Archive for category Science
Biology Chapter 4: Inside the Cell
The cell is the smallest structural and functional unit of an organism, consisting of cytoplasm and a nucleus surrounded in a membrane. Cells are microscopic in size. Cells must remain small in order to have an adequate amount of surface area per cell volume.
All cells have a plasma membrane, cytoplasm, and genetic material. Prokaryotic cells do not have a membrane-bound nucleus. Eukaryotic cells have a membrane-bounded nucleus and also do various membranous organelles. Bacteria are representative of the prokaryotes. They have a cell wall and capsule, in addition to a plasma membrane. Their DNA is in the nucleoid. They have many ribosomes and three possible appendages.
The plasma membrane of both prokaryotes and eukaryotes is a phospholipid bilayer. The phospholipid bilayer regulates the passage of molecules and ions into and out of the cell. The fluid-mosaic model of membrane structure shows that the embedded proteins form a varying pattern. The types of embedded proteins include channel, transport, cell recognition, receptor, enzymatic proteins.
Biology Chapter 2
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is organized into discrete units called atoms. The Greek word rendered “atom” meaning ‘indivisible’ was applied to the basic particle that constituted a chemical element, because the chemists of the era believed that these were the fundamental particles of matter. Not until around the turn of the 20th century, through various experiments with electromagnetism and
radioactivity, did physicists discover that the so-called “indivisible atom” was actually a conglomerate of various particles called subatomic particles- electrons, protons and neutrons- which can exist separately from each other. Since atoms were found to be actually divisible, physicists later invented the term “elementary particles” to describe subatomic particles. The electron is a subatomic particle with a negative electric charge. It is generally thought to be an elementary particle. The periodic table is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom’s atomic nucleus. Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation of the atom as a particular element. A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges between electrons and nuclei. Covalent bonding is a common type of bonding, in which the electronegativity difference between the bonded atoms is small or nonexistent. Bonds within most organic compounds are described as covalent. Ionic bonding is a type of electrostatic interaction between atoms which have a large electronegativity difference. A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond. A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. The substances initially involved in a chemical reaction are called reactants. Chemical reactions are usually characterized by a chemical change, and they produce one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction method. Chemical reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products. Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds.
Biology Chapter 1: A View of Life
Biology is a natural science involved with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is an extensive subject containing many subdivisions, topics, and disciplines. Among the most important topics are five principles that can be said to be the fundamental guidelines of modern biology:
- Cells are the basic unit of life
- New species and inherited traits are the product of evolution
- Genes are the basic unit of heredity
- An organism regulates its internal environment to maintain a stable and constant condition
- Living organisms consume and transform energy.
Cell theory states that the cell is the fundamental unit of life, and that all living things are made up of one or more cells or the produced products of those cells. All cells arise from other cells through cell division. In multicellular organisms, every cell in the organism’s body originates from a single cell in a fertilized egg. Also, the occurrence of energy flow occurs in cells in processes that are part of the function known as metabolism. Finally, cells contain hereditary information called deoxyribonucleic acid (DNA) which is passed from cell to cell during cell division.
A fundamental concept in biology is that life changes and develops through evolution, and that all life-forms known have a common origin. Evolution was established by Charles Darwin as a practical theory when he showed its inspiration: natural selection. Darwin theorized that species and breeds developed through the processes of natural selection and artificial selection or selective breeding.
Now evolution is used to explain the great variations of life found on Earth. Genetic drift was accepted as an additional means of evolutionary development in the creation of the theory.
The theory of evolution proposes that all organisms on the Earth, both living and extinct, have descended from a common ancestor or an ancestral gene pool. Biologists generally consider the universality of the genetic code as great support in favor of the theory of universal common descent for all Bacteria, Achaea, and Eukaryotes.
Genes are the primary units of inheritance in all organisms. A gene is a unit of heredity and corresponds to a region of DNA that influences the form or function of an organism in specific ways. All organisms, from bacteria to animals, share the same basic machinery that copies and translates DNA into proteins. Cells transcribe a DNA gene into an RNA version of the gene, and a ribosome then translates the RNA into a protein, a sequence of amino acids. The translation code from RNA to amino acid is the same for most organisms, but slightly different for some. For example, a sequence of DNA that codes for insulin in humans also codes for insulin when inserted into other organisms, such as plants.
A chromosome is an organized structure consisting of DNA and histones. DNA usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell and any other hereditary information found in the mitochondria, chloroplasts, or other locations is collectively known as its genome. In eukaryotes, genomic DNA is located in the cell nucleus, along with small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nuclei. The genetic information in a genome is held within genes, and the complete assemblage of this information in an organism is called its genotype.
Homeostasis is the ability of an open system to regulate its internal environment to maintain stable conditions by means of multiple dynamic equilibrium adjustments controlled by interrelated regulation mechanisms. All living organisms, whether unicellular or multicellular exhibit homeostasis.
To maintain dynamic equilibrium and effectively carry out certain functions, a system must detect and respond to physiological disturbances. After the detection of a disturbance, a biological system normally responds through negative feedback. This means stabilizing conditions by either reducing or increasing the activity of an organ or system. One example is the release of glucagon when sugar levels are too low.
The survival of a living organism depends on the continuous input of energy. Chemical reactions that are responsible for its structure and function are tuned to extract energy from substances that act as its food and transform them to help form new cells and sustain them. In this process, molecules of chemical substances that constitute food play two roles; first, they contain energy that can be transformed for biological chemical reactions; second, they develop new molecular structures made up of biological molecules.
The organisms responsible for the introduction of energy into an ecosystem are known as producers. Nearly all of these organisms originally draw energy from the sun. Plants and other phototrophs use solar energy by a process known as photosynthesis to convert raw materials into organic molecules. Some of the captured energy is used to produce biomass to sustain life and provide energy for growth and development.
Craig Venter and team make a historic announcement: they’ve created the first fully functioning, reproducing cell controlled by synthetic DNA.
Here is the video announcement from Washington D.C.:
For the first time, to a degree scientists have created life. Craig Venter’s team at the J. Craig Venter Institute in Rockville, Maryland, and San Diego, California, have made a bacterial genome from smaller DNA subunits, and then transplanted the whole string into another cell. So what exactly is the science behind this, and what are its broader applications to this discovery?
The cell was created by stitching together the genome of a pathogen called Mycoplasma mycoides from smaller pieces of DNA synthesised in the lab, and inserting the genome into the empty cytoplasm of a related bacterium. The transplanted gene booted up in its host cell, and then divided over and over to make billions of M. mycoides cells.
Venter and his team added a bunch of representative markers into their synthesised genome. All of them were found in the synthetic cell when it was sequenced.
These markers do not make any proteins, but they contain the names of 46 scientists on the project and several quotations written out in a secret code. The markers also contain the key to the code.
Venter’s work was just proof of what could be done in the future, future synthetic cells could be used to create drugs, bio-fuels and other useful products. He is expected to join up with with Exxon Mobil to produce biofuels from algae and with Novartis to create vaccines.
But such advances come with uncertainty, Robert Field, professor of Law and Health Management and Policy at Drexel University said: “The ability to create new life forms may be emerging from the world of science fiction; but will everything we create be benign, or is Frankenstein now in the realm of possibility?”