Chapter 7; Photosynthesis: Light Reactions and the Calvin Cycle

Photosynthesis

Process converting CO2 and H2O to sugars.

Autotrophs

Organisms that produce their own food.

Photoautotrophs

Use light energy to produce organic molecules.

Chemoautotrophs

Prokaryotes using inorganic chemicals for energy.

Heterotrophs

Organisms that consume other organisms for energy.

Light-dependent reactions

Capture sunlight energy to produce ATP and NADPH.

Calvin Cycle

Uses ATP and NADPH to synthesize sugars.

Chloroplasts

Organelles where photosynthesis occurs in plants.

Mesophyll

Green tissue in leaves containing chloroplasts.

Stomata

Pores allowing gas exchange in leaves.

Thylakoids

Membranous sacs in chloroplasts for light reactions.

Stroma

Thick fluid inside chloroplasts surrounding thylakoids.

Chlorophyll

Pigment in thylakoids capturing light energy.

Redox process

Involves oxidation and reduction reactions.

Oxygen production

O2 produced from H2O during photosynthesis.

Isotopes in research

Used to trace oxygen source in photosynthesis.

Chemical equation

6CO2 + 12H2O → C6H12O6 + 6O2.

Electron transport chain

Pathway for electrons during cellular respiration.

Oxidation

Loss of electrons from a molecule.

Reduction

Gain of electrons by a molecule.

Energy conversion

Light energy converted to chemical energy.

ATP

Energy currency produced during light reactions.

NADPH

Electron carrier produced in light-dependent reactions.

Light Reactions

Convert solar energy to chemical energy.

Calvin Cycle

Cyclic reactions assembling sugars from CO2.

Water Splitting

Provides electrons and releases oxygen.

ATP Generation

Produced from ADP and phosphate group.

NADPH Production

Reduces NADP+ using electrons from water.

Carbon Fixation

Incorporates CO2 into organic compounds.

Chlorophyll

Main pigment absorbing blue-violet and red light.

Accessory Pigments

Absorb different wavelengths, enhancing photosynthesis.

Carotenoids

Broaden light spectrum and provide photoprotection.

Photons

Discrete packets of light energy.

Electromagnetic Spectrum

Full range of electromagnetic wavelengths.

Wavelength

Distance between crests of adjacent waves.

Photosystem

Complex of pigments capturing solar energy.

Antenna Complex

Hundreds of accessory pigments in photosystems.

Reaction Center

Contains chlorophyll a for energy transfer.

Thylakoid Membrane

Location of light-dependent reactions in chloroplasts.

Noncyclic Photophosphorylation

Uses two photosystems for ATP and NADPH.

Photosystem I

Reaction center pigment P700, absorbs at 700nm.

Photosystem II

First photosystem in light reactions.

Light-Dependent Reactions

Require light to produce ATP and NADPH.

Reducing Power

NADPH provides energy for Calvin cycle.

Heat Release

Excess energy from excited electrons dissipated as heat.

Visible Light

Small part of the electromagnetic spectrum.

Chloroplast

Organelles where photosynthesis occurs.

Photosystem II

First photosystem with P680 pigment, absorbs at 680nm.

Electron Transport Chain

Connects two photosystems, generates ATP and NADPH.

Light Reactions

Convert light energy into ATP and NADPH.

Water Splitting

Electrons are removed from water during light reactions.

NADP+

Electron acceptor, reduced to NADPH in photosynthesis.

Thylakoid Membrane

Site of ATP synthesis via chemiosmosis.

Photophosphorylation

ATP production driven by light energy.

H+ Gradient

Created across thylakoid membrane, drives ATP synthase.

G3P

Three-carbon sugar produced in the Calvin cycle.

Carbon Fixation

First phase of Calvin cycle, incorporates CO2.

RuBP

5-carbon sugar, reacts with CO2 in Calvin cycle.

PGA

3-carbon compound formed from RuBP and CO2.

Glucose Production

Requires 2 G3P molecules from Calvin cycle.

ATP Requirement

Calvin cycle needs 18 ATP molecules for synthesis.

NADPH Requirement

Calvin cycle requires 12 NADPH molecules for reduction.

Cellulose

Polysaccharide made from glucose, forms cell walls.

Excess Glucose Storage

Stored in roots, tubers, seeds, and fruits.

Cellular Respiration

Uses carbohydrates from photosynthesis as fuel.

Organic Molecules

Sugars serve as precursors for proteins and lipids.

Greenhouse Effect

Solar radiation warms Earth's surface, affects plants.

Global Climate Change

Rising CO2 levels impact plant growth and health.

Photosynthesis Significance

Provides food and oxygen for nearly all life.

Greenhouse Effect

Natural heating from greenhouse gases retaining heat.

Greenhouse Gases

Gases like CO2 and methane trapping heat.

Global Warming

Increase in Earth's average temperature due to greenhouse gases.

Polar Ice Melting

Result of rising global temperatures affecting ice caps.

Rising Sea Levels

Increase in ocean levels due to melting ice.

Extreme Weather Patterns

Unusual weather events linked to climate change.

Droughts

Extended periods of deficient rainfall impacting ecosystems.

Increased Extinction Rates

Higher species loss due to changing habitats.

Tropical Diseases Spread

Expansion of diseases into new areas from climate change.

CO2 Levels

Higher concentrations can enhance plant productivity.

Growth Chambers

Controlled environments for studying plant responses to CO2.

Long-term Field Studies

Research involving large-scale CO2 manipulations over time.

Poison Ivy Growth Increase

149% growth in elevated CO2 compared to controls.

FACE Experiment

Study monitoring CO2 effects on forest ecosystems.

Ozone Layer

Protective layer absorbing harmful UV radiation.

CFCs

Industrial chemicals damaging the ozone layer.

Nobel Prize 1995

Awarded for research on CFCs and ozone depletion.

Ozone Recovery Timeline

Expected recovery of ozone layer by around 2060.

UV Radiation Effects

Increased UV linked to skin cancer and crop damage.

Autotrophs

Organisms producing their own food via photosynthesis.

Heterotrophs

Organisms obtaining food by consuming others.

Chloroplast Structure

Organelles in plants where photosynthesis occurs.

Photosynthetic Pigments

Molecules capturing light energy for photosynthesis.

Electron Transport Chain

Series of proteins generating ATP in light reactions.

Calvin Cycle

Process converting CO2 into glucose in plants.