Photosynthesis and Cellular Respiration

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Photosynthesis Process by which plants and some other organisms use light energy to produce food Autotrophs- organisms that make their own food Photosynthesis- uses light Chemosynthesis- uses chemicals

Heterotrophs Can not make their own food Must eat autotrophs or other heterotrophs for energy or are decomposers

Adenosine Triphosphate (ATP) Both autotrophs and heterotrophs store energy as ATP                                                

ATP W= adenine (a nucleotide) X= ribose (5-carbon sugar) Y= phosphate (there are 3 phosphate groups) Z= high energy bond When the cell needs energy, it breaks a bond between two phosphates Energy is released and ADP is created

History of Plant Nutrition Priestley In 1700’s discovered that plants could grow in a closed container and support a flame and an animal Lavoisier discovered that the animals and flame required oxygen, while the plants gave off oxygen Ingenhousz discovered that plants give off oxygen only in sunlight By the 1800’s it was known that plants require carbon dioxide, light, water

Photosynthesis (Introduction) Process of capturing energy of sunlight and transforming it into chemical energy Plants use CO2 and H2O to produce O2 and glucose Plants produce most of the atmosphere’s oxygen

Light Energy Sunlight travels in waves Wavelength is the distance between the crests (or troughs) of two waves

Light Energy (continued) Sunlight is a mixture of different wavelengths (visible spectrum) Each wavelength contains different amounts of energy Pigments are chemicals in plant cells that absorb this energy

Photosynthetic Pigments Chlorophylls- Chlorophyll a- primary pigment that absorbs light Chlorophyll b- absorbs light and transfers it to chlorophyll a Carotenes and Xanthophylls also absorb different wavelengths of light They are responsible for the autumn colors

Chloroplasts Organelles containing membranes which hold photosynthetic pigments Membranes are in the shape of flattened sacs called thylakoids Stacks of thylakoids are grana Stroma is the area between grana

Light Reactions Photosynthesis occurs in many small steps The light reactions occur in the grana Light is absorbed by chlorophyll The light energy excites electrons and they pass through a series of reactions (electron transport chain) Water is broken down and oxygen is released as a waste product ATP and NADPH (contain energy) are produced

Dark Reactions Occur in the stroma Can occur with or without light CO2 is used to make glucose- this is carbon fixation Series of reactions called the Calvin Cycle The energy needed for this series of reactions comes from the ATP and NADPH made in the light reactions 6 CO2 molecules are needed to make 1 glucose molecule

Photosynthesis Equation 6 CO2 + 6 H2O → C6H12O6 + 6O2 light Carbon + water → glucose + oxygen + dioxide water In the presence of light, chlorophyll and enzymes

Factors Affecting Photosynthesis Light Intensity Water availability Mineral availability Temperature- too hot or cold damages enzymes

Cellular Respiration Energy- the ability to do work Living organisms need energy to perform life functions Living organisms get energy from food Food is broken down and most of the energy is stored as chemical energy Some is released as heat energy, which maintains body temperature

Cellular Respiration- Overview The process of breaking down food in the cell and releasing the energy Takes place in many small steps Many ATP molecules are formed from 1 molecule of glucose

Glycolysis Occurs as the first step of cellular respiration in ALL cells, even ones that go on to aerobic cellular respiration Glyco –glucose Lysis – to break

Anaerobic Respiration Occurs without oxygen Not as efficient as aerobic (requires oxygen) Not as many ATP produced

Glycolysis- The first step in Cellular Respiration Takes place in the cytoplasm 2 ATP molecules are needed to start the process 2 phosphate groups attach to a glucose molecule Glucose then goes through a series of reactions Glucose becomes PGAL and then pyruvic acid 1 glucose molecule becomes 2 pyruvic acid molecules

Glycolysis (continued) 2\2 NADH2 (an electron acceptor) which produce 4 ATP, are produced 2 ATP were used up to start the process, so there is a net gain of 2 ATP

Fermentation No more ATP are produced! The pyruvic acid from glycolysis is converted to another compound

Two Types of Fermentation Alcoholic Fermentation- Ethyl alcohol and carbon dioxide are produced Makes alcohol and the carbon dioxide makes bread rise Occurs in yeast cells and some bacteria

Fermentation (continued) Lactic Acid Fermentation- Lactic acid is formed Occurs in human muscle cells

Aerobic Respiration Much more efficient than anaerobic Starts with glycolysis Pyruvic acid moves from the cytoplasm into the mitochondria The pyruvic acid is broken down into CO2, NADH2, and a 2 carbon compound called acetyl CoA

Krebs Cycle (Citric Acid Cycle) Is a repeating cycle Starts with 1 molecule of acetyl CoA Acetyl CoA moves through a series of reactions, yielding 1 ATP, 3 NADH2, 1 FADH2 , 2 CO2 1 molecule of glucose produces 2 turns of the Krebs Cycle

Electron Transport Chain Last step of aerobic cellular respiration The energy in FADH2 and NADH2 needs to be converted into ATP This is done in a series of reactions called the electron transport chain It occurs in the mitochondria Oxygen is the final electron acceptor!! Oxygen combines with 2 H to form water

Total ATP Produced Each NADH2 produces 3 ATP Each FADH2 produces 2 ATP The net amount of ATP produced in aerobic cellular respiration- Glycolysis- 2 ATP Krebs- 2 ATP Glycolysis- 2 NADH2 x 2 ATP/ NADH2 =4 ATP Pyruvic Acid breakdown- 2 NADH2 x 3=6 ATP Krebs- 6 NADH2 x 3= 18 ATP 2 FADH2 x 2= 4 ATP 36 ATP are produced in aerobic cellular respiration from 1 molecule of glucose!! Krebs cycle animation

Krebs (or citric acid) Cycle

Cellular Respiration Equation C6H12O6 + 6 H2O + 6 O2→ 6 CO2 + 12 H2O + Energy (36 ATP) Glucose + water + oxygen → carbon dioxide + water+ 36 ATP This is a very efficient process!!

Respiration of Fats and Proteins Cells can break down fats and proteins to produce ATP Fats produce twice as much ATP as glucose Proteins produce the same number of ATP as glucose, but the breakdown of proteins is not preferred by cells

Comparing Aerobic and Anaerobic Respiration 2 ATP produced NO oxygen needed Products are- lactic acid, alcohol, CO2, 2 ATP Aerobic 36 ATP produced Oxygen IS needed Products are- CO2, H2O, 36 ATP

Comparing Photosynthesis and Cellular Respiration Where Chloroplasts Mitochondria Reactants H2O, CO2, light Glucose, O2, H2O Products CO2, H2O, energy (36 ATP) Function Energy storage Energy release Equation Know it!!