Tài liệu Sinh Học

When he mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain, some living cells became pathogenic He called this phenomenon transformation, now defined as a change in genotype and phenotype due to assimilation of foreign DNA

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Human somatic cells (any cell other than a gamete) have 23 pairs of chromosomes A karyotype is an ordered display of the pairs of chromosomes from a cell The two chromosomes in each pair are called homologous chromosomes, or homologs Chromosomes in a homologous pair are the same length and shape and carry genes controlling the same inherited ch...

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All the DNA in a cell constitutes the cell’s genome A genome can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells) DNA molecules in a cell are packaged into chromosomes

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Leaves are the major locations of photosynthesis Their green color is from chlorophyll, the green pigment within chloroplasts Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf Each mesophyll cell contains 30–40 chloroplasts

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The breakdown of organic molecules is exergonic Fermentation is a partial degradation of sugars that occurs without O2 Aerobic respiration consumes organic molecules and O2 and yields ATP Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2

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Catabolic pathways release energy by breaking down complex molecules into simpler compounds Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a pathway of catabolism

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The steroid cholesterol has different effects on membrane fluidity at different temperatures At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids At cool temperatures, it maintains fluidity by preventing tight packing

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Eukaryotic cells are characterized by having DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells

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Carbohydrates include sugars and the polymers of sugars The simplest carbohydrates are monosaccharides, or single sugars Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks

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The electron configuration of carbon gives it covalent compatibility with many different elements The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules

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