Transformation of Energy

Energy is the ability to do work.

8.1 How Organisms Obtain Energy

Cellular Energy

Thermodynamics is the study of the flow and transformation of energy in the universe.

Chapter 8

Laws of Thermodynamics

First law—energy can be converted from one form to another, but it cannot be created nor destroyed.

8.1 How Organisms Obtain Energy

Cellular Energy

Second law—energy cannot be converted without the loss of usable energy.

Chapter 8

Autotrophs and Heterotrophs

Autotrophs are organisms that make their own food.

8.1 How Organisms Obtain Energy

Cellular Energy

Heterotrophs are organisms that need to ingest food to obtain energy.

Chapter 8

Metabolism

All of the chemical reactions in a cell

8.1 How Organisms Obtain Energy

Cellular Energy

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

Chapter 8

ATP: The Unit of Cellular Energy (adenosine triphosphate)

ATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate group.

8.1 How Organisms Obtain Energy

Cellular EnergyChapter 8

ATP

Overview of Photosynthesis

Photosynthesis occurs in two phases.

Cellular Energy

Light-dependent reactions

Light-independent reactions

8.2 Photosynthesis

Chapter 8

Phase One: Light Reactions

The absorption of light is the first step in photosynthesis.

Cellular Energy

Chloroplasts capture light energy.

8.2 Photosynthesis

Chapter 8

Electron Transport

Light energy (excites electrons in photosystem II and also) causes a water molecule to split, releasing an electron into the electron transport system (source of energy for the reactions to occur H+ (a proton), which helps in the production of ATPO2 as a waste product (which we kinda like)

Cellular Energy

8.2 Photosynthesis

Chapter 8

The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane.

The electron-acceptor molecule transfers the electrons along a series of electron-carriers to photosystem I.

Cellular Energy

8.2 Photosynthesis

Chapter 8

Cellular Energy

8.2 Photosynthesis

Photosystem I transfers the electrons to a protein called ferrodoxin.

Ferrodoxin transfers the electrons to the electron carrier NADP+, forming the energy-storing molecule NADPH.

Chapter 8

Cellular Energy

8.2 Photosynthesis

Phase Two: The Calvin Cycle

In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose.

Chapter 8

Cellular EnergyChapter 8

Cellular Energy

8.2 Photosynthesis

Six CO2 molecules combine with six 5-carbon compounds to form twelve 3-carbon molecules called 3-PGA.

The chemical energy stored in ATP and NADPH is transferred to the 3-PGA molecules to form high-energy molecules called G3P.

Chapter 8

Cellular Energy

8.2 Photosynthesis

Two G3P molecules leave the cycle to be used for the production of glucose and other organic compounds.

An enzyme called rubisco converts the remaining ten G3P molecules into 5-carbon molecules called RuBP.

These molecules combine with new carbon dioxide molecules to continue the cycle.

Chapter 8

Cellular Energy

8.2 Photosynthesis

Alternative Pathways

C4 plants

CAM plants

Chapter 8

The Importance of Pigments

Light absorbing pigments in plants are found in the thylakoid membranes of chloroplasts

There are several kinds of chlorophyll that each absorb a different wavelength of light (why could this be important?)

In addition there are other accessory pigments such as carotenoids that absorb light

The importance of the Thylakoid structure

The thylakoid has a stacked structure to allow more surface area and thus a more efficient energy transfer during the electron transport.

The folded structure provides the space needed to hold large numbers of electron-transporting molecules AND the protein complexes called PHOTOSYSTEMS (remember them, 1 & 2)

Chemiosmosis

This is the process in which ATP is made in conjunction with electron transport

Chemiosmosis is the mechanism by which ATP is produced as a result of the flow of electrons down a concentration gradient

SO….

The water molecule going into electron transport gives its electrons to photosystem II (to make NADP into NADPH) and the H+ (proton) to make ATP (from ADP)

Overview of Cellular Respiration

Organisms obtain energy in a process called cellular respiration.

8.3 Cellular Respiration

Cellular Energy

The equation for cellular respiration is the opposite of the equation for photosynthesis.

Chapter 8

8.3 Cellular Respiration

Cellular Energy

Cellular respiration occurs in two main parts.

Glycolysis

Aerobic respiration

Chapter 8

Anaerobic versus Aerobic

Anaerobic processes do not require oxygen

The first stage of cellular respiration is glycolysis, it is an anaerobic process

Aerobic processes require oxygen

respiration includes the Krebs cycle and electron transport

Glycolysis

Glucose is broken down in the cytoplasm through the process of glycolysis.

8.3 Cellular Respiration

Cellular Energy

Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down.

Chapter 8

Glycolysis (breakdown)

Krebs Cycle

Glycolysis has a net result of two ATP and two pyruvate.

8.3 Cellular Respiration

Cellular Energy

Most of the energy from the glucose is still contained in the pyruvate.

The series of reactions in which pyruvate is broken down into carbon dioxide is called the Krebs cycle.

Chapter 8

The Krebs Cycle

Is also called:

Tricarboxylic acid cycle (TCA)

or

The Citric Acid Cycle

8.3 Cellular Respiration

Cellular Energy

The net yield from the Krebs cycle is six CO2 molecules, two ATP, eight NADH, and two FADH2.

Chapter 8

8.3 Cellular Respiration

Cellular Energy

Electron Transport

Final step in the breakdown of glucose

Point at which ATP is produced

Produces 24 ATP

Chapter 8

8.3 Cellular Respiration

Cellular Energy

Anaerobic Respiration

The anaerobic pathway that follows glycolysis

Two main types

Lactic acid fermentation

Alcohol fermentation

Cellular Respiration

Chapter 8

Fermentation• There are two kinds of fermentation

• Fermentation is breaking down sugar without oxygen

• In one type sugar breaks down into lactic acid

C6H12O6 2 H+ + 2 C3H5O3-

Lactic Acid Fermentation

• This is done by your muscles when the demand for ATP is high, but you are low in oxygen. (while working out) This can cause soreness in the muscles.

Alcoholic Fermentation

• sugar breaks down into carbon dioxide and ethanol

• C6H12O6 2 CO2 + 2 C2H5OH

• Ethanol is the active ingredient in wine, beer and spirits.

• The Carbon Dioxide produced in this manner can be used to allow bread to rise