Principles of Biology: Molecules and Cells module 2

Describe how elements combine into molecules and compounds, based only on the atoms involved in a bond identify the bond type, predict the types of bond an atom can form based on electronegativity, based only on the atoms involved identify if the molecule is hydraulic or hydrophobic, predict which kinds of molecules will form hydrogens, distinguish between a chemical bond and van de Waals attractions, explain how the structure of water leads ti hydrogen bond formation, explain how hydrogen bonds relate to the properties of water

cytosol

water environment

what are atoms composed of?

atoms are composed of 3 subatomic particles: protons, neutrons, and electrons

what are electrons used for?

electrons are shared or transferred to make chemical bonds

How many protons and neutrons of neutral atoms have?

neutral atoms have the same amount of protons and neutrons

Cations

• have more protons than electrons

• net positive charge

Anions

• more electrons than protons

• net charge is negative

what is determined by electronegativity?

bond types

non polar covalent bond

• small difference in electronegativity

• equal sharing of electrons

polar covalent bond

• medium difference in electronegativity

• unequal sharing of electron

• partia charges

ionic bond

• very large difference in electronegativity

• electrons are taken

• charges

what is the difference of electronegativity for ionic bonds

a difference in electronegativity larger than 2hat is w

what is the difference in electronegativity for polar covalent bonds

a difference in electronegativity larger than .5

what is the difference in electronegativity for non polar covalent bonds

a difference in electronegativity less than .5

hydrophobic molecules

• water fearing

• no charges

• no attraction

hydrophilic molecules

• water loving

• full or partial charges

What is a bond

shared or transferred electrons between two atoms (non polar covalent, polar covalent, ionic)

What is a bind

chemical attraction between molecules ( charge to charge interactions, ionic bonds in water, hydrogen bonds, chemical attraction)

what is electronegativity

an atom’s attraction for electrons

what is a hydrogen bond

electropositive hydrogen from a polar molecule is attracted to an electronegative atom that is often negative

what produces hydrogen bonds

attraction

what is the strength and length of a hydrogen bond

each individual bond is weak and temporary

What are hydrogen bonds responsible for

most of water’s important physical characteristics

what is van de Waals attraction

a weak bond

what type of force is associated with van de Waals attraction

a non directional attractive force

how is van de Waals attraction formed

when two atoms are very close to one another

what to antibodies recognize with the van de Waals attraction bond

they recognize the shape of an invading organism

What is the polarity of water

the bond between hydrogen and oxygen atoms are polar covalent with hydrogen having a partial positive charge and oxygen having a partially negative charge

What about a water molecule makes hydrogen bonding possible?

The shape of a water molecule and its polarity

Why does water have a high heat capacity

the many hydrogen bonds allow water to absorb a large amount of thermal energy with out a lot of temperature change

what is the speed for water temperature rising and falling

Water temperature rises and falls at a slow speed

what allows organisms to maintain their normal temperature and protect them from rapid temperature changes

water

water has a high what

heat evaporation

what must be broken to evaporate water

hydrogen bonds

What is water

why is water a good solvent

its polarity

what does a solution contain

a solution contains dissolved substances or solutes

Is ice more or less dense than water

ice is less dense than liquid water

What happens at temperatures below 4 degrees celsius

at below 4 degrees celsius hydrogen bonds between water molecules become more rigid and open

What happens at 0 degrees celsius

water expands and freezes

what would happen if ice was more dense than water

ice would sink and the ocean would freeze solid instead of from the top down

Ice acts as a what on top of a frozen body of water

an insulator

water molecules are blank and blank

cohesive and adhesive

what is cohesion

ability of water to cling to each other during hydrogen bonding

what is adhesion

ability of water molecules to cling to other polar surfaces because of water’s polarity

high specific heat

hydrogen bonds absorb heat when they break and release heat when they form minimizing temperature changes

high heat of vaporization

many hydrogen bonds must be broken for water to evaporate

lower density of ice

water molecules in an ice crystal are spaced relatively far apart because of hydrogen bonding

solubility

polar water molecules are attracted to ions and polar compounds, making these compounds more soluble

hydrophobic exclusion

water repels hydrophobic compounds forcing them to associate together