Bioenergetics and Energy Sources
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Questions and Answers

Which of the following statements about heterotrophs is true?

  • Heterotrophs obtain energy by consuming other organisms. (correct)
  • Heterotrophs can synthesize energy from inorganic substances.
  • Heterotrophs only include carnivores and herbivores.
  • Heterotrophs can produce their own food through photosynthesis.

What is the primary difference between photosynthesis and chemosynthesis?

  • Photosynthesis occurs in plants, while chemosynthesis occurs in animals.
  • Photosynthesis requires sunlight, while chemosynthesis occurs without sunlight. (correct)
  • Photosynthesis uses inorganic materials, while chemosynthesis uses sunlight.
  • Photosynthesis produces energy; chemosynthesis does not.

Which of the following best describes the classification of carnivores, herbivores, and omnivores?

  • They are groups based on the type of food they consume. (correct)
  • They are all omnivores that consume decaying matter.
  • They can all produce energy through photosynthesis.
  • They are types of saprotrophs.

In redox reactions, what happens to the atom that loses electrons?

<p>It is called the reducing agent. (C)</p> Signup and view all the answers

What is true about saprotrophic fungi?

<p>They obtain energy from decaying organic matter. (C)</p> Signup and view all the answers

Which type of organism relies solely on consuming plants for energy?

<p>Herbivores (A)</p> Signup and view all the answers

What characterizes the process of chemosynthesis?

<p>It can occur in extreme environments. (D)</p> Signup and view all the answers

Which of the following statements about redox reactions is accurate?

<p>They always happen together and involve electron transfer. (B)</p> Signup and view all the answers

What is the primary purpose of fermentation in cells?

<p>To generate ATP in the absence of oxygen (A)</p> Signup and view all the answers

Which of the following processes occurs during alcoholic fermentation?

<p>Pyruvate is converted to acetaldehyde (B)</p> Signup and view all the answers

What is the net gain of ATP from glycolysis before fermentation occurs?

<p>2 ATP (C)</p> Signup and view all the answers

Which product is formed as a result of lactic acid fermentation?

<p>Lactic acid (D)</p> Signup and view all the answers

How much ATP is theoretically produced from glucose during aerobic respiration?

<p>36-38 ATP (B)</p> Signup and view all the answers

What happens to NADH during fermentation?

<p>NADH donates electrons to pyruvate (B)</p> Signup and view all the answers

Which organisms are known to undergo lactic acid fermentation?

<p>Bacteria and Human muscle cells (A)</p> Signup and view all the answers

In the absence of oxygen, which compound does pyruvate produce in lactic acid fermentation?

<p>Lactic acid (D)</p> Signup and view all the answers

What is the modern definition of oxidation?

<p>Loss of electrons (B)</p> Signup and view all the answers

Which process do photosynthetic autotrophs use to produce food?

<p>Light energy (C)</p> Signup and view all the answers

What does ATP hydrolysis produce?

<p>ADP and phosphate (A)</p> Signup and view all the answers

What is the function of ATP in cells?

<p>Instant energy source (A)</p> Signup and view all the answers

Which combination of molecules makes up ATP?

<p>Adenine, ribose, three phosphate groups (D)</p> Signup and view all the answers

In the ATP cycle, what happens during phosphorylation?

<p>ADP gains a phosphate group (B)</p> Signup and view all the answers

What type of energy do chemosynthetic autotrophs utilize?

<p>Chemical energy from inorganic substances (A)</p> Signup and view all the answers

What is the significant result of the ATP-ADP cycle?

<p>Continuous energy supply for cellular functions (B)</p> Signup and view all the answers

What is a key characteristic of enzymes in the context of biological reactions?

<p>They serve as biological catalysts. (C)</p> Signup and view all the answers

What happens to enzymes when the temperature is too low?

<p>They will not work and get deactivated. (C)</p> Signup and view all the answers

Which of the following is NOT a property of VIPs (Very Important Proteins)?

<p>They can absorb light. (B)</p> Signup and view all the answers

What role do accessory pigments play in photosynthesis?

<p>They absorb additional wavelengths of light not absorbed by chlorophyll a. (D)</p> Signup and view all the answers

Which enzyme is known to be slow and has two substrates?

<p>RuBisCO (D)</p> Signup and view all the answers

Where are enzymes located in eukaryotic cells involved in photosynthesis?

<p>In the thylakoid membrane of chloroplasts (A)</p> Signup and view all the answers

Which statement about the denaturation of enzymes is true?

<p>Denaturation can happen due to excessive high temperatures. (D)</p> Signup and view all the answers

What are light harvesting complex pigments also referred to as?

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What is the first step of pyruvate oxidation?

<p>Addition of a water molecule to form citric acid (A)</p> Signup and view all the answers

During which process does pyruvate lose carbon dioxide and hydrogen ions?

<p>Transition step (C)</p> Signup and view all the answers

What molecule is formed when pyruvate combines with coenzyme A?

<p>Acetyl-CoA (C)</p> Signup and view all the answers

Which molecule carries electrons and hydrogen ions away after the oxidative decarboxylation of isocitrate?

<p>NADH (B)</p> Signup and view all the answers

What is the result of the conversion of isocitrate to alpha-ketoglutaric acid?

<p>Release of carbon atoms as CO2 (D)</p> Signup and view all the answers

What directly enters the Krebs cycle after the transition step?

<p>Acetyl-CoA (A)</p> Signup and view all the answers

Which compound is not directly usable by the cell for work?

<p>NADH (D)</p> Signup and view all the answers

What step generates a small amount of ATP during the Krebs cycle?

<p>Conversion of succinyl-CoA to succinate (A)</p> Signup and view all the answers

What is the primary function of succinyl CoA in the Krebs cycle?

<p>It is converted into succinic acid. (A)</p> Signup and view all the answers

What role does NADH play during cellular respiration?

<p>It carries electrons to the electron transport chain. (B)</p> Signup and view all the answers

What is produced when fumaric acid reacts with water?

<p>Malic acid (D)</p> Signup and view all the answers

How does the electron transport chain contribute to ATP production?

<p>By pumping protons across a membrane to create a gradient. (A)</p> Signup and view all the answers

What ensures the continuous operation of the Krebs cycle?

<p>The regeneration of oxaloacetic acid. (D)</p> Signup and view all the answers

Which of the following is a product of the oxidation of succinic acid?

<p>FADH2 (D)</p> Signup and view all the answers

What type of energy-carrying molecules are produced in the Krebs cycle?

<p>Both ATP and GTP (B)</p> Signup and view all the answers

Which molecules are organized into the electron transport chain complexes?

<p>Flavoproteins, quinones, iron-sulfur proteins, and cytochromes (A)</p> Signup and view all the answers

Flashcards

Bioenergetics

The study of how living things obtain and use energy.

Heterotrophs

Organisms that cannot make their own food and obtain energy by consuming other organisms.

Carnivores

Animals that eat other animals.

Herbivores

Animals that eat plants.

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Omnivores

Animals that eat both plants and animals.

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Fungi

Organisms that absorb nutrients from their environment, often from decaying matter.

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Photosynthesis

The process by which plants use sunlight to convert carbon dioxide and water into glucose (food) and oxygen.

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Chemosynthesis

The process by which some organisms (mainly bacteria) obtain energy by breaking down inorganic substances, without sunlight.

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Enzymes

Biological catalysts that speed up chemical reactions in living organisms.

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RuBisCO

A slow enzyme involved in photosynthesis, responsible for fixing carbon dioxide into organic molecules.

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ATP Synthase

An enzyme that generates ATP (energy currency) by using the flow of hydrogen ions across a membrane.

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Ferredoxin-NADP reductase

An enzyme that facilitates the transfer of electrons in photosynthesis, reducing NADP+ to NADPH.

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Light Harvesting Complex pigments

Pigments in photosystems that capture light energy and transfer it to chlorophyll a.

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Autotrophs

Organisms that can produce their own food using simple substances like light or chemical energy.

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Photosynthetic Autotrophs

Autotrophs that use light energy to make food. They include plants, algae, and some bacteria.

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Reaction Center chlorophyll a

The key pigment in a photosystem that undergoes a chemical change upon absorbing light energy.

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Optimum Temperature Range

The temperature range where an enzyme functions most efficiently.

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Chemosynthetic Autotrophs

Autotrophs that use chemical energy to make food.

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Oxidation

The loss of electrons from a substance.

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Denatured Enzyme

An enzyme that has lost its functional shape due to excessive heat, disrupting its ability to catalyze reactions.

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Reduction

The gain of electrons by a substance.

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ATP

Adenosine Triphosphate, an unstable, high-energy molecule that acts as an instant source of energy for cells.

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ATP Hydrolysis

The process of breaking down ATP into ADP and a phosphate group, releasing energy for the cell.

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Phosphorylation

The process of adding a phosphate group to a molecule, often using energy from ATP.

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Transition Step

A series of reactions that occur after glycolysis, where pyruvate is further oxidized and converted into acetyl-CoA, which enters the Krebs cycle.

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Oxidative Decarboxylation

A reaction that removes a carbon dioxide molecule, hydrogen ions, and electrons from a molecule, such as pyruvate during the transition step, and alpha-ketoglutarate in the Krebs cycle.

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Acetyl-CoA

The activated two-carbon compound formed during the transition step that enters the Krebs cycle, carrying its energy for further ATP production.

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Krebs Cycle

A series of reactions in the mitochondria that oxidizes acetyl-CoA, releasing carbon dioxide, electrons, and energy in the form of ATP, NADH, and FADH2.

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FADH2

Another molecule that carries high-energy electrons produced during the Krebs cycle, involved in ATP production through oxidative phosphorylation.

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Oxidative Phosphorylation

The process that utilizes the energy stored in NADH and FADH2 to generate ATP by transferring electrons through a series of protein complexes in the mitochondria.

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Fermentation

A metabolic process that produces ATP in the absence of oxygen, utilizing glycolysis to generate energy. It involves the reduction of pyruvate or its derivative by NADH to regenerate NAD+ for continued glycolysis.

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Glycolysis in Fermentation

Fermentation begins with glycolysis, a process that breaks down glucose into pyruvate, producing a net gain of 2 ATP molecules and 2 NADH molecules.

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NADH role in Fermentation

Unlike aerobic respiration, NADH in fermentation does not enter the electron transport chain. Instead, it directly reduces pyruvate or its derivative, regenerating NAD+ essential for sustaining glycolysis.

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Ethanol Fermentation

A type of fermentation where pyruvate is decarboxylated to acetaldehyde, which is then reduced by NADH to form ethanol. This process generates CO2 as a byproduct.

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Lactic Acid Fermentation

A type of fermentation where pyruvate is directly reduced by NADH, producing lactic acid (or lactate).

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ATP yield in Fermentation

Fermentation produces significantly less ATP (only 2 molecules) compared to aerobic respiration (36-38 ATP) because it relies solely on glycolysis and does not use the ETC for energy production.

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Organisms that use Fermentation

Various organisms, including bacteria (Lactobacillus, Streptococcus) and human muscle cells (under low oxygen conditions), utilize fermentation to produce ATP in the absence of oxygen.

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Fermentation's significance

Fermentation plays a vital role in sustaining glycolysis by regenerating NAD+ in the absence of oxygen, providing an alternative mechanism for ATP production.

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Succinyl CoA Conversion

Succinyl CoA is transformed into succinic acid (succinate) by adding a water molecule, releasing energy to produce ATP or GTP.

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FADH2 Formation

Succinic acid is oxidized into fumaric acid, a process that produces FADH2 by capturing hydrogen ions and electrons.

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Malic Acid Formation

Fumaric acid reacts with water to form malic acid (malate).

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OAA Regeneration

Malic acid is oxidized back into oxaloacetic acid (OAA) by removing hydrogen ions and electrons, reducing a NAD molecule to NADH.

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Electron Transport Chain (ETC)

A series of molecules, including flavoproteins, quinones, iron-sulfur proteins, and cytochromes, organized into four complexes. Electrons from NADH and FADH2 flow through the ETC, releasing energy to pump protons across a membrane.

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Proton Gradient

The ETC pumps protons across the membrane, creating a concentration difference (gradient). This gradient stores potential energy.

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Krebs Cycle Summary

The Krebs cycle is a series of reactions that oxidize glucose completely, producing ATP, GTP, NADH, and FADH2. It regenerates oxaloacetic acid, ensuring the cycle can continue.

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Study Notes

Bioenergetics

  • Branch of biology studying how living things obtain and use energy.

Heterotrophs

  • Cannot make their own food
  • Obtain energy and nutrients by consuming other organisms

Animals

  • Carnivores: Eat animals
  • Herbivores: Eat plants
  • Omnivores: Eat both plants and animals

Fungi

  • Do not consume food by eating
  • Absorb nutrients from their environment
  • Eat decaying organic matter

Autotrophs

  • Produce their own food using simple substances.
  • Photosynthetic: Use light energy (plants, algae, some bacteria), CO2, H2O to make glucose, O2
  • Chemosynthetic: Use chemical energy

Photosynthesis

  • 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O
  • Makes glucose, oxygen, and water
  • Two stages: Light Reactions, Calvin Cycle
  • Requires reactants (CO2 and H2O), energy (visible light), and photosynthetic pigments (chlorophyll).

Redox Reactions

  • Oxidation-Reduction: Always happen together.
  • Oxidation: Loss of electrons (or addition of oxygen)
  • Reduction: Gain of electrons (or removal of oxygen)
  • Important in energy transfer reactions

ATP (Adenosine Triphosphate)

  • Immediate source of energy for cells
  • Unstable molecule due to negatively charged phosphate groups
  • Broken down (hydrolyzed) to release energy

ATP-ADP Cycle

  • ATP → ADP + Pi + Energy (Hydrolysis)
  • ADP + Pi + Energy → ATP (Phosphorylation)

History

  • Adenosine from Adenine, Ribose (5-carbon sugar) and Triphosphate

Triphosphate

  • Alpha Phosphate Group: Attached to ribose
  • Beta Phosphate Group: Connected by a high-energy phosphoanhydride bond
  • Gamma Phosphate Group: Joined to Beta by a high-energy phosphoanhydride bond

Phosphoanhydride Bond

  • High-energy bond, stores energy
  • Unstable because of negatively charged phosphate groups

Photosynthetic Pigments

  • Chlorophyll a: Primary pigment in photosynthesis, absorbs red and blue light, reflects green light
  • Chlorophyll b: Accessory pigment, absorbs light that chlorophyll a cannot
  • Carotenoids: Accessory pigments, absorb blue and green light, reflect yellow, orange, and red light(beta carotene)

Photosystem

  • Contains chlorophyll a molecules and accessory pigments
  • Light-harvesting complex: Collects light energy
  • Reaction center: Chlorophyll a to initiate electron transfer.

Enzymes

  • Biological catalysts, speed up reactions
  • Sensitive to temperature and pH
  • RuBisCO: Enzyme for carbon fixation in the Calvin Cycle (slow enzyme with two substrates
  • ATP Synthase: Enzyme that produces ATP (through chemiosmosis)
  • Ferredoxin-NADP reductase: Enzyme to reduce NADP to NADPH

Factors Affecting Photosynthesis

  • Light intensity
  • Temperature
  • CO2 concentration
  • Water availability
  • Nutrient availability

Light Reactions

  • Occur in the thylakoid membrane.
  • Reactants: H2O, ADP, NADP+
  • Products: O2, ATP, NADPH

Optimal Temperature Range

  • Varies depending on the species
  • High temperatures can denature enzymes

Photophosphorylation

  • The process of making ATP using light energy. (This typically refers to the process in Photosynthesis)

Calvin Cycle

  • Occurs in the stroma of the chloroplast.
  • Uses ATP and NADPH from the light reactions
  • Converts CO2 into glucose
  • RuBisCO: Enz. that catalyzes rx. between CO2 and RuBP

Cellular Respiration

  • Aerobic Respiration: Involves glycolysis, Krebs (Citric Acid) Cycle, Electron Transport Chain
  • Anaerobic: Fermentation (Ethanol, Lactic Acid)
  • Breakdown of glucose to produce ATP

Glycolysis

  • Occurs in the cytoplasm (cytosol)
  • Glucose broken down into two pyruvate molecules
  • Two stages: Energy investment, Energy harvest
  • Net gain: 2 ATP, 2 NADH

Pyruvate Oxidation (Transition Step)

  • Pyruvate converts to Acetyl-CoA
  • CO2 is released
  • NAD+ is reduced to NADH

Krebs Cycle (Citric Acid Cycle)

  • Occurs in the mitochondrial matrix
  • Acetyl-CoA reacts with oxaloacetate to form citrate (6 carbon molecule)
  • Series of redox reactions
  • Produces ATP, NADH, FADH2, and CO2

Electron Transport Chain (ETC)

  • Located in the inner mitochondrial membrane
  • Electrons from NADH and FADH2 pass through complexes, releasing energy
  • Pumps H+ across the inner mitochondrial membrane
  • H+ gradient used by ATP synthase to produce ATP through chemiosmosis.

Fermentation

  • Anaerobic process when oxygen is unavailable
  • Regenerates NAD+ so glycolysis can continue
  • Ethanol and lactic acid fermentation.

Energy Yield

  • Theoretical yield: 36-38 ATP per glucose
  • Actual yield: Around 30 ATP per glucose.
  • Varies by species and specific conditions.

Anaerobic Respiration

  • Alternative respiration where electron acceptor is something other than oxygen (e.g., sulfate, nitrate)
  • Results in lower ATP yield than aerobic respiration

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Description

This quiz explores the various ways living organisms obtain and utilize energy, focusing on processes such as photosynthesis and the roles of different types of organisms like autotrophs and heterotrophs. Test your knowledge on the intricacies of bioenergetics and energy transformations within biological systems.

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