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Witness how structure and function are related in enzymes, which are a group of proteins that stimulate biochemical reactions to run at astonishing speed. One example is OMP decarboxylase, an enzyme that produces a crucial component of DNA in a blistering 0.02 second, versus the 78 million years that the reaction would normally take! Analyze the mechanisms behind these apparent superpowers.
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The products from the reactions in the previous lecture now enter the Krebs citric acid cycle. The outcome of these reactions, in turn, link to many other pathways, with the Krebs cycle serving as the hub directing the intricate traffic of metabolic intermediates. After decoding the Krebs cycle, use it to illuminate a deep mystery about cancer cells, which suggests new therapies for the disease.
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Discover how to eat in a way that minimizes harm and efficiently fixes the inevitable damage from living. Learn that certain cooking methods can increase the formation of harmful compounds. And substances such as antioxidants found in some foods can reduce the impact of damaging chemical reactions within cells. Also cover recent findings about gut bacteria that have changed our views about diet.
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Learn how peptide bonds join amino acids to form an almost unlimited number of protein types. The order of amino acids matters, but even more important are the shapes they form. Survey primary, secondary, tertiary, and quaternary protein structures, with examples from silk (a fibrous protein with mostly secondary structure) to the intricately folded hemoglobin protein (a quaternary structure).
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Hemoglobin is the protein in red blood cells that carries oxygen from lungs to tissues and then takes away carbon dioxide for exhalation. Learn how structure is the key to this complicated and vital function. Also see how variant forms of hemoglobin, such as fetal hemoglobin and the mutation behind sickle cell anemia, can have life-saving or fatal consequences - all depending on structure.
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Advance into the last third of the series, where you cover molecular biology, which deals with the biochemistry of reproduction. Zero in on DNA and how its double-helix structure relates to its function. Then look at the single-stranded RNA molecule, which is a central link in the process, "DNA makes RNA makes protein." Also consider how viruses flourish with very little DNA or RNA.
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Discover how proteins fold into complex shapes, often with the help of molecular chaperones. Then learn the deadly consequences of proteins that do not fold properly, leading to degenerative conditions such as Alzheimer's, Parkinson's, and prion diseases. Also look at intrinsically disordered proteins, which lack a fixed structure, permitting flexible interactions with other biomolecules.
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A metabolic pathway is a series of biochemical reactions, where the product of one serves as the substrate for the next. Biochemists compare these pathways to road maps that show the network of reactions leading from one chemical to the next. Follow the metabolic pathway called glycolysis that breaks up glucose and other sugars. Then trace the route for fatty acid oxidation.
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Nitrogen is a key component of amino acids, DNA, and RNA, yet animal and plant cells are unable to extract free nitrogen from air. See how bacteria come to the rescue. Then follow the flow of nitrogen from bacteria to plants to us. Also look at strategies for reducing our reliance on environmentally unsound nitrogen fertilizers by exploiting the secret of 16-feet-tall corn plants found in Mexico.
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Examine the cell cycle of eukaryotic cells and the cycle's effect on DNA replication. Discover that a quirk in the copying of linear DNA leads to the shrinking of chromosomes as cells age, a problem reversed in egg and sperm cells by the telomerase enzyme. For this reason, telomerase might appear to be the secret to immortality except its unregulated presence in cells can lead to cancer.
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Investigate why water is so singularly suited to life. Composed of two hydrogen atoms for each oxygen atom, water molecules have a polar charge due to the uneven arrangement of shared electrons. See how this simple feature allows water to dissolve sugars and salts, while leaving oils and fats untouched. Also learn what makes water solutions acidic or basic.
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Explore the controls that determine which genes are expressed at a given time, where in the body, and to what extent. Controls that act over and above the information in DNA are called epigenetic, and they can be passed on to offspring for a generation or two. Consider the case of honeybees, where a special food affects which genes are expressed, turning an ordinary larva into a queen bee.
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Trace the pathways of two widely ingested molecules: caffeine and fructose. Caffeine fools the body (usually harmlessly) into increasing glucose in the blood, while too much fructose can lead to unhealthy accumulation of fat in the liver. Then focus on two topics that link with the upcoming molecular biology segment of the series: androgen insensitivity and the molecular mechanisms of aging.
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Lipids are a varied group of molecules that include fats, oils, waxes, steroids, hormones, and some vitamins. Survey the fats that obsess us in our diets and body shapes, notably triglycerides in their saturated and unsaturated forms. Then explore the role lipids play in energy storage and cell membrane structure, and cover the multitude of health benefits of the lipid vitamins: A, D, E, and K.
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Thus far, your investigations have accounted for only part of the energy available from food. So where's all the ATP? In this episode, see how ATP is produced in abundance in both animal and plant cells, largely via mitochondria (in animals and plants) and chloroplasts (in plants only). You also learn why we need oxygen to stay alive and how poisons such as cyanide do their deadly work.
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Study how plants use sunlight and reduction reactions to build carbohydrates from carbon dioxide and water. This synthesis of food from air and water occurs in a series of reactions called the Calvin cycle. While humans exploit plants for food and fiber, we also utilize a multitude of other plant molecules called secondary metabolites. These include flavors, dyes, caffeine, and even catnip.
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Delve deeper into DNA replication, learning that a process called genetic recombination assures that no two individuals will have the same DNA, unless they are twins derived from a single fertilized egg. Trace the new technologies that have arisen from our understanding of recombination and repair of DNA, notably CRISPR, which permits precise alteration of gene sequences.
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Take a tour through the 20 amino acids that link together in different combinations and sequences to build proteins. Besides water, proteins are the most abundant molecules in all known forms of life. Also the most diverse class of biological molecules, proteins make up everything from enzymes and hormones to antibodies and muscle cells.
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RNA is more than simply a copy of the DNA blueprint. Focus on the synthesis of RNA, covering how it differs from DNA replication. Also learn how human cells shuffle their genetic code to make about 100,000 different proteins using fewer than 30,000 coding sequences. Finally, see how knowledge of transcription occurring after death helps forensic scientists establish the time of death accurately.
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Most of the reactions you have studied so far occur outside everyday awareness. Now investigate the most important biochemical signals that we habitually notice: the molecular reactions that give rise to the five senses. Analyze the sensory origins of colors, sounds, tastes, smells, and touch, mapping them through the nervous system. Observe how the senses are "tuned" to enhance our survival.