ALE #3 Energy
Name___________________________________
Energy general
1) Discuss how photosynthesis and respiration are related to each other, using the first law of thermodynamics in your answer.
The first law of thermodynamics states that energy cannot be created or destroyed, only changed to different forms. In photosynthesis, plants absorb energy from the sun, and store it in the chemical bonds of glucose. This energy stored in glucose is then harvested by all organisms on earth (plants and animals both) as fuel for cellular respiration. In cellular respiration, cells break down glucose and store the energy from its bonds in the molecule ATP. ATP can then be used to power all of the cell’s work. The products of photosynthesis, oxygen and glucose, are the reactants of cellular respiration. The products of cellular respiration, carbon dioxide and water, are the reactants of photosynthesis.
2) What is ATP and how is it generated?
ATP is adenosine triphosphate. It is a high-energy carrier molecule, which is used to power all cellular work. ATP gives up phosphate group to molecules, which gives them energy to react (called phosphorylation). It is generated by electron transfer chains.
Photosynthesis
3) What is the purpose of the Calvin cycle? What molecules are produced?
The purpose of the Calvin cycle is to convert carbon dioxide into glucose molecules. The molecule produced in its reactions are glucose, ADP, and NADP+
4) Where do the Calvin cycle reactions occur? (specific) Oxygen gas is released as a byproduct of the splitting of water in the photosystem.
5) Where do the oxygen atoms (in oxygen gas) come from in photosynthesis?
The splitting of water by photosystem II
6) Where do the light reactions of photosynthesis occur? (specific)
The thylakoid membrane of the chloroplast
7) Which pigment is directly involved in the light reactions of photosynthesis? What role does it play in the light reactions?
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Chlorophyll is the main photosynthesis pigment. Chlorophyll molecules work together to absorb photons of light. As the molecules absorb sunlight, they kick their electrons up to a high energy state. These electrons are then passed down the electron transfer chain, generating ATP.
8) In the following space, describe the steps of the light reactions. With the description of each step, draw a diagram that helps to understand what happens in that step.
Description of step
Photosystem absorbs light, splitting water into H+, electrons, and O2.
Drawing
These will vary. Use the diagrams in your textbook as a guide
Further light absorption by the photosystem kicks the electrons up to an excited state.
Excited electrons are passed along an electron transport chain (proteins in the thylakoid membrane)
Energy released at every step of electron transport used to drive ATP synthesis
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Further light absorption by a second photosystem kicks the electrons up to another excited state, passing the electrons off to generate NADPH.
9) Why is chlorophyll green? It reflects green light and absorbs all other wavelengths of visible light.
10) What is a photosystem and what do they do?
Photosystems are units of chlorophyll & accessory pigments. They work together to absorb a photon of light. The absorbtion of light kicks electrons up to an excited, high energy state.
Cellular Respiration
11) What is cellular respiration? Define.
The breakdown of glucose to create ATP, which is used to power all cellular work.
12) Fill in the following summary table for Aerobic cellular respiration:
Step:
Glycolysis
Reactants (going into)
Glucose, ATP
Products (coming out)
2 pyruvic acid, ATP,
NADH
# ATP produced (net)
2
Kreb’s cycle
Electron transfer chain
Acetyl Co-A (derived from pyruvic acid),
NAD
+
, FAD, ADP
NADH, FADH
2
, ADP,
O
2
CO
2
, ATP, NADH,
FADH
2
2
ATP, H
2
0, NAD
+
, FAD 32-34
13) Why is oxygen needed for Aerobic cellular respiration?
Oxygen is the final electron acceptor of the electron transfer chain.
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14) From your reading (plants and people page 86): How does skunk cabbage grow up through the snow and attract insect pollinators?
Skunk cabbage produces a large amount of heat that melts through the snow, allowing the plant to grow up out of the snow. The heat is generated by cellular respiration. The plants produce a large amount of heat, due to a large concentration of mitochondria. The heat also helps to produce volatile organic compounds (odors). Both the heat and odor help to attract insects. Have you ever smelled skunk cabbage? It stinks!
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