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Answered on 09 Apr Learn Chapter 8-Cell-The Unit of Life
Sadika
The cell is the fundamental unit of life, and it forms the structural and functional basis of all living organisms. Here's an overview of the cell:
Cell Theory: The cell theory, proposed by Matthias Schleiden, Theodor Schwann, and Rudolf Virchow in the 19th century, states:
Cell Structure: Cells vary in size, shape, and structure, but they all have certain common features:
Cell Types: Cells can be broadly classified into two types:
Cell Functions: Cells perform a wide range of functions essential for life, including:
Cell Diversity: Cells exhibit remarkable diversity in structure and function, reflecting the diverse roles they play in different organisms and tissues. For example, nerve cells are specialized for transmitting electrical signals, while muscle cells are specialized for contraction.
Overall, the cell is the basic structural and functional unit of life, and understanding its properties and functions is essential for understanding the biology of living organisms.
Answered on 09 Apr Learn Chapter 8-Cell-The Unit of Life
Sadika
Mesosome in a Prokaryotic Cell: A mesosome is a membrane-bound invagination of the plasma membrane in prokaryotic cells, such as bacteria. It is not a universally observed structure in all prokaryotic cells, but it is commonly found in many bacterial species. The functions performed by mesosomes include:
Answered on 09 Apr Learn Chapter 8-Cell-The Unit of Life
Sadika
Movement of Neutral Solutes Across the Plasma Membrane: Neutral solutes move across the plasma membrane through a process called simple diffusion. In simple diffusion, solutes move from an area of higher concentration to an area of lower concentration until equilibrium is reached. This process occurs down the concentration gradient and does not require the input of energy. Polar molecules, however, cannot move across the plasma membrane through simple diffusion because the lipid bilayer is impermeable to them due to its hydrophobic nature. Instead, polar molecules move across the membrane through facilitated diffusion or active transport. Facilitated diffusion involves the use of transport proteins to facilitate the movement of polar molecules across the membrane, while active transport requires energy expenditure to transport molecules against their concentration gradient.
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Affordable fees Flexible Timings Choose between 1-1 and Group class Verified Tutors Answered on 09 Apr Learn Chapter 8-Cell-The Unit of Life
Sadika
A centromere is a specialized region of a chromosome that serves as the attachment point for spindle fibers during cell division. It plays a crucial role in ensuring the proper segregation of chromosomes into daughter cells during mitosis and meiosis. The centromere typically contains repetitive DNA sequences and specific protein complexes that help in the formation of the kinetochore, a structure that interacts with spindle fibers.
Classification of Chromosomes based on Centromere Position:
The position of the centromere on a chromosome can vary, and this variation forms the basis of classification of chromosomes into different types. There are four main types of chromosomes based on the position of the centromere:
Metacentric: In metacentric chromosomes, the centromere is located approximately in the middle, resulting in two arms of equal length.
Submetacentric: Submetacentric chromosomes have the centromere located off-center, resulting in one long arm (q arm) and one short arm (p ar
m).
Acrocentric: Acrocentric chromosomes have the centromere located close to one end, resulting in one very long arm (q arm) and one very short arm (p arm), which may appear as a satellite.
Telocentric: Telocentric chromosomes have the centromere located at one end, resulting in only one chromosome arm.
Diagram showing the Position of Centromere on Different Types of Chromosomes:
The classification of chromosomes based on centromere position provides valuable information about chromosome structure and organization, which can aid in understanding genetic processes, such as chromosome segregation during cell division.
Answered on 09 Apr Learn Chapter 9- Biomolecules
Sadika
Macromolecules are large molecules composed of repeating subunits called monomers, which are covalently bonded together through polymerization reactions. These molecules are essential for various biological processes and structures in living organisms. There are four main classes of macromolecules found in biological systems:
Proteins: Proteins are macromolecules composed of amino acid monomers linked together by peptide bonds. They play diverse roles in cells, including enzymatic catalysis, structural support, transport of molecules, signaling, and immune defense. Examples of proteins include enzymes (e.g., amylase, catalase), structural proteins (e.g., collagen, actin), and antibodies.
Nucleic Acids: Nucleic acids are macromolecules that store and transmit genetic information. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA carries the genetic instructions necessary for the development, functioning, and reproduction of organisms, while RNA is involved in protein synthesis and regulation. Examples of nucleic acids include DNA, RNA, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
Carbohydrates: Carbohydrates are macromolecules composed of sugar monomers (monosaccharides) linked together by glycosidic bonds. They serve as a major source of energy for cells and play structural roles in organisms. Examples of carbohydrates include glucose, cellulose, starch, glycogen, and chitin.
Lipids: Lipids are a diverse group of macromolecules that are hydrophobic (insoluble in water). They include fats, oils, phospholipids, steroids, and waxes. Lipids serve as energy storage molecules, structural components of cell membranes, and signaling molecules. Examples of lipids include triglycerides, phospholipids (e.g., phosphatidylcholine), cholesterol, and hormones (e.g., testosterone, estrogen).
These macromolecules are essential for the structure, function, and regulation of biological systems, and they interact with each other to form complex cellular structures and pathways.
Answered on 09 Apr Learn Chapter 9- Biomolecules
Sadika
O H O
|| | ||
H-O-C-C-O-H + H-O-C-C-O-H → H-O-C-C-O-C-C-O-H + H2O
| | |
H OH H
Glucose Glucose Glycosidic Bond
In the illustration, two glucose molecules undergo a condensation reaction, resulting in the formation of a glycosidic bond between them. Water (H2O) is released as a byproduct.
Peptide Bond:
In the illustration, two amino acid molecules undergo a condensation reaction, resulting in the formation of a peptide bond between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of the other amino acid. Water (H2O) is released as a byproduct.
O P O
| || |
H-O-C-C-C-OH + H-O-C-C-C-OH → H-O-C-C-C-O-P-O-C-C-OH + H2O
| | |
OH OH OH
Nucleotide Nucleotide Phosphodiester Bond
In the illustration, two nucleotide molecules undergo a condensation reaction, resulting in the formation of a phosphodiester bond between the phosphate group (-PO4) of one nucleotide and the hydroxyl group (-OH) of the other nucleotide. Water (H2O) is released as a byproduct.
These illustrations demonstrate the formation of glycosidic, peptide, and phosphodiester bonds through condensation reactions, leading to the synthesis of larger macromolecules.
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Sadika
The tertiary structure of a protein refers to its three-dimensional arrangement in space, resulting from interactions between amino acid side chains (R-groups). It represents the folding and twisting of the polypeptide chain into a specific three-dimensional shape, which is essential for the protein's function.
The tertiary structure of a protein is stabilized by several types of interactions between amino acid residues, including:
Hydrophobic Interactions: Nonpolar amino acid side chains tend to cluster together in the interior of the protein, away from the surrounding aqueous environment. This minimizes their contact with water molecules and stabilizes the protein structure.
Hydrogen Bonds: Hydrogen bonds form between polar or charged amino acid side chains, contributing to the folding and stabilization of the protein structure.
Disulfide Bonds: Covalent disulfide bonds can form between cysteine residues, creating bridges that help stabilize the tertiary structure of proteins. These bonds are particularly important for maintaining the structure of proteins in extracellular environments or under oxidative conditions.
Ionic Interactions: Ionic interactions occur between positively and negatively charged amino acid side chains, contributing to the overall stability of the protein structure.
Van der Waals Forces: Weak interactions between nonpolar amino acid side chains also contribute to the tertiary structure by promoting close packing of atoms within the protein.
The specific arrangement of these interactions gives rise to the unique three-dimensional shape of each protein, which is crucial for its biological function. The tertiary structure determines how proteins interact with other molecules, such as substrates, cofactors, or other proteins, and ultimately dictates their biological activity. Any disruption or alteration in the tertiary structure can lead to loss of protein function, known as denaturation, which may be reversible or irreversible depending on the extent of structural changes.
Answered on 09 Apr Learn Chapter 10-Cell Cycle and Cell Division
Sadika
The average cell cycle span for a mammalian cell can vary depending on factors such as the cell type, environmental conditions, and the specific stage of the cell cycle being considered. However, in general, the cell cycle duration for mammalian cells typically ranges from about 18 to 24 hours.
This time frame is divided among different phases of the cell cycle:
Interphase: This is the longest phase of the cell cycle and can last anywhere from 12 to 24 hours. During interphase, the cell grows, carries out its normal functions, and replicates its DNA in preparation for cell division.
Mitosis (M Phase): Mitosis itself is relatively short, typically lasting around 1 to 2 hours in mammalian cells. During mitosis, the cell divides its nucleus into two identical daughter nuclei.
Cytokinesis: Cytokinesis, the final stage of cell division, involves the physical separation of the cytoplasm and organelles to form two distinct daughter cells. This process usually occurs concurrently with the later stages of mitosis and takes only a few minutes.
It's important to note that the duration of the cell cycle can vary significantly depending on the cell type and its specific physiological state. For example, rapidly dividing cells such as those in embryonic tissues or certain cancer cells may have shorter cell cycle durations, while differentiated cells in adult tissues may have longer cell cycle durations. Additionally, external factors such as growth factors, nutrients, and signaling molecules can also influence the duration of the cell cycle.
Answered on 09 Apr Learn Chapter 10-Cell Cycle and Cell Division
Sadika
Cytokinesis and karyokinesis are two distinct processes that occur during cell division, specifically during the mitotic phase of the cell cycle. Here's how they differ:
Cytokinesis:
Karyokinesis:
In summary, cytokinesis refers to the division of the cytoplasm, while karyokinesis refers to the division of the nucleus. Together, these processes ensure the faithful replication and distribution of cellular and genetic material to the daughter cells during cell division.
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Affordable fees Flexible Timings Choose between 1-1 and Group class Verified Tutors Answered on 09 Apr Learn Chapter 10-Cell Cycle and Cell Division
Sadika
Interphase is the longest phase of the cell cycle and encompasses the period between cell divisions. It is divided into three main stages: G1 (Gap 1), S (Synthesis), and G2 (Gap 2). During interphase, the cell prepares for cell division by growing, replicating its DNA, and synthesizing proteins necessary for various cellular processes. Here's a description of the events that take place during each stage of interphase:
Gap 1 (G1) Phase:
Synthesis (S) Phase:
Gap 2 (G2) Phase:
Overall, interphase is a dynamic and highly regulated period during which the cell prepares for division by growing, replicating its DNA, and synthesizing the necessary components for cell division. It is a crucial stage of the cell cycle that ensures the faithful transmission of genetic information to the daughter cells.
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