Unit 3 – ENERGY Conversion 1

Laws of Energy- Thermodynamics 1 st Law of Thermodynamics- Energy can neither be created nor destroyed. 2 nd Law of thermodynamics- energy changes form as it moves through a system. 2

The Sun is the ultimate source of energy on Earth

Energy flow through ecosystems Autotrophs (Producers) – organisms that can make their own food (glucose) Ex. Plants, alga, some bacteria

Heterotrophs (Consumers) – Organisms that obtain energy from the food they eat Ex. Fungi, Animals… anything that has to EAT to get ENERGY

PS and CR: Chloroplasts and Mitochondria Can PRODUCERS do both? Can CONSUMERS do both? 6

Question Why are eukaryotes able to be larger and more complex than prokaryotes? 7

8 Energy stored in the bonds between phosphate molecules is released when a phosphate molecule breaks off. Enzyme: ATPase Energy must be added to create a high energy bond between the 2 nd and 3 rd Phosphate.

9 Chemiosmosis Powers ATP synthesis Powers ATP synthesis Located in the thylakoid membranes Located in the thylakoid membranes Uses ETC and ATP synthase (enzyme) to make ATP Uses ETC and ATP synthase (enzyme) to make ATP Photophosphorylation: addition of phosphate to ADP to make ATP Photophosphorylation: addition of phosphate to ADP to make ATP

Peter Mitchell 1978 Nobel prize for describing Chemiosmosis 10 Chemiosmosis occurs in both photosynthesis and cellular respiration.

Chemiosmosis 11

Cellular Respiration Why do we eat? Why can’t we make energy like plants (producers/ autotrophs) do? 12

Pulmonary Respiration VERSUS Cellular Respiration PULMONARY RESPIRATION AKA Breathing: – Alternation of inhalation and exhalation. – Exchange of gases in which organisms obtain oxygen from the air (or water) and release carbon dioxide. – Exchange occurs in lungs (or gills). CELLULAR RESPIRATION: – Harvesting of energy from food molecules by cells. – Aerobic process (requires oxygen). – Occurs inside cells (cytoplasm and mitochondria). “Respiration” comes from Latin word for breathing. Pulmonary and cellular respiration are closely related, but not the same processes.

Breathing versus Cellular Respiration

Where Does Cellular Respiration Take Place? It actually takes place in two parts of the cell: Glycolysis occurs in the Cytoplasm Krebs Cycle & ETC Takeplace in the Mitochondria Krebs Cycle & ETC Take place in the Mitochondria

CELLULAR RESPIRATION BANKS ATP REACTION: C 6 H 12 O 6 + 6O > 6CO 2 + 6H 2 O + ENERGY (Glucose) (Oxygen) (Carbon dioxide) (Water) What happens to the energy in glucose or other food molecules? u Only about 40% of energy is turned into ATP u The rest is lost as metabolic heat (think: CALORIES) u One ATP molecule has about 1% of the chemical energy found in glucose.

ENERGY CONVERSIONS ARE INEFFICIENT Second Law of Thermodynamics By Comparison Living Organisms Are Efficient

n ATP = adenosine triphosphate n The phosphates are attached by high energy bonds n Enzymes break off the last high energy bond and energy is released to do cell work leaving ADP (Adenosine Diphosphate)

In an ATP molecule: where’s the energy stored? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O energy P O–O– O–O– O –O–O +

Using ATP to do work? A working muscle recycles over 10 million ATPs per second Can’t store ATP  too unstable  only used in cell that produces it  only short term energy storage  carbohydrates & fats are long term energy storage ATP ADP + P work

ATP is recycled Fully charged battery ATP Half charged battery ADP

CATABOLISM: Process of splitting larger molecules to smaller ones. Catabolic reactions are exergonic and release free energy. THREE MAJOR CATABOLIC PATHWAYS IN LIVING ORGANISMS A. Cellular respiration (Aerobic) B. Anaerobic respiration C. Fermentation

MAJOR CATABOLIC PATHWAYS A. Cellular respiration (AKA Oxidative or Aerobic respiration): u Requires oxygen. u Occurs in Mitochondria (steps 2 and 3) u Most commonly used catabolic pathway. u Used to extract energy from glucose molecules. u Most efficient: 1 glucose = 36 net ATP.

Cellular Respiration REACTION: C 6 H 12 O 6 + 6O 2 ---> 6CO 2 + 6H 2 O + ENERGY Glucose Oxygen Carbon dioxide Water ATP

CR vs PS

THREE MAJOR CATABOLIC PATHWAYS B. Anaerobic respiration: u Does not require oxygen. u Used by bacteria that live in anoxic environments. u 1 glucose = 2 ATP u Final products: Carbon dioxide, water, and other inorganic compounds.

THREE MAJOR CATABOLIC PATHWAYS C. Fermentation: u Does not require oxygen. u Used by yeast, bacteria, and other cells when oxygen is not available. u Final electron acceptor: Organic molecule. u 1 glucose = 2 ATP u Products depend on type of fermentation: F Lactic acid fermentation: Used to make cheese and yogurt. Carried out by muscle cells if oxygen is low. F Alcoholic fermentation: Used to make alcoholic beverages. Produces alcohol and carbon dioxide.

FERMENTATION OCCURS WHEN OXYGEN IS NOT AVAILABLE n Yeasts normally use aerobic respiration to process food. n If oxygen is not available, they use fermentation, which is less efficient.

Types of fermentation: Alcoholic fermentation Glucose ----> 2 pyruvate ----> 2 Ethanol + 2 CO 2 Lactic acid fermentation Glucose ----> 2 pyruvate ----> 2 Lactic acids

In a 2 minute footrace… n All your stored ATP is used up, so you begin lactic acid fermentation

Fermentation Occurs When Oxygen is Unavailable Why do you breathe heavily after AEROBIC activity?

Alcoholic and Lactic Acid Fermentation: An Alternative to Aerobic Respiration

Three Stages of Cellular Respiration n Glycolysis (in cytoplasm) n Krebs Cycle (in mitochondria) n Electron Transport Chain (in mitochondria)

Three Stages of Aerobic Respiration

A. Glycolysis: “Splitting sugar” u Occurs in the cytoplasm of the cell u DOES NOT require oxygen u Net result: 2 ATP u IF OXYGEN IS PRESENT, Cellular Respiration will proceed and more ATP can be made. u IF NO OXYGEN PRESENT, fermentation occurs and you ONLY GET 2 ATP.

Glycolysis: “Splitting” of Glucose into Two Molecules of Pyruvic Acid

B. Kreb’s Cycle (Citric Acid Cycle) B. Kreb’s Cycle (Citric Acid Cycle) Occurs in the matrix of the mitochondrion u Carbons are released as CO 2 u Yield per glucose molecule: 2 ATP Electron carrying molecules (NADH, FADH 2 ), and H+ Analogy: Kreb’s Cycle is to CR as Calvin Cycle is to PS

C. Electron Transport Chain & Chemiosmosis u Most ATP is produced at this stage u Occurs on inner mitochondrial membrane u Electrons from NADH and FADH 2 are transferred to electron acceptors, which produces a proton gradient u Proton gradient used to drive synthesis of ATP. u Chemiosmosis: ATP synthase allows H + to flow across inner mitochondrial membrane down concentration gradient, which produces ATP. u Ultimate acceptor of H + and electrons is OXYGEN, producing water. Analogy: ETC is to CR as Light RXNs are to PS

Electron Transport & Chemiosmosis: Generates Most ATP Produced During Cellular Respiration

Electron Transport Chain Animation

NOTE: The electron transport chain ONLY works when OXYGEN is available at the end of the chain to accept the electrons and H + to form water. NOTE: The electron transport chain ONLY works when OXYGEN is available at the end of the chain to accept the electrons and H + to form water. So… in order to make LOTS of ATP, what GAS is necessary?

Net Total Energy from cellular respiration ~36 ATP from 1 glucose molecule (Approx. 38 made, BUT 2 are used for active transport of pyruvate across mitochondrial membrane)