Energy for Living Systems

Energy Ability to do work Types of energy Potential Energy Energy of position   For living organisms, potential energy is stored in chemical bonds   Kinetic Energy  Energy of motion   Breaking of chemical bonds in various life processes.   Activation Energy   Energy necessary to trigger a chemical reaction   Lighted match held to a piece of paper

Energy All living things require energy. Necessary for carrying out all life processes - building, repairing, growing, and reproducing.   Energy comes from food (glucose)   Energy is stored in glucose bonds - potential energy   No organism can make energy - comes from the sun.   Law of Conservation of Energy - Energy can be neither created nor destroyed, but can only be changed from one form to another.  

Energy Organisms divided into 2 groups according to the way they get their food.   Autotrophs – organisms that can combine inorganic molecules into organic molecules for use as food; make their own food   Heterotrophs - organisms that don't make their own food but depend directly on other organisms for food.  

Energy Energy is not recycled, matter is recycled Energy available for use decreases with each transformation   Some of the energy used to break bonds and some is lost as heat.   New energy must be constantly supplied - must come from sunlight.   Materials used in producing new molecules can be reused.  

Energy Energy processes of living organisms Photosynthesis Process in which carbon dioxide and water is used to form glucose.   Requires light energy from the sun.   Takes place in the presence of chlorophyll.   Respiration   Process in which glucose molecule is broken down and chemical energy it contains is released.   Carbon dioxide and water released.   Performed by all cells - releases energy of food

Adenosine Triphosphate Usable energy from by one reaction may be stored by another molecule and used in a later reaction.   Many times the storage molecule for the released energy is ATP.  

Adenosine Triphosphate Composed of 3 parts   Adenine - a nitrogen base   Ribose - a 5-carbon sugar   Three (3) phosphate groups   Adenine joins with ribose to form adenosine   Phosphate groups attach in sequence to adenosine   Adenosine monophosphate - AMP - 1 phosphate group   Adenosine diphosphate - ADP - 2 phosphate groups   Adenosine triphosphate - ATP - 3 phosphate groups

Adenosine Triphosphate

Adenosine Triphosphate High energy bonds form between the phosphate groups - indicated by a wavy line (~)   Requires a great deal of energy to form bond.   Energy is released when bond is broken.   ATP - A - P ~ P ~ P   ADP - A - P ~ P  

Adenosine Triphosphate Normally reaction is cyclic - moves between ADP and ATP Controls the cell's production through cycle of energy storage and release. ADP + P + energy ---> ATP - energy is stored ATP ---> ADP + P + energy - energy is released Normally cell does not use ADP as energy source; ADP not converted to AMP

Photosynthesis Process by which green plants convert the sun's light energy into chemical energy stored as food in the form of glucose.   Photo - means "light"   Synthesis - means "to build a complex substance from simple substances"  

Photosynthesis Raw materials - the reactants of the reaction   Carbon dioxide - CO2   Water - H2O   Light energy

Photosynthesis Products Glucose - C6H12O6   Oxygen - O2   Water - H2O

Photosynthesis Chlorophyll is necessary Acts as a catalyst - causes the reaction to move forward.   Pigment in green plants that gives them their color   Primary light absorbing pigment of green plants.  

Photosynthesis Represented by the following reaction: chlorophyll 6 CO2 + 12 H2O + light -----------> C6H12O6 + 6 O2 + 6 H2O

Photosynthesis Process is series of reactions that change reactants to the products - divided into 2 main reactions   Light Reactions - require light energy   Dark Reactions - Do not require light energy

Light Sunlight is white light; mixture of different wavelengths of light   Each wavelength of light has a characteristic color -   Colors that make up white light can be separated by prism to produce the visible part of the spectrum - ROYGBIV – Red, Orange, Yellow, Green, Blue, Indigo, Violet   Shorter the wavelength of light, the more energy it has Blue – shorter wavelengths; more energy Red – longer wavelengths; less energy

Light

Light Objects appear to be a certain color because they transmit or reflect light of that color.   Colors absorbed by an object are not seen   Color of object is the wavelength of light that is reflected or transmitted by the object.   Plants appear green because they reflect green light and absorb other colors of light.  

Light Absorption by Green Plants

Plant Pigments Primary pigment in plants that absorbs light energy is chlorophyll   Green in color - reflects green wavelengths   Absorbs mainly red and blue wavelengths of light   Act as catalysts to speed the reaction of photosynthesis.   Types   Chlorophyll a Chlorophyll b Chlorophyll c Chlorophyll d Bacteriochlorophyll    

Plant Pigments Accessory Pigments - may be used to transfer some energy to chlorophyll Types Carotenoids - yellow, brown and orange pigments of plants Carotene Xanthophyll Phycobilins - accessory pigments of red algae and blue-green bacteria Not normally visible in tree leaves - masked by chlorophyll; appear when chlorophyll production ceases  

Chloroplasts Organelle in plant cells where photosynthesis occurs. Contain the Chlorophyll pigment.   Structure   Grana - tiny stacked structures in the chloroplasts   Contains the chlorophyll   Also contains the accessory pigments.   Site of light reactions   Stroma - protein-rich solution around the grana   Site of dark reaction  

Chloroplasts

Light Reactions Chlorophyll traps the light energy Causes chlorophyll molecules to become energized; electrons released from molecule   Two different photosystems active in photosynthesis   Photosystem I   Photosystem II   Water molecules are split and oxygen is released.   Energy is stored in ATP and NADPH2 (electron acceptor)   Both used in the Dark Reactions   Supply the energy for the Dark Reactions  

Light Reactions

Dark Reactions Light is not required; energy comes from ATP and NADPH2; Called the Calvin cycle Carbon dioxide bonds to 5-carbon sugar called ribulose diphosphate, RuDP - forms unstable 6-carbon compound 6-carbon compound immediately breaks down into two 3-carbon molecule of phosphoglyceric acid, PGA. Each PGA reacts with hydrogen atoms in NADPH2 to produce 3-carbon molecule of phosphoglyceraldehyde, PGAL, water reformed Two molecules of PGAL combine to produce glucose molecule. Some PGAL used to reform RuDP.

Dark Reactions

Respiration Process in which cells take energy, stored in chemical bonds of food and incorporates it into chemical bonds of ATP   Occurs in the mitochondria   Series of chemical reactions  

Respiration Reactants   Glucose - C6H12O6   Oxygen - O2

Respiration Products Carbon dioxide - CO2 Water - H2O   Carbon dioxide - CO2   Water - H2O   ATP - adenosine triphosphate  

Respiration Overall equation of cellular respiration (aerobic) enzymes C6H12O6 + 6 O2 ----------> 6 CO2 + 6 H2O + 36 ATP

Respiration Types Anaerobic Respiration - doesn't require oxygen   Anaerobic Respiration - doesn't require oxygen   Aerobic Respiration - requires oxygen  

Stages of Aerobic Respiration Glycolysis - Anaerobic Kreb’s (Citric Acid)Cycle - Aerobic Electron Transport Chain - Aerobic

Glycolysis First stage of respiration; occurs outside the mitochondria Does not require oxygen. Glucose breaks down into two 3-carbon molecules of pyruvic acid Requires 2 molecules of ATP to supply activation energy Produces 4 molecules of ATP; net gain of 2 ATP's Pyruvic acid can go in two directions - depends on of organism type and oxygen availability Aerobic respiration - oxygen required Anaerobic respiration - oxygen not needed

Glycolysis

Transition to Aerobic Respiration

Aerobic Phases Divided into two major reactions Citric acid cycle (Krebs Cycle)   Electron Transport Chain

Citric Acid Cycle Pyruvic acid loses a carbon dioxide forms 2-carbon molecule that enters cycle.   Process takes place in the mitochondria   Hydrogen atoms released during the cycle - will carry electrons to the next reactions 2 molecules of ATP are produced  

Citric Acid Cycle

Electron Transport Chain Involves a series of electron acceptors   Accepts electrons and H ions from NADH &FADH  24 hydrogen atoms produce 24 electrons and 24 hydrogen ions form 12 pairs of hydrogen ions and 12 pairs of electrons   Near end of chain 12 molecules of hydrogen bond with 6 oxygen molecules to produce 12 molecules of water.   32 molecules of ATP produced  

Electron Transport Chain

Summary of ATP Production In Aerobic Respiration Glycolysis 2 ATP   Citric Acid Cycle 2 ATP   Electron Transport 32 ATP   Total 36 ATP  

Anaerobic Repiration Occurs when cell obtains energy from breakdown of food molecules in the absence of oxygen   Also known as Fermentation First step similar to aerobic respiration - glucose converted to pyruvic acid - glycolysis   Types of Fermentation   Alcoholic Fermentation   Lactic Acid Fermentation

Alcoholic Fermentation Pyruvic acid is converted to ethyl alcohol Most of the energy is still stored in the alcohol. Summary equation: enzymes C6H12O6 ----------> 2 C2H5OH + 2 CO2 + 2 ATP Industries that depend on alcoholic fermentation   Baking - carbon dioxide; makes bread rise.   Brewing - ethyl alcohol in alcoholic beverages

Alcoholic Fermentation

Lactic Acid Fermentation Occurs in muscle tissue especially during heavy exercise   Blood can't bring oxygen fast enough; lactic acid builds up causing soreness (cramps); muscles go into oxygen debt.   Summary equation:   enzymes   C6H12O6 -----------> 2 CH3CHOHCOOH + 2 ATP    

Lactic Acid Fermentation