AP Bio Exam Review: Unit 3 & 4: Cells Energy (Respiration & Photosynthesis)

Catabolic pathways release energy by breaking down complex molecules into simpler compounds. (exergonic) C6H12O6 + 6O2 6H2O + 6CO2 + E Anabolic pathways consume energy to build complex molecules from simple ones.(Endergonic) 6H20 + 6CO2 + E C6H12O6 + 6O2

Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction An enzyme is a catalytic protein Ex: Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction

Substrate Specificity of Enzymes The reactant that an enzyme acts on is called the enzyme’s substrate The enzyme binds to its substrate, forming an enzyme-substrate complex The active site is the region on the enzyme where the substrate binds

Cofactors Enzyme Inhibitors Cofactors are nonprotein enzyme helpers Coenzymes are organic cofactors such as vitamins Enzyme Inhibitors

Allosteric Regulation Allosteric regulation may either inhibit or stimulate an enzyme’s activity

Mitochondrion Structure Citric Acid Cycle (matrix) ETC (inner membrane)

Cellular Respiration

Glycolysis Without O2 O2 present Fermentation Cell Respiration Occurs in plants and animals Occurs in cytosol Keep glycolysis going No oxygen needed Anaerobic respiration Creates alcohol [+ CO2] or lactic acid Release E from breakdown of food with O2 Occurs in mitochondria O2 required (final electron acceptor) Aerobic respiration Produces CO2, H2O and up to 38 ATP (NADH, FADH2)

PURPOSE = NAD+ recycled for glycolysis Types of Fermentation Alcohol fermentation Lactic acid fermentation Pyruvate  Ethanol + CO2 Ex. bacteria, yeast Used in brewing, winemaking, baking Pyruvate  Lactate Ex. fungi, bacteria, human muscle cells Used to make cheese, yogurt, acetone, methanol PURPOSE = NAD+ recycled for glycolysis

Food  NADH & FADH  ETC  O2 Energy Harvest Broken down into steps: Food  NADH & FADH  ETC  O2 Consumes glucose (sugar) pyruvates Aerobic or anaerobic respiration Acetyl CoA or lactic acid/ethanol Krebs cycle NADH & FADH carries electrons to the electron transport chain (ETC) ETC: transfers e- to O2 to make H2O ; releases ATP

Various sources of fuel Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration Monomers enter glycolysis or citric acid cycle at different points

ENERGY glycolysis Respiration Krebs cycle fermentation ethanol + CO2 aerobic (with O2) anaerobic (without O2) glycolysis (cytosol) Respiration (mitochondria) substrate-level phosphorylation Krebs cycle (citric acid cycle) fermentation electron transport chain Oxidative Phosphorylation ethanol + CO2 (yeast, some bacteria) lactic acid (animals) chemiosmosis

Photosynthesis = Light Reactions + Calvin Cycle

Parts of a chloroplast

Sites of Photosynthesis Leaf cross section Vein Mesophyll Stomata CO2 O2 Mesophyll cell Chloroplast 5 µm Outer membrane Intermembrane space Inner membrane Thylakoid Granum Stroma 1 µm mesophyll: chloroplasts mainly found in these cells of leaf stomata: pores in leaf (CO2 enter/O2 exits) chlorophyll: green pigment in thylakoid membranes of chloroplasts

Light Reactions

Calvin Cycle = produce 3C sugar (G3P)

Overview of Photosynthesis

Both respiration and photosynthesis use chemiosmosis to generate ATP

Photorespiration: low carbon-fixation when stomata closed in hot, dry climate CAM C fixation & Calvin together C fixation & Calvin in different cells C fixation & Calvin at different TIMES Rubisco (normally fixes CO2) PEP carboxylase fixes CO2 Organic acid Mesophyll cells Mesophyll: fix CO2 Bundle Sheath: Calvin Cycle Night: fix CO2 in 4C acids Day: Calvin Cycle Ex. rice, wheat, soybeans Ex. sugarcane, grass Ex. cacti, pineapple, succulent

Parts of a plant used to adapt to environment Roots – uptake of water (transpiration) Leaves – stomata Branches or trunk of plant Vascular bundle (veins) = (xylem & phloem) Seeds – reproduction

Transpiration *upward movement of water and minerals from roots and shoots via the xylem *water is lost from the leaves of the plant to oxygen *Large leaf surface are increases photosynthesis but also increases water loss by the plant through stomata. *Stomata are open – CO2 moves inward *Stomata are closed – preserve H2O *Water is pulled up by cohesion forces, adhesion forces

Plant hormones Important plant hormones: Auxin – stimulate cell elongation Cytokinins – cell division (cytokinesis) & differentiation Gibberellins – stem elongation, leaf growth, germination, flowering, fruit development Abscisic Acid – slows growth; closes stomata during H2O stress; promote dormancy Ethylene gas – promote fruit ripening (positive feedback!); involved in apoptosis (shed leaves, death of annuals)

Photoperiodism Tropisms Plants detect light & wavelength Ex: flowering of plants Tropisms Growth of plant toward or away from stimulus Thigmotropism – Touch Geotropism – gravity Phototropism - light

Comparison RESPIRATION PHOTOSYNTHESIS Plants + Animals Needs O2 and food Produces CO2, H2O and ATP, NADH Occurs in mitochondria membrane & matrix Oxidative phosphorylation Proton gradient across membrane Plants Needs CO2, H2O, sunlight Produces glucose, O2 and ATP, NADPH Occurs in chloroplast thylakoid membrane & stroma Photorespiration Proton gradient across membrane

The End