biology Chapter 9

how does energy flow through most ecosystems

Energy enters ecosystems primarily as sunlight and is captured by producers during photosynthesis. This energy is then transferred to consumers through the consumption of producers or other consumers. Ultimately, energy exits the ecosystem as heat.

What is the primary function of cellular respiration?

Cellular respiration is the process by which cells break down organic molecules, such as glucose, to generate ATP, the primary energy currency of the cell.

Describe the role of redox reactions in cellular respiration?

Redox reactions involve the transfer of electrons between molecules. In cellular respiration, glucose is oxidized (loses electrons), while oxygen is reduced (gains electrons). This electron transfer releases energy, which is used to generate ATP.

Why is NAD+ an important molecule in cellular respiration?

NAD+ acts as an electron carrier, accepting electrons from glucose during glycolysis and the citric acid cycle. Its reduced form, NADH, carries these electrons to the electron transport chain, where their energy is used to generate ATP.

What are the three main stages of cellular respiration?

glycolysis, citric acid cycle, and oxidative phosphorylation

What does glycolysis do?

breaks down glucose into two molecules of pyruvate

What does citric acid cycle do?

oxidizes pyruvate, generating NADH and FADH2

What does oxidative phosphorylation do?

utilizes the electrons from NADH and FADH2 to create a proton gradient, powering ATP synthesis.

Aerobic Respiration

A catabolic process that consumes oxygen to completely break down organic molecules and generate ATP.

Anaerobic Respiration

A catabolic process that uses an electron transport chain but does not rely on oxygen as the final electron acceptor.

ATP:

Adenosine triphosphate, the primary energy currency of the cell.

Catabolism

Metabolic pathways that break down complex molecules into simpler ones, releasing energy.

Chemiosmosis:

An energy-coupling process that uses the proton-motive force generated by the electron transport chain to drive ATP synthesis

Citric Acid Cycle

The second stage of cellular respiration, where acetyl CoA is oxidized, generating NADH, FADH2, and ATP.

Electron Transport Chain

A series of protein complexes embedded in the inner mitochondrial membrane that carries out electron transport and generates the proton-motive force.

Fermentation

An anaerobic process that regenerates NAD+ for glycolysis by transferring electrons from NADH to pyruvate or its derivatives.

Glycolysis

The first stage of cellular respiration, where glucose is broken down into pyruvate, generating ATP and NADH.

NAD+

Nicotinamide adenine dinucleotide, an electron carrier that accepts electrons during glycolysis and the citric acid cycle.

Oxidation

The loss of electrons from a molecule.

Oxidative Phosphorylation

The process of ATP synthesis powered by the proton-motive force generated by the electron transport chain.

Proton-Motive Force

The potential energy stored in the form of a proton gradient across a membrane, used to drive ATP synthesis.

Redox Reactions

Chemical reactions involving the transfer of electrons between molecules.

Reduction

: The gain of electrons by a molecule.

Substrate-Level Phosphorylation

The direct transfer of a phosphate group from a substrate molecule to ADP to form ATP

What is the main difference between substrate-level phosphorylation and oxidative phosphorylation?

Substrate-level phosphorylation directly transfers a phosphate group from a substrate molecule to ADP to form ATP. In contrast, oxidative phosphorylation generates ATP indirectly by utilizing the proton gradient created by the electron transport chain.

How is the electron transport chain involved in ATP synthesis?

As electrons are passed along the electron transport chain, energy is released, which is used to pump protons across the inner mitochondrial membrane, creating a proton gradient. This gradient drives ATP synthesis by ATP synthase through chemiosmosis.

What is the purpose of fermentation in the absence of oxygen?

Fermentation allows glycolysis to continue by regenerating NAD+ from NADH. This occurs by transferring electrons from NADH to pyruvate or its derivatives. This process enables ATP production in the absence of oxygen, albeit at a lower yield than aerobic respiration.

Compare and contrast the ATP yield of fermentation and aerobic respiration

Fermentation produces only 2 ATP molecules per glucose molecule through substrate-level phosphorylation. Aerobic respiration, however, yields up to 32 ATP molecules per glucose through both substrate-level and oxidative phosphorylation.

How do glycolysis and the citric acid cycle contribute to anabolic pathways?

Intermediates of glycolysis and the citric acid cycle can serve as precursors for the biosynthesis of other molecules, such as amino acids, fatty acids, and glucose. This demonstrates the interconnectedness of catabolic and anabolic pathways in cellular metabolism.