue-violet and red wavelengths of visible light are captured by the chlorophyll pigments in the thylakoid
membranes. The electrons in the photosystems are energized and used to establish an electrochemical gradient
of H+ ions inside the thylakoids. Extra electrons come from the photolysis (splitting) of H2O, which ultimately
produces the O2 produced in photosynthesis. The reenergized electrons are captured by NADP+ to form NADPH
(High energy electron carrier) to later fuel the Calvin Cycle. The H+ ion concentration is used to turn the ATP
synthase enzyme in the thylakoid membrane to phosphorylate ADP into ATP, which will also be used to fuel the
Calvin Cycle.
12. Briefly summarize what happens in the “Light In-Dependent” reaction of photosynthesis. Make sure you
describe the reactants and products of the reaction.
The Dark Reaction occurs in the stroma of the chloroplasts and it begins with a recycled molecule RuBP, each
turn of the cycle 3CO2 molecules combine with that molecule and it goes through several transformations, using
energy from NADPH and ATP. At a point in the cycle a 3 Carbon sugar is extracted from the transforming
molecule. The cycle happens twice, using 6 CO2 molecules and produces a 6 Carbon Glucose (C6H12O6)
13. What factors affect the rate at which photosynthesis occurs? Please explain how the affect it.
Light Intensity – the greater the intensity of light the faster photosynthesis occurs
Temperature - the greater the temperature the faster photosynthesis occurs
CO2 concentration – the more CO2 in the air the more efficient the process is
H2O concentration – provides electrons for the LD reaction
14. Why is it important that chlorophyll, the pigment responsible for capturing the sun’s rays, be located in the
leaves of plants, rather than the trunk or stalk?
The leaves of the plants are more exposed to the sunlight as they are usually higher on the plant and the plant
has adaptations to allow the leaves to move in order to capture the highest amount of light possible.