OCN621: Biological Oceanography-Bioenergetics

Zackary JohnsonMSB614

zij@hawaii.edu

<http://www.soest.hawaii.edu/oceanography/zij/ocn621.html>

Bioenergetics – Life Processes

●USE OF EXTERNAL ENERGY TO PRODUCE ORGANIC MOLECULES

● TRANSFORMATION OF ORGANIC MOLECULES INTO USEFUL CHEMICAL ENERGY

● USE OF CHEMICAL ENERGY TO DO BIOLOGICAL WORK

Review of Cell Structures

Prokaryotic

Review of Cell Structures

Eukaryotic

Bioenergetics – Cell Structures

PROKARYOTIC and EUKARYOTIC cells are fundamentally different in structure

Prokaryotes (eubacteria & archaebacteria) are generally small and have little cellular structure; a single circular strand of genetic material DNA lies loose in the cytoplasm. The larger eukarote cells have discrete subcellularstructures (presumably evolved from endosymbiotic relationships with prokaryotes) with specific functions.

Eukaryotic DNA is complexed with proteins and organized into chromosomes within a membrane-bound NUCLEUS. MITOCHONDRIA function in cellular respiration. CHLOROPLASTS are the organelles where photosynthesis occurs in plant cells, The GOLGI APPARATUS is a secretory organelle and the ENDOPLASMIC RETICULUM is a double-membrane system often coated with RIBOSOMES, the sites where genetic material is translated into proteins.

Bioenergetics – Some definitionsACTIVE TRANSPORT - The process of concentrating molecules or ions against the direction of diffusion.ACTOMYOSIN - The molecular complex of two proteins, actin and myosin, which comprises the basic contractile element in muscle fiber.AEROBES - Cells that live in and utilize oxygen; strict aerobes cannot live without oxygen.AMINO ACIDS - organic acids containing the amino group, -NH2. The major components of proteins.ANAEROBES - Cells that can live without oxygen; strict anaerobes cannot live in the presence of oxygen.ATP - Adensoine triphosphate, a molecule with three high-energy phosphate (7 Kcal energy per bond) used to power energy requiring processes in living organisms. Exists in lower energy states as diphosphate (ADP) and monophosphate (AMP).AUTOTROPHlC - Cells which can synthesize their own macromolecules from CO2 and simple nutrient molecules, such as ammonium.AUXOTROPHIC - Cells which require small amounts of organic matter (e.g., essential vitamins or amino acids) for growth.

Bioenergetics – Definitions (cont)CARBOHYDRATES - Organic molecules consisting entirely of carbon, hydrogen, and oxygen with the ratio H:O generally 2:1. Most dissolve in water but not organic solvents. Major functions as structural molecules (chitin, cellulose) and storage products (starch, glycogen).CHEMOSYNTHESIS - The utilization of chemical energy from the oxidation of inorganic molecules (e.g., NH4

+, NO2-, Fe2+, H2S) to drive the

reduction of CO2 to organic molecules.CHLOROPHYLL - Family of lipid-based green pigments which absorb light energy and transfer excited electrons in the initial stages of photosynthesis. Requires structural association with Mg2+.DNA - Deoxyribose nucleic acid. Large organic molecule associated with cell nuclei and functioning as a store of genetic information.EFFICIENCY - (In bioenergetics) the ratio of useful energy produced (or conserved) to the energy supplied.ELECTRON CARRIERS - Enzymes such as flavoprotein and cytochromeswhich can gain or lose electrons reversibly; the respiratory chain consists of a series of electron carriers.ELECTRON TRANSPORT - The movement of electrons from organic substrates to oxygen catalyzed by the respiratory chain during respiration.

Bioenergetics – Definitions (cont)ENTROPY - The degree of randomness or disorder of a system.ENZYME - Protein which enhances or accelerates a biochemical reaction without being altered in the process.EQUILIBRIUM - The state of a system in which there are no unbalanced forces and in which free energy is at a minimum and the entropy at a maximum.EXCITED STATE - That state of an atom or molecule occurring after an electron has been moved from its normal stable orbit to an outer orbit having a higher energy level. Such a molecule has a higher energy content than its normal or ground state.FERMENTATION - Energy-yielding enzymatic breakdown of organic molecules under anaerobic conditions.GLYCOLYSIS - Fermentation of glucose to two molecules of lactic acid,HETEROTROPHIC - Cells which require organic molecules such as glucose, amino acids, etc. as energy and substrate sources for growth (synthesis).LIPIDS - Heterogeneous group of organic molecules defined operationally by their tendency to dissolve in organic solvents. Major functions are structural molecules (e.g., phospholipidsin membranes); pigments, hormones, and storage products (fats, oils, waxes).

Bioenergetics – Definitions (cont)NAD, NADP - Nicotinamide adenine dinucleotide and nicotinamideadenine dinucleotide phosphate. Important carriers of electrons in many enzymatic, oxidative-reduction reactions.OXIDATION - The loss of electrons from a molecule; an oxidizing agent is an electron acceptor.OXIDATIVE PHOSPHORYLATTON - The enzymatic phosphorylation of ADP to ATP which is coupled to electron transport to oxygen via the electron chain .PHOTOSYNTHESIS - The utilization of energy from sunlight to drive the reduction of CO2 to organic molecules.PROTEINS - Large organic molecules formed from joined amino acids. Major functions are structural molecules, enzymes, and contractile fibrils.REDUCTION - The gain of electrons by a molecule; a reducing agent is an electron donor.RESPIRATION - The breakdown of organic molecules (aerobic cells) utilizing oxygen and generating chemical energy (ATP).RNA - Ribonucleic acid. Large organic molecules generally in association with cell nuclei or ribosomes where they function as templates during protein synthesis.

Bioenergetics – Definitions (cont)SUBSTRATE - The specific substance acted upon by an enzyme.THERMODYNAMICS

FIRST LAW - In all processes, the total energy of the universe remains constant Energy is not created or destroyed.SECOND LAW - The entropy or degree of randomness of the universe increases.

PhotosyntheticCells

HeterotrophicCells

O2

Glucose

CO2

H2O

Utilization of External Energy SourcesPhotosynthesis: (photolithotrophy) process in which radiant energy from sunlight is used by green plants and some bacteria to convert carbon dioxide,CO2, into an organic molecule (glucose). The major pathway through which energy enters biological world

OXYGENIC PHOTOSYNTHESIS :Green plants & cyanobacteria (different in details)

light

6 CO2 + 6 H2O C6H12O6 + 6 O2

● 100+ chemical reactions, tightly organized on:Lamellae membranes (in algal chloroplasts)Thylakoid membranes (cyanobacteria)

● Pigments - absorb light energy (photons)."Excited" pigment must pass an electron to neighbor molecule very rapidly(one billionth of a second) or lose energy to fluorescence.

● Two photosynthetic systems:PS I - mostly Chl a molecules PS II - accessory pigments + Chl a

● Electron Transport System (ETS) – transfers electrons, extracting chemical energy and reducing (electron donor) power

● Enzyme system (Calvin Cycle) - uses chemical energy and reducing power to "fix" CO2 into organic molecules

Components of Thylakoid Membrane

(Oxygenic) Photosynthesis Reaction Summary:PS II: breakdown of water to O2 and free electrons, drive ETS ATP

12 H20 6 02 + 24 e- + 24H+18 ADP +18 Pi 18 ATP Photophosphorylation(adenosine diphosphate + phosphate adenosine triphosphate)

"Excited" electrons are passed to Chl a - P680 "reaction center". The electrons come from the breakdown of water into H+ and O2 (i.e., one of the products of photosynthesis occurs at the very first step). At P680, the electrons are passed to the ETS where some energy is conserved as high energy phosphate bonds.

PS I: recharges ETS & puts NADP in reduced state24 H+ + 12 NADPox + 24 e- 12 NADPre

Electrons passed to pigment P700 are recharged to a higher energy level and ultimately passed to NADP (Nicotinamide Adenine DinucleotidePhosphate). NADPre is a powerful "reducing agent" or "electron donor". PS I does not create O2 or its own supply of electrons. Only PS I will work with red light (λ > 680 nm). P700 becomes excited, but electrons have to be returned - via CYCLIC PHOSPHORYLATION - and pigment discharges energy by fluorescence.

Z-Scheme of Photosynthesis(“light” reactions)

Photosynthetic Carbon Reduction (Calvin) Cycle

Photosynthesis Reaction Summary:“Dark” Reactions: Reduces CO2 to sugar in the CALVIN CYCLE

12 NADPre + 6 CO2 C6H12O6 + 6 H2O + 12 NADPox18 ATP 18 ADP + 18 Pi

Reduction (= gain of electrons) of CO2 into sugar can occur in the dark using the products of light reactions (ATP-energy from PSII and NADP-reducing power from PS I).

Anoxygenic PhotosynthesisPurple & Green Sulfur Bacteria (obligate anaerobes)

use light energy to split H2S (hydrogen sulfide) light

6 CO2 + 12 H2S C6H12O6 + 6 S2 +6 H2O

Purple Nonsulfur Bacteriause H2 as reductant for CO2 fixation (but can grow chemoheterotrophically in the dark)

light

6 CO2 + 12 H2 C6H12O6 + 6 H2O