Cell Biology Chapter 2

Cell Biology Chapter 2

element

a substance that cannot be broken down to other substances by chemical reactions

molecules

the atoms of elements are linked together by covalent bonds to form ____

covalent bond

sharing of a pair of valence electrons by 2 atoms

• important to form backbones of macromolecules

non-covalent bonds

ionic bonds, hydrogen bonds, and Van Der Waals interactions

hydrogen bonds

-commonly form between molecules that contain oxygen or nitrogen

hydrophilic

substance has an affinity for water (water-loving)

hydrophobic

does not have an affinity for water (water-fearing)

oil molecules

are hydrophobic because they have many relatively non polar covalent bonds

4 types of noncovalent attractions help bring molecules together in cells

• hydrogen bonds

• ionic bonds (electrostatic attractions)

• Van der Waals attraction

• hydrophobic force

ionic bonds

• atoms sometimes strip electrons from their less electronegative bonding partners

• the two resulting oppositely charged atoms are called IONS

• a cation= + charge ion

• a anion= - charge ion

• attraction between cation and anion

van der Waals attraction

• electrons may be distributed asymmetrically

• the resulting regions of positive or negative charge enable all atoms or molecules to stick to one another

• these weak van der Waals attractions occur only when atoms and molecules are very close together

hydrophobic force

• caused by a pushing of non polar surfaces out of the hydrogen-bonded water network, where they would otherwise physically interfere with the highly favorable interactions btwn water molecules

• protein folding

• base stacking of DNA

true

2 macromolecules with complementary surfaces can bind tightly to one another through non covalent interactions