Chapter 8 Flashcards
(21 cards)
Distinguish between heterotrophs and autotrophs and describe energy cycling in the biosphere. Relate this to the First Law of Thermodynamics.
Heterotrophs (animals, fungi, most bacteria, protists):
consume food in evironment for energy.
Autotrophs (plants, algae, some bacteria):
capture energy (mainly from sun) and make food
Ex: sunlight to food to movement
Explain why plants have to do photosynthesis and cellular respiration.
Plants do photosynthesis to make food(energy)
Cellular respiration: turns food into energy
Explain how autotrophs like plants affect atmospheric CO2 levels, and describe how this relates to fossil fuels and increased CO2 levels in the atmosphere due to the burning of fossil fuels.
Plants take in CO2 from the atmosphere
Burning fossil fuels releases CO2 back into the air
Define photosynthesis and write the overall reaction of photosynthesis.
Photosynthesis: process where plants make their food using sunlight, water, and CO2.
CO2 + H2O + sunlight → C6H12O6 (glucose) + O2.
identify the parts or structures of a plant that helps it get the reactants it needs or eliminate waste:
Water:
-Roots absorb water from the soil.
Gas exchange (CO2 and O2):
-Stomata let CO2 in and O2 out.
Light:
-Leaves capture sunlight for photosynthesis.
Define the term photon and explain what a wavelength tells you about the amount of energy and the appearance of light.
Photon: tiny particle of light that carries energy.
A wavelength tells us how much energy the light has:
*Shorter wavelengths (violet light): more energy and more powerful.
*Longer wavelengths (red light): less energy and weaker.
Define the term pigment and explain the two things that happen when light hits pigments. Explain why pigments appear a certain color.
Pigment: substance that absorbs light.
When light hits a pigment:
-It absorbs some colors.
-It reflects the other colors, which is what we see.
Pigments look a certain color because they reflect that color and absorb others.
Explain what an action spectrum and absorption spectrum show you.
Action spectrum: shows which light helps photosynthesis.
Absorption spectrum: shows which light a pigment absorbs.
Based on absorbance/reflection, predict the most effective and least effective colors for photosynthesis and explain why. Don’t forget about white light.
Best colors for photosynthesis:
-Red and blue because plants absorb them.
Worst color:
-Green because plants reflect it.
White light:
-Has all colors, so plants can use it for photosynthesis.
List the 2 parts of a photosystem and describe what happens when light hits a photosystem. What’s the major structural difference between PSII and PSI?
- Light-harvesting complex – absorbs light.
- Reaction center – uses light to start photosynthesis.
When light hits a photosystem, the light is absorbed and used to make energy for the plant.
Difference between PSII and PSI:
-PSII splits water and makes oxygen.
- PSI makes energy molecules (NADPH).
Describe how ATP is made as electrons flow from PS II to PS I. Make sure to mention electron transport chain, H+ gradient, and ATP Synthase.
As electrons move from PSII to PSI:
- Electron Transport Chain moves electrons, releasing energy.
- The H+ gradient builds up.
- ATP Synthase uses the flow of H+ to make ATP.
This flow of protons makes ATP for the plant.
Explain the role of NADP+ and NADP+ reductase in the light reactions. What does NADP+ accept and take to the Calvin Cycle?
NADP+ picks up electrons and H+ during the light reactions.
NADP+ reductase helps turn NADP+ into NADPH.
NADPH carries energy to the Calvin Cycle to make sugar.
Explain why cyclic electron flow periodically occurs during photosynthesis instead of noncyclic electron flow
Cyclic electron flow makes extra ATP when needed, using only PSI.
It happens instead of noncyclic flow when more ATP is required than NADH
Compare and contrast noncyclic and cyclic electron flow
Noncyclic electron flow:
-Uses both PSII and PSI.
-Makes ATP and NADPH.
-Produces oxygen.
Cyclic electron flow:
-Uses only PSI.
-Makes ATP, but not NADPH.
-Does not produce oxygen.
Summarize the 3 major steps of the Calvin Cycle.
- Carbon fixation: CO2 is added to a molecule called RuBP.
- Reduction: Energy from ATP and NADPH turns the new molecule into G3P (a sugar).
- Regeneration: Some G3P is used to make RuBP, so the cycle can continue.
Explain why the Calvin Cycle stops when the light reactions stop. Think about what the Calvin Cycle will run out of
Calvin Cycle stops without ATP and NADPH from the light reactions and can’t make sugar
Explain why the Calvin cycle requires ATP and NADPH from the light reactions. Use the term endergonic.
Calvin Cycle is endergonic (needs energy) to make sugars.
Requires ATP for energy and NADPH for electrons, both from the light reactions, to drive the cycle.
Describe the energy transformations (one form of energy becoming another form of energy) that occur during the light reactions and the Calvin Cycle.
In the light reactions:
-Light energy is turned into chemical energy (ATP and NADPH).
In the Calvin Cycle:
-ATP and NADPH (chemical energy) are used to make sugar (stored energy).
Compare and contrast photosynthesis and cell respiration in terms of reactants/products and energy input/output. Use the terms endergonic and exergonic.
Photosynthesis:
-Reactants: CO2, water, light energy.
-Products: Glucose, oxygen.
-Energy: Endergonic (requires energy from light).
Cell Respiration:
-Reactants: Glucose, oxygen.
-Products: CO2, water, ATP.
-Energy: Exergonic (releases energy as ATP).
Define photorespiration and explain why and when it happens at higher levels in C3 plants
Photorespiration : when plants use oxygen instead of CO2, wasting energy.
It happens more in C3 plants when it’s hot and dry, and the plant can’t get enough CO2.
Describe the evolutionary modifications in C4 and CAM Plants that help them keep CO2 high inside their photosynthetic cells. Relate this to the environments for which they are best adapted.
C4 Plants:
-Capture and store CO2 in a separate cell to use later.
-Best for hot, sunny places like deserts.
CAM Plants:
-Capture CO2 at night and use it during the day.
-Best for dry places like deserts, helping save water.
