ENERGY CONVERSIONS IN LIVING THINGS

ENERGY AND METABOLISM

Energy is the capacity to do work.

What is energy?

Why do living organisms need energy?

Movement, growth, homeostasis, active transport, protein synthesis

Metabolism• Anabolic Catabolic

Basal metabolic rate : is the amount of energy that is needed by the basic body reactions , when at rest, after 12 hours of hunger.

Oxygen used or CO2 formed is measured.

Age, surface area, weight, hormones affect BMR.

• How do living organisms get their energy?

• How does a cell get its energy?

*Can you list the given molecules/elements from the least energized to the most?

Na

methane

glucose

Fatty acid

Light energy

PhotosynthesisATP energy (chemical bond )

Protein, Lipid and Carbohydrate synthesis

Aerobic and /or anaerobic cellular respiration

ATP energy (chemical bond )

Cellular work

By All living organsims

By Autotrophs (Chemical energy)

• CHEMICAL BOND ENERGY : Energy stored in the covalent bonds. So molecules in food store energy. Some organisms (autotrophs) produce their own food or chemical energy from light energy.

•

• During changes from one form of energy to another, some unusable energy dissipates, usually as heat. So the amount of usable energy decreases.

• In any system, the total energy includes the usable energy that can do work and the unusable energy that is lost

Total energy = usable + unusable energy energy

The first law: Energy can not be created or destroyed. In any conversion of energy from one form to another, the total energy before and after the conversion is the same.

The second law: Not all energy can be used, when energy is converted from one form to another, some of that energy becomes unavailable to do work. Therefore the amount of usable energy decreases

The Fundamental molecule of Energy (ATP )

ATP is a special nucleotide that contains Adenine ( purine nucleotide), Ribose( 5C pentose sugar ) , and 3 phosphate units

ADENINE RIBOSE P PP ~~

2 HIGH ENERGYPHOSPHATE BONDSGLUCOSIDE BOND

ESTER BOND

ATP is a source of chemical energy and the cell can use it easily and quickly.

ATP + water ADP+ Pi + Energy (7.3kcal)

Addition of a P group to ADP is called as Phosphorylation.Takes in energy (endergonic)

Removal of a P group from ATP is called as Dephosphorylation. Gives out energy (exergonic)

Which reactions in the living things are exergonic ? And endergonic?

Dephosphorylation

Phosphorylation

• Cells can use directly only ATP to get energy

• ATP can not be stored in the cell.• ATP can not pass across the cell

membrane.So each cell should produce its own ATP by respiration. Only viruses ?? can’t produce their own ATP

• Phosphorylation is a kind of dehydration. Dephosphorylation is a kind of hydrolysis

• ATP,provides the activation energy to begin the chemical reactions that in the cells. So it is needed in each living cell.

*

Activation Energy

* Active Transport * Biosynthesis reaction *

Movement

* Nerve transmission

• Dark reactions in photosynthesis

• ENDERGONIC• (take in energyfrom

ATP)

*Aerobic respiration

( with oxygen -38ATP)

*Anaerobic respiration

(without oxygen-2ATP)

*Light reactions in photosynthesis

EXERGONIC

(give out energy)

Phosphorylation Dephosphorylation

• There are 4 major ways that are used to synthesize ATP in living things :

• 1. Substrate Level Phosphorylation :

How? It is the P group transfer from an organic molecule to ADP with the help of only enzyme activity .

Where? Glycolysis (in aerobic and anaerobic respiration IN CYTOPLASM ), Krebs cycle IN MITOCHONDRIA (in aerobic respiration)

SLP can be seen in all living things. And O2 is not used.

• Substrate level phosphorylation

• 2. Oxidative Phosphorylation : How? It is the ATP synthesis during

the break down of organic molecules by aerobic respiration. Electrons that are derived from organic(food) molecules are carried by electron transport system ( ETS ) and with this energy ATP is produced

Where? Electron Transport system in Mitochondrial cristae (in aerobic respiration) . O2 is used as last electron acceptor and water is formed.

In prokaryotes it occurs in mesosomes.

• 3.Photophosphorylation: How? In photoautotrophs cells that

have chlorophyll absorb sunlight and they produce ATP by using ETS. But all these ATP is used during photosynthesis not in metabolic activities

Where? During light reactions in photosynthesis. (At thylakoid membrane- grana in chloroplast in eukaryotes.) In prokaryotes it occurs in the cell membrane foldings.

4. Chemosynthetic Phosphorylation: How? Some bacteria oxidize the inorganic molecules around such as H2S and NH3 , and by using the released chemical energy they synthesize ATP . Then they use ATP to make food so chemosynthetic bacteria are autotrophs.Where? Cytoplasm in chemosynthetic bacteria 2NH3 + 3O2 2HNO2+ 2H2O+Energy

ATP

• * Substrate Level Phosphorylation

* Oxidative phosphorylation

• In which reaction, the synthesized ATP can’t be used in biochemical reactions as active transport

• I. Substrate level phosphorylation• II.Oxidative phosphorylation• III.Photophosphorylation• IV.Kemophosphorylation • Answer :

• What is the main purpose of nutrition in living things ?

• I. Take in foods that is needed for respiration

• II. Storage of lipids to protect body from cold and injury

• III. Production of ATP during digestion

• Answer :

Al 106.5 Cells get energy from electrons “falling” from organic

fuels to oxygen• When the carbon-hydrogen bonds of glucose are broken, electrons are transferred to oxygen.

• More specifically, electrons from glucose or other food molecules are passed through a series of steps, releasing part of their energy in each step, and ultimately ending up attached to oxygen. The energy from the electrons going down the energy hill is used to create ATP from ADP and phosphate.

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6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen

• A cellular respiration equation is helpful to show the changes in hydrogen atom distribution– Glucose loses its hydrogen atoms and is

ultimately converted to CO2

– At the same time, O2 gains hydrogen atoms and is converted to H2O– Loss of electrons is called oxidation– Gain of electrons is called reduction

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CELLULAR RESPIRATION

• Cells obtain energy from glucose by the chemical process of oxidation, which is carried out through a series of metabolic pathways.

• Each reaction in a pathway is catalyzed by a specific enzyme

C6H12O6 + 6 O2

Glucose

Loss of hydrogen atoms(oxidation)

6 CO2 + 6 H2O + Energy

Gain of hydrogen atoms(reduction)

(ATP)

Why do we use cellular respiration ?

• Energy can be released from glucose by simply burning it. But this energy is dissipated as heat and light and is not available to living organisms.

• On the other hand, cellular respiration is the controlled (by enzymes) breakdown of organic molecules.

• Energy is– gradually released in small

amounts, – captured by a biological system,

and– stored in ATP.

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen

• Enzymes are necessary to oxidize glucose and other foods.

• NAD+ (Nicotinamide Adenine Dinucleotide)– is an important enzyme in oxidizing

glucose,– accepts electrons, and– becomes reduced to NADH.

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NAD+ + 2 H→NADH + H+ ReductionNADH + H++ 1⁄2 O2 → NAD++ H2O Oxidation

•FAD (Flavin Adenine Dinucleotide), is also involved in transferring electrons during glucose metabolism ( only in oxidative phosphorylation ) FAD + 2H → FADH2

Cellular respiration occurs in three main stages:1. Glycolysis

2. Krebs (citric acid cycle)3. Electron transport system (ETS) oxidative

phosphorylation

CELLULAR RESPIRATION

If there is oxygen products of glycolysis

enters

If there is NO oxygen products of glycolysis enters

fermentation

1. GYCOLYSIS• Glycolysis takes place

in the cytoplasm of all cells.Metabolic pathways are similar in all organisms, from bacteria to humans.

• That means we have common enzymes, genes and genetic ancestors.

Glucose

NAD+

+2

2 ADP

NADH2

P2

2

ATPNet 2 +

H+

2 PyruvateCH3COCOOH

• In glycolysis, a single molecule of glucose(6C) is enzymatically cut in half (3C) through a series of steps to produce two molecules of pyruvate (3C)– In the process, two molecules of ATP are used

to energize glucose– two molecules of NAD+ are reduced to two

molecules of NADH– At the same time, two molecules of ATP are

produced by substrate-level phosphorylation

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CH3COCOOH

Steps of Glycolysis1.Glucose is a stable molecule.

Therefore 2 ATP is used for activation of Glucose. Firstly glucose monophosphate then fructose monophosphate is formed. And fructose diphosphate forms which is unstable ( 6C- 2P)

2. 6C-2P compound is broken into two 3C-P (PGAL).

3. Electrons are transfered to 2 NAD ( reduced) and 2 NADH2 forms. Also free Pi molecules added where H departs and DPGA forms.

• 4. 2 phosphate groups of each 2 DPGA molecules detach and they are added to ADP molecules and forms 2 ATP by substrate level phosphorylation. PGA is formed.

• 5. 2 phosphate from 2 PGA detach and bind to ADP to form ATP.

• As a result 2 pyruvate (3C) are formed.Glucos

e2 Pyruvate

2 ATP 2 NADH+H+

CH3COCOOHC6H12O6

At the end of the Glycolysis : • Net energy gain is 2 ATP (4 ATP are formed by substrate

level phosphorylation but 2 ATP are used for activation of Glucose )

• 2 molecule pyruvate (3C)• 2 NADH2 forms• Glycolysis occurs in cytoplasm in

all cells and Oxygen isn’t used during the reaction !

Homework

• Draw steps of glycolysis to a cardboard.• Show each step and names.

You will have a quizz : (

At the end of the glycolysis of 2 maltose molecules

a.How many pyruvates are produced?

b.How many NADH+H+ molecules are formed?

c.What is the total ATP production ?

d.What is the net ATP gain?

• When oxygen is present (aerobic conditions), most organisms will undergo the following reactions.

• 1. oxidation of pyruvate.• 2. Krebs cycle• 3. Electron Transport System

In eukaryotes, these processes occur in the mitochondria(matrix and cristae), while in prokaryotes they occur in the cytoplasm and mesosomes(ETS) .

Oxidation of PyruvateFor a glucose molecule (2 Pyruvate ) :- 2 Acetyl CoA- 2 CO2

- 2 NADH+ H+ are produced

• All reactions occur in matrix of mitochondria. (cytoplasm in prokaryotes)

• Inputs of Krebs Cycle : • Acetate(2C) ( In the form of Acetyl CoA)• Water• Electron carriers ( NAD+ and FAD )• Outputs of Krebs Cycle : • 2 CO2

• Reduced electron carriers ( NADH2 , FADH2)

• Small amount of ATP for for 1 acetate.

KREBS CYCLE(CITRIC ACID CYCLE)

• 1. Acetyl-CoA separates from Co-A. The two-carbon acetyl group and 4-carbon oxaloacetic acid combine to form 6-carbon citric acid.

• 2. CO2 is released from 6C compound. 5C compound is produced. NAD is reduced to NADH2

• 3. CO2 is released from 5C compound. 4C compound is produced. NAD is reduced to NADH2 and also ATP is formed by substrate level phosphorylation

• 4. FAD is reduced to FADH2• 5. NAD is reduced and 4C oxaloacetic

acid is produced again

• Krebs Cycle :• For 2 Acetyl-CoA ( from 2

pyruvates or 1 glucose )• 4 CO2

• 2 ATP(Substrate level phosphorylation )

• 6 NADH + H+

• 2 FADH2 are formed

• Glycolysis, pyruvate oxidation and the citric acid cycle generate large amounts of reduced electron carriers ( NADH+H+ and FADH2 ) containing trapped energy. To activate this energy and produce ATP, something must happen to these reduced carriers.• ETS is the stage that the largest amount of ATPs and water are produced. • ATP molecules are produced by oxidative phosphorylation.• During these reactions NADH2 and FADH2 are oxidized.

ELECTRON TRANSPORT SYSTEM

Electron transport chain

–High-energy electrons (fromNADH and FADH2) jump from molecule to molecule in the ETC, losing small amounts of energy at each step. – The enzymes are embedded on the cristae from the highest energy level to the lowest .

NADH-Q reductase ubiqinoncyt. reductasecyt c cyt.oxidaseoxygen

–Chemiosmosis is the process by which energy is first used to generate a gradient of H+, and then captured in the bonds of ATP as H+ flows down its gradient

These reactions are formed in the cristae of the mitochondria in eukaryotes and mesosomes of prokaryotes.

• Electrons from NADH and FADH2 travel down the electron transport chain to O2.

• Oxygen picks up e’ and H+ to form water.

• Energy released by these redox reactions is used to pump H+ from the mitochondrial matrix into the intermembrane space.

• In chemiosmosis, the H+ diffuses back across the inner membrane through ATP synthase complexes, driving the synthesis of ATP.

Steps of ETS• 1.The electrons (from NADH2 and

FADH2 ) pass through a series of membrane- electron carriers called the respiratory chain or the electron transport chain.

• 2. The flow of electrons along the chain provides energy to active transport of protons across the inner mitochondrial membrane, out of the matrix, creating a proton concentration gradient.

3. The protons diffuse back into the mitochondrial matrix through a proton channel, which provides the synthesis of ATP.

• ATP synthetase is an enzyme found

in cristae membrane.

• H+ create a chemical potential

energy• The H+ pass

through a channel to the matrix and

produce ATP

• Electrons from NADH2 pass through a long ETS chain. Electrons from FADH2 pass through a shorter ETS. So the ATP produced from the e- of NADH2 is more than the e- of FADH2.

1 NADH2 3 ATP1 FADH2 2 ATP

ATP Production• During aerobic respiration the

energy ( ATP ) is produced by substrate level and oxidative phosphorylation

• By substrate level phosphorylation :

• During glycolysis 4 ATP molecules are produced. 2 of them used as activation energy of glucose so the net ATP gain is only 2 ATP

• During Krebs cycle 2 ATP molecules are produced

• By Oxidative Phosphorylation: • During glycolysis; 2 NADH+2H+

forms. If 2H atoms carried by NAD to ETS, 3 ATP molecules are produced , so 4H in 2NADH+2H+ provides 2x3=6 ATP

• During oxidation of pyruvate (Conversion of pyruvate to Acetyl-CoA) 2NADH+2H+ are forms. By 4H, 6 ATP molecules are synthesized in ETS

• During Krebs Cycle 12H atoms in 6NADH+6H+ produce 18 ATP , 4H atoms in 2FADH2 produce 2x2= 4 ATP

1 molecule of Glucose

SubstrateLevelPhosphorylation

ETS (Oxidative phosphorylation)

ATP FADH2 NADH+H+ Net yield

Glycolysis 2 2x3 8

Pyruvate- Acetyl- CoA

- - 2x3 6

KrebsCycle

2 2x2 6x3 24

Total 4ATP 4ATP 30ATP 38ATP

2NADH+H x 3 6 ATP Glycolysis ( Cytoplasm )

2NADH+H x 3 6 ATP Pyruvate-Acetyl-CoA(M)

6NADH+H x 3 18 ATP Krebs Cycle (M)

2FADH+H x 2 4 ATP Krebs Cycle ( M)

34 ATP

Water Formation

• The last e- acceptor is the OXYGEN in ETS . So at the last step of ETS Hydrogen couples that are carried by NAD and FAD combine with oxygen and produce water.

• NAD and FAD carry 24 H atoms so they can make 12 H2O but 6 water molecules are used during Krebs cycle so the net water yield is 6H2O

CO2 Formation ( in mitochondria )

• Pyruvate (3C) is oxidized to a Acetyl group (2C) and a CO2

molecule is released• During Krebs Cycle CO2 is released

between the convertion of 6C to 5C compound also 5C to 4C compound

• Therefore if a pyruvate produces 3CO2 2 pyruvates that are produced by glycolysis produce 6 CO2

CATABOLIC INTERCONVERSIONS

• Polysaccharides, lipids, and proteins can all be broken down to provide energy.

• Polysaccharides are hydrolyzed to glucose. Glucose then passes through glycolysis and the citric acid cycle, where its energy is captured in NADH2 FADH2.

Figure 6.15Food, such aspeanuts

Sugars Glycerol Fatty acids Amino acids

Aminogroups

OxidativePhosphorylation

CitricAcidCycle

PyruvateOxidation

Acetyl CoA

ATP

Glucose G3P PyruvateGlycolysis

Carbohydrates Fats Proteins

•Lipids are broken down into their monomers, glycerol and fatty acids. Glycerol is converted into PGAL and passes through glycolysis, and fatty acids are converted to acetate and then acetyl CoA in the mitochondria. •Proteins are hydrolyzed to their amino acids. The 20 different amino acids enter end of the glycolysis or the citric acid cycle at different points.

• What is the net ATP yield of a cell that uses 5 molecules fructose-mono phosphate in aerobic respiration ?

• How many ATP molecules are produced from 12 couple of H atoms carried by NAD+ , 4 couple of H atoms carried by FAD in aerobic respiration?

• 179 water molecules are using during hydrolysis of a polysaccharide, so how many ATP molecules can be produced from this polysaccharide by oxidative phosphorylation ?

• How many glucose and pyruvates should be used during formation of 42 ATP molecules by substrate level phosphorylation ?

• Fermentation is a way of harvesting chemical energy that does not require oxygen. Fermentation, like glycolysis, occurs in the cytoplasm.

• Fermentation– takes advantage of glycolysis,– produces two ATP molecules per glucose,

and– reduces NAD+ to NADH.

• The trick of fermentation is to provide an anaerobic path for recycling NADH back to NAD+. (to keep glycolysis running)

FERMENTATION

• Different types of fermentation are carried out by different bacteria and eukaryotic body cells. These different fermentation processes are named by the final product produced.

Alcoholic Fermentation• Certain yeasts,bacteria and

some plant seeds carry on a process called alcoholic fermentation under anaerobic conditions ( Beer,wine, vinegar )

• The baking and winemaking industries have used alcohol fermentation for thousands of years.

• In this process yeasts (single-celled fungi)– oxidize NADH back to NAD+ and– convert pyruvate (3C) to CO2 and ethanol (2C).

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Figure 6.13B

2 NAD

2 NADH

2 NAD

2 NADH

2 Ethanol

2 Pyruvate

Glucose

2 ADP

2 ATP

2 P

Gly

coly

sis

2 CO2

NADH2

NAD+

Pyruvate (3C)

CO2

Acetaldehyde (2C)

Ethyl Alcohol (2C)

C6H1206 +2ATP 2C2H5OH +2CO2 + 4ATP

• Firstly, CO2 is removed from pyruvate

and 2C compound acetaldehyde forms.• Second, the acetaldehyde is reduced

by NADH+H+ to producing NAD+ and ethyl alcohol(2C) (ethanol).

• If the amount of Ethyl alcohol becomes more than %18 it will be poisonous for the cells

• A yeast cell produces 10 molecules of CO2 by alcoholic fermentation. How many ATP should be used by the yeast cell for activation of glucose during glycolysis?

Lactic Acid Fermentation• It is seen in some bacteria and in

muscle cells of vertebrates and red blood cells during absence of oxygen

• Pyruvate is reduced to lactate (C3H6O3) -(3C compound) by adding to Hydrogens in NADH+H+

• No CO2 is released from the reaction

Figure 6.13A

2 NAD

2 NADH

2 NAD

2 NADH

2 Lactate

2 Pyruvate

Glucose

2 ADP

2 ATP

2 P

Gly

coly

sis

Lactic Acid

Pyruvate

Liver

Brain ( sleep center)Feeling tired

GlucoseAerobic respirationKrebs cycle

Glycogen

OXYGEN

• When there is enough oxygen lactate is carried by the blood to the liver, where it is converted back to pyruvate and oxidized in the mitochondria of liver cells.

• If a cell uses 10 molecule of Fructose-1,6-diphosphate during fermentation what is the net energy yield?

AIM: Oxidation of NADH2 . In that way glycolysis can proceed and

ATP can be formed.

Lactic acid fermentation

Ethyl alcohol fermentation

2 ATP 2 ATP

2 Lactic acid 2 ethyl alcohol,2 CO2

Muscle cells in vertebrates, bacteria,

Yeast, bacteria, plant

ANAEROBIC(Fermentation)

AEROBIC

Cytoplasm Cytoplasm and mitochondria

Products are organic (lactic acid, ethyl alcohol). Energy is kept in these molecules.

Products are inorganic (CO2 and H2O).

No ETS ETS exists. Large amounts of ATP is formed there by oxidative phosphorylation

ANAEROBIC(Fermentation)

AEROBIC

2 ATP net yield(2 ATP is used) by Substrate level phosphorylation

38 ATP net yield (2 ATP is used in glycolysis) (Substrate level ph. is in glycolysis and krebs cycle, Oxidative ph. in ETS)

ANAEROBIC (Fermentation)

AEROBIC

NAD is reduced and oxidized

NAD and FAD are reduced and oxidized

Last electron acceptor is pyruvate or acetaldehyde

Last electron acceptor is oxygen and water is formed.

CO2 is formed only in ethyl alcohol fermentation no water forms

CO2 and water forms

ATP synthesis depends on Substrate level phosphorylation

ATP synthesis depends on Substrate level p. andOxidative phosphorylation

REVIEW QUESTIONS

The role of oxygen gas in our cells is to

a. Catalyze reactions in glycolysis.

b. Produce CO2. c. Form ATP. d. Accept electrons from the

electron transport chain. e. React with glucose to split

water.

2. Oxidation and reduction

a. entail the gain or loss of proteins.

b. are defined as the loss of electrons.

c. are both endergonic reactions.d. always occur together.e. proceed only under aerobic

conditions

3. NAD+ is a. a type of organelle. b. a protein c. present only in mitochondria. d. a part of ATP. e. formed in the reaction that

produces ethanol.

4. Glycolysis a. takes place in the

mitochondrion. b. produces no ATP. c. has no connection with the

respiratory chain. d. is the same thing as

fermentation. e. reduces two molecules of NAD+

for every glucose molecule processed

5. Fermentation a.takes place in the

mitochondrion. b. takes place in all animal cells. c. does not require O2.

d. requires lactic acid. e. prevents glycolysis.

6. Which statement about pyruvate is not true?

a. It is the end product of glycolysis.b.It becomes reduced during fermentation.c. It is a precursor of acetyl CoA.d. It is a protein.e. It contains three carbon atoms.

7. The citric acid cyclea. takes place in the mitochondrion.b. produces no ATP.c. has no connection with the respiratory chain.d. is the same thing as fermentation.e. reduces two NAD+ for every glucose processed

8. The electron transport chaina. operates in the mitochondrial

matrix.b. uses proteins embedded within

a membrane.c. always leads to the production

of ATP.d. regenerates reduced

coenzymes.e.operates simultaneously with

fermentation.

9. Compared to anaerobic metabolism, aerobic breakdown of glucose produces

a. more ATP. b. more pyruvate. c. fewer protons for pumping in mitochondria. d. less CO2.

e. more oxidized coenzymes.

10. Which statement about oxidative phosphorylation is not true?

a. It is the formation of ATP by the respiratory chain.

b. It is brought about by the chemiosmotic mechanism.

c. It requires aerobic conditions. d. In eukaryotes, it takes place

in mitochondria. e. Its functions can be served

equally well by fermentation.