PHOTOSYNTHESIS AND CELLULAR RESPIRATION Chap 5 Section 1

ENERGY AND LIVING THINGS Metabolism involves either using energy to build molecules or breaking down molecules in which energy is stored PHOTOSYNTHESIS - the process by which light energy is converted to chemical energy of carbohydrates - sugar and starches

AUTOTROPHS – organisms that use energy from sunlight or from chemical bonds inorganic substances to make organic compounds (food)

Some prokaryotes use chemosynthesis to produce organic compounds

HETEROTROPHS – organisms that must get energy from food instead of directly from sunlight or inorganic substances

CELLULAR RESPIRATION – a metabolic process similar to burning fuel, but it converts food energy to ATP ATP provides cells with the energy needed to carry out the activities of life

Chemical energy stored in food is released gradually The product of one chemical reaction becomes a reactant in the next reaction Some of the energy is released as heat, but the remaining energy is stored as ATP – portable form of energy Adenosine triphosphate

Flow of Energy Energy flows from sunlight or inorganic substances to autotrophs, such as grasses, and then to heterotrophs, such as rabbits and foxes

Energy Storage in Organisms Plants store energy in the form of starch Animals store energy in the form of glycogen

Complete sentences P.96 section review 1-6 P. 112 5a,6,12

PHOTOSYNTHESIS section 2 Using the Energy in Sunlight

Requirements for Photosynthesis Sunlight – nearly all organisms on Earth depend on sun for energy Pigments – colored substance that absorb or reflect light

Energy-Storing Compounds – stored in the bonds of compounds Most important compound – one used by every living cell – ATP Adenosine triphosphate Inorganic substances – Water and Carbon Dioxide

White Light – perceived as ”colorless” Actually a mixture of different wavelengths of light Visible spectrum – wavelengths visible to our eyes Infrared and ultraviolet – not visible to our eyes

About 1 % of the energy in the sunlight is converted to chemical energy Three stages of Photosynthesis Stage 1: Energy is captured from sunlight. Stage 2: Conversion of Light Energy Stage 3: Storage of Energy

Stage 1 Absorption of Light Energy First & second stages are sometimes called “light reactions” Light is a form of radiation – energy in the form of waves Pigments absorb only certain wavelengths and reflect all the others Chlorophyll absorbs mostly blue & red lights

Plants contain two types of chlorophyll, a and b, a being the most important Carotenoids – pigments that produce yellow & orange colors – absorb wavelengths of light different from chlorophyll Most of the pigments reflect the color green, making the leaves appear green

Production of Oxygen Thylakoids-located in the chloroplasts & contain the pigments necessary for photosynthesis Light energy is transferred to electrons causing them to be “excited”

Electrons jump to other molecules where they are used to power the second stage Replacement electrons come from water molecules Water molecules are split by enzymes, leaving H+ ions, and O atoms, forming Oxygen gas,

Stage Two: Conversion of Light Energy Electron Transport Chains (2)- series of molecules through which excited electrons are passed along a thylakoid membrane First, provides the energy needed to change ADP to ATP – needed by dark reaction

A second electron transport chain provides energy used to make NADPH- which is needed by the dark reaction NADPH – electron carrier that provides the high-energy electrons needed to make carbon-hydrogen bonds in the third stage Excited electrons combine with hydrogen ions & NADP+ to form NADPH

Animated Light Reaction http://www.uic.edu/classes/bios/bios100/lectures/light_reaction.htm

Photosynthesis Problem http://www.uic.edu/classes/bios/bios100/lectures/photorespiration.htm

Dark Reaction (Light Independent Reaction) Dark reactions generally take place in sunlight; light does not play a role in the dark reactions The simple inorganic molecule carbon dioxide is used to make a complex organic molecule Melvin Calvin, American, worked out cycle

Stage Three: Storage of Energy CARBON DIOXIDE FIXATION – transfer of carbon dioxide to organic compounds Considered light-independent “dark reactions” Most common method is the Calvin cycle Calvin cycle- a series of enzyme-assisted chemical reactions that produces a 3-C sugar

The reactions are cyclic – they recycle the five-carbon compound needed to begin the cycle again The energy used in the Calvin cycle is supplied by ATP and NADPH made during the second stage of photosynthesis

Calvin Cycle Animated http://www.uic.edu/classes/bios/bios100/lectures/calvin.htm

Light and Dark Reactions http://leavingbio.net/PHOTOSYNTHESIS.htm

Factors that Affect Photosynthesis Light – photosynthesis increases as light intensity increases until all the pigments are being used –limited by Calvin reaction which is the slowest step Carbon dioxide concentration – once a certain concentration is reached photosynthesis is limited Temperature- certain range is more efficient

Water – the availability of water and the amount of rainfall Nutrients – how much organic matter that soil contains

P. 103 Section 2 review 1-6 P. 112 1,2, 5c,8,9, 11 Standardized Test Prep 1-3

Cellular Respiration Food contains usable energy in the form of protein, fat, & carbs (considered organic) Energy has to be transferred to ATP, which is done through cellular respiration AEROBIC respiration- metabolic processes that require oxygen, more efficient in making ATP ANAEROBIC-metabolic processes that do not require O2

Stages of Cellular Respiration Stage I: Breakdown of Glucose Stage II: Production of ATP

Stage I: Breakdown of Glucose Glycolysis: takes place in the cytoplasm- an enzyme-assisted anaerobic process that breaks down one 6-C molecule of glucose to 2 3-C pyruvic ions 4 Steps in the series on page 105 – you can copy them from the book

Glycolysis uses two ATP but produces four ATP

Stage 2: Production of ATP Krebs Cycle enzyme-assisted reactions named for Hans Krebs, 1937 5 steps on p. 106 & 107 Much of the energy that was stored in glucose & pyruvate is now stored in NADH and FADH2

Krebs Cycle http://www.1lecture.com/Biochemistry/How%20the%20Krebs%20Cycle%20Works/index.html

Electron Transport Chain The electron transport chain pumps hydrogen ions, H+, out of the inner compartment. At the end of the chain, electrons & hydrogen ions combine with oxygen, forming water. ATP is produced as hydrogen ions diffuse into the inner compartment through a channel protein.

Respiration in the Absence of Oxygen Electron transport chain does not function if oxygen is not available as final electron acceptor. Electrons in NADH are transferred to pyruvate; enables the recycling of NAD+ which is needed to make ATP Fermentation- recycling of NAD+ using an organic hydrogen acceptor

Lactic Acid Fermentation Pyruvate is converted to lactate Lactate is the ion of lactic acid Vigorous exercise –muscles must operate without enough O2 – ATP produces only while glucose supply lasts Blood removes excess lactate, but if not quickly-can cause muscle soreness

Alcoholic Fermentation Two step process Pyruvate is converted to 2-C compound, releasing CO2 Electrons are transferred from NADH to the two-C compound, producing ethanol Yeast, a fungus, uses alcoholic fermentation. Yeast is used in bread industry and alcoholic beverages Ethanol (12%) kills yeast

Production of ATP Total of ATP produced from glucose depends on the absence or presence of O2 2 ATP molecules are made during the Krebs cycle 34 ATP are produced by the electron transport chain

Types of chemical reactions An exothermic reaction is a chemical reaction that releases energy in the form of heat..

An endothermic reaction is any chemical reaction that absorbs heat from its environment. These examples could be written as chemical reactions, but are more generally considered to be endothermic or heat-absorbing processes: melting ice cubes melting solid salts evaporating liquid water

converting frost to water vapor (melting, boiling, and evaporation in general are endothermic processes) splitting a gas molecule cooking an egg

Homework Page 110 - section review 1-6 Page 112 – 3,4, 5b, 5d,7,10,13,14,19 Test Part 2 over section 3 Monday 8th 10 true false 14 multiple choice and discussion