Questions and Answers
Which of the following cell organelles are present in Eukaryotic cells?
What is the primary function of the cell nucleus?
Control Center of the cell.
Prokaryotic cells have a true nucleus.
False
The __________ is the protective outer covering of a cell.
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What are the two components of cytoplasm?
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Which statement is true about mitochondria?
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What is the structure of DNA?
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Which components make up a nucleotide?
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How many chromosomes does a child normally inherit from each parent?
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The two strands of DNA are __________.
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What is the function of the lysosome?
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Study Notes
Cell and Cell Structures
- Cells serve as the basic living units of organisms, with eukaryotic cells found in multicellular organisms and prokaryotic cells in unicellular organisms like bacteria.
- Eukaryotic cells have a true nucleus, while prokaryotic cells lack a defined nucleus and organelles.
- The cell structure comprises a nucleus, cytoplasm, organelles, and cytosol, all protected by the plasma membrane.
Plasma Membrane
- The plasma membrane is thin, flexible, and selectively permeable, regulating material passage between the internal and external environments.
- Composed mainly of a phospholipid bilayer (55% proteins, 42% lipids, 3% carbohydrates), it maintains cell integrity and function.
- Fluid Mosaic Model describes its structure as a mosaic of proteins floating in or on the fluid lipid bilayer.
Cytoplasm
- Cytoplasm contains cytosol (the fluid portion) and organelles, facilitating numerous chemical reactions.
- Composed of microfilaments (thinnest), intermediate filaments (medium thickness), and microtubules (thickest), the cytoskeleton provides support and movement.
- The centrosome organizes microtubules and forms the mitotic spindle during cell division.
Organelles
- Mitochondria: Powerhouse of the cell; generates ATP. Higher quantities in cells with greater energy needs (e.g., liver, muscle).
- Endoplasmic Reticulum: Network of tubules and vesicles; Rough ER synthesizes proteins, while Smooth ER synthesizes lipids and detoxifies drugs.
- Golgi Complex: Modifies, sorts, and packages proteins received from the ER for transport.
- Lysosomes: Contain hydrolytic enzymes for intracellular and extracellular digestion, engaged in autophagy and autolysis.
- Peroxisomes: Smaller than lysosomes; contain oxidases for detoxifying harmful substances, such as alcohol.
Nucleus
- The nucleus is the control center of the cell, housing most genetic material (DNA).
- Features a nuclear envelope that contains nuclear pores for substance transport; nucleolus synthesizes ribosomal RNA.
DNA Structure and Organization
- DNA (deoxyribonucleic acid) is a double helix composed of nucleotides, the basic repeating units.
- Nucleotides consist of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, thymine, guanine, or cytosine).
- Base pairing follows Chargaff’s rule: Adenine pairs with Thymine, and Guanine pairs with Cytosine.
Chromosomes
- Chromosomes are tightly coiled DNA structures, visible during metaphase, consisting of two sister chromatids.
- Humans possess 46 chromosomes (23 pairs), including 22 pairs of autosomes and 1 pair of sex chromosomes.
- The centromere is the region where sister chromatids join; telomeres protect chromosome ends.
Chromatin Structure
- Chromatin is DNA complexed with proteins. Euchromatin is gene-rich and active, while heterochromatin is gene-poor and inactive.
- Types of chromosomes based on centromere location include metacentric, submetacentric, acrocentric, and telocentric.
Genetic Information and Function
- Genes, functional units of DNA, determine traits and control cell reproduction.
- The complete genetic makeup of an organism is referred to as the genome.
Cellular Replication
- The centrosome aids in cell division by organizing microtubules which form the mitotic spindle.
- Mitochondria can self-replicate and contain their own DNA, playing a significant role in apoptosis.
Summary Points
- Key organelles have distinct structures and functions essential for maintaining cellular activities and homeostasis.
- The organization of DNA into chromatin and chromosomes is crucial for genetic regulation and inheritance.
- Understanding cellular structures and functions provides foundational knowledge essential for the study of biology and medicine.
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Description
Test your understanding of DNA, chromosomes, and cell division with this quiz. Explore the differences between eukaryotic and prokaryotic cells, as well as the characteristics and structures of human chromosomes. Perfect for reinforcing lesson objectives in cytology.
