Cellular Respiration and Photosynthesis

Adenosine Triphosphate (ATP) -One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP)

ATP -ATP can easily release and store energy by breaking and forming bonds between its phosphate groups. -The “energy currency” of the cell -An efficient way to continuously store energy and then release it when needed by one reaction.

Composition of ATP Adenine + Ribose = Adenosine 1.Adenine 2.Ribose (5-C Sugar) 3. 3 Phosphate Groups Adenine + Ribose = Adenosine

Adenosine Triphosphate (ATP)

Composition of ADP ADP is structurally like ATP, except that it has two phosphate groups instead of three. 1. Adenine 2. Ribose 3. 2 Phosphate Groups ADP contains less energy than ATP. ADP is formed by the hydrolysis of ATP.

ADP

Converting between ATP and ADP

Building or breaking -When your body needs to use energy, you break down ATP to ADP. -When your body is storing energy, you are building up ADP to ATP.

The need for ATP -ATP is continuously produced and then consumed in our cells. Without it, our cells would not be able to perform all of the functions we need to survive. How can our cells continuously reassemble ATP? Where does the energy come from? Cellular Respiration

Cellular Respiration -Process by which the chemical energy of “food” molecules is released & captured in the form of ATP

Cellular Respiration can be divided into 3 processes 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain -Each step releases more and more of the energy stored in glucose.

Stages of Cellular Respiration

Where does this happen? 1. Glycolysis 2. Krebs Cycle in the cytoplasm 2. Krebs Cycle in the mitochondrial matrix 3. Electron Transport Chain at the surface of the inner mitochondrial membrane

ATP production -Each molecule of glucose can generate a total of 36 ATP molecules during the 3 steps of cellular respiration.

Glycolysis -Process in which glucose is broken down in order to utilize potential energy stored in the molecule

Gylcolysis Products -Net gain of 2ATP molecules & 2NADH molecules -Glucose is broken down into pyruvate (Pyruvic acid) -Glycolysis does not require oxygen; it is an anaerobic process.

Glycolysis

If oxygen is present after glycolysis: Pyruvate will move to the Krebs cycle when oxygen is present (aerobic respiration)

If oxygen is not present after glycolysis: -If oxygen is not present (anaerobic respiration), then pyruvate will go through the process of fermentation.

Fermentation -Fermentation is a process by which energy can be released from food molecules in the absence of oxygen. Fermentation occurs in the cytoplasm of cells.

Fermentation -During fermentation, cells convert NADH produced by glycolysis back into the electron carrier NAD+, which allows glycolysis to continue producing ATP.

2 types of fermentation 1.Lactic Acid Fermentation -In animals, pyruvic acid is converted to lactic acid when it accepts electrons from NADH, regenerating NAD+

Lactic Acid Fermentation

Alcoholic Fermentation -Only occurs in yeast and some other microorganisms -Pyruvic acid is broken down into alcohol & CO2

Alcoholic fermentation -Causes bread dough to rise, produces tiny bubbles in beer & sparkling wine as well as the alcohol content

Alcoholic Fermentation

In aerobic conditions… -In the second stage of cellular respiration, pyruvic acid produced in glycolysis is broken down into carbon dioxide in a series of energy-extracting reactions.

Energy Capture -Energy released by the breaking and rearranging of carbon bonds is captured in the forms of ATP, NADH, and FADH2.

Kreb’s Cycle Products Per Glucose Molecule -For each glucose molecule, 6 CO2 molecules, 2 ATP molecules, 8 NADH molecules, and 2 FADH2 molecules are produced. -FADH2 accepts electrons from FAD the same way NADH does from NAD+.

ETC -The electron transport chain produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor.

Electron Transport Chain ETC -The electron transport chain uses high-energy electrons to convert ADP into ATP; it allows the release of the large amount of chemical energy stored in NADH and FADH2

Energy Totals -In the presence of oxygen, the complete breakdown of glucose through cellular respiration results in the net production of 36 ATP molecules. -This represents about 36 percent of the total energy of glucose. The remaining 64 percent is released as heat.

Overall equation for Cellular Respiration

Photosynthesis

What is photosynthesis? -Photosynthesis is the process by which green plants and certain other organisms use the energy of light to convert carbon dioxide and water into glucose. -The glucose can be used in cellular respiration, used structurally (cellulose), or stored (starch).

Glucose source for animals -Humans and other animals depend on glucose as an energy source, but they are unable to produce it on their own and must rely ultimately on the glucose produced by plants.

Take a breath… -An extremely important byproduct of photosynthesis is oxygen, the same oxygen humans and other animals breathe.

Overall Equation for Photosynthesis

Pigments -Plants gather the sun’s energy with these light-absorbing molecules. -The plants’ principal pigment is chlorophyll.

Leaf structures - A leaf takes in carbon dioxide through openings called stomata, small pores on the underside of the leaf. Stomata open to let carbon dioxide in and oxygen out. They close to prevent water loss when temperatures are high. -Water enters through the roots into tube like vascular tissue where it is transported to the cells where it is needed.

Where does photosynthesis occur? -Photosynthesis occurs in leaves and green stems within specialized cell structures called chloroplasts that surround the central vacuole. -One plant leaf is composed of tens of thousands of cells, and each cell contains 40 to 50 chloroplasts.

Chloroplasts -The chloroplast, an oval-shaped structure, is divided by membranes into numerous disk-shaped compartments containing chlorophyll, called thylakoids suspended in a fluid known as stroma.

Stages Photosynthesis is divided into two stages: 1. Light –dependent reactions 2. Light-independent reactions

Light-Dependent Reactions

Summary of Light-Dependent Reactions -The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH, which provide the energy needed to build high-energy sugars from low-energy carbon dioxide in the next stage.

Light-Independent Reactions -No light is required to power the light-independent reactions, but products of the first stage are used. -The light-independent reactions take place outside the thylakoids, in the stroma.

Light-Independent Reactions -During light-independent reactions, ATP and NADPH molecules (unstable) produced in the light-dependent reactions are used to produce high-energy sugars(stable) from carbon dioxide. -Also known as the Calvin Cycle….

Summary of the Calvin Cycle -When other organisms eat plants, they can use the energy and raw materials stored in plants. - A single six carbon sugar is produced, but 6 carbon dioxide molecules are removed from the atmosphere to make it.

Factors Affecting Photosynthesis What factors affect the rate of photosynthesis? -Among the most important factors that affect photosynthesis are 1.Temperature 2. light intensity 3. availability of water 4.Carbon dioxide levels

Comparing Photosynthesis and Cellular Respiration What is the relationship between photosynthesis and cellular respiration? Photosynthesis removes carbon dioxide from the atmosphere, and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release energy from food.

Comparing Photosynthesis and Cellular Respiration The release of energy by cellular respiration takes place in plants, animals, fungi, protists, and most bacteria. Energy capture by photosynthesis occurs only in plants, algae, and some bacteria.

Comparing Photosynthesis and Cellular Respiration Photosynthesis and cellular respiration are opposite processes. The energy flows in opposite directions. Photosynthesis “deposits” energy, and cellular respiration “withdraws” energy. The reactants of cellular respiration are the products of photosynthesis and vice versa.

Photosynthesis and Cellular Respiration