Lecture 3

Question 1

What 4 elements make up most of the cell’s mass?

Answer 1

C H O N

Question 2

. What is the difference between an ionic bond and a covalent bond? Give examples of each

Answer 2

Ionic – transfer (loss or gain) of electrons to complete outer shell; ex: NaCl, KCl Covalent - sharing of electrons to complete outer shell; ex: H2, O2, CN, etc.

Question 3

What kind of bond holds the atoms of a water molecule together?

Answer 3

Polar covalent bonds

Question 4

What type of bond holds water molecules together?

Answer 4

Hydrogen bonds

Question 5

What kinds of molecules are soluble in water?

Answer 5

Hydrophilic molecules

Question 6

How can weak bonds such as Van der Waals interactions, hydrophobic interactions, ionic bonds and hydrogen bonds hold large macromolecules together? Understand each kind of interaction.

Answer 6

Many weak chemical interactions form an overall strong interaction

Question 7

List the number of covalent bonds formed by C, H, N, and O. What determines the number of covalent bonds that these elements form?

Answer 7

C – 4 covalent bonds; H – 1; N – 3; O – 2 Number of electrons in outer shell

Question 8

What makes a covalent bond polar (i.e. polar covalent bond)?

Answer 8

Differences in electronegativity between atoms (making partial negative and/or partial positive portions
on the molecule).

Question 9

Define electronegativity.

Answer 9

Strength of attachment between an atom and electrons

Question 10

Put the following in order of decreasing electronegativity: C, H, N, O

Answer 10

O>N>C>H

Question 11

Which combinations of C, H, N and O result in polar bonds? Write in the partial charges to help you see how they can interact.

Answer 11

C=O, N-H, O-H (the ones we are concerned with)

Question 12

Define pH mathematically.

Answer 12

–log[H+]

Question 13

Which of these groups is acidic or basic: Carboxyl, amino and phosphate

Answer 13

a) carboxyl – acidic (proton donor)
b) amino – basic (proton acceptor)
c) phosphate – acidic (proton donor)

Question 14

Discuss the distinction between strong and weak acids and between strong and weak bases. What do they do to the pH of the solution they are in?

Answer 14

Strong acids dissociate to put a lot of H+ in solution; lowers pH Weak acids put few H+ in solution Strong bases remove many H+ in solution; raises pH Weak bases remove few H+ in solution

Question 15

What is a hydrocarbon? List a hydrocarbon that you use every day.

Answer 15

C-C backbone with bonds to H; Octane, methane

Question 16

List the building blocks (monomers) that make up each macromolecule and where they are found within the typical cell:

Answer 16

a) polysaccharides – monosaccharides; cell wall of plants and in energy storageb) fats/lipids/membranes – fatty acids; membranesc) proteins – amino acids; ribosomed) nucleic acids – nucleotides; nucleus

Question 17

Name the functional groups in a monosaccharide.

Answer 17

Aldehyde or ketone

Hydroxyl

Question 18

Discuss how disaccharides and polysaccharides form.

Answer 18

Condensation reactions

Question 19

What is the significance of alpha vs. beta hydroxyl (OH) at C1 when glucose molecules form a ring in solution?

Answer 19

Glycogen and starch function in energy storage; cellulose is a strong cell wall component

Question 20

Draw the following disaccharides with the following configurations (made from glucose):

Answer 20

a) with an alpha 1-4 linkage (maltose)b) with a beta 1-4 linkage (cellobiose, if anyone asks…)

Question 21

What are the different polysaccharides used in energy storage and structural support? Discuss the configurations of the glycosidic bond in each.

Answer 21

Energy storage:
=Glycogen- alpha 1-4 glucose with alpha 1-6 branches =Starch- (amylose) unbranched alpha 1-4 glucose

Structural support:
=Cellulose- unbranched beta 1-4 glucose

Question 22

What are condensation and hydrolysis reactions? Why are they important for cells?

Answer 22

Condensation – remove water to join molecules
Hydrolysis – add water to break bond
Needed to build and degrade macromolecules