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is a substance that cannot be broken down chemically into any other substances. Gold,carbon, and copper are elements you might be familiar with.
- The individual component pieces of an element.
- is a bit of matter that cannot be subdivided any further without losing its essential properties.
At the center of an atom, which is usually made up of two types of particles, called protons and neutrons
- are particles that have a positive electrical charge
- are particles that have no electrical charge.
- The amount of matter in a particle
- protons and neutrons have approximately the same mass
- Whirling in a cloud around the nucleus of every atom are negatively charged particles.
- An electron weighs almost nothing—less than one-twentieth of one percent of the weight of a proton
- is made up of the combined mass of all of its protons and neutrons
- corresponds to how many protons a atom has
An atom that has extra neutrons or fewer neutrons than the number of protons
- Most elements and their isotopes have perfectly stable nucleithat remain unchanged virtually forever, never losing or gaining neutrons, protons, or electrons. A few atomic nuclei are not so stable, however, and break down spontaneously sometime after they are created.
- in the process of decomposition they release, at a constant rate, a tiny, high-speed particle carrying a lot of energy. (The particle may be a proton, neutron, electron, or just energy.)
All the known elements can be arranged in a scheme, in the order of their atomic number
- Electrons move around the nucleus in designated areas called electron shells. An atom can have as many as seven electron shells in total
- Atoms become stable when their outermost shell is filled to capacity.Stable atoms tend not to react or combine with other atoms.
- An atom that loses one or more electrons becomes positively charged, while an atom that acquires electrons becomes negatively charged. This transfer of electrons is driven by the fact that atoms with full outer electron shells are more stable.
chemical characteristics of an atom
depend on the number of electrons in its outermost shell. Atoms are most stable and least likely to bond with other atoms when their outermost electron shell is filled to capacity.
Groups of atoms held together by bonds
amount of energy to break a bond between two atoms
- When two atoms share electrons.
- 1)An atom of hydrogen has one electron in its first shell. One more electron is needed to fill the shell.
- 2)The nuclei of two hydrogen atoms come closer together and share the two electrons,which circle around both of them. The new H2 molecule is more stable.
- The sharing of two electrons between two atoms.
- When one atom transfers one or more of its electrons completely to another, each atom becomes an ion, since each has an unequal number of protons and electrons. The atom gaining electrons becomes negatively charged, while the atom losing electrons becomes positively charged.
A hydrogen bond is formed between a hydrogen atom in one molecule and another atom, often an oxygen or nitrogen atom, in another molecule (or even in another part of the same molecule). This bond is based on the attraction between positive and negative charges.
HYDROGEN BONDS #2
- 1)In a water molecule, oxygen’s eight positively charged protons attract electrons more readily than does the single proton in the hydrogen atoms. As a result, the electrons are pulled toward the oxygen side of the molecule, making it slightly negative in charge, while the hydrogen side is slightly positive.
- 2)Hydrogen bonds are formed between the slightly positively charged hydrogen atoms of one molecule and the slightly negatively charged oxygen atom of another.
ELEMENTS IN THE HUMAN BODY BIG 4
water hydrogen bonds
- Large heat capacity.
- Low density as a solid.
- Good solvent.
- Any fluid with a pH above 7.0 has fewer H+ ions (and more OH− ions) and is considered a base
- Any fluid with a pH below 7.0 has more H+ ions (and fewer OH− ions) and is considered an acid
the amount of H+ in a solution is a measure of its acidity
these chemicals can quickly absorb excess H+ ions to keep a solution from becoming too acidic, and they can quickly release H+ ions to counteract any increases in OH− concentration. Therefore, buffers are chemicals that act to resist changes in pH
- large molecules made up from smaller building blocks or subunits
- are essential to the building and functioning of living organisms
- carbohydrates,lipids, proteins, and nucleic acids.
- are molecules that contain mostly carbon, hydrogen, and oxygen
- they are the primary fuel for running all of the cellular machinery and also form much of the structure of cells in all life forms.
monosaccharides (simple sugars)
- the monomer of a carbohydrate
- The simple sugars contain anywhere from three to six carbon atoms and,when they are broken down, the products usually are not carbohydrates. Two common monosaccharides are glucose,found in the sap and fruit of many plants, and fructose,found primarily in fruits and vegetables, as well as in honey.Fructose is the sweetest of all naturally occurring sugars. The suffix -ose tells us that a substance is a carbohydrate.
- The carbohydrate of most importance to living organisms
- Circulating glucose, also called “blood sugar,” has one of three fates
- 1)Fuel for cellular activity. (immediate use)
- 2)Stored temporarily as glycogen.(short term storage)
- 3)Converted to fat. (long term storage)
- two simple sugars are bonded together
- example the joining of glucose and galactose to make disaccharide lactose, which is the sugar found in milk
- When large numbers of simple sugars are joined together—sometimes as many as 10,000 may be linked
- may function as“time-release” stores of energy or as structural materials that may be completely indigestible by most animals. An example of such a structural material is the polysaccharide cellulose—the primary component of plant cell walls.
- important sources of fuel for cells
- consists of a hundred or more glucose molecules joined together in a line.
- In plants, starch is the primary form of energy storage, found in roots and other tissues
- Grains such as barley, wheat, and ryeare high in starch content, and corn and rice are more than70% starch.
Chitin (pronounced kite-in)
forms the rigid outer skeleton of most insects and crustaceans (such as lobsters and crabs)
- forms a huge variety of plant structures that are visible all around us. We find cellulose in trees and the wooden structures we build from them, in cotton and the clothes we make from it, in leaves and in grasses. In fact, it is the single most prevalent compound on earth.
- cellulose is almost identical in composition to starch. Nonetheless, because of one small difference in the chemical bond between the simple sugar units, cellulose has aslightly different three-dimensional structure. Even tiny differences in the shape of a molecule can have a huge effect on its behavior. In this case, the difference in shape makes it impossible for humans to digest cellulose as they can starch.Consequently, the cellulose we eat passes right through our digestive system unused.
The cellulose in our diet is known as “fiber”. It is also appropriately called “roughage”because, as the cellulose of celery stalks and lettuce leaves passes through our digestive system, it scrapes the wall ofthe digestive tract. Its bulk and the scraping stimulate the more rapid passage of food and the unwanted, possibly harmful products of digestion through our intestines. That is why fiber reduces the risk of colon cancer and other diseases (but it is also why too much fiber can lead to diarrhea).
Maintain a stable internal environment even when external environment changes