chapter 9+39

Question 1

What are the three major stages of cellular respiration?

Answer 1

Glycolysis, Pyruvate Oxidation & Citric Acid Cycle, and Oxidative Phosphorylation.

Question 2

Where does glycolysis occur and what does it produce?

Answer 2

Glycolysis occurs in the cytosol and produces 2 pyruvate molecules, 2 ATP, and 2 NADH.

Question 3

What happens during pyruvate oxidation?

Answer 3

Pyruvate is converted into acetyl CoA, producing NADH and releasing CO2.

Question 4

What are the main products of the citric acid cycle per glucose molecule?

Answer 4

6 NADH, 2 FADH2, 2 ATP, and 4 CO2.

Question 5

What is the role of the electron transport chain in cellular respiration?

Answer 5

It transfers electrons from NADH and FADH2 to oxygen, creating a proton gradient that drives ATP synthesis.

Question 6

How does chemiosmosis contribute to ATP production?

Answer 6

Protons flow back into the mitochondrial matrix through ATP synthase, driving the conversion of ADP to ATP.

Question 7

What is the net ATP yield from one molecule of glucose after cellular respiration?

Answer 7

Approximately 32 ATP.

Question 8

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

Answer 8

Substrate-level phosphorylation directly transfers a phosphate group to ADP to form ATP, while oxidative phosphorylation uses energy from the electron transport chain to drive ATP synthesis.

Question 9

What is etiolation in plants?

Answer 9

Etiolation is the growth adaptation of plants in darkness, characterized by pale stems, unexpanded leaves, and reduced root systems.

Question 10

What triggers de-etiolation in plants?

Answer 10

Exposure to light triggers de-etiolation, leading to stem elongation slowing, leaf expansion, and chlorophyll production.

Question 11

What is the role of phytochrome in plant signaling?

Answer 11

Phytochrome is a light receptor that detects light and initiates the de-etiolation process.

Question 12

How do second messengers like cGMP and Ca²⁺ function in plant signal transduction?

Answer 12

They amplify the signal received by phytochrome, leading to various cellular responses.

Question 13

What are the two main mechanisms of enzyme activity regulation in response to light signals?

Answer 13

Transcriptional regulation (changes in mRNA levels) and post-translational modification (phosphorylation of proteins).

Question 14

What is the function of protein kinases in signal transduction?

Answer 14

Protein kinases phosphorylate specific proteins, altering their activity and triggering cellular responses.

Question 15

What is the role of protein phosphatases in signal transduction?

Answer 15

Protein phosphatases remove phosphate groups from proteins, turning off the signal transduction pathway.

Question 16

How do transcription factors regulate gene expression in response to light?

Answer 16

They are activated by phosphorylation and either enhance or inhibit the transcription of specific genes.

Question 17

Polymers are made of monomer subunits that are joined by what type of bonds?

Answer 17

Polymers are made of monomer subunits that are joined by covalent bonds. These bonds are formed through dehydration reactions, where a water molecule is removed as the bond is created. This process is catalyzed by enzymes and is essential for the formation of macromolecules such as proteins, nucleic acids, and polysaccharides.

Question 18

Which four chemical elements are used in the cell to form fatty acids and carbohydrates?

Answer 18

The four chemical elements used in the cell to form fatty acids and carbohydrates are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). These elements are fundamental building blocks for organic molecules. Carbon forms the backbone of these molecules, hydrogen and oxygen are involved in forming hydroxyl groups and water, and nitrogen is essential for amino acids and nucleotides.

Question 19

Lipids cannot be considered polymers because:

Answer 19

they contain polar covalent bonds.
their structure includes carbon rings.
they can be artificially created.
they are not composed of monomer subunits. Answer: Lipids cannot be considered polymers because they are not composed of monomer subunits. Unlike proteins, nucleic acids, and polysaccharides, which are made up of repeating monomer units, lipids are formed from a variety of smaller molecules, such as glycerol and fatty acids, that do not form long chains of repeating units.

Question 20

All lipids have in common that they:

Answer 20

are made from glycerol and fatty acids.
contain nitrogen.
have low energy content.
do not dissolve well in water. Answer: All lipids have in common that they do not dissolve well in water. This hydrophobic property is due to the nonpolar nature of their hydrocarbon chains, which do not interact favorably with water molecules. This characteristic is crucial for the formation of cell membranes, where lipids create a barrier that separates the aqueous interior of the cell from the external environment.

Question 21

What is the role of calcium ions (Ca²⁺) in signal transduction pathways?

Answer 21

Calcium ions (Ca²⁺) act as second messengers in signal transduction pathways. They are involved in various cellular processes, including muscle contraction, secretion, and cell division. When a signal is received, calcium channels open, allowing Ca²⁺ to flow into the cytoplasm from the extracellular space or internal stores like the endoplasmic reticulum. The increase in cytosolic Ca²⁺ concentration activates various proteins and enzymes, leading to a cellular response.

Question 22

How do G protein-coupled receptors (GPCRs) function in cell signaling?

Answer 22

G protein-coupled receptors (GPCRs) function in cell signaling by transmitting signals from extracellular molecules to intracellular pathways. When a ligand binds to a GPCR, it causes a conformational change in the receptor, activating an associated G protein by exchanging GDP for GTP. The activated G protein then interacts with other proteins or enzymes in the cell, triggering a cascade of events that lead to a specific cellular response. GPCRs are involved in many physiological processes, including sensory perception, immune response, and hormone signaling.

Question 23

What is the significance of the citric acid cycle in cellular respiration?

Answer 23

The citric acid cycle, also known as the Krebs cycle, is significant in cellular respiration because it completes the oxidation of glucose by breaking down acetyl-CoA into carbon dioxide. This cycle generates high-energy electron carriers (NADH and FADH2) and a small amount of ATP through substrate-level phosphorylation. The NADH and FADH2 produced are crucial for the electron transport chain, where their high-energy electrons are used to generate a large amount of ATP through oxidative phosphorylation.

Question 24

Describe the process of oxidative phosphorylation.

Answer 24

Oxidative phosphorylation is the process by which ATP is produced in the mitochondria through the electron transport chain and chemiosmosis. Electrons from NADH and FADH2 are transferred through a series of protein complexes in the inner mitochondrial membrane, releasing energy that pumps protons (H⁺) into the intermembrane space. This creates a proton gradient, which drives protons back into the mitochondrial matrix through ATP synthase, generating ATP from ADP and inorganic phosphate. Oxygen acts as the final electron acceptor, forming water.

Question 25

How do plants respond to light signals during de-etiolation?

Answer 25

During de-etiolation, plants respond to light signals by activating phytochrome receptors. These receptors detect light and trigger a signal transduction pathway that leads to changes in gene expression. This results in the production of proteins necessary for photosynthesis, chlorophyll synthesis, and the development of leaves and stems. The process involves second messengers like cyclic GMP (cGMP) and calcium ions (Ca²⁺), which amplify the signal and activate transcription factors that regulate gene expression.

Question 26

What is the role of apoptosis in development and disease?

Answer 26

Apoptosis, or programmed cell death, plays a crucial role in development and disease by eliminating damaged, infected, or unnecessary cells. During development, apoptosis shapes organs and tissues by removing excess cells. In the immune system, it helps maintain homeostasis by eliminating cells that could cause autoimmunity. Dysregulation of apoptosis can lead to diseases such as cancer, where cells evade death and proliferate uncontrollably, or neurodegenerative disorders, where excessive cell death leads to tissue damage.