Autotrophs  Autotrophs are organisms that obtain energy by making their own food. (sugar- glucose) 8.1 How Organisms Obtain Energy Cellular Energy

What do we call the energy sources (molecules) that are used for biological chemical reactions? ATP and NADPH

ATP ATP and NADPH are both biological energy storage molecules ATP: adenosine triphosphate ATP is the most important provider of chemical energy

ATP Structure

ATP

ATP: The Unit of Cellular Energy  ATP: releases energy when the bond between phosphate groups is broken 8.1 How Organisms Obtain Energy Cellular Energy

 When those bonds are broken, ATP forms adenosine diphosphate (ADP) and a free phosphate group.

Think of ATP as a fully charged battery ADP (adenosine diphosphate) as a half charged battery AMP (adenosine monophosphate) as an empty battery Which provides the most energy?

How is ATP made?

ATP is formed during photosynthesis

Photosynthesis: the process by which green plants use the light energy to produce carbohydrates 6CO2 + 6H2O → C6H12O6 + 6O2 carbon dioxide + water (light) glucose + oxygen

In other words, light energy is converted into chemical energy!

 Photosynthesis occurs in two phases. Cellular Energy  Light-dependent reactions 8.2 Photosynthesis Chapter 8  Light-independent reactions

Light Dependent Reaction Energy from the sun is absorbed by the chloroplasts found mainly in green leaves The light energy is used to produce two energy-storing molecules ATP and NADPH

The light dependent reaction occurs in the thylakoids where the chlorophyll (green pigment) is located A stack of thylakoids is called a granum

Light energizes the electrons found in the chlorophyll molecules The light energy also causes a water molecule to split into 2 hydrogen and one oxygen The O2 is released as waste

Through a series of events, the excited electrons are transported to an electron carrier called NADP+ The electrons bond to the NADP+ and form the chemical energy-storage molecule NADPH

The H+ (hydrogen ion) stay in the thylakoid and accumulate until they move out of the thylakoid space through ion channels called ATP synthases As H+ moves through ATP synthase, ATP is formed in the stroma from ADP

ATP Synthase

ATP and NADPH are not stable enough to store energy for long periods of time Instead, it is stored as glucose in the plant This occurs during the second phase of photosynthesis called the Calvin Cycle or the Light Independent Reaction

Light Independent Reaction Light Independent Reaction: uses energy stored in ATP and NADPH to make glucose Occurs in the stroma during light or dark

Light Independent Reaction Hydrogen and energy from the light reaction combine with CO2 from the atmosphere to form glucose Glucose can store energy for long periods of time 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2

Alternative Photosynthesis Pathways The environment an organism lives in can impact it’s ability to conduct photosynthesis. Some environments have less water, less carbon dioxide, etc. In order to combat these environmental inhibitors, plants use alternative pathways to produce sugars. C4 Plant – use a pathway that helps maintain photosynthesis while minimizing water loss. This process produces molecules that supply CO2 for later steps of photosynthesis. Examples include corn and sugarcane. CAM Plants – used in plants that live in areas where water is limited. During this process, a lot of the steps of photo. Work at night. Examples include cactuses.

Overview of Cellular Respiration  Organisms obtain energy in a process called cellular respiration.  Formula: 8.3 Cellular Respiration Cellular Energy Chapter 8

8.3 Cellular Respiration Cellular Energy  Cellular respiration occurs in three main parts.  Glycolysis (Anaerobic)  Aerobic respiration (Kreb’s Cycle)  Electron Transport Chain Chapter 8

Glycolysis  Glycolysis: Glucose is broken down in the cytoplasm of the cell. Not in an organelle! 8.3 Cellular Respiration Cellular Energy  The process does NOT require oxygen: anaerobic Chapter 8

Glycolysis Enzymes break down one molecule of glucose (C 6 H 12 O 6 ) into 2 pyruvic acid (C 3 H 4 O 3 ) molecules and 4 hydrogens The process needs 2 ATP molecules to get started—it creates 4 ATP Net gain of ATP in glycolysis is 2 ATP

Aerobic Respiration Stage (Kreb’s Cycle)  Glycolysis has a net result of two ATP and two pyruvic acid molecules. 8.3 Cellular Respiration Cellular Energy  Most of the energy from the glucose is still contained in the pyruvic molecules.  The pyruvate needs to be broken down.  The Krebs Cycle is sometimes referred to as the TCA cycle or the citric acid cycle. Chapter 8

The two pyruvic acid molecules move into the mitochondria by active transport (this requires 2 ATP) Aerobic respiration takes place in the mitochondria (must have oxygen)

The pyruvic acid is acted upon by enzymes and broken down into acetic acid —2 ATPs are formed Acetic acid is acted upon by enzymes and broken down into citric acid CO 2 and H 2 O are given off as waste

Electron Transport Chain Last step and the one that produces the most ATP High energy carriers convert ADP to ATP through ATP synthase Overall, ETC produces 24 ATP molecules.

ATP are formed, but 2 are used to get the pyruvate into the mitochondria 2 ATP from glycolysis ATP from aerobic respiration = ATP (net result)

Anaerobic Respiration

Fermentation: the anaerobic respiration that follows glycolysis ATP is made in the absence of oxygen Occurs in the cytoplasm of cells. NOT IN MITOCHONDRIA!

One form occurs in some prokaryotes – They grow and reproduce without oxygen

Two Main Types of Fermentation: Lactic Acid Fermentation Alcohol Fermentation

Lactic Acid Fermentation Enzymes convert the pyruvic acid made during glycolysis into lactic acid (a different molecule) Muscle cells produce lactic acid when the lungs and blood stream cannot keep up with the muscles’ need for ATP

Causes the burn and fatigue that you feel while working out

Lactic Acid Some microorganisms produce lactic acid that is used in making dairy products

Alcohol Fermentation Pyruvic acid is converted to ethyl alcohol and carbon dioxide This occurs in yeast and some bacteria Used for making bread and some forms of alcohol