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Questions and Answers
What are microfilaments primarily composed of?
Which type of cell is defined as lacking a nucleus?
What structure becomes visible during cell division?
How many pairs of chromosomes are typically found in dividing human cells, excluding reproductive cells?
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What is the primary role of the histone molecules in the nucleus?
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What distinguishes multinucleated cells from uninucleated cells?
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What is the function of the nuclear membrane?
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What is the smallest unit that has all the characteristics of life?
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Which of the following statements is true regarding cells?
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What defines a group of cells having similar functions?
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How is a chromosome formed?
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Which statement correctly describes a cell?
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How do most cells reproduce?
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Which statement best describes cell death?
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What unique feature does a neuron have compared to other cells?
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Which of the following is not a characteristic of cells?
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What is the primary function of the rough endoplasmic reticulum?
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Which of the following correctly describes the appearance of the rough endoplasmic reticulum?
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What distinguishes smooth endoplasmic reticulum from rough endoplasmic reticulum?
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What is the diameter of the lumen of the endoplasmic reticulum?
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Which organelle is responsible for the degradation of worn-out organelles?
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Which function is primarily associated with smooth endoplasmic reticulum?
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What connects the cell membrane with the nuclear membrane?
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How do rough and smooth endoplasmic reticulum relate to each other?
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Study Notes
Introduction
- Cells are the basic structural & functional units of all living organisms.
- A single cell possesses all the characteristics of life.
- The cell is defined as the structural and functional unit of the living body.
Cell
- The cell is the smallest unit of life.
- All living organisms are composed of cells.
- A single cell is the smallest unit that has all the characteristics of life.
- Cells respond immediately to the entry of invaders like bacteria or toxic substances into the body.
- Cells reproduce by division. There are exceptions like neurons, which do not reproduce.
Tissue
- A group of cells with similar structures and functions.
Structure of the Cell
- The cell membrane forms the outer boundary of the cell.
- Cytoplasm is the jelly-like substance that fills the cell and contains various organelles.
- There are two types of organelles: organelles with limiting membranes and organelles without limiting membranes.
Organelles With Limiting Membrane
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Endoplasmic reticulum (ER): A network of interconnected membranes involved in protein synthesis, lipid synthesis, and other metabolic functions.
- Rough ER: Has ribosomes attached, involved in protein synthesis & degradation of worn-out organelles.
- Smooth ER: Lacking ribosomes, involved in lipid and steroid synthesis, cellular metabolism, calcium storage, and detoxification.
- Golgi apparatus: Stack of flattened sacs involved in modifying, sorting, and packaging proteins and lipids.
- Lysosomes: Membrane-bound organelles containing enzymes that breakdown waste materials.
- Peroxisomes: Small organelles responsible for detoxifying harmful substances.
- Centrosome and Centrioles: Centrosomes are involved in cell division, and centrioles are microtubule-organizing centers.
- Secretory vesicles: Membrane-bound sacs that transport substances out of the cell.
- *Mitochondria: Powerhouse of the cell, responsible for generating ATP through cellular respiration.
- Nucleus: The control center of the cell, containing genetic material (DNA).
Organelles Without Limiting Membrane
- Ribosomes: Made up of RNA and proteins, involved in protein synthesis.
- Cytoskeleton: A network of protein filaments that provide support and shape to the cell and enable movement.
Nucleus
- The nucleus is present in all cells except red blood cells.
- Cells with a nucleus are called eukaryotes, and those without are called prokaryotes.
- The presence of a nucleus is necessary for cell division.
- Most cells have one nucleus (uninucleated), but some, like skeletal muscle cells, have multiple nuclei (multinucleated).
Structure of the Nucleus
- The nucleus is surrounded by the nuclear membrane, a double-layered porous membrane that allows communication with the cytoplasm.
- The nucleus contains nucleoplasm, chromatin, and the nucleolus.
Nuclear Membrane
- The nuclear membrane is double-layered and porous.
- The pores in the membrane allow communication between the nucleoplasm (the fluid inside the nucleus) and the cytoplasm.
Nucleoplasm
- A fluid medium inside the nucleus.
Chromatin
- The complex of DNA and proteins that makes up chromosomes.
- The DNA in chromatin is loosely packed, allowing for gene expression.
- Chromatin is organized into packing units called nucleosomes.
Nucleosomes
- Nucleosomes are packed together tightly with the help of histone molecules to form a chromatin fiber.
- During cell division, chromatin condenses to form chromosomes.
Chromosomes
- Rod-shaped structures carrying genetic information.
- Each chromosome consists of a single DNA molecule coiled around histone molecules.
- Most cells have 23 pairs of chromosomes (46 total).
- Chromosomes are not usually visible under a microscope, but become visible during cell division when DNA becomes more tightly packed.
DNA
- Deoxyribonucleic acid, a molecule carrying genetic information that is passed from parent to offspring.
- Each DNA molecule contains many genes.
Genes
- Segments of DNA that code for specific traits or characteristics.
RNA
- Ribonucleic acid, a molecule involved in protein synthesis.
Gene Expression
- The process by which information encoded in genes is used to produce proteins.
Growth Factors
- Substances that stimulate cell growth and division.
Cell Death
- The process by which cells die naturally or through injury or disease.
Cell Adaptation
- The ability of cells to change in response to environmental stimuli or stress.
Cell Degeneration
- The process by which cells deteriorate or break down.
Cell Aging
- The gradual deterioration and loss of function of cells over time.
Stem Cells
- Undifferentiated cells that can divide and differentiate into specialized cell types.
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Description
This quiz covers the fundamental concepts of cells as the basic units of life and their organization into tissues. It highlights the structure of cells, their functions, and the role of various organelles. Test your knowledge on the characteristics of life exhibited by cells and their importance in living organisms.
