BIOL 2051 Chapter Notes - Chapter 7: Thylakoid, Light-Independent Reactions, Hydrogen Sulfide
2 May 2018
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Chapter 7 Notes
Introduction
• Photosynthesis: process in which the energy from light is captured and used to
synthesize glucose and other organic molecules
o Nearly all living organisms rely on photosynthesis for their nourishment, either
directly or indirectly.
o Responsible for producing oxygen (makes up a large portion of the earth’s
atmosphere)
o Two Stages
▪ Light Reaction: light energy is absorbed by pigments and converted to
chemical energy in the form of two energy intermediates: ATP and
NADPH
▪ Calvin Cycle: ATP and NADPH are used to drive the synthesis of
carbohydrates
7.1 Overview of Photosynthesis
• Carried out by certain species of bacteria, algae, and plants
• Most photosynthetic organisms use water but some bacteria use hydrogen sulfide instead
• Biosphere: places on earth and in the atmosphere where living organisms exist
o Autotrophs: sustain themselves by producing organic molecules from inorganic
sources
▪ Ex. Plants making glucose from CO2 and H2O
o Heterotrophs: must consume food or organic molecules from their environment
to sustain life
▪ Ex. Most species of bacteria and protists
• Photoautotrophs make up a large portion of earth’s organic molecules via photosynthesis,
using light energy, CO2, and H2O
o Also produce O2
• Living organisms use energy
• Photosynthetic species capture light energy and store it in organic molecules
o Used in photosynthetic and non-photosynthetic organisms as energy sources
▪
• Chloroplast: organelles found in plan and algal cells that carry out photosynthesis
o In chloroplast, both chlorophyll a and b are bound to integral membrane proteins
in the thylakoid membrane which transverse the membrane
• Chlorophyll: pigment that gives plants their green color
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o
▪ Chlorophyll a: pigment found in plants, algae, and cyanobacteria
• Has a –CH3 group
▪ Chlorophyll b: pigment found in plants, green algae, and some other
photosynthetic organisms
• Has a –CHO group
o Contain a porphyrin ring and a hydrocarbon tail (phytol tail)
▪ Mg is bound to this ring
▪ A long hydrocarbon that is hydrophobic
• Function: to anchor the pigment to the surface of the hydrophobic
proteins within the thylakoid membrane of chloroplasts
• Mesophyll: internal part of leaf
o Must receive light, water, and CO2 in order to perform photosynthesis
• Stomata: pores
• Contains an inner membrane, outer membrane, and intermembrane space (located
between inner and outer)
• There’s a third membrane called the thylakoid membrane
o Contains pigment molecules including chlorophyll
o Thylakoids: flattened fluid filled tubules
▪ Enclosed in a thylakoid lumen (compartment)
o Stroma: fluid-filled region of the chloroplast between the thylakoid membrane the
inner membrane
• Photosynthesis Occurs in Two Cycles
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o
o Light Reaction
▪ Take place in the thylakoid membrane
▪ Start with light energy and end with chemical energy that is stored in the
form of covalent bonds
▪ Produce ATP, NADPH, and O2
• ATP and NADPH are energy intermediates that provide needed
energy and electrons to make carbohydrates during the Calvin
Cycle
• NADPH: an electron carrier that can accept two electrons
o Calvin Cycle
▪ Occurs in the stroma
7.2 Reactions That Harness Light Energy
• Light is a type of electromagnetic radiation
o Energy is in the form of electric and magnetic fields
• Wavelength: distance between the peaks in a wave pattern
• Electromagnetic Spectrum: encompasses all possible wavelengths of electromagnetic
radiation
• Photons: massless particles traveling in a wavelike pattern and moving at the speed of
light
o Each photon contains a specific amount of energy
▪ Ex. Gamma rays contain more energy than radio waves
• When light strikes light, one of three things happen
o 1. Passes through object
o 2. Object may change the path of light towards a different direction
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Document Summary
Nadph: calvin cycle: atp and nadph are used to drive the synthesis of carbohydrates. Plants making glucose from co2 and h2o: heterotrophs: must consume food or organic molecules from their environment to sustain life, ex. Cycle: nadph: an electron carrier that can accept two electrons, calvin cycle, occurs in the stroma. Gamma rays contain more energy than radio waves: when light strikes light, one of three things happen, 1. Object may change the path of light towards a different direction: 3. On a hot sunny day sidewalk heats up because it absorbs light energy this is released as heat: can release energy in the form of light, ex. Initially, the ees move from one pigment molecules called p680 in. O2 is produced in the thylakoid lumen through oxidation of water in psii: 2. Nadph is produced in stroma through usage of high- energy electrons that come from the light-harvesting complex in psii: boosted a second time in psi, 3.
