SS5 General Biology 1 PDF

SS5 - General Biology 1 o Cell Membrane -All cells, prokaryotic and eukaryotic, have cell membranes to control what enters and leaves the cell. o DNA: All cells contain DNA as their genetic material. o Mitochondria (Only in eukaryotes): Mitochondria are the energy powerhouses of...

SS5 - General Biology 1 o Cell Membrane -All cells, prokaryotic and eukaryotic, have cell membranes to control what enters and leaves the cell. o DNA: All cells contain DNA as their genetic material. o Mitochondria (Only in eukaryotes): Mitochondria are the energy powerhouses of eukaryotic cells, but prokaryotes don't have them. o Ribosomes: Both prokaryotes and eukaryotes use ribosomes for protein synthesis. o Cell wall- To provide structural support and protection. The cell wall is a rigid outer layer, providing structure and shielding Cell Theory foundation o The fundamental unit of life (cells) o Structure and function of living organisms o The basis for new technologies in medicine and agriculture (through cell biology and manipulation) o New cells are formed by the division of existing cells § This is the core principle of cell division (mitosis and meiosis), where a parent cell replicates its DNA and organelles to create daughter cells. Cell theory applied in medicine Antibiotics: Target bacterial cells. Chemotherapy: Targets cancer cells. Stem cells: Used for tissue regeneration. Cell theory applied in agriculture Genetically modified crops: Engineered at the cellular level. Fertilizers: Influence plant cell growth. ·Pesticides: Target pest cells. The cell theory is unable to provide insight into how life first arose. Its focus is on the characteristics and functions of cells once they exist. Prokaryotes Size: Prokaryotes are generally smaller. Presence of a nucleus: Prokaryotes lack a nucleus. Method of reproduction: Prokaryotes primarily reproduce asexually. Eukaryotes Eukaryotes evolved from prokaryotes. The endosymbiotic theory suggests that eukaryotic organelles like mitochondria and chloroplasts were once free-living prokaryotes that were engulfed by other cells. Organelles The nucleus controls cellular activities, while the mitochondrion generates energy. The cytoplasm provides a protective environment, while vacuoles store substances. DNA is found in the nucleus, while proteins are synthesized at ribosomes. The Golgi apparatus has stacked membrane sacs called cisternae, while the o mitochondrion has a fluid-filled inner compartment called the matrix. Cilia are short and numerous, while flagella are longer and fewer. The nuclear envelope surrounds the DNA, while histones help package DNA into chromosomes. The cytosol is the liquid part of the cytoplasm, while the stroma is the fluid-filled space within a chloroplast. The hydrophilic head of a phospholipid is polar, while the hydrophobic tail is nonpolar and consists of fatty acids. Membrane Protein Functions § Receptor Proteins - They facilitate exchange of signals with other cells by changing its shape. § Cytoskeleton Proteins- They maintain cell shape and motility. § Enzymatic Proteins - They participate in metabolic reactions such as degradative and synthesis. § Channel Proteins - They help cells to import or export materials and expel wastes by forming tunnels.  § Transport Proteins - They help materials cross the membrane by extending it. Cell Cycle Phases Interphase is the longest phase of the cell cycle. It's when the cell grows, replicates its DNA, and prepares for cell division. It's divided into three stages: Ø G1 phase: The cell grows, synthesizes proteins, and prepares for DNA replication. They help materials cross the membrane by extending it Ø S phase: The cell's DNA is replicated. Each chromosome is duplicated to form two sister chromatids. The DNA molecule undergoes replication Ø G2 phase: The cell continues to grow and prepares for mitosis. Proteins are synthesized to help with cell division. Cells produce a copy of microtubule that will later help the cell organize its contents Ø Prophase – Chromatin condenses Into tightly coiled chromosomes. The centrosomes begin to migrate to opposite poles of cell. Ø Metaphase – Chromosomes appear to line up along a plane equidistant from a microtubule region Ø Anaphase- They help materials cross the membrane by extending it. Ø Telophase –The nuclear membrane start to rebuild Ø Cytokinesis-The chromosomes are no longer visible in this place A mutation in a gene that controls the formation of spindle fibers would likely disrupt the process of mitosis. Spindle fibers are essential for separating chromosomes during cell division. If their formation is impaired due to a mutation, the following consequences could occur: Chromosomal abnormalities: The chromosomes might not align properly at the metaphase plate, leading to unequal distribution during anaphase. This could result in cells with too many or too few chromosomes, a condition known as aneuploidy. Cell cycle arrest: The cell might be unable to proceed through mitosis and enter a state of cell cycle arrest, preventing cell division. Cell death: In severe cases, the disruption of spindle fiber formation could lead to cell death. Overall, a mutation affecting spindle fiber formation can have significant consequences for cell division and potentially lead to various cellular abnormalities or dysfunction. ü A fertilized human egg cell, also known as a zygote, would have 46 chromosomes. ü Here's why: ü Sperm and Egg: Human sperm and egg cells each contain 23 chromosomes. ü Fertilization: When a sperm fertilizes an egg, their 23 chromosomes combine. ü Resulting Zygote: The resulting zygote, the first cell of a new individual, has 23 chromosomes from the sperm and 23 chromosomes from the egg, totaling 46 chromosomes. ü This set of 46 chromosomes will be inherited by all subsequent cells in the developing organism. A mutation in a gene that controls the formation of spindle fibers would most likely prevent the chromosomes from aligning at the equator during metaphase. Here's a breakdown of why: Spindle Fibers: These protein structures are essential for separating chromosomes during mitosis. They attach to the centromere of each chromosome and pull them apart to opposite poles of the cell. Mutation: If a mutation disrupts the formation of spindle fibers, they might be unable to attach to the chromosomes or might be defective in their function. Alignment Failure: This would prevent the chromosomes from lining up at the metaphase plate, a critical step before the chromosomes are separated. Therefore, a mutation affecting spindle fiber formation would likely lead to chromosomal abnormalities and potentially disrupt the entire process of mitosis This is a well-structured and informative review of Cell Theory concepts. Here's a breakdown of the explanations and additional insights: Reviewer: Key Cell Biology Terms Term: Homologous Chromosomes Definition: Chromosomes that are similar in size, shape, and genetic content. They are paired during meiosis. Related Term: Sister Chromatids: The identical copies of a chromosome produced during DNA replication. Term: Y Chromosome Definition: The sex chromosome that is present in males and is responsible for the development of male sex characteristics. Related Term: X Chromosome: The other sex chromosome found in both males and females. Term: n + n = 2n Definition: This equation represents the process of fertilization, where the haploid (n) sperm cell combines with the haploid (n) egg cell to form a diploid (2n) zygote. Related Term: Diploid: Having two sets of chromosomes. Term: Storehouse of Nutrients Definition: This refers to the abundant cytoplasm in a mature ovum, which provides nourishment for the developing embryo if fertilization occurs. Related Term: Oogenesis: The process of egg cell formation in females. Term: Unequal Cytoplasmic Divisions Definition: This refers to the unequal distribution of cytoplasm during cell division, as seen in oogenesis where one daughter cell receives most of the cytoplasm and becomes the ovum, while the others become polar bodies. Related Term: Polar Body: A small, non-functional cell produced during oogenesis. Term: Chromosomal Abnormalities Definition: These are deviations from the normal number or structure of chromosomes. Related Term: Aneuploidy: A condition where an individual has an abnormal number of chromosomes. Term: Monosomy Definition: A condition where an individual has only one copy of a particular chromosome. Related Term: Trisomy: A condition where an individual has three copies of a particular chromosome.