Photosynthesis & Respiration

CHAPTERS 6 & 7 Photosynthesis & Respiration

During photosynthesis, plants (also called autotrophs or producers) use the energy of sunlight, CO2, and H2O to produce glycogen & O2 • During respiration, animals (also called heterotrophs or consumers) and plants use glucose and “burn” it in the presence of O2 to produce useable energy and give off CO2 and H2O • Thus, O2 , CO2 and H2O are constantly recycled as they are in any biological system Biochemical pathways

Both photosynthesis & respiration are examples of reactions called Biochemical Pathways – reactions that occur in a series of steps. Energy generated by one step of the reaction is stored and used to power later steps. In most cases, this energy is stored in a molecule called ATP. Biochemical pathways

ATP – Adenosine triphosphate consists of: • Adenine – a nitrogen containing compound • Ribose sugar • 3 phosphate groups (PO4) • ATP is symbolized as A – P ~ P ~ P (~ represents bonds that, when broken, release just the right amount of energy) Biochemical pathways

ATP – ADP Cycle(ATP-ADP Cycle, ATP-ADP Cycle 2) • In order for ATP to be used as an energy source, the last phosphate group must be broken off using an enzyme called ATPase • This releases energy and degrades the ATP into ADP + P (adenosine diphosphate plus low energy phosphate) • The energy released is used to perform any function (such as the Na+ - K+ pump) and some of the released energy is used to “re-glue” the P back on to ADP to recycle it back to ATP – this uses another enzyme known as ATP Synthase • This recycling of ATP from ADP + P is called Phosphorylation Biochemical pathways

CHAPTER 6 PHOTOSYNTHESISPlanet Earth: PlantsCRASH COURSE - PHOTOSYNTHESIS

Photosynthesis Intro Video • General Equation • Sunlight + 6 CO2 + 6H2O C6H12O6 + 6O2 • 2 Major Steps to Photosynthesis • Light Reactions • Light Independent, Dark Reactions or the Calvin Cycle • Photosynthesis Animation PHOTosynthesis

LIGHT REACTIONS • Must occur during the day b/c sunlight is the energy source that powers them • Light reactions take place in the chloroplast which contains photosynthetic pigments called chlorophylls located in the disc-like thylakoids • Granum – a stack of thylakoids PHOTosynthesis

LIGHT REACTION PROCESS • Chlorophyll electrons are oxidized by sunlight. These “energized” electrons link a P onto ADP to recycle ATP (called phosphorylation) • These “energized” electrons split H2O. The hydrogen gets attached to NADP to form NADPH – which, like ATP, is a chemical “battery” that will power the next set of reactions • The O2 exits the leaves through pores on the underside of leaves called stomata • Light Reactions Animation PHOTosynthesis

LIGHT INDEPENDENT, DARK REACTIONS or the CALVIN CYCLE • Can occur day or night, they are powered by the products of Light Reactions – ATP and NADPH • Dark Reactions occur in the stroma – the cytoplasmic-like region of the chloroplast PHOTosynthesis

DARK REACTION PROCESS • CO2 enters the plant leaves through the stomata & combines with another chemical compound • Then the energy of ATP & NADPH is used to change this compound into glucose. Once the ATP is used it degrades into ADP + P. The NADPH degrades to NADP – both will be recycled during the Light Reactions • Dark Reaction Animation • There's always an exception to the rule:) PHOTosynthesis

CHAPTER 7 respiration CRASH COURSE – CELLULAR RESPIRATION

CELLULAR RESPIRATION • Process where the energy of glucose is converted into usable energy – ATP • RESPIRATION PROCESS • Glycolysis – first step of respiration which occurs in the cytoplasm • During glycolysis, the fuel (glucose) is broken down into 2 molecules of Pyruvic Acid. Only a few bonds of glucose are broken, so only 2 ATP’s are produced as a net gain • EQUATION:2ATP + 4ADP + 4P + C6H12O6 2ADP + 2P + 4ATP + 2CH3CHOHCOOH (Pyruvic Acid) RESPIRATION

RESPIRATION PROCESS • 2 Major Types of Respiration – after glycolysis, the second step of respiration depends on 2 criteria: 1. type of beastie (plant, animal, yeast, etc.), and 2. whether or not O2 is used • Aerobic – burn glucose in the presence of O2 • Anaerobic – burn glucose in the absence of O2 RESPIRATION

RESPIRATION PROCESS • SCENARIO 1: Aerobic Phase – if the beastie is plant or animal and O2 is present • This occurs in the mitochondria • 2 Parts: • Kreb’s Cycle or Citric Acid Cycle • Electron Transport Chain • During the aerobic phase, the fuel (2 pyruvic acid molecules left over from glycolysis) are completely “blown apart” into CO2 and H2O. • The net gain is 36 ATP’s RESPIRATION

RESPIRATION PROCESS • SCENARIO 1: Aerobic Phase (cont.) • For “complete respiration” (glycolysis + aerobic phase) has a net gain of 38 ATP’s (2 from glycolysis, 36 from aerobic phase) • EQUATION: 2ATP + 38ADP + 38P + 6O2 + 2CH3CHOHCOOH 2ADP + 2P + 38ATP + 6CO2 + 6 H2O RESPIRATION

RESPIRATION PROCESS • SCENARIO 2: Anaerobic Lactic Acid Fermentation – if the beastie is an animal or microorganism (bacteria) and O2 is NOT present • Occurs in the cytoplasm • The pyruvic acid from glycolysis is broken down into Lactic Acid – makes muscles sore – no ATP gain RESPIRATION

RESPIRATION PROCESS • SCENARIO 3: Anaerobic Alcoholic Fermentation – if the beastie is a yeast and O2 is NOT present • The pyruvic acid from glycolysis is broken down into CO2 and ethyl alcohol RESPIRATION

Photosynthesis & Respiration