bbyet-141-solved-assignment-2024-ss-8648076a-dc1c-446a-986b-96f21861d046

1. Describe the structure, composition and functions of mitochondria along with suitable diagram.

1. Outer Membrane: The outer membrane is the smooth, semi-permeable outer layer of the mitochondrion. It contains numerous proteins, including porins, that allow the passage of small molecules and ions.
2. Intermembrane Space: The space between the outer and inner membranes is called the intermembrane space. It contains enzymes involved in certain metabolic reactions.
3. Inner Membrane: The inner membrane is a highly folded, convoluted membrane that forms numerous projections called cristae. The inner membrane is impermeable to most ions and molecules and is the site of many critical metabolic reactions.
4. Cristae: Cristae are the infoldings or inner folds of the inner mitochondrial membrane. They provide a large surface area for enzymes involved in oxidative phosphorylation, the process by which ATP (adenosine triphosphate) is produced.
5. Matrix: The matrix is the central compartment enclosed by the inner mitochondrial membrane. It contains enzymes responsible for the Krebs cycle (citric acid cycle) and fatty acid oxidation, both of which play vital roles in cellular respiration.

1. Phospholipid Bilayers: Like all cellular membranes, mitochondria have phospholipid bilayers that form the outer and inner membranes.
2. Proteins: Mitochondria contain a variety of proteins, including those involved in energy production, transport of molecules across membranes, and enzymes for metabolic pathways.
3. DNA (Mitochondrial DNA or mtDNA): Mitochondria contain their own small circular DNA molecules (mtDNA), which carry genes encoding some of the proteins needed for mitochondrial function. This is a relic of their evolutionary history as free-living bacteria.
4. Ribosomes: Mitochondria have their own ribosomes, similar to bacterial ribosomes. These ribosomes are involved in protein synthesis within the mitochondria.

1. ATP Production: Mitochondria produce ATP through a process called oxidative phosphorylation. This involves the electron transport chain, which transfers electrons through protein complexes on the inner mitochondrial membrane, creating a proton gradient. The flow of protons back into the matrix through ATP synthase generates ATP.
2. Krebs Cycle: Mitochondria host the Krebs cycle (also known as the citric acid cycle or TCA cycle), which is a central metabolic pathway that oxidizes acetyl-CoA derived from carbohydrates, fats, and proteins. This cycle generates high-energy electron carriers (NADH and FADH2) for the electron transport chain.
3. Fatty Acid Oxidation: Mitochondria are involved in the oxidation of fatty acids, breaking them down to produce energy.
4. Calcium Regulation: Mitochondria play a role in regulating intracellular calcium levels, which are critical for cell signaling and muscle contraction.
5. Apoptosis: Mitochondria are involved in the regulation of apoptosis (programmed cell death). Release of specific proteins from the intermembrane space can trigger apoptosis.
6. Heat Production: In specialized brown adipose tissue, mitochondria can generate heat through a process called thermogenesis. This is essential for temperature regulation in some animals, including newborns.

2. Explain the concept of Operon. Describe their role in gene regulation along with suitable diagram.

1. Structural Genes: These are the genes that encode proteins with related functions. They are transcribed together as a single mRNA molecule and are typically involved in a specific metabolic pathway.
2. Promoter Region: Located upstream of the structural genes, the promoter region is a DNA sequence where RNA polymerase binds to initiate transcription.
3. Operator Region: The operator is a DNA sequence situated between the promoter and the structural genes. It acts as a regulatory region where a protein called the repressor can bind.
4. Regulatory Gene: This gene encodes the repressor protein. It is located either adjacent to the operon or at a distant location in the genome.

1. Repressor Protein: The regulatory gene encodes a repressor protein that can bind to the operator region. When the repressor is bound to the operator, it physically blocks RNA polymerase from binding to the promoter.
2. Inducer Molecule: In many operons, the repressor’s ability to bind to the operator is regulated by the presence of an inducer molecule. The inducer can bind to the repressor, causing a conformational change in the repressor protein, making it unable to bind to the operator.
3. Activation and Repression: Depending on the operon type, the presence or absence of the inducer molecule determines whether transcription of the structural genes occurs:
   • Inducible Operon: In the absence of the inducer, the repressor binds to the operator, blocking transcription (repression). When the inducer is present, it binds to the repressor, releasing it from the operator, allowing transcription to occur (activation).
   • Repressible Operon: In the presence of the co-repressor molecule (usually a product of the pathway), the repressor is activated and binds to the operator, preventing transcription. When the co-repressor is absent, the repressor cannot bind to the operator, allowing transcription (de-repression).

• The promoter is where RNA polymerase binds to initiate transcription.
• The structural genes encode proteins with related functions.
• The operator is a regulatory region where the repressor protein can bind.
• The regulatory gene encodes the repressor protein.
• The repressor protein can bind to the operator and block transcription.
• The presence or absence of an inducer molecule determines whether the repressor is active or inactive.

1. Lac Operon: The lac operon in E. coli controls the metabolism of lactose. It is an inducible operon regulated by the presence of lactose and the inducer molecule allolactose.
2. Trp Operon: The trp operon in E. coli controls the synthesis of tryptophan. It is a repressible operon regulated by the presence of tryptophan as a co-repressor.