Click below to find brief notes that may help you study for exams in biology. Review summaries, watch animations, and take unlimited practice exams. This animation demonstrates translation in protein synthesis.
Describe the photosynthetic process that allow organisms to capture and store energy. Leaves convert sunlight into usable energy in a complex pathway. Always on exams.
Aerobic respiration is the process by which organisms use oxygen to turn fuel, such as fats and sugars, into chemical energy. In contrast, anaerobic respiration does not use oxygen. Respiration is used by all cells to turn fuel into energy that can be used to power cellular processes.
Cellular organelles explained, from ribosomes to mitochondria. The cell nucleus, where the DNA is located, is surrounded by a wealth of other protein structures in a substrate of protoplasm.
DNA replication occurs through the help of several enzymes. These enzymes "unzip" DNA molecules by breaking the hydrogen bonds that hold the two strands together. Each strand then serves as a template for a new complementary strand to be created. Complementary bases attach to one another (A-T and C-G).
Mutations is the process by which a gene or chromosome changes; structurally and the end result of that process. All mutations are not harmful' as beneficial mutations occur frequently among various viruses, and bacteria and also in higher organisms. CRISPR is a technology that can be used to edit genes. It's a way of targeting a specific bit of DNA inside a cell, editing precisely in order to alter that segment of DNA.
Enzymes are chemical catalysts that accelerate chemical reactions at physiological temperatures by lowering their activation energy. Enzymes are usually proteins consisting of one or more polypeptide chains. Enzymes have an active site that provides a unique chemical environment, comprised of certain amino acid R groups (residues). This unique environment is perfectly suited to convert particular chemical reactants for that enzyme, scientists call substrates, into unstable intermediates that they call transition states. Enzymes and substrates bind with an induced fit, which means that enzymes undergo slight conformational adjustments upon substrate contact, leading to full, optimal binding. Enzymes bind to substrates and catalyze reactions in four different ways: bringing substrates together in an optimal orientation, compromising the bond structures of substrates so that bonds can break down more easily, providing optimal environmental conditions for a reaction to occur, or participating directly in their chemical reaction by forming transient covalent bonds with the substrates.
Enzyme action must be regulated so that in a given cell at a given time, the desired reactions catalyze and the undesired reactions are not. Enzymes are regulated by cellular conditions, such as temperature and pH. They are also regulated through their location within a cell, sometimes compartmentalized so that they can only catalyze reactions under certain circumstances. Enzyme inhibition and activation via other molecules are other important ways that enzymes are regulated. Inhibitors can act competitively, noncompetitively, or allosterically. Noncompetitive inhibitors are usually allosteric. Activators can also enhance enzyme function allosterically. The most common method by which cells regulate the enzymes in metabolic pathways is through feedback inhibition. During feedback inhibition, metabolic pathway products serve as inhibitors (usually allosteric) of one or more of the enzymes (usually the first committed enzyme of the pathway) involved in the pathway that produces them.
DNA (deoxyribonucleic acid) consists of two biopolymer strands, coiled around each other to form a double helix. These two DNA strands are called polynucleotides since they are composed of several monomer proteins. Each nucleotide is made up of nitrogen-containing cytosine (C), guanine (G), adenine (A), or thymine (T), one deoxyribose sugar molecule, and a phosphate group. The nucleotides are joined to one another in a chain by covalent hydrogen bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone, according to base-pairing rules. The total amount of DNA in all living organisms is estimated to weigh 50 billion tons (Wikipedia). That's a lot of DNA, especially as protein molecules are microscopic and thus invisible to the naked eye.
The DNA backbone is resistant to cleavage, unless there is a mutation, and both pieces of the double-stranded structure store the same biological information. When a cell divides, it RNA transcription must replicate the DNA in its genome so that the two daughter cells are afforded an exact copy of the genetic information stored in the parent cells. The double-stranded structure of DNA provides a simple mechanism for DNA replication. The two strands are separated and then each strand's complementary DNA sequence is recreated by an enzyme called DNA polymerase. A large part of DNA (almost 99% in humans) is non-coding, meaning that these sections do not serve as patterns for protein sequences, but rather perform little-known functions.
Microbiologists held about 23,200 jobs in 2017. The median annual wage for microbiologists was $66,850 in May 2017. The lowest 10 percent earned less than $39,480, and the highest 10 percent earned more than $128,190. Employment of microbiologists is projected to grow 8 percent from 2017 to 2026. More microbiologists will be needed to contribute to basic research and solve problems of industrial production, and develop new medicines, such as vaccines and antibiotics. In addition, pharmaceutical and biotechnology companies will need to hire experts in order to develop drugs that are produced with the aid of microorganisms.
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