CELLULAR ENERGY Unit 4 Chapter 8

ORGANISMS OBTAIN ENERGY All living organisms use energy to carry out all biological processes

TRANSFORMATION OF ENERGY All processes require energy

ENERGY The ability to do work

THERMODYNAMICS Study The flow of energy The transformation of energy

LAWS OF THERMODYNAMICS I. Law of conservation Energy can be converted, one form to another Energy cannot be created nor destroyed II. Law of entropy Energy cannot be converted without the loss of usable energy (thermal energy)

ENERGY All organisms need Begins with the sun Directly from the sun or indirectly

AUTOTROPHS Convert light energy to food Make their own food Photoautotrophs Chemoautotrophs

HETEROTROPHS Organisms that need to ingest food to obtain energy

METABOLISM All the chemical reactions in a cell

METABOLIC PATHWAY A series of chemical reactions The product of one becomes the substrate for the next Catabolic – releases energy (big molecules to small) Anabolic – uses catabolic energy (small to big) Continual flow of energy in an organism from catabolic to anabolic pathways

PHOTOSYNTHESIS Anabolic pathway Light from sun Converted to chemical energy Use by the cell

PHOTOSYNTHESIS Plant (autotrophs) Use light energy, carbon dioxide and water Produce glucose and oxygen

CELLULAR RESPIRATION Catabolic pathway Organic molecules are broken down Energy is released Cell uses the energy

CELLULAR RESPIRATION Oxygen is used to break down organic molecules Produces carbon dioxide and water

ATP THE UNIT OF CELLULAR ENERGY Adenosine triphosphate Most important biological molecule Provides chemical energy

ATP STRUCTURE Most abundant energy-carrier molecule in cells Found in all types of organisms

ATP FUNCTION Releases energy when the bond between the 2nd and 3rd is broken

ATP ADP CYCLE

8.2

PHOTOSYNTHESIS Light energy

PHOTOSYNTHESIS Light energy Trapped

PHOTOSYNTHESIS Light energy Trapped Converted into chemical energy

PHOTOSYNTHESIS 6CO2 + 6H2O C6H12O6+ 6O2

PHOTOSYNTHESIS Two steps I. Light-dependent reaction II. Light-independent reaction

PHASE ONE: LIGHT REACTION The absorption of light Two energy storage molecules NADPH and ATP Are produced

CHLOROPLAST Large organelle Cells of leaves Thylakoid – flattened disc arranged in grana Stroma – fluid-filled space outside the grana

PIGMENT Light absorbing colored molecules In the thylakoid membranes of chloroplasts Different ability to absorb specific wavelengths of light Most common Chlorophyll a and chlorophyll b Absorb violet-blue Reflect green

CAROTENOIDS Carrots and sweet potatoes Absorb blue and green

ELECTRON TRANSPORT Structure of the thylakoid Large surface area Holds electron transporting molecules Two types of photosystems (protein complexes)

1. ELECTRON TRANSPORT Light energy excites electrons in photosystem II Also causes a water molecule to split Releases an electron into the ET system A hydrogen ion (H+) into thylakoid space Oxygen as a waste product

1. ELECTRON TRANSPORT Light energy excites electrons in photosystem II Also causes a water molecule to split Releases an electron into the ET system A hydrogen ion (H+) into thylakoid space Oxygen as a waste product

2. ELECTRON TRANSPORT The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane

3. ELECTRON TRANSPORT The electron-acceptor molecule transfers the electrons along a series of electron-carriers to photosystem I

4. ELECTRON TRANSPORT In the presence of light Photosystem I transfers electrons to ferrodoxin Lost electrons by photosystem I are replaced by electrons from photosystem II

5. ELECTRON TRANSPORT Ferrodoxin transfers the electrons to the electron carrier NADP+ Forms the energy-storage molecule NADPH

PHASE TWO: THE CALVIN CYCLE NADPH and ATP not stable to store energy for a long time Calvin Cycle is where energy is stored in organic molecules (glucose)

1. CALVIN CYCLE Carbon fixation, 6 CO2 combine with 5-carbon compounds Form 12 3-carbon molecules (3-phosphoglycerate) 3-PGA

2. CALVIN CYCLE ATP and NADPH energy Transferred to 3-PGA molecules Form G3P high energy molecules glyceraldehyde ATP – supplies the phosphate groups NADPH – supplies the H+ and e-

3. CALVIN CYCLE 2 G3P molecules leave the cycle Used for production of glucose and other organic compounds

4. CALVIN CYCLE Rubisco (enzyme) converts G3P to 5-carbon molecules called ribulose 1, 5-bisphosphates These combine with new CO2 to continue cycle

ALTERNATIVE PATHWAYS Environments low in water or carbon dioxide Maximize energy conversion

C4 PLANTS Maintain photosynthesis minimizing water loss Sugar cane and corn Fix CO2 into four-carbon compounds Significant structural modifications, leaves Stomata close during hot days

CAM PLANTS Crassulacean acid metabolism Water conserving plants in the desert Cacti, orchids and pineapple Water limited environments Allow CO2 to enter only at night, release it during the day

CELLULAR RESPIRATION Unit 4 Chapter 8.3

CELLULAR RESPIRATION Living organisms obtain energy by breaking down organic molecules during cellular respiration

FUNCTION Harvest electrons from carbon compounds And use the energy to produce ATP

CELLULAR RESPIRATION I. Glycolysis – anaerobic process II. Krebs cycle – aerobic respiration Anaerobic – without oxygen Aerobic – oxygen

GLYCOLYSIS Cytoplasm One molecule of glucose Makes 2 ATP and 2 NADH

GLYCOLYSIS 2 phosphate groups join glucose 6-carbon molecule is broken down to two 3-carbon compounds Two phosphates, e- and H+ are added = NADH Two 3 carbon compounds converted into two molecules of pyruvate AND four molecules of ATP

TWO ATP & TWO PYRUVATE

KREBS CYCLE Pyruvate is transported into the mitochondrial matrix Converted to CO2 TCA – tricarboxylic acid

KREBS CYCLE Acetyl CoA combines with 4-carbon = 6-carbon (citric acid) Citric acid broken down to 5-carbon compound Carbon dioxide breaks off and forms a 4-carbon compound Two pyruvate formed from glycolysis Two turns of the Krebs cycle Each turn = 6CO2, 2ATP, 8NADH and 2FADH2

ELECTRON TRANSPORT Final step in breaking glucose ATP is produced Electrons move along the mitochondrial membrane from one protein to another End result protons and electrons transferred to oxygen to form water

ELECTRON TRANSPORT 24 ATP

ANAEROBIC RESPIRATION Organisms live with low oxygen Grow & reproduce without oxygen Fermentation – anaerobic pathway that follows gylcolysis

LACTIC ACID FERMENTATION Enzymes convert pyruvate to lactic acid Muscles become fatigued and feel sore due to lactic acid.

ALCOHOL FERMENTATION Yeast and some bacteria Pyruvate converts to ethyl alcohol and CO2