Download Chapter 10 – Photosynthesis (Overview) Anthony Todd atodd24

Chapter 10 – Photosynthesis (Overview)
Anthony Todd
[email protected]
http://by123si.yolasite.com/
Part 1: Warm-UP
Please define the following terms…
1. photosynthesis: The conversion of light energy to chemical energy that is stored in
sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes
2. chlorophyll: A green pigment within the chloroplasts of plants and algae and in the
membranes of certain prokaryotes
3. stoma: A microscopic pore surrounding the guard cells in the epidermis of leaves and
stems that allow gas exchange between the environment and the interior of the plant
4. stroma: Within the chloroplast, the dense fluid of the chloroplast surrounding the
thylakoid membrane
5. thylakoids: A flattened membranous sac inside a chloroplast; exist in an interconnected
system in the chloroplast and contain the molecular “machinery” used to convert light
energy to chemical energy
6. NADP+: Nicotanimide adenine dinucleotide phosphate; an electron acceptor that, as
NADPH, temporarily stores energized electrons produced during the light reactions.
7. Pigment: A substance that absorbs visible light; in plants, pigments are chlorophylls a
and b and carotenoids
Part II: Overview
Just a few short-answer questions. You can work alone or with your neighbor…
1. What is the overall equation for photosynthesis?
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
2. What is the direct product of photosynthesis?
A 3-carbon sugar (G3P) that can be used to make glucose
3. What are the two stages of photosynthesis? Define each, and state where each takes
place in a plant cell.
Light reactions – the 1st stage; these reactions, which occur in the thylakoid membranes
of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the
chemical energy of ATP and NADPH, releasing oxygen in the process
Calvin cycle – the 2nd stage; involves fixation of atmospheric CO2 and reduction of the
fixed carbon into carbohydrate; occurs in the stroma
4. What process occurs in the light reactions? What does this process do?
Photophosphorylation – the process of generating ATP from ADP and phosphate by
means of a proton-motive force generated across the thylakoid membrane of the
chloroplast or the membrane of certain prokaryotes during the light reactions of
photosynthesis
5. What process occurs in the Calvin cycle, and what does it do? What is another name for
the Calvin cycle?
Carbon fixation – the initial incorporation of carbon from CO2 into an organic compound
by an autotrophic organism; a.k.a. “dark reactions”
6. What are the three types of photosynthetic pigments found in chloroplasts? Describe
each.
Chlorophyll a – participates directly in the light reactions, which convert solar energy to
chemical energy; has a methyl group
Chlorophyll b – an accessory pigment that transfers energy to chlorophyll a; has a
carbonyl (aldehyde) group
Carotenoids – an accessory pigment, either yellow or orange, that absorbs wavelengths
of light that chlorophyll can’t, thus broadening the spectrum of colors that can drive
photosynthesis
7. What is the metal found in chlorophyll, and what structure is it found in?
Magnesium; prophyrin ring
8. Why does photosynthesis rely primarily on visible light and not other forms of
electromagnetic radiation?
Chlorophyll a absorbs light between 380 and 750 nm
9. What are the parts of a photosystem? How many photosystems are involved in the light
reactions, and how are they arranged?
Parts: reaction center complex, light-harvesting complex, special pair or chlorophyll a
molecules, primary electron acceptor
How many: 2 photosystems
Arrangement: PS II (P680)  PS I (P700)
10. What is rubisco?
Ribulose bisphosphate (RuBP) carboxylase; the enzyme that catalyzes the 1 st step of the
Calvin cycle (the addition of CO2 to RuBP)
11. Describe C3 plants, C4 plants, and CAM plants.
C3: a plant that uses the Calvin cycle for the initial steps that incorporate CO2 into
organic material, forming a 3-C compound as the 1st stable intermediate
C4: a plant that in which the Calvin cycle is preceded by reactions that incorporate CO 2
into a 4-C compound, the end product of which supplies CO2 for the Calvin cycle
CAM: a plant that uses crassulacean acid metabolism, an adaptation for photosynthesis
in arid conditions; CO2 entering open stomata during the night is converted to organic
acids, which release CO2 for the Calvin cycle during the day, when stomata are closed
12. What is photorespiration, and why does it occur?
A metabolic pathway that consumes O2 and ATP, releases CO2, and decreases
photosynthetic output; generally occurs on hot, dry, bright days, when stomata close
and the oxygen concentration in the leaf exceeds that of carbon dioxide; rubisco has
higher affinity for oxygen and CO2
Part III: Closing
We are short on time because of this short summer semester. BE SURE to go over these items at
home, in your dorm, at the library – basically anywhere you study:
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Know the structure of the chloroplast (Figure 10.3, p. 187)
Know the overview of photosynthesis (Figure 10.5, p. 189)
Know the general order of the electromagnetic spectrum, including the order of visible
light (Figure 10.6, p.190)
Understand the basic structure of a chlorophyll molecule (Figure 10.10, p. 192)
Know how a photosystem harvests light (Figure 10.12, p. 193)
UNDERSTAND linear electron flow, a.k.a. noncyclic photophosphorylation (Figure 10.13,
p. 195)
UNDERSTAND cyclic electron flow, a.k.a. cyclic photophosphorylation (Figure 10.15, p.
196)
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Understand how chemisosmosis compares in mitochondria and chloroplasts (Figure
10.16, p. 196)
UNDERSTAND the three phases of the Calvin cycle (Figure 10.18, p. 199)
UNDERSTAND the C4 anatomy and pathway (Figure 10.19, p. 201)
Understand how C4 plants compare to CAM plants (Figure 10.20, p. 202)
Know the review of photosynthesis (Figure 10.21, p. 203)