Biology [Chapter # 07]

 

UNIT# 07

BIOENERGETICS

Q. Define Bioenergetics.

BIOENERGETICS

The study of conversion of free energy into different forms by living organisms is called Bioenergetics.

Q. How does the energy transfer?

The energy is transferred through gain or loss of electrons during formation and breaking of chemical bonds. There are two chemical processes where it occurs, known with the name of oxidation and reduction.

In living organisms these oxidation - reduction (Redox) reactions occur continuously to transfer energy from one molecule to other molecule, without these reactions energy transfer becomes impossible in living system.

Q. What is Oxidation reaction and Reduction reaction? Describe with example.

OXIDATION REACTION

Those reactions in which loss of electron (e-) and proton occurs.

REDUCTION REACTION

Those reactions in which gain of electrons (e^-) and H⁺ occurs.

EXAMPLE

These electrons carry energy from the molecules from where they release to the molecules where they added e.g. iron reacts with oxygen to form a chemical called rust, in this reaction iron (Fe) loses some e- which transfer to oxygen. In this reaction Fe is oxidized and it transfers its energy to oxygen through electrons (the reduction takes place). This gain of e- also brings energy which is stored in it.

Q. What is photosynthesis?

PHOTOSYNTHESIS

Word photo means light and synthesis means to prepare.

Plants utilize simple inorganic molecules carbon dioxide (CO₂) and water (H₂O) which react by using light energy in the presence of pigments like Chlorophyll to form glucose and oxygen

EQUATION

Chlorophyll + Water       ⟶                   Glucose + Oxygen

6CO₂ + 6H₂O                      ⟶                   C₆H₁₂O₆ + 6O₂

Chlorophyll is the green pigment found in the chloroplast of higher plant cell. The fundamental molecule produced during photosynthesis is simple sugar i.e. Glucose.

Q. Describe Light reaction.

LIGHT REACTION

In this phase light energy is captured and converted into chemical energy. Some of the light is utilized to split water into oxygen and H with e- (electrons), this splitting of water is called Photolysis. H⁺ together with CO₂ are used in building Glucose.

In the thylakoid membrane other pigments and electron carrier molecules form highly organized assemblies in a series called photosystems. Each thylakoid contains thousands of copies of two different kind of photosystems called photosystems I and II. Each consists of two major parts, a light harvesting complex and an electron transport system.

The conversion of light energy takes places when the chlorophyll of reaction center receives energy. One of the electrons from chlorophyll “a” molecule leaves and jump over the electron transport system. This energized electron moves from one carrier to next. The electron releases energy, when it comes down, this energy drives reactions and produces two energy rich compounds. These are:

·        ATP (Adenosine Triphosphate)

·        NADPH₂ (Reduced Nicotinamide Adenosine Dinucleotide Phosphate)

ADP is the compound which is already present in cell. It combines with phosphate by using energy of photon released from when moving through e - carriers in photosynthesis.

ADP + P                                ATP

NADP also present in chloroplast is reduced into NADPH₂ by accepting Hydrogen ions (H₂), released from splitting of water.

NADP + 2 H⁺ 2e^-                NADPH₂

ATP and NADPH both are energy rich compounds which provide energy, Hydrogen (H⁺) and e^- for the conversion of atmospheric CO₂ into carbohydrates in chloroplast during light independent Phase of photosynthesis.

Q. Explain Dark reaction.

DARK REACTION

This phase of photosynthesis does not require energy of photon but also takes place in day simultaneously with the light reaction.

The ATP and NADPH₂ synthesized during the light dependent reaction are dissolved in stroma there, they provide energy to power the synthesis of Glucose from CO₂ and H₂O (i.e. H⁺ and e^- of water). This Phase occurs independently, without light as long as ATP and NADPH₂ are available.

Dark reaction occurs in set of reactions also called Calvin – Benson Cycle due to it’s discover or the C₃ (three Carbon Containing Compounds formed initially) Cycle. The C₃ Cycle requires:

1) CO₂ - normally from air some of it also comes from respiration

2) CO₂ Capturing Sugar - a Pentose Sugar.

3) Enzymes to catalyze all the reactions.

4) Energy from ATP and NADPH come from light dependent reaction.

Q. What is limiting factor?

LIMITING FACTOR

Rate of biochemical reaction depend on some factors which affect the rate are called limiting factor.

For example at low light intensity rate of photosynthesis increase continuously but at high light intensity the rate becomes constant.

Light intensity, Carbon dioxide concentration and temperature can all be limiting factors for the rate of photosynthesis.

Q. Define breathing and its phases.

BREATHING

Breathing can be define as the exchange of gases.

It is followed by two phases:

·        Inhalation: Intake of Oxygen gases

·        Exhalation: out take of Carbon dioxide gas     

Q. Define Respiration and its types.

RESPIRATION

Respiration is the chemical reaction takes place in cells to release energy from food.

OR

The breakdown of food molecules to release energy is called respiration.

Glucose + Oxygen Carbon dioxide + water + Energy

C₆H₁₂O₆ + 6O₂        ⟶       6CO₂ + 6H₂O + ATP

TYPES OF RESPIRATION

There are two types of respiration.

·        Anaerobic respiration

·        Aerobic respiration

ANAEROBIC RESPIRATION

The type of respiration which occurs in the absence of oxygen is called anaerobic respiration or fermentation.

It takes place in some bacteria, fungi, and endo-parasite and sometimes in animal.

There are two types of respiration.

·        Alcoholic fermentation

·        Acidic fermentation

Alcoholic fermentation

The bacteria and fungi respire aerobically but when they are deprived of oxygen they stop respiration aerobically and start respiring anaerobically instead, during this anaerobic respiration they produce ethyl alcohol with CO₂.

Glucose                    ⟶                   Ethanol + CO₂ + Some energy

C₆H₁₂O₆                    ⟶                   2C₂H₅OH + 2CO₂ + Some ATP

Acidic fermentation

In animals, when aerobic respiration is not enough to produce required energy they start anaerobic respiration. During this process glucose breaks down into a substance called lactic acid.

Glucose                    ⟶                   Lactic acid + some energy

C₆H₁₂O₆                    ⟶                   2C₃H₆O₃

A limited amount of energy is produced as compared to aerobic respiration but this is enough to power the athlete's muscles during start time of sprint. He experiences pain, this condition of pain is called Muscle fatigue. The lactic acid is produced in his muscles and bool stream.

 

Q. What do you know about importance of anaerobic respiration?

IMPORTANCE OF ANAEROBIC RESPIRATION

·        Organisms can survive without O₂ or can work for short period

·        Vinegars are organic acids that are produced commercially by acidic formulations.

·        Anaerobic respiration also produces ethyl alcohol

·        Baking industry is also based on it because anaerobic respiration produces CO₂ which gives fluffy and soft shapes to cakes and breads

AEROBIC RESPIRATION

The type of respiration which occurs in the presence of Oxygen to produce energy is called aerobic respiration.

The end products of aerobic respiration are CO₂ and H₂O.

Glucose + oxygen             ⟶       Carbon dioxide + water + Energy (36 ATP)

C₆H₁₂O₆ + 6O₂                    ⟶       6CO₂ + 6H₂O + 36 ATP

 

Q. Describe the mechanism of aerobic respiration.

MECHANISM OF AEROBIC RESPIRATION

Aerobic respiration occurs in three steps at different places in cell.

·        Glycolysis

·        Kreb’s cycle OR Citric acid cycle

·        Electron transport chain

GLYCOLYSIS

In this stage, a molecule of glucose (Six carbon sugar) is broken down into two molecules of pyruvic acid (three carbon acid). It does not require oxygen. It takes place in both aerobic and anaerobic respiration.

This splitting of glucose releases small amount of energy of glucose which is enough to generate 2 molecules of ATP. It occurs in cytosol.

KREB'S OR CITRIC ACID CYCLE

The second stage of aerobic respiration in which pyruvic acid produced during glycolysis enters the mitochondria where O₂ available.

Cellular 2 respiration uses this O₂ to break pyruvic acid completely into CO₂ and H₂O in a cyclic manner. During Kreb's Cycle some ATP produce and some coenzymes like NAD and FAD are reduced to NADH and FADH.

It takes place in matrix of mitochondria.

ELECTRON TRANSPORT CHAIN

The last stage of aerobic respiration in which NADH (Nicotinamide 2 Adenosine Di-nucleotide) and FADH2 (Flavinamide Adenosine Dinucleotide) are oxidized to produce ATP and H₂O.

It takes place at the cristae of mitochondria.

Q. Write down the usages of Respiration Energy in the body of Organisms.

USAGE OF RESPIRATION ENERGY IN THE BODY OF ORGANISMS

·        Formation of different molecules as well as large molecules from small molecules requires energy.

·        During cell division formation of large molecules like DNA and protein takes place which require energy

·        Movement of ions and molecules from low concentration to high concentration requires energy.

·        Movement of muscle requires energy which is produced from chemical energy, chemical energy converted into kinetic energy.

·        In higher animal's body temperature is maintained at constant level, this temperature maintenance requires energy of respiration.

Q. Differentiate between Photosynthesis and Respiration.

Photosynthesis	Respiration
Photosynthesis is the process where light energy converted in chemical energy.	Respiration is the process where chemical energy converted into energy of ATP.
It occurs only in chlorophyll containing organisms.	It occurs in all organisms.
It requires light sources i.e. occur only in the presence of light	It does not requires light source so occurs throughout the life.
It occurs in chloroplast.	It occurs in mitochondria.
The reactants are Carbon dioxide and water	Reactants are carbohydrates and oxygen usually.