Biology Chapter 6 Chemistry in Biology

Atoms, Elements and Compounds Matter is anything that has mass and takes up space Atoms are the building blocks of matter Atoms are the smallest thing that can be called “matter” but are in fact made up of even smaller particles

The Structure of an Atom The nucleus is the dense center region of the atom. It has an overall positive charge. Inside the nucleus are: – Protons– positively charged particles – Neutrons- particles with no charge Outside the nucleus, in energy levels, are negatively charged electrons The overall charge in an atom cancels out to be zero

Element An element is a pure substance that cannot be broken down by chemical or physical means Examples: Hydrogen, Nitrogen, Sodium Elements are organized on the Periodic Table

Isotope An isotope is an atom of the same element that differs in the number of neutrons only Everything else is the same Radioactive isotopes are unstable isotopes that decay Radioactive isotopes have many different uses

Compounds A pure substance formed when two or more elements combine Always a specific combination of elements in a fixed ratio Cannot be easily broken down Ex. Water

Chemical Bonds When two or more substances combine to form a compound, it is held together by chemical bonds The reason why atoms bond together is to fill the outer shell with electrons, therefore becoming stable There are two types of chemical bonds, ionic and covalent

Covalent Bond Atoms join together and share electrons Most compounds in living organisms are held together with covalent bonds Called molecules Ex: Water

Ionic Bond Electrical attraction between atoms Electrons are transferred meaning one atom loses and the other gains Atoms are now called ions and are either positive (loses e-) or negative (gains e-) Ex: NaCl

Van der waals Forces Attraction between molecules that hold them together Geckos use van der Waals forces to climb walls The hairs on their toes are attracted to the smooth surface

Water and Solutions

Water’s Polarity Molecules that have an unequal distribution of charges are called polar molecules. Polarity is the property of having two opposite poles. The oxygen and hydrogen in water share electrons, oxygen is bigger and holds the electrons closer so oxygen becomes a little negative and hydrogen becomes a little positive

Surface tension Surface of a liquid acting like an elastic sheet Produces a “skin” or a “film” on the surface Water drop – water strider

Cohesion The ability of molecules that are alike to stick together One water molecule sticking to another water molecule This ability gives water capillary action abilities – ability to draw a substance up a tube – plants

Adhesion Ability of molecules of different types to stick together Water molecule sticking to the metal of the faucet This ability makes water the universal solvent

Like Dissolves Like Water is polar so it will dissolves all polar molecules (example salt, sugar) Water will not dissolve non- polar molecules (example Oil, grease) Soap is both polar and nonpolar, the nonpolar end binds to the oil and the polar end is then attracted to water and the soap and oil or dirt is washed away

Chemistry in Biology Water is polar like the poles of a magnet

Mixtures Combination of two or more substances in which each substance retains its individual properties Homogenous- The mixture has uniform composition throughout (salt water) – Solvent– the substance that does the dissolving (water) – Solute- The substance that is dissolved (salt) Heterogeneous– the mixture has different composition throughout (chex mix)

Chemistry in Biology  Substances that release hydrogen ions (H + ) when dissolved in water are called acids.  Substances that release hydroxide ions (OH – ) when dissolved in water are called bases. Acids and Bases

Chemistry in Biology  The measure of concentration of H + in a solution is called pH.  Acidic solutions have pH values lower than 7.  Basic solutions have pH values higher than 7. pH and Buffers

Chemistry in Biology  Buffers are chemicals that react with acids or bases to keep the pH within a particular range.  Reactions in the body happen at a pH between 6.5 and 7.5  In a cell, buffers help keep the environment of the cell between 6.5 and 7.5 Buffers

The Building Blocks of Life Organic Chemistry

Chemistry in Biology Organic Chemistry  Carbon is the most abundant element in biological molecules.  Living things also contain the elements H, O, N, P and S

 The four electrons in Carbon’s outermost energy level can form four covalent bonds with other atoms Chemistry in Biology  Carbon compounds can be in the shape of straight chains, branched chains, and rings. Carbon Is Special

Macromolecules Chemistry in Biology  Macromolecules are large molecules formed by joining smaller organic molecules together.  Living things are made of 4 types of macromolecules  Polymers are molecules made from repeating units of identical or nearly identical molecules.

Chemistry in Biology Carbohydrates  Compounds composed of carbon, hydrogen, and oxygen – Carbohydrates are the energy of the cells, they are fast energy

Chemistry in Biology  Disaccharide - Two monosaccharides joined together.  Polysaccharide - Longer carbohydrate molecules  Monosaccharides are simple one ring sugars

Chemistry in Biology Lipids  Molecules made mostly of carbon and hydrogen also contain some oxygen

Lipid uses Stored energy for the cell (slow energy) Waxes –ear wax, bees wax Oils Fats Biological membranes – cell, mitochondria, nucleus Chemical messengers

Chemistry in Biology  Saturated fats - Lipids that have tail chains with only single bonds between the carbon atoms (saturated or covered in Hydrogen) solid at room temperature  Unsaturated fats - Lipids that have at least one double bond between carbon atoms in the tail (not saturated or covered in Hydrogen) liquid at room temperature  Fats with more than one double bond in the tail are called polyunsaturated fats. Lipid Types

Chemistry in Biology Proteins  A compound made of small carbon compounds called amino acids – building blocks of cells  Amino acids are made of carbon, oxygen, hydrogen and nitrogen.  Amino acids join together in chains, like a string of beads and fold many times to make a protein  Peptide Bonds – covalent bond between amino acids

Protein Uses Involved in almost every cell function Structural support – membranes Transport – gated channels Communication within and between cells Enzymes Control cell growth Muscles, hair, skin

Enzymes Remember enzymes are proteins Enzyme names end in “ase” Enzymes speed up reactions and are reused Enzymes are specific – one enzyme for each type of substrate Lock and Key Theory – enzyme and substrate fit together like a key in a lock or puzzle pieces

Chemistry in Biology  Amino acids have a central carbon atom.  One of the four carbon bonds is with hydrogen.  The other three bonds are with an amino group (–NH 2 ), a carboxyl group (–COOH), and a variable group (–R).

Chemistry in Biology  After an amino acid chain is formed, the protein folds into a helix or a pleat.

Amino acids and Proteins

Chemistry in Biology  Nucleic acids are complex macromolecules that store and transmit genetic information.  Nucleic acids are made of smaller repeating subunits called nucleotides, composed of carbon, nitrogen, oxygen, phosphorus, and hydrogen atoms. Nucleic Acids

Types of Nucleic Acids DNA – deoxyribonucleic acid RNA – ribonucleic acid Genetic information Cell and organism replication