Biology 2.8 - 2.14 Section Notes

Necessary for the Functioning of the Cell

Has strong covalent chemical bonds that links atoms that form a cell’s molecules and weaker bonds within and between molecules

Hydrogen Bonds

An important type of weak chemical bond that forms when a positive hydrogen atom of polar covalent bond is drawn to a negative hydrogen atom of a polar covalent bond

Polar Molecules

A molecule with polar covalent bonds and unequal distribution of changes throughout the molecule

Classification of a Water Molecule

Hydrogen atoms are connected to oxygen using polar covalent bonds and it has a wide V shape. It is a polar molecule

Flirtations

Has a V shape that has a negative charge at the point and a positive charge on the ends. The positive charge allows hydrogen to be attracted to negative charges (ex. oxygen, nitrogen.) They are called hydrogen bonds since a hydrogen atom is always involved

The Role of Hydrogen Bonds

They help create the shape of proteins and how it functions. The flow of information depends on them. They hold 2 strands of DNA molecule together and it translates hereditary information into proteins

Cohesion

The tendency of molecules of the same kind to stick together

Cohesion of Water

Cohesion is much stronger for water. Cohesion of water is vital in the living world. (Ex. trees need cohesion to transport water and nutrients from the roots to the leaves)

Adhesion

The clinging of one substance to another

Structure and Function Example

Thin plant veins enhances the adhesion of water to cell walls and helps go against the pull of gravity

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid

Surface Tension Example with Hydrogen Bonds

Hydrogen bonds make water have high surface tension and it makes it act like the water is coated with a film. Slightly overfilling a glass will cause the water to stand above the rim.

Thermal Energy

The energy connected to random movement of atoms and molecules

Heat

Thermal energy that transfers from warmer to a cooler body of matter

Temperature

Measures the intensity of heat which is the average speed of molecules in a body of matter

Temperature Example

You burn your finger on a metal pot while waiting for the water to boil. Hydrogen bonds in water causes it to have a stronger resistance to temperature change

Hydrogen Bonds Reaction to Heat

Heat has to be absorbed to break the bonds and heat is released when bonds are formed. If you want to raise the temperature of the water, the bonds have to be broken to make the molecules move faster. Water absorbs a lot of heat. When water cools, molecules slow down, more bonds form, and heat is released

Impact of Earth’s Giant Water Supply

The giant water supply helps keep the temperatures within limits that allow life. Bodies of water store a lot of heat. The water’s resistance stabilizes ocean temperatures and helps moderate a human’s temperature

Evaporative Cooling

The process where the surface of an object becomes cooler during evaporation because the molecules with the greatest energy is changing from a liquid to a gas

Water’s Three Forms and Unusual Property

The three forms are gas, liquid, and solid. Density changes in different forms. This is caused by hydrogen bonds. (Ex. solid is less dense than liquid)

Process of Freezing Water

Molecules form strong hydrogen bonds with nearby bonds and it gets held together at arm’s length. It also creates a three-dimensional crystal

Density of Ice and Liquid Water

Molecules in ice crystal has wide spacing, stable molecules, and fewer molecules. Molecules in liquid water are packed close together and has a greater quantity. Ice is less dense and it floats on top of liquid water

When Body of Water Cools

Floating ice protects water from the cold air above. It prevents water from freezing and it allows aquatic forms of life to live underneath the frozen surface

Result of Broken Down Molecules in Liquid Water

A small percentage of water molecules break apart into hydrogen ions (H +) and hydroxide ions (OH-). The ions are radioactive and the changes in the concentration can affect a cell’s proteins and molecules

Acid

A substance that donates hydrogen ions to solutions. Ex. Hydrochloric acid (gastric juice in stomach)

Base

A substance that reduces hydrogen ions concentration for a solution. Ex. Sodium Hydroxide donates OH- and it combines with H+ to create H2O. This reduces H+ concentration.

pH Scale

It describes how acidic or basic a solution is. pH stands for the potential of hydrogen. The scale ranges form 0 to 14 or most acidic to most basic. Each pH unit represents a 10-fold change in the concentration of H+ in solution

Neutral Solutions

Pure water and aqueous solutions aren’t acidic or basic. They have a pH of 7 and concentrations of H+ and OH- are equal

Buffers

They are substances that resist changes in pH. This is achieved by accepting H+ when it has an excess amount ord to 7.4 donating H+ when depleted. Ex. Biological fluids in the human body has buffers that keep pH of blood to 7.4

Hydrogen Ions

H+

Hydroxide Ions

OH-