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Cellular Respiration and Photosynthesis
Imagine an abandoned house that is falling apart. Restoring order to the house will require an input of energy (for example: hammering nails, applying paint). Living things also need energy in order to stay in good repair, or maintain HOMEOSTASIS. Every organism must maintain HOMEOSTASIS as long as it lives. Therefore, all organisms require a constant source of energy!
Chemical Energy Energy in organic compounds (like carbohydrates)
comes from the sun.
SOLAR energy (energy from our sun) enters living systems when plants make organic compounds from carbon dioxide and water through the process of PHOTOSYNTHESIS.
We cannot (and other animals) cannot perform photosynthesis, so why does this matter to us?
We eat plants! So we are getting our energy from the sun!
Chemical Energy Continued… Food molecules that are made or consumed by an
organism are the fuel for its cells.
Cells use these molecules to release the energy stored in the molecules bonds.
What organelle in the cell is responsible for releasing this energy?
Mitochondria
So what is happening when photosynthesis takes place???? Energy enters an ecosystem when organisms use
sunlight during photosynthesis to convert carbon dioxide molecules (stable) into glucose (less stable).
In which organelle of a plant cell does photosynthesis take place?
Chloroplast
So what is happening when photosynthesis takes place???? Once a plant has made that GLUCOSE, energy can be
extracted through the process of CELLULAR RESPIRATION.
What percent of the energy in sunlight is used for photosynthesis?
Only 1%!
Harvesting Light Energy Chloroplast organelles convert light energy into
chemical energy.
Chloroplasts have a membrane much like the plasma membrane on the outside of the cell.
The space inside the membrane is called the STROMA.
Within the stroma is a membrane called the THYLAKOID MEMBRANE.
This membrane is folded in a way that produces flat, disc-like sacs called THYLAKOIDS.
Stacks of THYLAKOIDS are called GRANUM
Harvesting Light Energy The THYLAKOIDS contain molecules that absorb light
energy for photosynthesis.
The first stage of photosynthesis begins when light waves hit these stacks.
Light Light travels in waves.
Sunlight contains all of the wavelengths of visible light. We see these different wavelengths as different colors.
For Example: The wavelength of purple light is from 400-425 nm. Green: 475-500 nm.
Pigments Why can you see light?
Cells in the back of the eye contain pigments!
A pigment is a substance that absorbs certain wavelengths (colors) of light and reflects all of the others.
In plants, light energy is harvested by pigments that are located in the thylakoid membrane of chloroplasts.
What is the pigment in chloroplasts that absorbs light energy?
Chlorophyll
Pigments Cont. Chlorophyll is a green pigment in chloroplasts that absorbs
light energy to start photosynthesis. Chlorophyll absorbs mostly blue and red light and reflects
green and yellow light. ***look at your classmates. The pigments in their shirts are
reflecting colors back at your eye. Plants have two types of chlorophyll:
Chlorophyll a Chlorophyll b
Plants also have pigments called carotenoids that absorb blue and green light and reflect yellow, orange, and red.
Why do leaves turn redish orange in the fall? Chlorophyll regresses and carotenoids are exposed.
The organelle in which photosynthesis occurs: A. Mitochondria
B. Nucleus
C. Endoplasmic Reticulum
D. Chloroplast
E. Golgi Apparatus
While performing an experiment using green spinach leaves, Jamie identifies Chlorophyll and other pigments of several colors. What is the most accurate conclussion Jamie can make about pigments in spinach leaves.
A. Chlorophyll decomposes to reveal other pigments
B. Chlorophyll absorbs light while other pigments reflect light
C. Chlorophyll passes light energy to other pigments in leaves
D. Chlorophyll appears in higher concentrations than other pigments
Photosynthesis converts light energy into energy A. mechanical
B. kinetic
C. chemical
D. fast
The chemical energy produced from photosynthesis is found in the bonds of: A. Glucose
B. Enzyme
C. Lipid
D. Water
Which of the following pigments is most soluble in solvent? A. Chlorophyll b
B. Chlorophyll a
C. Xanthophylls
D. Carotene
Which of the following pigments has the greatest affinity for chromatography paper?
A. Chlorophyll b
B. Chlorophyll a
C. Xanthophyll
D. Carotene
Pop Quiz hot shot… Where are these pigments found?
Thylakoid (inside the Chloroplast)
The Reactions of Photosynthesis Scientists describe the reactions of photosynthesis in
two parts:
Light Dependent
Light Independent
The light dependent reaction takes place within the thylakoid membrane.
Where are the thylakoids found?
Inside the chloroplasts
The Reactions of Photosynthesis The light independent reaction (aka: the calvin cycle)
takes place in the stroma.
Where is the stroma?
Space inside the membranes of the chloroplasts.
The Reactions of Photosynthesis When sunlight is captured by pigments, electrons gain
a great deal of energy.
The electrons come from water!
What are the pigments found in the leaf? Chlorophyll A
Chlorophyll B
Carotein
Xanthophylls
These high-energy electrons require a special carrier. These carriers are called electron carriers!
The Reactions of Photosynthesis Electron Carriers
One of these carrier molecules is a compound known as NADP+. (Nicotinamide adenine dinucleotide phosphate)
The name is complicated, but its job is simple!
Accepts and holds 2 electrons that were excited from the pigments.
NADP+ is converted into NADPH when it holds the electrons
NADPH then carries electrons to other parts of the chloroplast
The Reactions of Photosynthesis ATP (energy) is also produced during the light
dependent reaction. When water is broke down to remove electrons used to
attach to NADP+, hydrogen ions are left behind in the cytoplasm.
These ions move through a protein channel to the outside of the cell. This protein is called ATP synthase.
As Hydrogen ions pass through ATP synthase, ADP is convernted to ATP
What is ATP? Energy!
ATP Synthase
The Reactions of Photosynthesis The light independent Reaction (aka Calvin Cycle)
The ATP and NADPH formed by the light-dependent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for any more than a few minutes.
During the Calvin Cycle, plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time. Sugar
Steps to the Calvin Cycle 1. Six carbon dioxide molecules enter the cycle.
Where does the plant get the carbon dioxide?
From the atmosphere!
Through a series of reactions, ATP and NADPH provide the energy to convert Carbon dioxide into Glucose.
Where did the ATP and NADPH come from?
The light dependent cycle
The light independent reaction takes place within the _________. A. Thylakoid
B. Mitochondria
C. Nucleus
D. Stroma
Energized electrons that initiate photosynthesis come from _____. A. Pigments
B. Carbon Dioxide
C. Water
D. Oxygen
How many electrons can NADP+ capture and hold? A. 1
B. 2
C. 3
D. 4
As Hydrogen ions move through ATP synthase, ADP is converted into____. A. ATP
B. Oxygen
C. Water
D. ASP
The reaction of photosynthesis that DOES NOT require light is known as the: A. Dark Reaction
B. Calvin Cycle
C. Light Independent Reaction
D. All of the above
Chemical Energy and Food Food provides living things with the chemical building
blocks they need to grow and reproduce.
Food serves as energy to the cells of the body.
Chemical Energy and Food We know food provides energy, but how is the stuff
that we put in our mouth converted to energy?
The process begins with a pathway called glycolysis.
Glycolysis takes place in the cytoplasm.
Glycolysis releases only a small amount of energy.
Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid.
Requries 2 ATP to get the process of glycolysis started, but 4 ATP are produced. NET OF 2!
Chemical Energy and Food Not only is ATP produced, but NAD+ accepts some
electrons during this process.
NAD+ is an electron carrier. What does this remind you of???
Glycolysis occurs VERY quickly.
Glycolysis does NOT require oxygen to occur.
When oxygen is present, the process proceeds to the Krebs Cycle
Chemical Energy and Food The Krebs Cycle (aka Citric Acid Cycle)
At the end of glycolysis, about 90 percent of the chemical energy that was available in glucose is still unused. What was created at the end of glycolysis?
If oxygen is present this pyruvic acid then moves into the Krebs Cycle. Occurs in the mitochondria.
During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions!
During this reaction 2 molecules of ATP are produced along with NADH and FADH2 (another electron carrier)
Krebs Cycle
Chemical Energy and Food Once the NADH and FADH2 are produced during the
Krebs Cycle, these electron carriers move into the ELECTRON TRANSPORT CHAIN.
The electron transport chain uses the high-energy electrons from the Krebs Cycle (carried by NADH and FADH2) to convert ADP into ATP.
Electron Transport Chain
Chemical Energy and Food The electron transport chain produces a total of 32
ATP.
The Totals
Total number of ATP molecules produced during cellular respiration ===== 36 ATP
The chemical equation for Cellular Respiration:
Carbon Dioxide is produced during which step of cellular respiration. A. Glycolysis
B. Krebs Cycle
C. Electron Transport Chain
D. Photosynthesis
How many net ATP are produced by glycolysis? A. 1
B. 2
C. 4
D. 32
How many net ATP are produced by the Krebs cycle? A. 1
B. 2
C. 4
D. 32
How many total ATP are produced by cellular respiration? A. 32
B. 34
C. 36
D. 42
The products of the equation for cellular respiration are: A. Glucose + Water
B. Carbon Dioxide + Water + ATP
C. ATP + Oxygen + Glucose
D. Carbon Dioxide + ATP
Which products of anaerobic respiration are used in the processes of aerobic respitation? A. ATP, NADH, Pyruvate
B. NADH, Pyruvate
C. Pyruvate
D. ADP, NADPH, ATP, Pyruvate
The process that is most directly responsible for ATP production in aerobic cellular respiration is: A. Glycolysis
B. Photosynthesis
C. Krebs Cycle
D. Electron Transport Chain
Which of the following organisms perform both cellular respiration and photosythesis? A. Pin Oak Tree
B. Ky-31 Tall Fescue Grass
C. African Acacia Tree
D. All of the above perform both processes
Which of the following is produced in the krebs cycle? A. NADH
B. FADH2
C. ATP
D. CO2
E. All of the above
Bromthymol Blue is an indicator for which of the following molecules? A. Water
B. Oxygen
C. Glucose
D. ATP
E. Carbon Dioxide
Fermentation If oxygen is present when glycolysis occurs, cell
respiration will proceed to the Krebs Cycle.
If oxygen is not present at the time of glycolysis, cell respiration will proceed to fermentation.
Glycolysis + oxygen Krebs Cycle
Glycolysis + NO oxygen Fermentation
Fermentation Fermentation releases energy from food molecules by
producing ATP in the absence of oxygen.
Why is this referred to as an anaerobic process?
Because NO oxygen is necessary for the process to proceed.
During fermentation, cells convert NADH to NAD+ by passing high energy electrons back to pyruvic acid.
Fermentation produces NAD+, the electron carrier, which allows glycolysis to continue.
This allows for a steady supply of ATP from glycolysis.
Alcoholic Fermentation Certain microorganisms use alcoholic fermentation,
forming ethyl alcohol and carbon dioxide as wastes.
The chemical equation is found below:
Pyruvic acid + NADH alcohol + CO2 + NAD+
Certain yeasts perform alcoholic fermentation, giving off bubbles of CO2 gas This is why bread rises!!!
Do you get drunk when you eat bread??? NO, the small amount of alcohol produced in the dough
evaporates when the bread is baking.
Lactic Acid Fermentation In many cells, the pyruvic acid that accumulates as a
result of glycolysis can be converted to lactic acid.
This process regenerates NAD+ so that glycolysis can continue
The equation is found below:
Pyruvic acid + NADH lactic acid + NAD+
Lactic acid is produced in your muscles during rapid exercise.
Movement of Water from Soil UP to the leaves of plants. Plants must receive a supply of water and nutrients
from soil to keep photosynthetic processes going.
Why is water needed to keep photosynthesis going?
The Xylem allows plants to move materials UP into the plant.
Xylem- plant tissue consisting of tubular cells that conduct most of the water and minerals upward from the roots to the rest of the plant.
Why does water move UP the plant against gravity? Water is lost through pores in leaves called STOMATA.
As water is lost, cohesion and adhesion properties allow water to move up the stem of plants.
Transpiration- The evaporative loss of water from plants.
Why, during hot, dry summer days, do the pores of plants close?
Movement of sugars DOWN the plant to the roots. Rapidly dividing cells in roots require glucose for
cellular respiration.
Most of the glucose produced by photosynthesis is done in the leaves.
Sugar flows down tubes called phloem in the plant.
Phloem- plant tissue consisting of living cells that transport sugar and other organic nutrients throughout the plant.
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