Biology Chapter 11: Bioenergetics

Questions and Answers

What carbon sources do aquatic photosynthetic organisms use?

Dissolved CO2, bicarbonates, and soluble carbonates

What is the atmospheric concentration of CO2?

0.03 - 0.04 percent

Stomata are responsible for the entry of CO2 into the leaves during photosynthesis.

True

What regulates the opening and closing of stomata?

Guard cells Signup and view all the answers

Which processes are part of photosynthesis?

Chemiosmosis Signup and view all the answers

What molecules are produced during light-dependent reactions?

ATP and NADPH Signup and view all the answers

Which type of molecule serves as the main energy carrier in cells?

ATP Signup and view all the answers

What is the primary function of the Calvin cycle in photosynthesis?

Synthesis of sugar from CO2 Signup and view all the answers

Which of the following enzymes is involved in the Calvin cycle?

Rubisco Signup and view all the answers

The dark reactions of photosynthesis can only occur in the presence of light.

False Signup and view all the answers

Match the following photosynthetic pigments with their associated functions:

Chlorophyll a = Primary pigment in photosystems Chlorophyll b = Accessory pigment Carotenoids = Protective pigments Signup and view all the answers

The process of energy synthesis in both cyclic and non-cyclic photophosphorylation is called ______.

Chemiosmosis Signup and view all the answers

What are the two main types of respiration in living organisms?

Aerobic and anaerobic respiration Signup and view all the answers

What is the end product of glycolysis?

Pyruvic acid Signup and view all the answers

What is bioenergetics?

The quantitative study of energy relationships and energy conversions in biological systems. Signup and view all the answers

Which of the following is a product of photosynthesis?

Oxygen Signup and view all the answers

Photosynthesis occurs both day and night.

False Signup and view all the answers

What is the function of chlorophyll in photosynthesis?

To absorb light energy Signup and view all the answers

What is the overall equation for photosynthesis?

6CO2 + 6H2O + light energy → C6H12O6 + 6O2 Signup and view all the answers

Plants release oxygen during ______.

photosynthesis Signup and view all the answers

What is the source of oxygen released during photosynthesis?

Water Signup and view all the answers

What is the role of NADPH in photosynthesis?

It acts as a reducing power to help convert carbon dioxide into sugar. Signup and view all the answers

What are accessory pigments in chloroplasts used for?

To broaden light absorption Signup and view all the answers

Chlorophyll a is the only pigment involved in the light-dependent reactions.

False Signup and view all the answers

Who proposed that water is the source of oxygen during photosynthesis?

Van Niel Signup and view all the answers

What does the absorption spectrum indicate?

It shows the relative abilities of different pigments to absorb various wavelengths of light. Signup and view all the answers

Photosynthesis contributes to the carbon dioxide concentration in the atmosphere.

False Signup and view all the answers

Chlorophyll is mainly located in the ______ of plant cells.

chloroplasts Signup and view all the answers

Which of the following chlorophylls absorbs mainly in the blue-green range?

Chlorophyll a Signup and view all the answers

Hydroponics are the plants grown in water culture.

True Signup and view all the answers

Calcium is an essential element for chlorophyll formation.

True Signup and view all the answers

Chlorosis means yellowing of leaves due to deficiency of certain essential elements of plant nutrition.

True Signup and view all the answers

List four features of a leaf which show that it is able to carry out photosynthesis effectively.

Thin structure, large surface area, presence of chlorophyll, and stomata for gas exchange. Signup and view all the answers

Summarise the role of water in photosynthesis.

Water provides electrons and protons, and is a reactant in the light-dependent reactions. Signup and view all the answers

What are T.W. Engelman and Melvin Calvin famous for?

T.W. Engelman is known for his work on photosynthesis and Melvin Calvin is famous for the Calvin cycle. Signup and view all the answers

What is the difference between an action spectrum and an absorption spectrum?

An action spectrum shows the rate of photosynthesis at different wavelengths, while an absorption spectrum shows which wavelengths are absorbed by pigments. Signup and view all the answers

What is the role of accessory pigments in light absorption?

Accessory pigments assist in capturing light energy and transferring it to chlorophyll. Signup and view all the answers

When and why is there not a net exchange of CO2 and O2 between the leaves and the atmosphere?

There is no net exchange during the night when photosynthesis halts but respiration continues. Signup and view all the answers

What is the net production of ATP during glycolysis?

The net production of ATP during glycolysis is 2 ATP molecules. Signup and view all the answers

What is the main difference between photophosphorylation and oxidative phosphorylation?

Photophosphorylation uses light energy to add a phosphate group to ADP, while oxidative phosphorylation uses the energy released by the electron transport chain. Signup and view all the answers

What is the location of the electron transport chain (ETC) and chemiosmosis in photosynthesis and cellular respiration?

In photosynthesis, it occurs in the thylakoid membrane; in cellular respiration, it occurs across the inner mitochondrial membrane. Signup and view all the answers

How did the evolution of photosynthesis affect the metabolic pathway?

It introduced the ability to convert light energy to chemical energy, altering energy dynamics on Earth. Signup and view all the answers

How does the absorption spectrum of chlorophyll a differ from that of chlorophyll b?

Chlorophyll a absorbs light primarily in the blue-violet and red parts of the spectrum, while chlorophyll b absorbs light in the blue and orange-red wavelengths. Signup and view all the answers

Why are the carotenoids usually not obvious in the leaves?

Carotenoids are masked by chlorophyll, which dominates in green leaves. Signup and view all the answers

How is the formation of vitamin A linked with the eating of carrots?

Carrots contain beta-carotene, which the body converts into vitamin A. Signup and view all the answers

Explain the roles of NAD+ and FAD in aerobic respiration.

NAD+ and FAD act as electron carriers, transporting electrons to the electron transport chain. Signup and view all the answers

Summarise how much energy (as ATP) is made available to the cell from a single glucose molecule by glycolysis, the formation of acetyl CoA, the citric acid cycle, and the electron transport chain.

Approximately 36 to 38 ATP molecules are produced from one glucose molecule through these processes. Signup and view all the answers

Trace the fate of hydrogen atoms removed from glucose during glycolysis when oxygen is present in muscle cells; compare this to the fate of hydrogen atoms removed from glucose when oxygen is insufficient to support aerobic respiration.

When oxygen is present, hydrogen atoms are used in the electron transport chain; when insufficient oxygen is available, they are converted to lactic acid. Signup and view all the answers

Sketch Krebs cycle and discuss its energy yielding steps.

The Krebs cycle involves several steps where acetyl CoA is oxidized, resulting in ATP, NADH, and FADH2 production. Signup and view all the answers

Describe various steps involved in oxidative breakdown of glucose to pyruvate.

The steps include glycolysis, oxidation of pyruvate to acetyl CoA, and entry into the Krebs cycle. Signup and view all the answers

Sketch respiratory electron transport chain. Discuss the significance of ETC.

The ETC is a series of proteins where electrons are transferred, leading to ATP synthesis via chemiosmosis. Signup and view all the answers

Compare photosynthesis with respiration in plants.

Photosynthesis converts light energy into chemical energy, while respiration breaks down glucose to release energy. Signup and view all the answers

Explain the difference between cyclic and non-cyclic photophosphorylation with the help of the Z scheme.

Cyclic photophosphorylation produces ATP only, while non-cyclic produces ATP and NADPH. Signup and view all the answers

Give an account of light-independent reactions of photosynthesis.

Light-independent reactions (Calvin cycle) use ATP and NADPH to convert CO2 into glucose. Signup and view all the answers

Study Notes

Bioenergetics Overview

Bioenergetics studies energy relationships and conversions in biological systems, adhering to thermodynamics.
All living organisms require free energy for survival, sourced primarily from solar energy.
While organisms can't use sunlight directly, they utilize chemical energy from food, like sugars.

Photosynthesis

Photosynthesis converts low-energy inorganic carbon (CO2) and hydrogen (water) into high-energy carbohydrates (glucose) using light energy, primarily through chlorophyll.
Overall photosynthesis equation:
6CO2 + 12H2O + light → C6H12O6 + 6O2 + 6H2O
Photosynthesis produces glucose and oxygen, while respiration uses products of photosynthesis.
Photosynthesis occurs only during daylight, contra respiration which happens day and night.

Compensation Point

At twilight, the rates of photosynthesis and respiration may equal, resulting in no net gas exchange; termed the compensation point.
Increased light intensity boosts photosynthesis, leading to higher CO2 demand, and oxygen release surpasses cellular respiration needs.

Source of Atmospheric Oxygen

Oxygen produced during photosynthesis derives from the splitting of water, confirmed through isotopic tracer experiments involving heavy oxygen (O18).

Chloroplasts

Chloroplasts, located in the mesophyll cells of leaves, are the primary sites for photosynthesis.
Each chloroplast contains thylakoids where light reactions occur and stroma for the dark reactions.
Chlorophylls embedded in thylakoid membranes absorb sunlight, generating ATP and NADPH.

Photosynthetic Pigments

Pigments absorb specific visible light wavelengths (380-750 nm); chlorophylls are the main pigments.
Accessory pigments, like carotenoids, broaden light absorption spectrum, protecting chlorophyll from excess light.
Absorption spectrum for chlorophyll peaks at blue (~430 nm) and red (~670 nm) wavelengths.

Light as Energy Source

Light is electromagnetic energy crucial for photosynthesis, but only about 1% is absorbed by leaves.
Action spectrum studies show that photosynthesis is most effective where chlorophyll absorbs light, though carotenoids enhance energy transfer.

Role of Carbon Dioxide

CO2 is essential for photosynthesis; terrestrial plants utilize atmospheric CO2, while aquatic organisms use dissolved forms.
Stomata regulate CO2 intake, opening during the day and closing at night, influenced by guard cells' structure and rhythm.

Reactions of Photosynthesis

Photosynthesis is a redox process composed of light-dependent (light) and light-independent (dark) reactions.
Light-dependent reactions harness sunlight directly, while dark reactions utilize products of the light phase (ATP and NADPH) to convert CO2 into sugars.### Photosynthesis Overview
Photosynthesis consists of light-dependent reactions (energy conversion) and light-independent reactions (energy conservation) that convert light energy into chemical energy stored in glucose.
Light-dependent reactions convert solar energy into ATP and NADPH, which provide power for the synthesis of sugars in the Calvin cycle.

Light-Dependent Reactions

Occur in thylakoid membranes, where photosynthetic pigments absorb sunlight, organized into photosystems (PS I and PS II).
PS II absorbs light at 680 nm (P680), while PS I absorbs at 700 nm (P700).
Light energy excites electrons in chlorophyll at the reaction centers, initiating electron transport.
The primary electron acceptor captures excited electrons from chlorophyll, leading to ATP production via chemiosmosis.
Non-cyclic electron flow involves both photosystems, producing ATP and NADPH and releasing oxygen from photolysis of water.
Cyclic electron flow involves only PS I and generates ATP but no oxygen or NADPH.

Photophosphorylation

ATP synthesis occurs during the light-dependent reactions driven by light energy.
Non-cyclic photophosphorylation produces ATP through a series of redox reactions involving electron transport chains and protons (H+) gradients in thylakoid membranes.

Light-Independent Reactions (Calvin Cycle)

Occur in the stroma of chloroplasts, using ATP and NADPH from light reactions to convert carbon dioxide into sugars.
The process consists of three stages: Carbon Fixation, Reduction, and Regeneration of RuBP.
Carbon fixation incorporates CO2 into ribulose bisphosphate (RuBP) via Rubisco, forming a 6-carbon intermediate that splits into two 3-carbon molecules (3-PGA).
Reduction converts PGA into glyceraldehyde 3-phosphate (G3P) using ATP and NADPH, yielding one net G3P for every six produced.
Regeneration of RuBP occurs with the rearrangement of G3P molecules, allowing the cycle to continue.

Respiration

Respiration is the metabolic process that provides energy to cells by breaking down carbon compounds.
Involves both external respiration (gas exchange) and cellular respiration (energy production).
Cellular respiration can be aerobic (with oxygen) or anaerobic (without oxygen).
Glycolysis splits glucose into pyruvate in the cytosol; oxygen availability determines the next steps.

Anaerobic Respiration

Alcoholic fermentation converts pyruvic acid into alcohol and CO2 in yeast.
Lactic acid fermentation converts pyruvic acid into lactic acid in anaerobic conditions, such as intense muscle activity.
Both fermentation pathways yield small energy amounts from glucose compared to aerobic respiration.

Role of Mitochondria

Mitochondria serve as cellular powerhouses, responsible for ATP production through respiration processes.
They have an outer membrane and an inner membrane organized into cristae, creating compartments that facilitate energy transfer via enzymes.

Adenosine Triphosphate (ATP)

ATP is a key energy carrier in cells, composed of adenine, ribose, and three phosphate groups.
The terminal phosphate bond releases energy (approximately 7.3 Kcal) upon hydrolysis, essential for various cellular processes like muscle contraction and active transport.

Biological Oxidation & Cellular Respiration

Biological oxidation involves energy-releasing reactions, primarily through oxidation-reduction processes.
Cellular respiration stages include glycolysis (anaerobic), pyruvic acid oxidation, Krebs cycle, and the respiratory chain (aerobic).
Glycolysis occurs in the cytosol, while subsequent stages occur in mitochondria, requiring oxygen for efficiency.### Glycolysis
Glycolysis breaks down glucose into pyruvic acid in both aerobic and anaerobic conditions.
It occurs in the cytosol and involves a series of enzyme-catalyzed steps.
ATP and NAD (nicotinamide adenine dinucleotide) are essential for glycolysis.
Divided into two phases: preparatory phase and oxidative phase.

Preparatory Phase

The first step involves transferring a phosphate from ATP to glucose creating glucose-6-phosphate.
Glucose-6-phosphate is converted into fructose-6-phosphate.
Another ATP adds a second phosphate, forming fructose 1,6-bisphosphate.
Fructose 1,6-bisphosphate splits into two three-carbon molecules: G3P and dihydroxyacetone phosphate (DHAP).

Oxidative Phase

PGAL (3-phosphoglyceraldehyde) is oxidized, transferring electrons to NAD, forming NADH.
Inorganic phosphate adds to PGAL, producing 1,3-bisphosphoglycerate (BPG).
A phosphate from BPG transfers to ADP, forming ATP and producing 3-phosphoglycerate (3-PG).
3-PG is further processed into 2-phosphoglycerate (2-PG), which transforms into phosphoenolpyruvate (PEP).
PEP donates its phosphate to ADP, yielding ATP and resulting in pyruvate.

Pyruvic Acid Oxidation

Pyruvate is converted into acetic acid (2-carbon) through decarboxylation, releasing CO2.
Acetic acid binds with coenzyme-A to form acetyl CoA.
Hydrogen atoms are transferred to NAD during this conversion.

Krebs Cycle (Citric Acid Cycle)

Acetyl CoA enters the Krebs cycle, combining with oxaloacetate to produce citrate (6-carbon).
The cycle involves a series of reactions, including the production of isocitrate and further oxidations.
Decarboxylation occurs, yielding a-ketoglutarate.
ATP is synthesized from the energy changes during the conversion of a-ketoglutarate to succinate.
Succinate is oxidized to fumarate, with FAD reducing to FADH2.

Completion of the Krebs Cycle

Fumarate converts to malate through hydration.
Malate undergoes another oxidation to regenerate oxaloacetate, completing the cycle.

Respiratory Chain and Oxidative Phosphorylation

NADH and H+ produced in the Krebs cycle transfer electrons to the respiratory chain.
Coenzyme Q and cytochromes aid in electron transport and oxidation-reduction reactions.
Electrons ultimately reduce oxygen, forming water and enabling ATP synthesis via oxidative phosphorylation.

Oxidative Phosphorylation Mechanism

Occurs within the inner mitochondrial membrane through chemiosmosis.
Proton movement across the membrane drives ATP synthesis.
Each pair of H atoms entering the chain yields three ATP molecules.

Other Key Points

Hydroponics refers to plants grown in nutrient-rich water solutions.
Calcium is critical for chlorophyll formation and overall plant health.
Chlorosis is a condition of yellowing leaves due to nutrient deficiency.

Energy Yield Summary

Glycolysis, formation of acetyl CoA, Krebs cycle, and electron transport chain release total ATP from a single glucose molecule.
Comparison of conditions with sufficient and insufficient oxygen availability influences hydrogen atom fate during respiration.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the concepts of bioenergetics in this quiz, focusing on the quantitative study of energy relationships and conversions in biological systems. Understand how organisms rely on free energy to remain functional, all while adhering to the principles of thermodynamics.