In which state of matter do the particles of iron have the lowest amount of cohesion?

Robert Hooke discovered the first cells in the mid-eighteenth century. The cell theory is a theory because it is supported by a significant number of experimental findings. The cell theory took many years to be developed because microscopes were not powerful enough to make such observations.

This theory, or in-depth explanation, about cells consists of three parts:

• All living things are composed of one or more cells.
• Cells are alive and represent the basic unit of life.
• All cells are produced from pre-existing cells.

Mendel was accurately able to predict the patterns of heredity by studying rules related to genetics. These rules helped shape his theory of heredity. Heredity is the characteristics offspring inherit from their parents.

From experiments with garden peas, Mendel developed a simple set of rules that accurately predicted patterns of heredity. He discovered that plants eitherself-pollinateorcross-pollinate, when the pollen from one plant fertilizes the pistil of another plant. He also discovered that traits are eitherdominantorrecessive. Dominant traits are expressed, and recessive traits are hidden.

Mendel’s Theory of Heredity

To explain his results, Mendel proposed a theory that has become the foundation of the science of genetics. The theory has five elements:

• Parents do not transmit traits directly to their offspring. Rather, they pass on units of information calledgenes.
• For each trait, an individual has two factors: one from each parent. If the two factors have the same information, the individual ishomozygousfor that trait. If the two factors are different, the individual isheterozygousfor that trait. Each copy of a factor, orgene, is called anallele.
• The alleles determine the physical appearance, orphenotype. The set of alleles an individual has is itsgenotype.
• An individual receives one allele from each parent.
• The presence of an allele does not guarantee that the trait will be expressed.

The duodenum is the first part of the small intestines, located between the stomach and the middle part of the small intestines (jejunum). Once food has mixed with acid in the stomach, it moves into the duodenum, where it then mixes with bile from the gallbladder and digestive juices secreted from the pancreas. In the duodenum, absorption of vitamins, minerals, and nutrients begins.

In this reaction, two elements are trading places hence double-replacement. In the reactants, zinc and bromide ions are together, and potassium and hydroxide ions are together. In the products, zinc and hydroxide ions are together, and potassium and bromide ions are together.

Pathogenis an infectious foreign body that enters the body and causes disease or illness to the person. There are five types of pathogens: viruses, bacteria, fungi, protozoa, and worms. Pathogens have antigen proteins found on their surface and are unique to each pathogen.

Antibodyis a protein produced by the body’s immune system when it detects harmful substances (antigens). There are many different antibodies found in the body. Each one is unique and protects the body against the specific antigen that it detects at any given time. If there are no antibodies for a specific antigen, the more likely you are to develop an illness.

Vaccinationsare the introduction of a dead or disabled pathogen or of a harmless microbe with the protein of a pathogen on its surface into the body. Often administered through needle injection, to stimulate the immune system to produce immunity to a specific disease Immunity protects the body from a disease when exposed to it.

There are four types of immunity: natural/passive, natural/active, artificial/passive, and artificial/ active.

• Natural/passive – Babies receive immunities from breastmilk.
• Natural/active – The body produces antibodies to combat an illness when a person becomes sick.
• Artificial/passive – This immunity is temporary and requires doses of serum to maintain the immunity.
• Artificial/active – A vaccination provides artificial/active immunity.

Once the food has been masticated in the oral cavity (mouth), it is then swallowed and travels back into the pharynx down into the esophagus, which leads into the stomach.

A pH of 7 is a neutral solution, which is how pure water is classified. Researchers can determine the strength of an acid or a base by measuring the pH of a solution. The pH value describes how acidic or basic a solution is. On pH scale, shown below, if the number is less than 7 the solution is acidic. A pH greater than 7 means the solution is basic. When the pH is exactly 7, the solution is neutral.

The protein disc that holds two sister chromatids together is what collectively makes a chromosome. A gene is a segment of DNA, deoxyribonucleic acid, which transmits information from parent to offspring. A single molecule of DNA has thousands of genes. A chromosome is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division.

Chromosomes have two components:

• Chromatids: two copies of each chromosome
• Centromeres: protein discs that attach the chromatids together

Human cells have 23 sets of different chromosomes. The two copies of each chromosome are called homologous chromosomes, or homologues. An offspring receives one homologue from each parent. When a cell contains two homologues of each chromosome, it is termed diploid (2n). A haploid (n) cell contains only one homologue of each chromosome. The only haploid cells humans have are the sperm and eggs cells known as gametes.

There are two major types of receptor molecules that respond to an intercellular chemical signal:

• Intracellular receptors: These receptors are located in either the cytoplasm or the nucleus of the cell. Signals diffuse across the cell membrane and bind to the receptor sites on intracellular receptors, of the same cell.
• Membrane-bound receptors: These receptors extend across the cell membrane, with their receptor sites on the outer surface of the cell membrane. They respond to intercellular chemical signals that are large, water-soluble molecules that do not diffuse across the cell membrane.

A neutralization reaction is a type of acid-base reaction where an acid and base react to form a salt and water.

In an aqueous solution, a base increases the hydroxide concentration (OH–), while an acid increases the hydrogen ion (H+) concentration. Sometimes,neutralization reactionsalso occur. This type of reaction happens when an acid and a base react with each other to form water and salt. Salt is typically defined as anionic compoundthat includes any cation except H+and any anion except OH–. Consider the following example of a neutralization reaction between hydrobromic acid (HBr) and potassium hydroxide (KOH).

HBr+KOH→KBr+H2O

Not all neutralization reactions proceed in the manner where all reactants are in the aqueous phase. In some chemical reactions, one reactant may be a solid. The neutralization reaction can still proceed to completion.