Anatomy & PhysiologyCh. 2 Part I

“Chemistry Comes Alive”

States of Matter

Solids- definite shape and volume, such as bones and teeth

Liquid- definite volume, but takes the shape of the container, such as blood plasma and urine.

Gas- no definite shape or volume, such as oxygen and carbon dioxide

Changes in Matter

Chemical change-alters the identity of the material, creating a new substance. Example: Digestion of food

Physical change-just changes the form of the substance, but not its identity

Example: Breaking a bone

Forms of Energy

Energy exists in two forms, each transformable to the other.

Kinetic energy- energy of movement, from atoms to larger objects

Potential energy- stored energy that can be used later

Forms of energy used by the body

Chemical energy- energy stored in the bonds of chemical substances, such as food molecules. Converted to ATP that is used by cells.

Electrical energy-energy created by the movement of charged particles. Nerve impulses are electrical energy

Forms of energy, cont.

Mechanical energy-energy directly involved in movement, such as walking

Radiant (electromagnetic) energy- energy that travels in waves. Light rays stimulate the retina for vision and the body to make vitamin D.

Energy does not have mass and does not take up space.

Energy is measured by its effect on matter. Both matter and energy are conserved—

they cannot be created or destroyed, but can change form

Energy is never “lost” when it changes form, but may become unusable.

How are matter and energy interrelated?

Properties of Matter

Physical properties-characteristics of a substance that can be detected with the senses. Ex) color, texture, boiling point

Chemical properties-pertain to the way atoms interact with other atoms Ex) reactivity, flammability

Basic atomic structure

Atoms are made up of a nucleus, consisting of protons (+) and neutrons (0).

Surrounding the nucleus are negatively charged electrons traveling in orbitals.

Since atoms have the same number of protons and electrons, they are electrically neutral.

Oxygen (O)- Major component of organic molecules. Gas is needed for cellular respiration (ATP production)

Carbon (C)- Found in all organic molecules, including carbohydrates, proteins, lipids, and nucleic acids

Hydrogen (H)- Component of all organic compounds, and as H+ it influences the pH of body fluids

Nitrogen (N)- Important in the structure of protein and nucleic acids

Common Elements in the Human Body

Calcium (Ca)- Calcium phosphate forms bones and teeth, Ca2+ is needed muscle contraction, nerve impulses, and blood clotting

Phosphorus (P)- found in bones, teeth, nucleic acids and ATP

Potassium (K)- K+ is the major positive ion in cells, needed for nerve impulses and muscle contraction

Sulfur (S)- found in the amino acid cysteine, involved in protein structure

Sodium (Na)- major cation found in extracellular fluids, important for water balance, conduction of nerve impulses, and muscle contraction

Common elements, cont.

Chlorine (Cl)- the most abundant anion in extracellular fluids

Magnesium (Mg)- present in bone, important cofactor in metabolic reactions

Iodine (I)- needed to produce functional thyroid hormones

Iron (Fe)- component of hemoglobin and some enzymes

**Carbon, hydrogen, oxygen, and nitrogen make up 96% of body weight

Common elements in the body, cont.

Isotopes

Isotopes are atoms of the same element that have a different number of neutrons, resulting in different atomic masses.

Radioisotopes are radioactive, producing radiation that can be detected by scanners.

Radioisotopes are valuable diagnostic tools for biological research and medicine. They can be used for diagnosing and treating cancers, and for PET scans.

Compounds Elements and compounds

are pure substances. Elements are composed

of the same type of atoms. Ex) O, N, Cl, Na

Compounds are formed when two or more atoms are chemically combined in definite proportions. Ex) NaCl

Mixtures

Mixtures are made of components that are physically intermixed, but not chemically combined

There are three basic types of mixtures: solutions, colloids, and suspensions

Solutions

Solutions are homogeneous mixtures of gases, liquids, or solids.

Examples: air we breathe, seawater, IV fluids

The substance present in the greatest amount is the solvent.

Substances present in smaller amounts are called solutes.

True solutions are described in terms of their concentration, such as molarity or % composition.

Colloids

Colloids, or emulsions, are heterogeneous mixtures with particles that do not settle out.

Colloids scatter light, and some can undergo sol-gel transformations, changing reversibly from liquid to more solid (gel) state.

Examples include gelatin and cytoplasm.

Suspensions

Suspensions are heterogeneous mixtures with large, often visible solutes that are undissolved and may settle out.

An example is blood—living blood cells are suspended in blood plasma

1) No chemical bonding occurs within the components of a mixture. Atoms in a molecule of a compound are chemically bonded

2) The components of a mixture can usually be separated by physical means, such as by filtering, evaporation, or centrifuging. Compounds can only be separated by breaking chemical bonds between the atoms.

3) Compounds are pure substances and are always homogeneous in nature. Mixtures may be homogeneous or heterogeneous.

Mixtures vs. Compounds

Valence electrons are the e- found in the outer energy shell of an atom. These e- are lost, gained, or shared during chemical reactions, and are the electrons involved in forming chemical bonds.

If an atom loses e-, a positive ion is formed (cation). Ex) Na+

If an atom gains e-, a negative ion forms (anion). Ex) Cl-

Ion formation

Chemical bonds Ionic bonds- form when

electrons are transferred from one atom to another. Can form crystals Ex) NaCl is an ionic compound

Covalent bonds- form when electrons are shared between atoms. Equal sharing = nonpolar, unequal sharing=polar Ex) Water (polar), cholesterol (nonpolar)

Organic macromolecules such as carbohydrates, proteins, lipids, and nucleic acids are formed by covalent bonds between carbon atoms.

Chemical bonds, cont.

Hydrogen bonds-form when hydrogen is bonded to a more electronegative atom like oxygen or nitrogen. Intramolecular bonds

Water forms hydrogen bonds between molecules, making it cohesive and slow to change temperature

Chemical reactions occur when chemical bonds are formed, rearranged, or broken.

Chemical reactions are represented by chemical equations.

Compounds are represented by formulas, with the reactants on the left side of the equation and products on the right.

NaOH + HCl H2O + NaCl reactants products

Chemical reactions

Synthesis: A + B ABDecomposition: AB A + BDisplacement: AB + C AC +

BRedox: decomposition reactions

that break down food to produce energy

Types of reactions

Exergonic vs. Endergonic Reactions

Exergonic reactions release energy. Includes catabolic and oxidative processes.

Ex) Digestion of food, Cellullar respiration

Endergonic reactions absorb energy. Includes anabolic/synthesis reactions that store energy.

Ex) Protein synthesis, Photosynthesis

Temperature- increasing temperature causes molecules to move faster, speeding up the reaction.

Size of particles- smaller particles move faster and react more rapidly than large ones.

Concentration of reactants- High concentration of reactants speeds up the process

Presence of catalysts- speed up the reaction rate. Ex) enzymes

Factors affecting reaction rates