Biology Chapter on Energy Requirements

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the main end product of lactic acid fermentation in muscle cells?

Acetic Acid

Carbon Dioxide

Ethanol

Lactate (correct)

What role does NADH play during lactic acid fermentation?

It is oxidized to NAD+. (correct)

It is converted into glucose.

It is utilized to create energy.

It is reduced to ethanol.

In alcohol fermentation, pyruvate is converted into which two substances?

Lactate and Oxygen

Acetic Acid and Ethanol

Glucose and Lactate

Ethanol and Carbon Dioxide (correct)

Which of the following is true about obligate anaerobes?

They cannot survive in the presence of oxygen. Signup and view all the answers

What happens to yeast when the alcohol concentration in wine reaches around 14%?

They die due to the toxic effects of ethanol. Signup and view all the answers

What is the primary purpose of cellular respiration?

To break down glucose and store energy in ATP Signup and view all the answers

Which of the following best describes the relationship between breathing and cellular respiration?

Breathing allows oxygen to be taken into the body for cellular respiration Signup and view all the answers

During cellular respiration, which of the following occurs?

Glucose is oxidized and oxygen is reduced Signup and view all the answers

How much ATP can be produced from one molecule of glucose during cellular respiration?

32 ATP molecules Signup and view all the answers

What percentage of the total energy available in glucose is stored as ATP during cellular respiration?

40% Signup and view all the answers

What is the role of hydrogen during the process of cellular respiration?

Hydrogen represents the electron donors in the oxidation process Signup and view all the answers

What effect does retinone have on the electron transport chain?

It inhibits ATP synthesis. Signup and view all the answers

What happens to the electrons during the breakdown of glucose?

They are transferred to oxygen, releasing energy Signup and view all the answers

Which process uses the energy from light to produce glucose?

Photosynthesis Signup and view all the answers

Which poison blocks the flow of protons through the ATP synthase channel?

Oligomycin Signup and view all the answers

Which statement best explains oxidation in the context of cellular respiration?

Oxidation is the loss of electrons from a molecule Signup and view all the answers

How many ATP molecules are typically produced from one NADH during oxidative phosphorylation?

2.5 ATP Signup and view all the answers

What is the primary role of oxygen in oxidative phosphorylation?

To act as an electron acceptor. Signup and view all the answers

Which poison acts as an uncoupler in the electron transport chain?

DNP Signup and view all the answers

What is the maximum ATP yield from glycolysis?

2 ATP Signup and view all the answers

Which of the following statements about fermentation is true?

The only ATP produced during fermentation is from glycolysis. Signup and view all the answers

What happens if oxygen is not present during cellular respiration?

Chemiosmosis cannot occur, leading to energy starvation. Signup and view all the answers

Which statement correctly describes the contribution of FADH2 in ATP production?

It generates enough energy to produce 1.5 ATP. Signup and view all the answers

What is the primary energy transformation that occurs in the citric acid cycle?

Substrate-level phosphorylation to produce GTP. Signup and view all the answers

What process is used to generate ATP during oxidative phosphorylation?

Chemiosmosis Signup and view all the answers

What is the end product of glycolysis?

2 molecules of pyruvate Signup and view all the answers

Which molecules bring electrons to the electron transport chain?

NADH and FADH2 Signup and view all the answers

What occurs as electrons move down the electron transport chain?

Energy is released and protons are pumped across the membrane Signup and view all the answers

What happens to the energy released from the breakdown of glucose during glycolysis?

It is stored in the form of NADH and ATP. Signup and view all the answers

What causes the H+ gradient in the mitochondria during oxidative phosphorylation?

The pumping of protons across the membrane Signup and view all the answers

What is substrate-level phosphorylation?

The direct transfer of a phosphate group to ADP from a substrate Signup and view all the answers

Which enzyme-catalyzed reactions occur during glycolysis?

10 different reactions occur, each catalyzed by a specific enzyme Signup and view all the answers

After glycolysis, what happens to the pyruvate molecules?

They move into the mitochondrion for further processing. Signup and view all the answers

How much ATP is generated from glycolysis?

2 ATP Signup and view all the answers

Which of the following statements about ancient prokaryotic cells is true?

They relied solely on glycolysis for energy generation. Signup and view all the answers

What are the initial products when fats are broken down for energy?

Fatty acids and glycerol Signup and view all the answers

During the process of protein digestion, what happens to the unused amino acids?

They are converted into glycolysis intermediates or citric acid cycle intermediates. Signup and view all the answers

What is the primary reason that glucose is not commonly found in our diet?

Our diet primarily consists of complex carbohydrates and fats. Signup and view all the answers

How does feedback inhibition function in cellular biosynthesis?

It inhibits an early enzyme in the synthesis pathway when an amino acid is abundant. Signup and view all the answers

What is the relationship between glycolysis and the citric acid cycle?

Glycolysis provides acetyl coA, which is essential for the citric acid cycle. Signup and view all the answers

Which of the following organic molecules can be processed to generate ATP?

Lipids, proteins, and starch Signup and view all the answers

What role do hydrolytic enzymes play in starch breakdown?

They break down starch to free glucose molecules. Signup and view all the answers

Why can animal cells not generate sugars from CO2 and H2O?

They cannot perform photosynthesis. Signup and view all the answers

Study Notes

Energy Requirements

Cells require energy to perform essential functions like growth, reproduction, material transport, movement, and maintaining structure.
Photosynthesis is the process that converts light energy from the sun into chemical energy stored in glucose and oxygen.
Organisms that conduct photosynthesis include bacteria, plants, and algae.

Cellular Respiration

Cellular respiration breaks down glucose and oxygen, produced by photosynthesis, to generate carbon dioxide and water.
It stores chemical energy in the form of ATP.
A small amount of energy is lost as heat during these conversions.

Breathing and Cellular Respiration

Breathing provides the oxygen needed for cellular respiration.
Respiration is the exchange of gases, where organisms obtain oxygen from their environment and release carbon dioxide as waste.
It is also defined as the aerobic harvesting of energy from food molecules by cells, distinguishing it from simply ‘breathing’.
Oxygen taken in during breathing enters the bloodstream and travels to all body cells, particularly muscle cells during physical activity.
These muscle cells utilize the oxygen in their mitochondria to generate ATP through cellular respiration.
This process provides the energy for muscle contraction and carbon dioxide is released as a waste product.

ATP as Energy Storage

Cellular respiration primarily generates ATP for cellular functions.
Glucose is a common energy source, but other organic molecules can also be utilized.
Energy is released as chemical bonds in glucose and oxygen break and reform into carbon dioxide and water.
This released energy is captured and stored in ATP.
Cellular respiration can produce up to 32 ATP molecules from a single glucose molecule.
The generated ATP represents only ~40% of the total energy available in a glucose molecule.
The remaining energy is lost as heat.

Bodily Functions that Utilize ATP

Breathing, maintaining a heartbeat, and regulating body temperature at 37°C require a constant supply of ATP.
Brain cells require an exceptional amount of energy, consuming about 120 grams of glucose per day and utilizing 15% of the body's total oxygen.
Approximately 75% of the total energy taken in each day is used to maintain basic life functions.
Voluntary activities, such as physical movement, are also powered by cellular respiration.

Energy Harvesting from Glucose

Chemical bonds within molecules store energy in the form of shared electrons.
These electrons are transferred to oxygen during cellular respiration, as C-H bonds in glucose are broken and H-O bonds in water are formed.
Oxygen attracts these electrons strongly, and as they move down a “staircase” from glucose to oxygen, lots of energy is released.
This energy is then captured and stored within the chemical bonds of ATP.
Glucose loses hydrogen atoms during its conversion to carbon dioxide.
Oxygen gains hydrogen atoms as it converts into water.
These hydrogen transfers represent electron transfers, as each hydrogen atom consists of one proton (H+) and one electron (e-).

Oxidation-Reduction Reactions

When electrons move from one molecule to another, it’s referred to as a redox reaction or oxidation-reduction reaction.
The loss of electrons from a molecule is called oxidation, and the atom that loses electrons is said to have been oxidized.
The gain of electrons by a molecule is called reduction, and the atom that gains electrons is said to have been reduced.
These reactions always occur together, requiring both a donor and recipient of electrons.
In cellular respiration, glucose loses electrons as H atoms and is oxidized, while oxygen gains electrons in the form of H atoms and is reduced.
During these hydrogen transfers, electrons lose potential energy, which is then released.

Oxidative Phosphorylation

Oxidative phosphorylation uses the electron transport chain and chemiosmosis to generate ATP.
NADH and FADH2, produced during stages 1, 2, and 3 of cellular respiration, carry electrons to the electron transport chain embedded within the inner mitochondrial membrane.
The majority of ATP produced during cellular respiration occurs during this step.
As electrons move down the chain from NADH and FADH2 to oxygen, they release large amounts of energy, which is used to phosphorylate ATP.

Electron transport Chain and Chemiosmosis

The electron transport chain is coupled to ATP synthesis.
As electrons move down the chain, energy is released and protons are pumped across the inner mitochondrial membrane into the intermembrane space.
This action creates a concentration gradient of H+ across the membrane, with a higher concentration of H+ between the two membranes than in the cytoplasm of the mitochondria.
Chemiosmosis then uses this H+ gradient to generate ATP by driving the diffusion of H+ through ATP synthases, protein complexes built into the inner mitochondrial membrane that synthesize ATP.

Glycolysis

Glycolysis represents the first stage of cellular respiration.
Literally meaning the splitting of sugar, this stage involves the breakdown of one glucose molecule into two pyruvate molecules.
This breakdown occurs over 10 chemical reactions, each catalyzed by a specific enzyme.
Glycolysis generates:
- 2 NADH + H+ from 2 NAD+
- 2 ATP, produced by substrate-level phosphorylation.

Substrate-level Phosphorylation

The direct transfer of a phosphate group from a substrate molecule to ADP, forming ATP.
This process is responsible for generating small amounts of ATP during the first and third stages of cellular respiration.
Following glucose breakdown in glycolysis, the released energy is stored in ATP and NADH.
The ATP is immediately available for use, but the NADH must first enter the electron transport chain within the inner mitochondrial membrane.
The majority of the energy available from glucose is still held within the two pyruvate molecules, which continue to be harvested in the citric acid cycle.

Pyruvate Preparation for the Citric Acid Cycle

The two pyruvate molecules formed at the end of glycolysis move from the cytoplasm into a mitochondrion.
Pyruvate enters the intermediate step, where it is converted into acetyl CoA.

Poisons that Inhibit Cellular Respiration

Retinone, used to kill insects and fish, binds to the first electron carrier in the electron transport chain.
It prevents electron transfer down the chain, inhibiting ATP synthesis and starving an organism's cells of energy.
Cyanide and carbon monoxide bind to the fourth electron carrier, blocking the flow of electrons to oxygen.
This prevents the generation of a proton gradient, halting ATP synthesis and starving cells of energy.

Other Substances that Inhibit Cellular Respiration

Oligomycin works by blocking the flow of protons through the H+ channel in ATP synthase.
It's used topically to treat fungal infections by inhibiting ATP production.
Uncouplers like DNP (dinitrophenol) make the mitochondrial membrane leaky to H+, depleting the proton gradient.
While electron transport continues, no ATP is synthesized.
Oxygen is still consumed, often at an accelerated rate.

Summary of ATP Production

Per one glucose molecule:
- Glycolysis: Produces 2 ATP in the cytoplasm.
- Citric Acid Cycle: Produces 2 GTP in the mitochondrial matrix.
- The above ATP equivalents are generated by substrate-level phosphorylation.
- The Electron Transport Chain and Chemiosmosis: Harvests energy from NADH and FADH2, generating approximately 28 ATP through oxidative phosphorylation.

NADH, FADH2, and ATP Calculation

Each NADH molecule transferring electron pairs to the electron transport chain is assumed to contribute enough protons to produce 2.5 ATP.
FADH2, entering the chain at a later point compared to NADH, is estimated to contribute to 1.5 ATP production.
These estimates represent theoretical maximums, and actual values can be slightly lower depending on factors like energy used for transport purposes.

Oxygen's Role in ATP Generation

The majority of ATP production from glucose (-28 ATP) occurs during oxidative phosphorylation, which depends on an adequate oxygen supply.
Oxygen is crucial as the final electron acceptor in the electron transport chain.
If oxygen is absent, chemiosmosis cannot occur, leading to cellular energy starvation and death.
Muscle cells can function for a limited time without oxygen, generating ATP through fermentation.

Fermentation

Fermentation is an anaerobic process that produces ATP only through glycolysis.
It generates 2 ATP by oxidizing glucose to 2 pyruvate molecules while reducing 2 NAD+ to 2 NADH.
The 2 ATP produced by fermentation is significantly less than the 32 ATP produced by oxidative phosphorylation.
This process helps maintain muscle contraction when oxygen delivery is insufficient to meet ATP demands.
Many microorganisms rely solely on fermentation to generate their energy.

Types of Fermentation

Lactic Acid Fermentation: Utilized by muscle cells and some bacteria, involves converting pyruvate to lactate.
This process regenerates NAD+ for glycolysis, but lactic acid buildup can lead to muscle fatigue.
Lactic acid is transported to the liver and converted back to pyruvate.
Widely used in the production of yogurt and cheese.
Alcohol Fermentation: Employed by yeast to produce wine, beer, and baking products.
It converts pyruvate to carbon dioxide and ethanol while regenerating NAD+ for glycolysis.
Carbon dioxide contributes to bubbles in champagne and beer and causes dough to rise.
Ethanol production can be toxic to the fermenting organism.

Evolution of Glycolysis

Glycolysis is a fundamental process found in all living cells, including bacteria, plants, fungi, and animals.
Early prokaryotic cells likely used glycolysis to generate all ATP before oxygen became prevalent in the atmosphere.
This process does not require membrane-bound organelles, which evolved much later than prokaryotic cells.

Utilizing Various Organic Molecules

While glucose is the starting point for glycolysis, it's not the most common dietary source of energy.
Lipids, proteins, starches, and disaccharides like glucose are readily available.
These molecules can also be used to generate ATP through a series of modifications before entering glycolysis.
Starches and glycogen are hydrolyzed to glucose by enzymes.
Proteins are broken down into amino acids, some of which are used for protein synthesis. Unused amino acids are converted into intermediates for glycolysis or the citric acid cycle.
Fats, containing a high energy content, are broken down into fatty acids and glycerol.
Glycerol is converted into a glycolysis intermediate, while fatty acids are broken down into acetyl CoA for the citric acid cycle.

Biosynthesis and Food Molecules

Not all food is digested solely for energy production but also provides building blocks for biosynthesis.
Cells require raw materials that can be synthesized to produce the organic molecules needed for life functions and cellular structures.
Amino acids from protein digestion can be directly used for protein synthesis.
Glycolysis intermediates are also used in biosynthesis after modification.

Cellular Respiration and Feedback Inhibition

Cellular respiration and biosynthesis are closely interconnected.
Feedback inhibition ensures the appropriate production of building blocks.
For example, if an amino acid is abundant, the pathway responsible for its production is turned off.
The end product inhibits a specific enzyme that works early in the pathway.
When the amino acid is depleted, the inhibition is lifted and production resumes.
Animals cannot convert carbon dioxide and water into sugars, but plants can, allowing them to photosynthesize.

Studying That Suits You

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

Description

Explore the fundamental concepts of energy requirements for cells, including photosynthesis and cellular respiration. This quiz will test your understanding of how organisms convert light energy into chemical energy and the role of breathing in respiration. Learn about the crucial processes that sustain cellular functions and energy transformation.