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Major Elements in Biological Molecules: Nucleic acids

By: HWC, Views: 7640

DNA and RNA are nucleic acids (polymers of nucleotides). Two polymers with complementary nucleotide sequences can pair with each other. This pairing endows nucleic acids with the ability to store, transmit, and retrieve genetic information. Two strands of DNA pair by hydrogen bonding. A compon...

Major Elements in Biological Molecules: Lipids

By: HWC, Views: 7059

A triglyceride (also called triacylglycerol) is composed of three fatty acid molecules and one glycerol molecule. The fatty acids attach to the glycerol molecule by a covalent ester bond. The long hydrocarbon chain of each fatty acid makes the triglyceride molecule nonpolar and hydrophobic. Pa...

HIV Infection: Viral life cycle

By: HWC, Views: 7089

The series of steps that HIV follows to multiply in the body. The process begins when HIV encounters a CD4 cell. The seven steps in the HIV life cycle are: 1) binding; 2) fusion; 3) reverse transcription; 4) integration; 5) replication; 6) assembly; and 7) budding. Many viruses f...

Introduction to Photolithography - WC, BLF, PA, Hard and Soft baking

By: HWC, Views: 7338

Prior to use, wafers are chemically cleaned to remove particulate matter on the surface as well as any traces of organic, ionic, and metallic impurities. Barrier Layer Formation After cleaning, the silicon wafer is covered with the material which will serve as a barrier layer. The most commo...

Double Vacuum Process (Illustration No Audio)

By: HWC, Views: 6939

In this so-called low-pressure process, the wood is first subjected to a short and relatively weak initial vacuum, after which the treatment vessel is flooded with preservative solution and reduced to normal pressure The double vacuum container is loaded with timber. A partial vacuum is draw...

Stages of Mitosis - Prophase, Prometaphase, Metaphase, Anaphase & Telophase

By: HWC, Views: 7442

In mitosis, the nucleus divides to produce two nuclei that are genetically identical to each other and to the parent nucleus. To prepare for division, the DNA replicates in the preceding interphase. Although the chromosomes are not yet compacted and visible as discrete bodies, we illustrate them ...

DNA Sequences - Dideoxy Sequencing

By: HWC, Views: 7058

A short, radiolabeled primer is annealed to the single-stranded DNA to be sequenced. The DNA serves as a template for in vitro DNA synthesis. The DNA-primer mixture is split into four separate tubes. DNA polymerase and a solution of dNTPs are added to each tube. One of the four 2',3' dideoxy-N...

Plant Defense Mechanisms from Pathogens

By: HWC, Views: 7194

Plants and pathogens have coevolved such that pathogens can recognize plants by the sugars, or other molecules, they produce. Plants, in turn, can recognize pathogens by the molecules they produce. The ability to recognize pathogens allows plants to activate defense systems that can prevent wides...

Phases of an Action Potential - Resting Potential, Threshold, Rising, Falling, & Recovery Phases

By: HWC, Views: 7154

In this tutorial, we will review the phases of an action potential measured from a small area of a neuron's membrane. The action potential can be divided into five phases: the resting potential, threshold, the rising phase, the falling phase, and the recovery phase. When the neuron is at rest,...