Name: ____________________________ Homework/class-work Unit#7 photosynthesis and cellular respiration(25 points)
Think and try every question. There is no reason for a blank response or an I don’t know. Any blanks will receive a zero.
Every assignment must be done on a separate piece of paper
1.
Cellular respiration reading:
Date:______________________
Cellular respiration
Organisms, such as plants, can
trap the energy in sunlight
through photosynthesis and
store it in the chemical bonds
or carbohydrates molecules.
The principle carbohydrate
formed through photosynthesis
is glucose. Other organisms,
such as animals, fungi,
protozoa, and a large portion of
bacteria, are unable to perform
this process. Therefore, these
organisms must rely on the
carbohydrates formed in plants
to obtain the energy necessary for their metabolic processes.
Animals and other organisms obtain the energy available in carbohydrates through the process of cellular respiration. Cells take the
carbohydrates into their cytoplasm, and though a complex series of metabolic processes, they break down the carbohydrates and
release the energy. The energy is generally not needed immediately; rather it is used to combine adenosine diphosphate (ADP) with
phosphate ions to form adenosine triphosphate (ATP) molecules. The ATP can then be used for processes in the cells that require
energy, much as a battery powers a mechanical device.
During the process of cellular respiration, carbon dioxide is given off. This carbon dioxide can be used by plant cells during
photosynthesis to form new carbohydrates. Also in the process of cellular respiration, oxygen gas is required to serve as an acceptor
of electrons. This oxygen is identical to oxygen gas given off during photosynthesis. Thus, there is an interrelationship between the
process of photosynthesis and cellular respiration, namely the entrapment of energy available in sunlight and the provision of the
energy for cellular processes in the form of ATP.
Cellular respiration:
The overall mechanism of cellular respiration involves four
processes: Glycolysis, The formation of acetyl coenzyme A,
The citric acid cycle and the electron transport chain.
Glycolysis:
Glycolysis is the process in which one glucose molecule is
broken down to form two molecules of pyruvate. The
glycolysis process is a multi-step metabolic pathway that
occurs in the cytoplasm of animal cells, plant cells, and the
cells of microorganisms. At least six enzymes operate in the
metabolic pathway.
In the first and the third steps of the pathway, ATP energizes
the molecules. Thus, two ATP molecules must be expended in
the process. Further along in the process, glucose is converted
into two three carbon pyruvate molecules.
During the latter stages of glycolysis, four ATP molecules are
synthesized using the energy given off during the chemical
reactions. Thus, four ATP molecules are synthesized and two
ATP molecules are used during glycolysis, for a net gain of
two ATP molecules.
Another reaction during glycolysis yields enough energy to
convert NAD to NADH. This NADH will later be used in the
electron transport system, and its energy will be released.
During glycolysis, two NADH molecules are produced.
Because glycolysis does not use any oxygen, the process is
considered to be anaerobic. For certain anaerobic organisms,
2 ATP
2 ATP
34 ATP
such as some bacteria and fermentation yeasts, glycolysis is the sole source of energy. Glycolysis is a somewhat inefficient process
because much of the cellular energy remains in the two molecules of pyruvate that are created.
Citric Acid Cycle (Krebs Cycle):
Following glycolysis, the mechanism of cellular respiration involves another multi-step
process-the citric acid cycle, which is also known as the Krebs Cycle. The citric acid
cycle uses the two molecules of pyruvate formed in glycolysis and yields high-energy
molecules of NADH and FADH2, as well as some ATP.
The citric acid cycle occurs in the mitochondria of a cell. This sausage-shaped organelle
possesses inner and outer
membranes and therefore, an inner
and outer compartment. The inner
membrane is folded over itself
many times: the folds are called
cristae. They are somewhat similar to the thylakoid membranes in
chloroplasts. Located along the cristae are the important enzymes necessary for
the production of ATP.
Prior to entering the citric acid cycle, the pyruvate molecules are altered into
acetyl coenzyme A. In this process, electrons and a hydrogen ion are
transferred to NAD to form 2 high-energy NADH.
Acetyl coenzyme A will enter the cirtic acid go through a series of reactions
releasing energy to form 6 NADH, 2 FADH2 and 2 ATP. Also during the
citric acid cycle, carbon atoms released during the reactions of the citric acid
cycle will form 6 molecules of CO2 (carbon dioxide) gas that are given off as a waste product. The NADH and the FADH 2 will be
used in the electron transport system.
Electron transport system:
The electron transport system occurs in the cristae of the mitochondria, where a series of enzymes exist. These enzymes accept highenergy electrons and pass the electrons to the next molecule in the system. The energy of the electrons is released to push the
formation of ATP from ADP. Each NADH and FADH2 molecule is highly energetic, releasing enough energy in the electron
transport chain to form 34 ATP.
The role of oxygen in cellular respiration is substantial. As a final electron acceptor, it is responsible for removing electrons from the
system. Oxygen is reduced by the electrons into 12 molecules of H2O (water).
Complete equation for aerobic cellular respiration:
C6H12O6 + 6 O2
6 CO2 + 6 H2O + 38 ATP
Reading Questions:
1. Do plants and animals both go through photosynthesis? Why or why not? Do both plants and animals go through cellular
respiration? Why or why not?
2. Briefly describe what happens during glycolysis?
3. What is an electron transport chain?
4. Where does cellular respiration take place? Do plants have these organelles also? Why or why not?
5. Describe the physical structure of the mitochondria.
6. Briefly describe what occurs during the light dependent reaction?
7. What are the four stages of cellular respiration?
8. What is NADPH? What is its role in the process of photosynthesis?
9. Where does photosynthesis take place? What molecules absorb sunlight?
10. Describe the physical structure of the chloroplast.
11. Briefly describe what happens in the light independent reactions?
12. Briefly describe what happens during the Krebs/citric acid cycle?
13. Why do animals need to drink water?
14. Do plants produce oxygen? Explain.
15. Why does glycolysis only net 2 ATP when 4 are produced?
2. Cellular respiration questions:
Date: ______________________
1. Write the chemical equation for cellular respiration:
A.
Tell where each molecule is used or made.
B.
Briefly explain how each is used or made.
2. Explain how the 38 ATP are produced from 1 glucose molecule.
3. What molecule do you make after you eat ATP or ADP? Explain?
4. What molecule do you make while you exercise ATP or ADP? Explain?
5. Draw an ADP molecule and an ATP molecule.
6. Draw and explain the ATP cycle.
7. What is the first stage of cellular respiration called? What are the starting materials?
8. How many ATP are made in glycolysis? What is the overall ATP gain in glycolysis?
9. What do you think are two physiological signs that you are low on energy (ATP)?
3. Respiration continued:
Date: ______________________
Copy Fill in the following table. Use arrows to connect molecules made in one stage and used in another.
Glucose
Pyruvate
Carbon
NADH
FADH2
ATP
oxygen
dioxide
GLYCOLYSIS
Water
KREB’S CYCLE:
2 TURNS PER
GLUCOSE
ELCTRON
TRANSPORT
SYSTEM
TOTALS:
Answer the questions based on what you discovered from the table.
1. What is the overall equation for the following parts of cellular respiration?
A. Glycolysis: B. Citric acid cycle: C. The electron transport chain:
2. Part 3: Label the equation below showing which stage each molecule is used or made. Remember one molecule below is made in
more that one stage.
6O2 + C6H12O6
6CO2 + 6H2O + 38 ATP
3. In which stage of cellular respiration is the oxygen used?
4. In which stage of cellular respiration is all carbon dioxide made?
5. What is the name of the molecule made in glycolysis and used in the citric acid cycle
6. Where is NADH made?
7. What is NADH?
8. Where is the energy in NADH released?
9. What is the overall gain of ATP from glycolysis?
10. In which stage is water produced
11. What does the body do with the carbon dioxide produced
12. How many ATP are produced in the electron transport chain from 1 NADH?
13. Where does glycolysis take place?
14. Where does the citric acid cycle take place?
15. Where do the reactions of the electron transport chain take place?