Energy Transfers Cells Unit Targets 17-20

Cells Unit Objectives 17-20 C17 I can write out the correct reactants and products in the photosynthesis and the respiration reactions. C18 I can describe the steps in the light and dark reactions of photosynthesis in terms of inputs and outputs. C19 I can describe the steps in anaerobic respiration in terms of inputs and outputs. C20 I can describe the steps in aerobic respiration in terms of inputs and outputs.

Introduction: Where do we get all of our energy on Earth? Directly or indirectly, almost all organisms get the energy needed for metabolism from the sun.

The Path: Primary Consumers Sunlight Producers Secondary Consumers

Target C17 – Photosynthesis portion I can write out the correct reactants and products in the photosynthesis and respiration reactions.

What is photosynthesis? A chemical reaction that changes light energy (sunlight) into chemical energy in the form of glucose (sugar). We consider glucose stored energy because that is the molecule our bodies break down in order to get usable energy.

Photosynthesis Reaction:

Light is a Main Ingredient White light is a combination of all colors in the visible light spectrum. Visible light ranges from wavlengths ~400 nm (violet) to ~700 nm (red) on the electromagnetic spectrum. ROY G BIV

How do we see color? Pigments absorb certain wavelengths of light and reflect all others. Look at the red heart. What colors are being absorbed? Reflected? Orange, Yellow, Green, Blue, Indigo, and Violet are absorbed; Red is reflected.

Where does it take place? All plants, some protozoans (algae), some bacteria (cyanobacteria). Most of the photosynthesis that takes place on Earth happens in the __________________ oceans (algae).

Why is it important? To autotrophs, or producers, it’s how they get their food and meet their energy requirements. To heterotrophs, or consumers, we meet our energy requirements by eating autotrophs directly (herbivores) or by eating another heterotroph (carnivores).

How Does it Work? There are two parts, the light reactions and the dark reactions. Both take place in the chloroplasts.

Target C18 I can describe the steps in the light and dark reactions of photosynthesis.

Light Reactions Has to happen in the light!!! Light energy is absorbed by pigments in the chloroplast: Chlorophyll a and b Absorb mostly red and blue light Reflect green and yellow Carotenoids Absorb blue-green to green Reflect red, yellow, orange

H2O splits, forming O2 gas and H+ ions H+ ions are used to make ATP and NADPH, which are high energy molecules that will be used in the dark reactions.

Dark (Light –Independent ) Reactions Can occur with or without light ATP and NADPH made in the light reaction are used to change CO2 into C6H12O6 (glucose/sugar)

The Process In General Light Glucose O2 CO2 Calvin Cycle Light Phase ATP Light Excites Electrons H2O Splits O2 Hits Chloroplast NADPH Dark Phase Calvin Cycle Glucose CO2

Target C19 – Cellular Respiration portion I can describe the steps in aerobic respiration in terms of inputs and outputs.

What is it? A chemical reaction carried out by ALL living things (including plants) that changes chemical energy into usable energy (ATP).

Formula 6 O2 + C6H12O6 6 H2O + 6 CO2 + ATP OR Oxygen + Glucose  Water + Carbon Dioxide + ATP

Why is it important? Respiration supplies the energy (ATP) living things need to carry out all the processes of life!

How Does it Work? There are two stages: A) Glycolysis B) Aerobic Respiration or Anaerobic Respiration

Step One - Glycolysis Takes place in the cytoplasm C6H12O6 (glucose) is broken down into two 3-Carbon molecules called pyruvate. This requires/uses 2 ATP, but it also makes/creates 4 ATP This means there is a net gain of 2 ATP

After Glycolysis… …if O2 is present, then aerobic respiration occurs. …if O2 is absent, then anaerobic respiration occurs.

If O2 is present… …then aerobic respiration occurs. Aerobic respiration has two parts: 1.) The Kreb’s Cycle 2.) The Electron Transport Chain

The Kreb’s Cycle aka the Citric Acid Cycle Takes place in the mitochondria Pyruvate molecules made during glycolysis are used to make 2 ATP, CO2, and NADPH.

The Electron Transport Chain NADPH made during the Kreb’s Cycle go into the Electron Transport Chain (ETC) It occurs in the inner membranes of the mitochondria. O2 combines with H+ ions, forming water and up to 34 ATP.

Total ATP made during aerobic respiration Up to 38 ATP!!!

All of Cellular Respiration Glucose Glycolysis 2 ATP (Net) O2 No O2 Krebs Cycle 2 ATP Fermentation 4 ATP 34 ATP Lactic Acid Ethanol ETC

Target C20 – Cellular Respiration portion I can describe the steps in anaerobic respiration in terms of inputs and outputs.

If O2 is NOT present… …then anaerobic respiration will occur after glycolysis. Another name for anaerobic respiration is fermentation. Fermentation is much less efficient than aerobic respiration. There are two types of fermentation: Lactic Acid Alcoholic

Lactic Acid Fermentation Pyruvate molecules that were made in glycolysis are converted into lactate (another word for lactic acid). Lactate buildup in muscles causes soreness. Pyruvate Glucose Lactic Acid

Alcoholic Fermentation Occurs in certain bacteria and fungi. Pyruvate molecules made during glycolysis are converted to CO2 and ethanol (alcohol). Ex. Yeast (a fungus) used in making bread, wine, and beer. Pyruvate Glucose Ethyl Alcohol CO2

Either way… …if fermentation (anaerobic respiration) occurs, then 4 ATP are produced!!!!