5.1 Energy & Photosynthesis Chapter 9

Energy:  All organisms require energy for survival  All energy in food ultimately comes from the sun

Energy: How do we get it?  Make it! Autotrophs  Organisms that make their own food (glucose) using energy from the sun  Examples: plants, algae & some bacteria

Energy: How do we get it?  Eat it! Heterotrophs  Organisms that eat plants or animals to get energy  Examples: animals & fungi

Energy: What’s it all for?  Why do organisms need energy?  To move, breathe & reproduce  Why do cells need energy?  Active transport, cell division & make biomolecules  Where does energy come from?  Food: Carbs – quick energy; Lipids – long term energy

Energy Molecules: ATP ADP

Energy Molecules: ATP  ATP (adenosine triphosphate)  1 ribose (sugar) molecule  3 phosphate groups  Adenine (nitrogenous base)

Energy Molecules: ADP  ADP (adenosine diphosphate)  1 ribose (sugar) molecule  2 phosphate groups  Adenine (nitrogenous base)  Created when ATP loses energy & a phosphate

Energy Molecules

So what happens?  ATP ADP  Bond between 2 nd & 3 rd phosphate is broken  Energy is released  Energy can be used by the cell

So what happens?  ADPATP  Energy is stored when 3 rd phosphate adds to ADP

How do cells get ATP?  Break down carbohydrates & lipids  Creates energy – energy used to make ATP  Where do animals get carbohydrates & lipids from?  Their FOOD  That food is produced by autotrophs in the process of photosynthesis

Photosynthesis  Ability to capture light energy from the sun and change it into chemical bond energy while making oxygen

Photosynthesis Equation 6CO 2 + 6H 2 O + Light energy C 6 H 12 O 6 + 6O 2

Photosynthesis Questions:  Where does it occur in plants?  What are the reactants?  How do the reactants get into the plant?  What are the products?  What happens to the products?

Location?  In the chloroplast of plant cells

Where does it occur?  Chloroplast structure: Thylakoids: Sacs of membrane with pigment molecules Grana: Stacks of thylakoids Stroma: Liquid surrounding thylakoids Contains enzymes for PS

Photosynthesis Pigments

 Pigments in the plant chloroplast & vacuole absorb light energy  Chlorophyll is the main pigment found in plant cell chloroplasts  Reflect green light

Photosynthesis process  Occur in two steps:  Light-dependent reactions  Purpose: Make energy for light-independent reactions  Light-independent reactions  Also called Calvin cycle  Purpose: Use energy from light reactions to make glucose

Light- dependent Reactions Light- independent Reactions Glucose thylakoid

Photosynthesis process: light-dependent reactions Location: Thylakoids 1. Light energy is absorbed by chlorophyll 1. Chlorophyll electrons gain lots of energy 2. NADPH carries high-energy electrons to the Calvin Cycle 3. Light Energy used to make ATP for Calvin Cycle

NADP+ NADPHNADP+

Photosynthesis process: light-dependent reactions 4. Water is split to produce oxygen and hydrogen atoms  2H 2 O + Light 2H 2 + O 2  Oxygen is released as a product; released through the stomata of leaves.

Photosynthesis process: light-dependent reactions Used: Light energy H2OH2O Made:  ATP  NADPH  Oxygen (product) Light-independent rxns

Photosynthesis process: light-independent reactions  Called Calvin cycle  No light required!  Location : Stroma of chloroplast

Photosynthesis process: light-independent reactions 1. ATP broken apart to release energy  ATP ADP + P + energy 2. Energy used to bond electrons from NADPH with CO 2 to make glucose 1. Equation: CO 2 + electrons C 6 H 12 O 6 3. ADP goes back to light reactions to get recharged  Turned back into ATP

Photosynthesis process: light-independent reactions Used: CO 2 ATP (from light rxns) NADPH (from light rxns) Made:  GLUCOSE !!!

Photosynthesis review:  Where did the CO 2 come from?  How did water enter the plant?  What absorbed the sunlight?  What reactant is used in the light- independent reactions?

Photosynthesis questions:  What is made in the light-dependent reactions that is used in the light- independent reactions?  What reactant is responsible for making oxygen?

Photosynthesis questions  Where do the light-dependent reactions take place?  Where do the light-independent reactions take place?  What is the final product of the light- independent reactions?

H H2OH2O Light O2O2 ATP NADPH CO 2 Glucose ADP

Factors that influence PS Rates  Lack of water  Example/Adaptation:  Desert plants/conifers (pines): waxy coating and “needle” leaves to reduce water loss

Factors that influence PS Rates  Temperature : influences enzymes involved in the PS reactions  What is the best temperature?

Factors that Influence PS rates  Intensity of light (varies by plant)  Excess UV rays/sunlight can decrease PS