Download Homework/class-work Unit#7 photosynthesis and cellular

Name: ____________________________ Homework/class-work Unit#7 photosynthesis and cellular respiration(25 points)
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1. Photosynthesis and cellular respiration reading:
Date:______________________
Photosynthesis
A great variety of living things on Earth, including all green plants,
synthesize their food from simple molecules, such as carbon dioxide
and water. For this process, the organisms require energy, and that
energy is derived from sunlight.
The figure shows the energy relationships in living cells. Light energy
is captured in the chloroplasts of plant cells and used to synthesize
glucose molecules. In the process, oxygen (O2) is released as a waste
product. The glucose and oxygen are then used in the mitochondria
of the plant and animal cell, and the energy is released and used to fuel
the synthesis of ATP from ADP and P. In the reaction, CO2 and
water are released in the mitochondria to be reused in photosynthesis
in the chloroplasts.
The process of utilizing energy to synthesize carbohydrate molecules
is referred to as photosynthesis. Photosynthesis is actually two
separate processes. In the first process, energy-rich electrons flow
through a series of coenzymes and other molecules. This electron
energy is trapped. During the trapping process, adenosine
triphosphate (ATP) molecules and molecules of nicotinamide
adenine dinucleotide phosphate hydrogen (NADPH) are formed.
Both ATP and NADPH are rich in energy. These molecules are used
in the second half of the process, where carbon dioxide molecules are
bound into carbohydrates to form organic substances such as glucose.
Chloroplasts
The organelle in which photosynthesis occurs (in the leaves and stems of plants) is
called the chloroplast. Chloroplasts are relatively large organelles, containing a
watery, protein-rich fluid called stroma. The stroma contains many small
structures composed of membranes that resemble stacks of coins. Each stack is a
granum (the plural form is grana). Each membrane in the stack is a thylakoid.
Within the thylakoid membranes of the granum, many of the reactions of
photosynthesis take place.
Chlorophyll
Pigment molecules capture sunlight in the chloroplasts. In the reaction center there
are about 200 molecules of a green pigment called chlorophyll and about 50
molecules of another family of pigments called carotenoids. In the reaction
center, the energy of sunlight is converted to chemical energy. The center is
sometimes called a light-harvesting antenna. The energy captured in the reaction
centers drive the production of ATP in the chloroplasts.
The process of photosynthesis
The process of photosynthesis is conveniently divided into two parts: the energy-fixing reaction (also called the light reactions) and
the carbon-fixing reaction (also called the light-independent reaction or the Calvin cycle)
Light reactions (energy-fixing reactions)
The light reactions of photosynthesis begin when light is absorbed in the thylakoid membranes. The energy of the sunlight captured
in the reaction center, activates electrons to jump out of the chlorophyll molecules. These electrons pass through a series of
cytochromes in the nearby electron-transport system.
After passing through the electron transport system, the energy-rich electrons eventually reduce NADP. This reduction occurs as two
electrons join NADP and energize the molecule. Because NADP acquires two negatively charged electrons, it attracts two positively
charged protons to balance the charges. Consequently, the NADP molecule is reduced to NADPH, a molecule that contains much
energy.
Electrons that are lost during the reduction of NADP
into NADPH are replaced by taking them from the
water molecules. Each split water molecule releases
two electrons that enter the chlorophyll molecules to
replace those lost. Another product of the split water
molecules is oxygen. Two oxygen atoms combine with
one another to form molecular oxygen, which is given
off as the byproduct of photosynthesis. Oxygen fills
the atmosphere and is used by all oxygen breathing
organisms, including plant and animal cells.
The ATP production in the energy-fixing reactions of
photosynthesis occurs by the process of chemiosmosis.
Essentially, this process consists of a rush of protons
across a membrane (the thylakoid membrane, in this
case), accompanied by the synthesis of ATP molecules.
Biochemists have calculated that the proton
concentration on one side of the thylakoid is 10,000
time that on the opposite side of the membrane. ATP is
formed in the energy-fixing reactions along with the
NADPH formed in the main reactions. Both ATP and
NADPH provide the energy necessary for the synthesis of carbohydrates that occurs in the second major set of events in
photosynthesis.
Light independent reactions (carbon-fixing reactions)
Glucose and other carbohydrates are synthesized in the carbon-fixing reaction of photosynthesis, often called the Calvin cycle for
Melvin Calvin, who performed much of the biochemical research. This phase of photosynthesis occurs in the stroma of the plant cell.
In the carbon-fixing reaction, an essential material is carbon dioxide, which is obtained from the atmosphere. The carbon dioxide is
attached to a five-carbon compound called ribulose diphosphate. A series of reaction convert the newly formed six-carbon
compound into glucose by using the energy in ATP and NADPH made during the light dependent reactions.
Glucose can be stored in plants in many ways. In some plants, the glucose molecules are joined to one another to form starch
molecules. Potato plants, for example, store starch in tubers (underground stems). In some plants, glucose converts to fructose (fruit
sugar), and the energy is stored in this form. In still other plants, fructose combines with glucose to form sucrose, commonly known
as table sugar. Plant cells obtain energy for their activities from these molecules. Animals use the same forms of glucose by
consuming plants and delivering the molecules to their cells. All living things on Earth depend in some way on photosynthesis. It is
the main mechanism for bringing the energy of sunlight into living systems and making that energy available for the chemical
reactions taking place in cells.
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,
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.
2 ATP
2 ATP
34 ATP
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 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
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:
Water
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?
4. Photosynthesis and advanced questions:
Date: ____________________
1. How do plants get energy from their environment?
2. When animals shiver in the cold, muscles move almost uncontrollably. Suggest how shivering helps as animal survive in cold.
3. Elodea springs were under white light, and the rate of photosynthesis was measured by counting the number of oxygen bubbles per
minute for ten minutes. Predict the rate of photosynthesis if a piece of red cellophane were placed over the white light.
4. A window plant native to the desert of South Africa has leaves that grow almost entirely under ground with only the transparent tip
of the leaf protruding above the soil surface. Suggest how this adaptation aids the survival of this plant.
5. Why would you not expect to find mitochondria in anaerobic organisms?
6. Cells of an onion are clear (white) why? The cells of an onion do not go through photosynthesis. Why? Only some cells in a plant
have chloroplast but all cells in a plant have mitochondria. Why?
7. Write the chemical equation for photosynthesis:
A.
Tell where each molecule is used or made.
B.
Briefly explain how each is used or made.
8. Which process do you think plants carry out faster, photosynthesis or respiration? Why?
5. Review:
Date: _______________
1. An organism that makes it’s own food.
2. What does ATP stand for?
3. Does ATP or ADP have more energy?
4. What does ROY G. BIV stand for?
5. Plants have light-absorbing substances called.
6. What is the net gain of ATP during glycolysis?
7. Where does glycolysis take place?
8. The starting materials for glycolysis are:
10. What products are derived from glycolysis?
11. The final step in cellular respiration uses what life giving molecule?
12. All of the carbon dioxide waste product is made in which stage?
13. Where is the electron transport system located?
14. In the electron transport system each NADH releases enough energy to produce how many ATP?
15. The total equation for cellular respiration is:
16. Where does the Calvin cycle take place?
17. What are the two starting materials for the Calvin cycle?
18. What two compounds made in the light reactions are used during the Calvin cycle?
19. The citric acid cycle occurs in what part of the cell?
25. What are the two electron carriers produced in the citric acid cycle?
26. How many carbon dioxide molecules are produced during the citric acid cycle per glucose?