Chapter 8 Biology: Photosynthesis

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Photosynthesis

in which the energy from light is captured and used to synthesize carbohydrates.

Biosphere

describes the regions on the surface of the Earth and in the atmosphere where living organisms exist.

Heterotrophs

must consume food - organic molecules from their environment to sustain life.

Autotrophs

organisms that make organic molecules from inorganic sources such as CO2 and H2O.

Photoautotrophs

autotrophs that use light as a source of energy to make organic molecules.

Chloroplasts

organelles found in plant and algal cells that carry out photosynthesis.

Chlorophyll

a pigment that gives plants their green color.

Mesophyll

located in the internal part of the leaf it contains cells with chloroplasts that carry out the bulk of photosynthesis in plants.

Stomata

pores that allow CO2 to enter the leaf and Oxygen to exit the leaf.

Thylakoid Membrane

contains pigment molecules, including chlorophyll.

Thylakoids

flattened, fluid-filled tubules formed in the thylakoid membrane.

Thylakoid Lumen

a single convoluted compartment enclosed by Thylakoids.

Granum

a structure of stacked thylakoids.

Stroma

the fluid-filled region of the chloroplast between the thylakoid membrane and the inner membrane.

Light Reactions

a series of conversions, starting with light energy and ending with chemical energy that is stored in the form of covalent bonds.

Calvin Cycle

the synthesis of carbohydrates occurs in the calvin cycle.

NADPH (nicotinamide adenine dinucleotide phosphate)

an electron carrier that can accept two electrons. it has an additional phosphate group.

Wavelength

the distance between the peaks in a wave pattern.

Electromagnetic Spectrum

encompasses all possible wavelengths of electromagnetic radiation, from relatively short wavelengths (gamma rays) to much longer wavelengths (radio waves).

Photons

massless particles traveling in a wavelike pattern and moving at the speed of light.

Pigment

used to describe a molecule that can absorb light energy.

Chlorophyll a & b

pigments found in green plants and green algae.

Carotenoids

pigment found in chloroplasts. yellow to red.

Absorption Spectrum

a diagram that depicts the wavelengths of electromagnetic radiation that are absorbed by a pigment.

Action Spectrum

shows the rate of photosynthesis plotted as a function of different wavelengths of light.

Photosystem 1 & 2

found in the thylakoid membrane they are two distinct complexes of proteins and pigment molecules.

Electron Transport-Chain

a series of electron carriers-located in the thylakoid membrane.

Cyclic Phosphorylation

a pattern of electron flow that is cyclic and generates only ATP. Also called the Cyclic Electron Flow.

Homologous Genes

When two or more genes are similar because they are derived from the same ancestral gene.

Light-Harvesting Complex

in the thylakoid membrane it is composed of several dozen pigment molecules that are anchored to transmembrane proteins. They directly absorb photons of light.

Resonance Energy Transfer

a process that transfers energy to adjacent pigment molecules.

Antenna Complex

another term for the light-harvesting complex because it acts like an antenna that absorbs energy from light and funnels that energy to P680 in the reaction center.

Primary Electron Acceptor

a molecule that is more stable and accepts the high energy electron from P680.

Manganese Cluster

where water oxidation occurs. it is located on the side of D1 that faces the thylakoid lumen.

X-Ray Crystallography

a method researchers used to determine the three-dimensional structure of photosystem 2. they must purify a protein or protein complex and expose it to conditions that cause the proteins to associate with each other in an ordered array.

Enhancement Effect

increasing the rate of photosynthesis by exposing algae to two wavelengths at the same time rather than just one.

Z-Scheme

a model that shows an electron proceeds through a series of energy changes during photosynthesis.

Carbon Fixation

CO2 becomes incorporated into ribulose biphosphate (RuBP), a five-carbon sugar. The product of the reaction is a six-carbon intermediate that immediately splits in half to form two molecules of 3-phosphoglycerate.

Rubisco

the enzyme that catalyzes carbon fixation. it is most abundant protein in chloroplasts and perhaps the most abundant protein on earth.

Photorespiration

uses O2 and liberates CO2. it decreases the efficiency of photosynthesis.

PEP Carboxylase

an enzyme that adds CO2 to phosphoenolpyruvate (PEP), a three carbon molecule, to produce oxaloacetate, a four carbon compound malate, which is transported into the bundle- sheath cell.

CAM Plants

they avoid water loss by keeping their stomata closed during the day and open them at night, when it is cooler and the relative humidity is higher.

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