Biology: Human Body and Metabolism

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Questions and Answers

What occurs to a molecule when it loses electrons during metabolism?

It becomes reduced.

It becomes oxidized. (correct)

It loses a negative charge.

It gains a positive charge. (correct)

What is the oxidized form of NAD when considering its electron state?

NAD-

NAD2+

NAD+ (correct)

NADH

In the process of cellular respiration, what happens to glucose?

It is oxidized to release energy. (correct)

It loses all its electrons.

It is reduced to release energy.

It remains unchanged.

What is produced from the energy captured during glucose oxidation?

ATP Signup and view all the answers

During cellular respiration, what is the ultimate fate of energy-poor electrons?

They are given to oxygen. Signup and view all the answers

What is the main purpose of ATP in cellular processes?

To store and release energy Signup and view all the answers

Which process is distinguished from substrate-level phosphorylation?

Electron transport chain Signup and view all the answers

What is the role of oxygen in cellular respiration?

It acts as the final electron acceptor Signup and view all the answers

Which of the following best describes endergonic reactions?

Reactions that absorb energy Signup and view all the answers

During which process is a proton gradient built across the inner mitochondrial membrane?

Electron transport chain Signup and view all the answers

What is the primary difference between catabolic and anabolic reactions?

Catabolic reactions break down molecules, whereas anabolic reactions build them up. Signup and view all the answers

What type of organisms perform lactic acid fermentation?

Some anaerobic bacteria and animal muscle cells Signup and view all the answers

Which component of ATP is primarily responsible for its ability to store energy?

The phosphate groups Signup and view all the answers

What are the starting materials for glycolysis?

glucose + 2 ATP + 2 NAD+ Signup and view all the answers

What is the main product of glycolysis?

2 pyruvate Signup and view all the answers

Where does pyruvate oxidation take place?

Mitochondrial matrix Signup and view all the answers

How many NADH are produced during the citric acid cycle for one glucose molecule?

6 NADH Signup and view all the answers

What is the ending material produced from pyruvate during pyruvate oxidation?

Acetyl Coenzyme A Signup and view all the answers

What is the main purpose of glycolysis?

To break down glucose and harvest energy Signup and view all the answers

What is the primary role of the pyruvate in cellular respiration?

To undergo oxidation in the mitochondria Signup and view all the answers

Which of the following occurs during the electron transport chain?

ATP is built as H+ re-enters the matrix Signup and view all the answers

How is ATP synthesized during the Krebs Cycle?

By substrate-level phosphorylation Signup and view all the answers

What initiates oxidative phosphorylation in cellular respiration?

Creation of a proton gradient by the ETC Signup and view all the answers

What is the net gain of ATP from glycolysis?

2 ATP Signup and view all the answers

Which statement about electron carriers is correct?

They transport high-energy electrons to chemical reactions Signup and view all the answers

What is the end result of cellular respiration as represented by the equation?

Carbon dioxide and water are formed with a release of energy Signup and view all the answers

What role does ATP synthase play in cellular respiration?

It converts ADP into ATP using energy from a proton gradient Signup and view all the answers

Which process describes the removal of energy-rich electrons from pyruvates?

Pyruvate oxidation Signup and view all the answers

Which component is NOT involved in oxidative phosphorylation?

Glycolysis Signup and view all the answers

What is the primary goal of fermentation in cells?

To regenerate the oxidized electron carrier NAD+ Signup and view all the answers

Which process occurs in mitochondrial locations during cellular respiration?

Electron Transport Chain Signup and view all the answers

What is the main byproduct of alcohol fermentation?

Ethanol Signup and view all the answers

Which statement about glycolysis is incorrect?

Glycolysis produces a significant amount of ATP directly. Signup and view all the answers

What roles do NADH and FADH2 play in cellular respiration?

They donate electrons to the Electron Transport Chain. Signup and view all the answers

Which of the following macromolecules cannot be catabolized in cellular respiration?

Nucleic acids Signup and view all the answers

What regulates the steps of cellular respiration?

pH change due to lactic acid buildup Signup and view all the answers

In the absence of oxygen, what would happen to most ATP production in a cell?

Glycolysis would occur but ATP production would stop. Signup and view all the answers

What is the direct function of the Electron Transport Chain in cellular respiration?

Oxidizing NADH back to NAD+ Signup and view all the answers

Which fermentation process yields lactic acid as a primary product?

Lactic acid fermentation in bacteria Signup and view all the answers

Study Notes

Why the Human Body Needs to Eat

Our bodies need to eat to obtain energy from food
This energy is stored in the chemical bonds of food molecules, primarily glucose
This energy is used to power cellular processes

Metabolism

Metabolism refers to all chemical reactions occurring within a living organism to maintain life
Metabolism encompasses two main categories:
- Catabolic reactions: break down larger molecules into smaller ones, releasing energy
- Anabolic reactions: build larger molecules from smaller ones, requiring energy

### Chemical Bonds

Chemical bonds are formed by electrons, which carry energy
The breaking and forming of these bonds releases or stores energy

### ATP & ADP

ATP (adenosine triphosphate) is the primary energy currency used by cells
It has three phosphate groups linked together.
The bond between the second and third phosphate groups holds a considerable amount of energy, making ATP suitable for energy storage
When this bond is broken, energy is released, and ATP becomes ADP (adenosine diphosphate)
The energy released from this bond is used to power various cellular processes, including muscle contraction, nerve impulse conduction, and protein synthesis.

### Endergonic & Exergonic Reactions

Endergonic reactions require energy input, often from the breakdown of ATP, to occur.
Exergonic reactions release energy, sometimes used to create ATP.

### Relationship Between Catabolic, Anabolic, Endergonic, and Exergonic Reactions

Catabolic reactions are typically exergonic, releasing energy.
Anabolic reactions are usually endergonic, requiring energy input.

Redox Reactions

Redox reactions involve the transfer of electrons between molecules.
Oxidation is the loss of electrons by a molecule.
Reduction is the gain of electrons by a molecule.
Redox reactions play a crucial role in cellular respiration, where glucose is oxidized, and oxygen is reduced.

### Cellular Respiration

Cellular respiration is the process by which cells break down glucose to generate energy in the form of ATP.
The overall chemical equation for cellular respiration is: C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + ~36 ATP
This process occurs in multiple steps within the cell:
- Glycolysis : Occurs in the cytoplasm
- Pyruvate oxidation : Takes place in the mitochondrial matrix.
- Citric Acid (Krebs) Cycle: Occurs in the mitochondrial matrix.
- Electron Transport Chain : Takes place in the inner mitochondrial membrane.

Substrate-level Phosphorylation

Involves the direct transfer of a phosphate group from a substrate molecule to ADP, forming ATP.
Occurs during glycolysis and the Citric Acid Cycle.

Chemiosmosis

A process that uses the energy stored in a proton gradient across a membrane to generate ATP.
Involves the movement of protons through ATP synthase, an enzyme embedded in the inner mitochondrial membrane.
The energy from this movement is used to drive the phosphorylation of ADP into ATP.

### Electron Carriers

Electron carriers are molecules that transport electrons from one location to another within the cell.
The energy carried by these electrons can be used to power various cellular processes
Important electron carriers in cellular respiration include NAD+ / NADH and FAD / FADH2.

### Glycolysis

Glycolysis is the initial stage of cellular respiration, where glucose is broken down into two molecules of pyruvate
It occurs in the cytoplasm of the cell
It does not require oxygen and is considered an anaerobic process
Starting materials: Glucose (C6H12O6) + 2 ATP + 2 NAD+
Ending products: 2 Pyruvate (C3H4O3) + 4 ATP - 2 ATP (net ATP = 2) + 2 NADH
Glycolysis generates ATP through substrate-level phosphorylation and produces NADH which can be further used in the electron transport chain

### Pyruvate Oxidation

The conversion of pyruvate to acetyl CoA occurs in the mitochondrial matrix.
Each pyruvate molecule is oxidized to form one molecule of acetyl-CoA.
Starting materials: 2 Pyruvate + 2 NAD+ + 2 Coenzyme A
Ending materials: 2 Acetyl CoA + 2 CO2 + 2 NADH
Pyruvate oxidation generates NADH, which is a crucial electron carrier

### Citric Acid (Krebs) Cycle

The Krebs cycle is a series of reactions that takes place in the mitochondrial matrix where acetyl-CoA is completely oxidized.
It is a cyclical process that starts with Acetyl-CoA and a 4-carbon molecule called oxaloacetate
Starting materials: 2 Acetyl CoA + 6 NAD+ + 2 FAD + 2 H2O
Ending materials: 4 CO2 + 2 ATP + 6 NADH + 2 FADH2 + 2 H2O
The Krebs cycle generates ATP through substrate-level phosphorylation, but its main contribution is the production of high-energy electron carriers (NADH and FADH2)

### Electron Transport Chain (ETC)

ETC occurs in the inner mitochondrial membrane.
The ETC is a series of protein complexes that accept electrons from NADH and FADH2
As electrons move down the ETC, they release energy that is used to pump protons across the inner mitochondrial membrane
This creates a proton gradient, a high concentration of protons in the intermembrane space and a low concentration in the mitochondrial matrix.

### Oxidative Phosphorylation

It is the process by which ATP is generated using the energy from a proton gradient.
This occurs through the movement of protons back across the inner mitochondrial membrane by an enzyme called ATP synthase
The energy from this movement drives the addition of a phosphate group to ADP, forming ATP.

### Role of Oxygen in Cellular Respiration

Oxygen is the final electron acceptor in the ETC
Oxygen is reduced to water, which is a byproduct of respiration.
Oxygen is essential for the ETC process.

### Fermentation

Fermentation is an anaerobic process that allows the cell to continue generating ATP without oxygen.
Its primary function is to regenerate NAD+ which is crucial for glycolysis.
There are two main types of fermentation:

### - Alcohol Fermentation

Used by yeast and some bacteria to regenerate NAD+
The end product is ethanol (alcohol) which is a byproduct.
It is used in baking and brewing

### - Lactic Acid Fermentation

Used by bacteria, fungi, and muscle cells.
Pyruvate is converted to lactic acid.
Used in the production of yogurt, cheese, and sourdough bread

### Regulation of Cellular Respiration

Cellular respiration is tightly regulated through feedback inhibition.
ATP levels play a major role in regulating respiration, as high levels of ATP inhibit some key enzymes involved in the process.
Other factors that can affect enzyme activity include pH changes.

### Other Macromolecules

While glucose is the primary energy source for cellular respiration, other macromolecules like fats and proteins can also be broken down to generate energy.
Some of these pathways are used for glucose metabolism, such as the Krebs cycle.

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Description

Explore the fundamental reasons why our bodies need to eat and the crucial role of metabolism in maintaining life. This quiz covers topics related to chemical bonds, energy storage, and the importance of ATP in cellular processes.