Photosynthesis and Cellular Respiration

Why do we eat? Present this question to students and have them take 60 sec to write an answer on their paper. write student responses on the board Possible responses: Because we get hungry Because we need food to live Because we need energy Because if we don’t, we’ll starve Because we need nutrients Leading questions: What happens if we don’t eat? Did you ever skip breakfast and lunch and then try to do gym? What happened?

Lunch (The Big Picture) So where does the energy come from? Food – where did the food get it from? Plants – how so? I ate a steak, that’s not a plant. The sun – how so? I can’t eat sun beams. Is there something that can? So how does the plant get its energy? photosynthesis

Energy Transformations Energy- is the ability to do work (you love physics) Thermodynamics- the study of how energy flows and changes in the universe In order to talk about how we get energy, we need to first discuss what energy is and how it works.

Laws of Thermodynamics 1st Law of Thermodynamics- Energy can change form, but it can not be created or destroyed When you eat- The chemical energy in your food changes to mechanical energy (movement) 2nd Law of Thermodynamics- Systems go from order to disorder (entropy) When your body changes the energy from chemical to mechanical, some energy is lost as heat

Energy can come from the Sun Heterotrophs -get their energy by eating food Autotrophs -make their energy from the sun

Picture of a Metabolic Pathway Metabolism Picture of a Metabolic Pathway Metabolism- all of the chemical reactions that take place inside cells Metabolic pathway- a series of reactions where the product of one reaction is the reactant for the next So now we know that energy comes from the sun because plants harness it and then when animals eat the plants, the animals pick up the plant’s energy. so how do plants and animals “pick up” energy? Energy is stored in chemical bonds. When bonds are made and broken, energy can be stored or used to do work. This is metabolism

Two types of Metabolic Pathways Catabolic- energy is released by breaking large molecules into small molecules Anabolic- energy is used to build large molecules from small ones Energy from catabolic pathways fuel anabolic pathways Anabolic Catabolic

Photosynthesis—light energy from the Sun is converted to chemical energy for use by the cell Cellular respiration—organic molecules are broken down to release energy for use by the cell

ATP: The Unit of Cellular Energy ATP – Cell Energy Releases energy when the bond between the second and third phosphate groups is broken

Photosynthesis

Photosynthesis Two phases Light dependent Reaction – Light energy absorbed and changed into chemical energy Light independent Reaction – chemical energy changes into a stable form (glucose)

The Light Reaction First light is absorbed by chloroplasts

Thylakoids Thylakoids contain light absorbing pigments Pigments absorb light and reflect others We see the reflected color

Electron Transport

Dark Reaction- Calvin Cycle Calvin cycle - energy is stored in organic molecules such as glucose

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Light Reaction Dark Reaction

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Cellular Respiration

Overview of Cellular Respiration Organisms obtain energy in a process called cellular respiration. The equation for cellular respiration is the opposite of the equation for photosynthesis.

Two Parts Glycolysis Aerobic Respiration

Glycolysis Glucose is broken down in the cytoplasm Takes place in ALL Cells Bacteria Protists Plants Animals Fungi Glucose converted into 2 pyruvate, 2 ATP and 2NADH are produced

Anaerobic- NO OXYGEN Two main types Lactic acid fermentation Alcohol fermentation Anaerobic Respiration- takes place when there are no mitochondria (bacteria) or oxygen is not available Downside  low ATP Payoff

Aerobic Respiration Krebs Cycle Most of the energy is still in the pyruvate The net yield from the Krebs cycle is 6 CO2 2 ATP (only useable energy) 8 NADH 2 FADH2.

Electron Transport Final step in the breakdown of glucose ~34 ATP produced O2 is the Final electron acceptor = H2O

Overview of Cellular Respiration Location Main Activity High Energy Molecules Made Glycolysis Krebs Cycle ETC Cytoplasm -Glucose is converted into pyruvate 2 ATP 2 NADH Mitochondria matrix (fluid) -Pyruvate converted to CO2 (continues cycle) -provides H for transport chain (NADH/FADH) 8 NADH 2 FADH Mitochondria cristae (membrane) -protons from NADH/FADH  ATP -Electrons and protons combine with oxygen to make water ~32-34 ATP