How Do Biological Organisms Use Energy?

The importance of ATP All organisms use a two-step process to

provide the energy needed for most of their biological activities:

First, chemical energy from organic molecules like glucose is used to make ATP. This process is called cellular respiration.

Then, ATP provides the energy for most biological processes.

Two steps: First, energy from cellular respiration is used to make ATP (adenosine triphosphate, with 3 phosphates) from ADP (adenosine diphosphate, with 2 phosphates) plus a phosphate.

The reverse reaction (breakdown of ATP to ADP and a phosphate) releases energy which is used for many different cellular processes.

The Importance of ATP Our cells are constantly using energy from

organic molecules like glucose to make ATP and using the ATP molecules to provide the energy for biological processes such as muscle contraction, synthesizing molecules, and pumping ions and molecules into and out of cells. On average, each ATP molecule in our body is used and re-synthesized more than 30 times per minute when we are at rest and more than 500 times per minute during strenuous exercise.

What Is ATP?

Energy used by all CellsEnergy used by all Cells

Adenosine TriphosphateAdenosine Triphosphate

Organic molecule containing Organic molecule containing high-energy Phosphate bondshigh-energy Phosphate bonds

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Chemical Structure of ATP

3 Phosphates

Ribose Sugar

Adenine Base

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What Does ATP Do for You?

It supplies YOU withIt supplies YOU with ENERGY!ENERGY!

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How Do We Get Energy From ATP?

By breaking the By breaking the high- energy high- energy bonds bonds between the between the last two last two phosphates phosphates in ATPin ATP

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What is the Process Called?

HYDROLYSIS (Adding HHYDROLYSIS (Adding H22O)O)

H2O

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How Does That Happen?

An An Enzyme!Enzyme!

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How is ATP Re-Made?

The reverse of the previous The reverse of the previous process occurs.process occurs.

Another Another Enzyme is Enzyme is used!used!ATP ATP SynthetaseSynthetase

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The ADP-ATP Cycle

ATP-ATP-asease

ATP ATP SynthetaSynthetasese

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When is ATP Made in the Body?

During a During a Process Process called called Cellular Cellular Respiration Respiration that takes that takes place in both place in both Plants & Plants & AnimalsAnimals Copyright Cmassengale

ATP ADP The energy that was held in that bond (now broken) is able to

fuel a cellular reaction. The remaining molecule now has only two phosphate groups

and is called ADP (adenosine diphosphate). This reaction is sped up by the enzyme ATPase.

... and in reverse Free energy obtained from an

exergonic reaction can also be used to add a phosphate group to ADP, converting it to ATP. The ATP-ADP cycle is the cells way of shuttling energy between reactions.

The addition of a phosphate group to an organic molecule of any sort is called phosphorylation.

Important Coenzymes

COENZYMEABBREVIATION

FUNCTIONLoaded

form

Unloaded

form

Adenosine triphosphate ATP ADP Energy transfer

Nicotine adenine dinucleotide(based on the vitamin niacin)

NADH NAD+ Transfer of electrons and protons

Nicotine adenine dinucleotide phosphate(based on the vitamin niacin)

NADPH NADP+ Transfer of electrons and protons

Flavine adenine dinucleotide(based on the vitamin B12)

FADH2 FAD Transfer of electrons and protons

PHOTOSYNTHESISPHOTOSYNTHESIS

Harnessing Energy

Heterotrophs and AutotrophsAll living organisms require organic compounds and energy for their cells.

Depending on how organisms obtain these compounds and energy, we classify them as being:

Heterotrophs: consumers- must consume organic molecules as they cannot produce them, themselves .Eg. Animals.

or autotrophs: Producers- they can produce organic molecules. Eg plants.

Organisms such as plants, algae and some protists (such as phytoplankton) are able to trap light energy and make organic compounds, such as sugars, from simple compounds such as carbon dioxide and water.

Photosynthesis is the process in which light energy is transformed into chemical energy stored in sugars.

Organisms with this ability are termed producers.

Other organisms, such as animals and fungi, that depend, directly or indirectly, on the organic compounds produced by producers, are called consumers.

Photosynthesis

Photosynthesis

carbon dioxide + water ---------------------------> glucose + water+ oxygen

6CO2 + 12H2O --------------------------> C6H12O + 6H2O + 6O2

lightchlorophyll

lightchlorophyll

Where does photosynthesis occur?In a terrestrial flowering plant, only some cells are able to carry out photo synthesis and these are principally located in green leaves. The shape and structure of leaves equips them to carry out photosynthesis.

are membrane stacks that form the grana. They contain chlorophyll and are the site of light dependent phase.

is the semi-liquid interior of the chloroplast , in which the light independent phase takes place.

Why are leaves so special?

Their flat shape provides a large surface area exposed to sunlight.

The presence of many stomata (pores) on one or both leaf surfaces provides access into the leaf for carbon dioxide.

The thinness and the presence of internal air spaces in the leaves enables the ready diffusion of carbon dioxide to photosynthetic cells in the leaf tissue.

The network of xylem vessels in the vascular tissue transports water to the photosynthetic cells.

Each photosynthetic cell possesses many chloroplasts enabling it to trap the energy of sunlight.

ChloroplastsPresent in some cells of plants and algae.

The boundary of each chloroplast is a double membrane (inner and outer).

The inner membrane extends to form a system of membranous sacs called lamella or thylakoids.

When several of these stack together they form grana.

Chlorophyll is located in the grana.

The semi-fluid substance between the grana is called the stroma.

Chlorophyll

Chlorophyll is pigment that absorbs or traps light.There are three types of chlorophyll – a, b and c. Chlorophyll a is the major photosynthetic pigment and is found in all photosynthetic plants, protists, and cyanobacteria.Chlorophyll molecules are embedded in the membrane structure of grana.Chlorophylls absorb wavelengths of violet-to-blue and red light. They reflect green which is why leaves appear green.

Stages of Photosynthesis

Photosynthesis from: “photo” – light “synthesis” – put together

The name reflects the two-stage nature of the process.

Light-dependent stage involving trapping of light energy

Light-independent stage in which energy trapped in the first stage is used to make organic compounds from carbon dioxide and water.

...now for the Chemical Reactions of photosynthesis

Photosynthesis involves two stages; Light dependent reactions in which light

energy trapped by chlorophyll in the chloroplast (grana) is used to produce ATP and split water into H+ and oxygen gas.

The light independent reactions, which use ATP to combine carbon dioxide and H+ to form glucose and water in the stroma.

Light-dependent ReactionAlso known as the light reaction.Occur within the grana of the chloroplastsRequires the input of water as well as light energy.

Can be summarised by the reaction below:

Steps in light-dependent reaction

Sunlight is trapped by chlorophyll a (or other pigments) and light energy is converted to chemical energy.

Absorbed energy is used to produce ATP and split water molecules to form H+ ions and oxygen (waste product). This involves the electron transport chain.

H+ ions are gathered by a carrier molecule or acceptor molecule (NADP in this case).

NADP becomes NADPH and transports H+ ions from the grana to the stroma.

H+ ions and ATP produced in light-dependent reaction are utilised in light-independent reaction.

Light dependent reaction

Light-independent ReactionAlso known as dark reaction or Calvin cycle.Occurs in the stroma and involves the reduction of carbon.Does not directly depend on light involvement but does dependent on previous stage occurring.

Can be summarised by the reaction below:

Steps in light-independent reaction

Carbon reduction (from CO2 to a sugar [C(H2O)]n) requires a supply of carbon dioxide and hydrogen ions, and an input of energy.

Carbon dioxide can come from the air surrounding the leaf or from cellular respiration reactions.

Energy required to drive these reactions comes from ATP and ‘loaded’ carriers (NADPH molecules) produced during the light-dependent stage.

H+ is the reducing agent and ATP is the source of energy for reducing carbon dioxide to organic compounds such as glucose and other sugars.

Plants do not build sugars simply by joining CO2 molecules together. Sugar formation involves a cyclic set of reactions in which intermediate substances are formed.

Light independent reaction

The Calvin Cycle

Each time the cycle proceeds, one carbon one carbon dioxide molecule enters the cycle and is fixed and reduced.

To produce a 6-carbon compound that is released from the cycle, six turns of the cycle must take place.

At the completion of each turn of the cycle, the starting compound is regenerated and so the cycle can proceed provided that CO2, ATP and NADPH are also available.

The Calvin Cycle

The importance of sugars

All cells can use sugars as a starting point for the manufacture of other carbohydrates and lipids.

They can react sugars with with nitrogen to form non-essential amino acids and nitrogenous bases that are found in nucleic acids.

The chemical energy is starch is used directly or indirectly by consumers in cellular respiration to produce ATP for their energy requirements.

Factors that influence photosynthesis

Light intensityCarbon dioxide availabilityTemperatureIndirect factors

Light intensity

The rate of photosynthesis usually increases with light intensity until there is another limiting factor, such as the saturation of chloroplasts.About 20% of light that hits the leaf is reflected.Only about 1% of light absorbed by the leaf is converted to chemical energy.

Carbon dioxideFor most plants, carbon dioxide from air dissolves in extracellular fluid before entering photosynthetic cells.

There are local variations in carbon dioxide levels in air, in different habitats and at different times of the day.

Aquatic plants can also use hydrogen carbonate (carbonic acid), which forms when carbon dioxide dissolves in water.

CO2 released as a product of cellular respiration can also be used for photosynthesis, but usually only provides a small amount of the total carbon dioxide requirements.

The degree to which the level of carbon dioxide affects the rate of photosynthesis is different for C3, C4 and CAM plants.

C4 and CAM plants are more efficient than C3 plants at trapping carbon dioxide when it is warm.

Compensation point

At low levels of light intensity, the rate of photosynthesis is less than the rate of cellular respiration, so there is net output of carbon dioxide by plants.

The light intensity at which the rate of carbon dioxide produced by cellular respiration equals the rate of carbon dioxide used in photosynthesis is known as the light compensation point.

Temperature

Photosynthesis increases with increasing temperature until around 20-40oC, depending on plant species, then it declines again.Plants that live in hotter climates are at higher end of the range.In C3 plants, oxygen displaces trapped carbon dioxide more rapidly as temperature increases (enzyme binds oxygen instead of carbon dioxide).

Indirect factorsWater

Required in photosynthesisOnly 1% of water passing up the xylem is used in photosynthesis. The rest is used in other chemical reactions, to hydrate cells or is lost in transpiration. If there is not enough water to hydrate the cells and keep them turgid, the stomata close. This prevents carbon dioxide entering the leaves, therefore photosynthesis decreases.

Level of chlorophyllLimits photosynthesisYellow leaves will have a lower rate of photosynthesis.

Nitrogen and Magnesium Chlorophyll contains the elements nitrogen and magnesium. If the soil is deficient in one or both these elements, the plants cannot make sufficient chlorophyll.

Rate of photosynthesisAny of the factors that influence photosynthesis may limit the rate of photosynthesis.

Photosynthesis will be limited by only one factor at a time, but if conditions in an individual chloroplast change, the particular factor that is limiting may also change.

For example, carbon dioxide levels that are adequate (not limiting) in conditions of low light may become limiting if light intensity increases.

Chemosynthetic organisms use the chemical energy within inorganic molecules.

This energy comes from oxidising reactions.

These reactions involve the addition of oxygen to (or the removal of electrons from) a substance.

Examples include bacteria who obtain energy by converting:Ammonium ions (NH4

+) to nitrite ions (NO2-)

Nitrite (NO2-) ions to nitrate (NO3-)

Sulfide ions (S2-) to sulfate ions (SO42-)

Whole communities of heterotrophic organisms live around volcanic vents on the deep ocean floors where light does not penetrate. They rely directly or indirectly on chemosynthetic bacteria for their food supply in much the same way as terrestrial communities depend on plants to trap energy.

Chemosynthesis