Cell Bio: Chapter 2

Ionic Bond

bond formed by attraction of oppositely charged electrons

Ionic Bond:

• electrons ___ from one atom to another

transfer

Ionic Bond: electron transfers ___ outer shells

complete

Ionic Bond: ___ charges attract

opposite

Salts

atoms held together by ionic bond

Which bond charges attractions and is weaker in water?

ionic bonds

Which bond involves some polar covalent molecules and are weak?

hydrogen bonds

Heat

disrupts weak bond

Salt and pH

disrupt bond

What affects ionization and interactions?

salt and pH

Ionic bonded atoms ___ in solution

dissociate

NaCl —>

Na+ and Cl-

(Sodium becomes positive and chlorine becomes negative)

Ion

charged atom due to electron gain or loss

Cation

positive charge

Anion

negative charge

In salt, water surrounds atoms and they ___.

separate

Na+ ion ___ electron

loses

(cation)

Cl- ion ___ electron

gains

(anion)

Cl- is

electronegative

Covalent Bonds

atoms share outer shell electrons

Molecule

atoms held together by covalent bonds

Number of covalent bonds ___ the number of electron needed to fill outer shell.

equals

Polar Covalent Bond

atoms share a pair of electrons unequally

• one atom is more electronegative

Nonpolar Covalent Bond

atoms share a pair of electrons equally

Single Covalent Bond

one pair shared

• i.e.

  • C-H

  • O-H

  • C-C

Double Covalent Bond

two bonds shared

• i.e.

  • O=O

  • C=C

Triple Covalent Bond

three bonds shared

• i.e.

  • N≡N

In polar covalent bonds, shared electrons located ___ to one atom

closer

In polar covalent bonds, atoms develop ___ ___ (due to the shared electrons being closer to one atom)

partial charges

Partial charges allows charge ___ between molecules.

interaction

oxygen and nitrogen have large attraction relative to carbon

partial negative charge

Hydrogen has low attraction relative to oxygen and nitrogen.

partial positive charge

Hydrophilic

dissolves in water

Water ____ makes it a versatile solvent

polarity

H2O ___ ionic compounds

dissolves

i.e. NaCl crystal dissolves as H2O surrounds the ions

ionic compounds dissolved in water are

uniformly distributed

In NaCl, the positive hydrogen end of H2O interacts and surrounds

the negative Cl- ion of crystal

In NaCl, the negative oxygen end of H2O interacts and surrounds

the positive Na+ ion in crystal

Polar Covalent Bond example

partially positive hydrogen - partially negative oxygen - partially positive hydrogen

Nonpolar Covalent Bond example

O=O

• no partial charges

electrostatic attractions between molecules are interactions between ___ grpups

charged

electrostatic attractions are ___ ___ ___ between molecules

weak ionic bonds

Noncovalent bonds are important for interactions between ___

biomolecules

Biomolecules

organic molecules: carbohydrates, proteins, lipids, and nucleic acids

Hydrophilic compounds ___ with water through charges

interact

Ionic bonds interact with hydrophilic compounds by

charges

Polar covalent bonds interact with hydrophilic compounds by

H bonds

Type of Noncovalent bonds

Ionic and Electrostatic bonds (can be used interchangeably—means there are interaction between charges. For example, opposite charges attract)

Noncovalent are ___ in absence of water

strong
- atoms forming salts

noncovalent bonds are ___ in water

weak

• between molecules

electrostatic attractions between molecules are interactions between ___ groups on molecules

charged

electrostatic attractions between molecules are ___ ___ ___

weak ionic bonds

i.e. “-” phosphate in DNA interacts with “+” charge; DNA-Protein interaction regulates gene expression; DNA histone interaction forms nucleosome

water is

asymetric

water molecules have ___ covalent bonds

polar

water can form ___ hydrogen bonds with other molecules

four

oxygen can form ___ hydrogen bonds

2

Hydrogen can form ___ bond

one

all 4 water molecules are linked by

H bonds

noncovalent bonds

hydrogen bonds and hydrophobic bonds

hydrogen bonds are weak and occur in some

polar covalent molecules

hydrophobic bonds are weak and occur in

noncovalent molecules

the H bond holds ___ ___ together

DNA strands

• the basis of genetic code

H bonds are important in ___ ___

protein structure

H binds are important in ___ molecule-___ molecule interaction

large; small i.e. receptor ligand interaction; enzyme substrate

H bonds are responsible for

unique water properties

unique water properties

• cohesion

• adhesion

• ice floats

• higher boiling point and evaporative cooling

• surface tension

hydrogen bonds occur with slightly ___ H atom and slightly ___ atom of another molecule

+; -

water molecules ___ protons (H+)

exchange

ionizes

dissociates into charged particles

H2O —>

H+ + O-

[ ]

concentration

Pure H2O distilled water

[H+] = [OH-]

In carbon hydrogem bonds, electrons are shared

equally

• no charge separation

C-C, C-H, H-H, and O=O are

nonpolar covalent bonds

Acids increase [H+] in solution by ___ protons (H+)

donating

HCL

H+ + Cl-

Bases decreases [H+] in solution by ___ protons (H+)

accepting

NaOH

←→ Na+ + OH-

OH- combines with ___ forming ___, lowering concentration of H+ in the solution

H+; H2O

bases decrease [H+]