Carbon dioxide C 6 H 12 O 6 Photosynthesis H2OH2O CO 2 O2O2 Water + 66 Light energy Oxygen gas Glucose + 6 Photosynthesis Chapter 8

Activating Prior Knowledge 1. List the eight characteristics of living things. 2. List the three subatomic particles, their charge, and location within an atom. 3. List the four classes of organic compounds. Include the monomer(s) and an example of each class of compounds. 4. List four differences between plant and animal cells. 5. Which organelle carries out photosynthesis? 6. Which organelle converts chemical energy stored in food into compounds that are more convenient for the cell to use? 7. What is the name of the energy currency molecule of the cell? 8. Why are most plants green?

Do you remember any of the eight characteristics of living things? 1. Living things are based on a universal genetic code (DNA) 2. Living things grow and develop 3. Living things respond to their environment (stimulus) 4. Living things reproduce 5. Living things maintain a stable internal environment (homeostasis) 6. Living things obtain and use material and energy (metabolism) 7. Living things are made up of CELLS 8. Taken as a group, living things evolve over time

Three Subatomic Particles  Proton: (+) charged particle found inside the nucleus  Neutron: neutral particle found inside the nucleus  Electron: (-) charged particle found outside the nucleus in various energy levels

Organic Compounds Carbohydrates Monomer: Monosaccharide Made up of: Carbon, Hydrogen, Oxygen (H:O in 2:1 ratio) Sugars – glucose, fructose, sucrose Lipids Monomer: Glycerol and Fatty Acids Made up of: Carbon, Hydrogen, Oxygen (H:O not in 2:1 ratio) Oils, Waxes, Butter Proteins Monomer: Amino Acid Made up of: Carbon, Hydrogen, Oxygen, Nitrogen Enzymes Nucleic Acids Monomer: Nucleotide 1) 5 Carbon sugar, 2) phosphate group 3)nitrogenous base Made up of: Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus DNA and RNA

Differences between plant and animal Plant Animal  Cell wall  Chloroplast  Photosynthesis  Lysosomes only in specialized cells  No centrioles  No cell wall  No chloroplast  No photosynthesis  Lysosomes  Centrioles (cell division)

More review…  Organelle for photosynthesis  chloroplast  Organelle to convert chemical energy into energy the cell can use  mitochondria  Energy currency of the cell  ATP  Why are plants green?  Chlorophyll

Chemical Energy and ATP  Energy is the ability to do work.  Your cells are busy using energy to build new molecules, contract muscles, and carry out active transport.  Without the ability to obtain and use energy, life would cease to exist.

Chemical Energy and ATP:  One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP).  ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups.

Why is ATP useful to cells?  ATP can easily release and store energy by breaking and re-forming the bonds between its phosphate groups. This characteristic of ATP makes it exceptionally useful as a basic energy source for all cells.

ADP and ATP  Cells store energy by adding a phosphate group to adenosine diphosphate (ADP) molecules  Cells release energy from ATP molecules by subtracting a phosphate group  The energy of ATP is locked in the bonds between the phosphate groups.  When the terminal phosphate group of the ATP molecule is removed by hydrolysis, energy is released and adenosine diphosphate (ADP) and phosphate are formed. ATP Synthase (3:21)

ATP Synthase Gradient (Virtual Cell Animation) 3:45

Autotrophs and Heterotrophs:  Autotrophs  Organisms that manufacture their own food (Plants)  Also known as producers  Heterotrophs  Organisms that cannot make their own food (Humans)  Also known as consumers

Autotrophs are the producers of the biosphere  Autotrophs are living things that are able to make their own food without using organic molecules derived from any other living thing – Autotrophs that use the energy of light to produce organic molecules are called photoautotrophs – Most plants, algae and other protists, and some prokaryotes are photoautotrophs – The ability to photosynthesize is directly related to the structure of chloroplasts – Chloroplasts are organelles consisting of photosynthetic pigments, enzymes, and other molecules grouped together in membranes Copyright © 2009 Pearson Education, Inc.

Autotrophs and Photosynthesis:  Autotrophs use the energy directly from sunlight and store it in organic compounds.  They convert solar energy to chemical energy stored in carbohydrates (glucose).  Photosynthesis is a series of complex reactions in which the product of one reaction is consumed in the next reaction.  A series of reactions linked in this way is called a biochemical pathway.

Biochemical Pathway:

Photosynthesis 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 LIGHT Carbon Dioxide Water Glucose Oxygen

What is Light ? Light Speed, c = x 10 8 m/s or million mph Which type of light carries more energy, blue or red? Light travels through space as waves of energy. Different colors have different wavelengths.

Why are plants usually green? Electromagnetic Spectrum Wave length and energy are inversely proportional The smaller the wave length, the more energy Blue light is high energy Red light is low energy They reflect green light

Plant (Chloroplast) Pigments  Membranes of the thylakoid contain a variety of pigments  Pigments – light absorbing molecules  Chlorophyll – the most abundant pigment in plants that absorbs blue and red light.  Chlorophyll a - blue-green pigment  Chlorophyll b - yellow-green pigment

Accessory Pigments – absorb light in other regions of the spectrum  Carotene - an orange pigment  Xanthophyll - a yellow pigment  Anthocyanin – a red pigment

Accessory Pigments  Why do plants need accessory pigments?  They absorb light in other regions of the spectrum  The accessory pigments are always present in most plants but masked by the chlorophyll.

Pigments  Why do leaves change color in the fall? Answer: Shorter day lengths stop chlorophyll production, and expose accessory pigments Why do leaves change color? 2:30

Photosynthesis chloroplast  Takes place in the chloroplast  Thylakoids – saclike photosynthetic membrane in the chloroplast  Grana – stacks of thylakoids  Stroma - the region outside of the thylakoid membranes

Photosynthesis (Overall) Light CO 2 H2OH2O Chloroplast LIGHT REACTIONS (in thylakoids) CALVIN CYCLE (in stroma) NADP + ADP +P ATP NADPH O Sugar Electrons Light Dark

An Overview of Photosynthesis:  Because light is a form of energy, any compound that absorbs light absorbs energy. Chlorophyll absorbs visible light especially well.  When chlorophyll absorbs light, a large fraction of the light energy is transferred to electrons. These high-energy electrons make photosynthesis work. Photosynthesis (3:39)

Light-Dependent Reactions:  Photosynthesis involves two sets of reactions.  The first set of reactions is known as the light- dependent reactions because they require the direct involvement of light and light-absorbing pigments.

Light-Dependent Reactions:  The light-dependent reactions use ENERGY from sunlight to produce energy rich compounds, like ATP and NADPH.  Water is required and Oxygen is a byproduct  These reactions take place within the THYLAKOID membranes of the chloroplast.

Light-Independent Reactions (Calvin Cycle) :  Plants absorb carbon dioxide from the atmosphere and complete the process of photosynthesis by producing sugars and other carbohydrates.  During light-independent reactions, ATP and NADPH molecules produced in the light-dependent reactions are used to produce high-energy sugars from carbon dioxide.

Light-Independent Reactions:  No light is required to power the light-independent reactions.  The light-independent reactions take place outside the thylakoids, in the STROMA.

An Overview of Photosynthesis: Sunlight H2OH2O O2O2 CO 2 Sugars (C 6 H 12 O 6 ) _____ + _____  _____ + _____ 6 CO 2 6 H 2 O6 O 2 C 6 H 12 O 6

How do gases enter/exit the leaf?  Gases = CO 2 and O 2  Gases enter/exit the leaf through the stomata (“mouths” in Greek)  Stomata (singular: stoma or stomate) = microscopic pores on the surfaces of leaves which controls gas exchange  stomata allow the plant to take in carbon dioxide to perform photosynthesis.

Stomata  The "lips" are actually individual cells called guard cells that can swell up to open the stomata or deflate to close them off.  But why would a plant want to close off its stomata, effectively cutting it off from essential carbon dioxide?  Plants also need water, and any time that a stoma is open, the plant loses water and oxygen.  By closing the stoma when the plant has enough carbon dioxide, the plant can preserve its water and prevent itself from drying out.

Stomata and Guard Cells

High Energy Electron Carriers (NADPH)  High energy electrons produced by chlorophyll are highly reactive an require a special “carrier”  An electron carrier is a compound that can accept a pair of high energy electrons and transfer them, along with most of their energy, to another molecule  NADPH can carry high energy electrons that were produced by light absorption in chlorophyll

Electron Carrier  A compound that can accept a pair of high energy electrons and transfer them, along with most of their energy, to another molecule  NADP + (nicotinamide adenine dinucleotide phosphate)  Accepts and holds 2 high E electrons and H + ions  Converts from NADP + to NADPH – one way in which some sunlight energy can be trapped in chemical form

Light Dependent Reactions: Generating ATP and NADPH  The light dependent reactions use energy from the sunlight to produce O 2 and convert ADP and NADP + into the high E carriers ATP and NADPH  Occurs in the thylakoids which contain clusters of chlorophyll and proteins known as PHOTOSYSTEMS  Photosystems absorb sunlight and generate high energy electrons

Photosystems II and I  Photosystem II ( P680 ) functions 1 st - absorbs light with a wavelength of 680 nm  Photosystem I ( P700 ) functions 2 nd – absorbs light with a wavelength of 700 nm

2 Photosystems connected by an ETC generate ATP and NADPH  Electrons removed from water pass from photosystem II to I and are accepted by NADP +  The bridge between the photosystems II and I is an electron transport chain (ETC) that provides energy for the synthesis of ATP  NADPH, ATP and O 2 are the products of the light reactions

 Light energy absorbed by electrons in the pigments increases the electrons’ energy levels  produces high energy electrons.  Water molecules are split to replace those electrons releasing H+ ions and oxygen  Enzymes on the inner surface of the thylakoid break up each water molecule into 2 e -, 2 H + ions and 1 oxygen atom

Electron Transport Chain (ETC)  Series of electron carrier proteins that shuttle high energy electrons during ATP generating reactions  High E electrons move down the ETC to Photosystem I  Energy generated is used to pump H + ions across the thylakoid membrane and into the thylakoid space.

Electron Transport Chain (ETC)

Photosystem I  Pigments in photosystem I use E from light to reenergize the electrons  E was used to pump H + ions across thylakoid membrane  Electrons do not contain as much E  At the end of a short 2 nd ETC, NADP + molecules in the stroma pick up the high E electrons along with H + ions at the outer surface of the thylakoid membrane to become NADPH.

Hydrogen Ions and ATP  H + ions cannot cross the membrane directly  ATP synthase spans the membrane and allows H + ions to pass through it  As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP

Hydrogen Ions and ATP  The buildup of H + ions makes the stroma negatively charged relative to the space within the thylakoids.  This gradient (difference in charge and H + ion concentration) across the membrane provides the energy to make ATP

Calvin Cycle

Light Independent Reactions aka Calvin Cycle  Plants use the E that ATP and NADPH contain to build stable high energy carbohydrate compounds that can be stored for a long time  ATP and NADPH from the light dependent reactions are used to produce high energy sugars

CO 2 and Sugar Production  CO 2 enters from the atmosphere  An enzyme in the stroma combines CO 2 with 5-C compounds that are present  produces 3-C compounds that continue into the cycle  For every 6 CO 2 that enter the cycle, a total of 12 3-C compounds are produced.  3-C molecules are removed from the cycle to become building blocks for the plant cell (sugars, lipids, amino acids and other compounds)

End Result of Photosynthesis  2 sets of photosynthetic reactions work together  Light dependent reactions trap the energy of sunlight in chemical form  Light independent reactions use the chemical E to produce stable, high energy sugars from CO 2 and water Photosynthesis: Light reaction, Calvin cycle, Electron Transport (7:26)

 Images for photosynthesis 

Rate of Photosynthesis:  Light Intensity :  Increase rate of photosynthesis, then levels off (maximum rate of photosynthesis)  Higher intensity, excites more electrons in chlorophyll  at some intensity, all available electrons are excited  Green light is mostly reflected by chlorophyll and will not affect the rate of photosynthesis

Rate of Photosynthesis:  Temperature :  The chemical reactions that occur during the light and dark reactions are controlled by enzymes  Higher temperature accelerates the chemical reactions.  certain temperature because the enzymes become ineffective and unstable  Too cold – enzyme substrates move slower  Too hot – photosynthesis occurs slowly because enzymes begin to denature

Rate of Photosynthesis:  Amount of CO 2 :  Increases rate of photosynthesis to a point, then levels off  Water Availability :  Plants need water for photosynthesis  In light reaction, water molecules split apart into electrons, H + ions and O.  Electrons and H + are needed to make ATP and NADPH  Increases rate of photosynthesis to a point, then levels off

Biochemical Pathway:

Equations:  Photosynthesis: (stores energy)  6 CO H 2 O  C 6 H 12 O O 2  Cellular Respiration: (releases energy) ATP  C 6 H 12 O O 2  6 CO H 2 O + ATP glucose

Structure of the Chloroplast

Chemical Energy and Food The two equations are exact opposites! PHOTOSYNTHESIS ___________ + _________ + ___________ → _______________ + __________ 6 CO 2 6 H 2 OC 6 H 12 O 6 6O 2 _____________ + _________ → ________ + __________ + __________ CELLULAR RESPIRATION C 6 H 12 O 6 6O 2 6 CO 2 6 H 2 O

Structure of the Mitochondria:

Cellular Respiration Chapter 9

Comparing Photosynthesis & Cellular Respiration: PhotosynthesisCellular Respiration Function Location Reactants Products Produces food (chemical energy) for the plant (glucose C 6 H 12 O 6 ) Produces chemical energy (ATP) for the cell ChloroplastMitochondria Water (H 2 O), Carbon dioxide (CO 2 ) and sunlight Oxygen (O 2 ) and Glucose (C 6 H 12 O 6 ) Oxygen (O 2 ) and Glucose (C 6 H 12 O 6 ) Water (H 2 O), Carbon dioxide (CO 2 ) and energy (ATP)

Comparing Photosynthesis & Cellular Respiration:  Which type(s) of organisms carry out photosynthesis ? AutotrophHeterotroph  Which type(s) of organisms carry out cellular respiration ? AutotrophHeterotroph

Chemical Energy and Food  Cellular respiration happens slowly and in many steps.  If all the energy was release in one step… Most would be lost as light and heat!  Cellular respiration breaks down glucose molecules and banks their energy in ATP

An Overview of Cellular Respiration:

Stages of Cellular Respiration:  The three main stages of cellular respiration are 1. Glycolysis 2. Krebs cycle 3. Electron transport chain.

Oxygen and Energy:  Glycolysis and fermentation are anaerobic processes. They do not directly require oxygen, nor do they rely on an oxygen- requiring process to run. However, glycolysis is still considered part of cellular respiration. Glycolysis takes place in the cytoplasm of a cell. Glycolysis Overview - Virtual Cell Animation (3:00) Glycolysis Reactions - Virtual Cell Animation (5:00)

Oxygen and Energy:  Pathways of cellular respiration that require oxygen are called AEROBIC. The Krebs cycle and electron transport chain are both aerobic processes. Both processes take place inside the mitochondria. Citric Acid Cycle An Overview (3:17) The Citric Acid Cycle The Reactions (4:13) Electron Transport Chain (3:48)

Compare Photosynthesis to Cellular Respiration NADH FADH 2 GLYCOLYSIS Glucose Pyruvate CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLA TION (Electron Transport and Chemiosmosis) Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion and High-energy electrons carried by NADH ATP CO 2 Cytoplasm Substrate-level phosphorylation Light CO 2 H2OH2O Chloroplast LIGHT REACTIONS (in thylakoids) CALVIN CYCLE (in stroma) NADP + ADP +P ATP NADPH OSugar Electrons How Cells Obtain Energy (14 min) Energy Consumption - Virtual Cell Animation (4:41)

Constructed Response Question  Leaves contain chlorophyll and are the sites of photosynthesis in plants. Their broad, flattened surfaces gather energy from sunlight while openings on their undersides bring in carbon dioxide and release oxygen. The cells of a leaf are sandwiched in between two layers of epidermal cells, which provide the leaf with a waxy, nearly impermeable cuticle that protects against water loss. The only way for gases to diffuse in and out of the leaf is through small openings on the underside of the leaf, the stomates. Stomata (plural) can open and close according to the plant's needs.