Energy Flow

Photosynthesis and Respiration

Ref: Page 58-63(11),503-504(11), 136-166(12)

Two conditions are required for life on our planet….

• The recycling of matter ( carbon cycle and nitrogen cycles for example)

• Energy must be continuously added

• Where does the energy come from to run our planet?

• What is the main link between the sun’s energy and life on earth?

Autotrophs vs heterotrophs

The Cell Does Three Kinds of Work

• Mechanical ( cilia, contraction of muscle cells, movement of chromosomes)

• Transport ( protein pumps)

• Chemical Work ( synthesis of polymers)

• Where does the energy come from to do this work?

Cellular Respiration

Summary reaction of aerobic respiration

Glucose + oxygen → carbon dioxide + water and energy is released

enzymes

Word equation

C6H12O6 + 6O2 → 6CO2 + 6H2O and energy is released

Chemical equation

The process of cellular respiration releases energy. Why?

• All chemical reactions involve breaking bonds of the reactants to form separate atoms.

• Breaking bonds requires energy.

• New bonds are formed between these atoms to form new products.

• Forming bonds releases energy.

The difference determines if the reaction releases energy or absorbs energy.

• In this reaction, the product molecules have less energy than the reactant molecules

• Therefore energy is released in the overall process

• Exergonic reactions

• In this reaction, the product molecules have more energy than the reactant molecules

• Therefore energy is absorbed in the overall process

• Endergonic reactions

Let’s see how this works…pg 59,60(12)

So, what happens to all of this available energy?

• Well, an estimated 64% is released as heat.

• An estimated 36% is used to make ATP• Adenosine triphosphate is the source of

chemical potential energy for cellular processes ( ATP activity)

Hydrolysis of ATP

~ 54kJ/mol

So, where does all that energy go?

• Phosphorylation• The hydrolysis of ATP

is coupled with another reaction

• The Pi causes the molecule to become more reactive

• Pi is then recycled back to ATP

Imagine….

• A working muscle recycles its entire pool of ATP in less than a minute.

• That turnover represents 10 million molecules of ATP consumed and regenerated per second per cell.

• If ATP could not be regenerated by the posphorylation of ATP, human would use up nearly their body weight in ATP per day.

Photosynthesis:is the process where solar energy is transformed into chemical bond energy.

Carbon Dioxide + Water → Glucose + Oxygen

Word equation

Chemical equation

6CO2 + 6H2O → C6H12O6 + 6O2

☼

Enzymes in chloroplast

Solar energy transformed and stored here in chemical bonds

Leaves are the major organs of photosynthesis in plants.

These pictures give you an inside look at a leaf….

then into a cell….

and, finally, into a chloroplast.

The Nature of Light

• Ref: Bio12-148• Light is a form of radiant (from the sun) energy• All radiant energy travel in the form of wave

packets called photons.• The amount of energy associated with a photon is

inversely proportional to the wavelength.• Photons with shorter wavelengths have high

energy.• The human eye is sensitive to radiant energy with

wavelengths between 380nm-750nm• nm= one billionth of a meter

Why are leaves green?

Absorption Spectrum

Photoexcitation

Photosystems

Photosynthesis overview….

• All photosynthetic reactions take place in the chloroplast.

• There are two sets of reactions:• 1. The light reactions, where:• light is captured and• ATP and NADPH are made• and 2. the Calvin Cycle,• where carbon dioxide is fixed into carbohydrates

Light Dependent Reactions

Light Dependent Reactions

Light Dependent Reactions

Light Dependent Reactions

Light Dependent Reactions