1. Biologically Important Molecules

Question 1

Explain or draw the basic amino acid structure

Answer 1

left - amino group (NH2)
middle - alpha carbon with hydrogen and R group attached
right - carboxyl group (COOH)

Question 2

What bond connects amino acids?

Answer 2

peptide bond (covalent bond)

Question 3

How is a peptide bond created?

Answer 3

Free electrons from an amino group attack the center carbon of a carboxyl group in a hydrolysis reaction (water is released).

By convention, polypeptide chains always start with the amino-terminus

Question 4

Hydrolysis of a protein by another protein (to break that protein down) is called?

Answer 4

proteolysis / proteolytic cleavage.

the enzyme that cuts the protein is called a protease.

Question 5

What is a thiol group? Which amino acid contains it?

Answer 5

a thiol is a sulfide-containing group (-SH).

Cysteine’s R group is a thiol

Question 6

What is a disulfide bond? What does it create?

Answer 6

A disulfide bond (covalent) is created by two cysteine groups. When created, cysteine is now called cystine. This covalent bond increases tertiary structure stability.

Question 7

t or f, denaturation refers to the disruption of proteins shape without breaking peptide bonds.

Answer 7

true! - denaturation does NOT break peptide bonds

Question 8

what can cause protein denaturation (n=4)?

Answer 8

1. urea
2. changes in pH extremes
3. temperature extremes
4. changes in salt concentrations

Question 9

Explain what each level of protein structure is determined by.

Answer 9

primary - peptide bond sequence
secondary - hydrogen bonds (between backbone NH and CO groups)
tertiary - R-group interactions (hydrophobic, electrostatic, etc.)
note: despite that disulfide bonds are covalent, they are still considered a part of the tertiary structure
quaternary - interactions between polypeptide subunits.

Question 10

t or f, a peptide bond may form in quaternary structure.

Answer 10

false

Question 11

carbohydrates may be broken down into CO2 in a process called?

Answer 11

oxidation

Question 12

what is the general chemical formula for monosaccharides?

Answer 12

CnH2nOn

glucose = C6H12O6

Question 13

what bond forms between two sugars?

Answer 13

glycosidic linkage (covalent bond) –> formed by a dehydration reaction requiring enzyme catalysis.

Question 14

t or f, mammals can digest alpha and beta glycosidic linkages.

Answer 14

false - mammals (typically) can only digest alpha linkages.

Question 15

What are glycogen, starch, and cellulose, briefly?

Answer 15

glycogen - alpha polymer of glucose used in mammals. short with many branches
starch - alpha polymer of glucose used in plants. less branched.
cellulose - beta polymer of glucose that creates cell walls and wood.

Question 16

what is a fatty acid? how large are they?

Answer 16

long unsubstituted alkane which ends in a carboxylic acid. FAs are typically 14-18 carbons long.

note: only even-numbered fatty acids are made in human cells

Question 17

what is a saturated fatty acid?

Answer 17

a fatty acid with NO carbon-carbon double/triple bonds. it is saturated with hydrogen molecules.

Question 18

what are cis (Z) / trans (E) fats?

Answer 18

these are unsaturated fatty acids (they contain one or more double bonds).
cis/Z –> bent fatty acid
trans/E –> not bent (compacts easier)

Question 19

what is micelle?

Answer 19

the molecule formed when fatty acids interact with water. the carboxyl heads face outwards while the hydrophobic tails point inwards to create a ball.

Question 20

what is triglyceride?

Answer 20

triglyceride is fat. Three fatty acids are esterified (bonded to) glycerol, forming triglyceride. This is how fatty acids are stored.

Question 21

what enzyme breaks down triglyceride?

Answer 21

Lipase (hydrolyzes triglycerides)

Question 22

t or f, fats are more efficient energy storage than carbs.

Answer 22

true.

they pack more tightly due to hydrophobic effects and have more energy per C-C bond

Question 23

what are phospholipids? What is diglycerol phosphate (DG-P)?

Answer 23

phospholipids create lipid bilayer membranes.

DG-P is essentially glycerol, except instead of three alcohol groups, the third is a phosphate group.

Question 24

Fatty acids spontaneously form micelles, phospholipids spontaneously form ?

Answer 24

the lipid bilayer which makes membranes

Question 25

how can you change the cell membrane fluidity (n=3)?

Answer 25

1. saturation status of the fatty acid tails. Saturated fatty acids pack more tightly and decrease fluidity
2. fatty acid length. longer tails pack more tightly and decrease fluidity
3. cholesterol.
   - low temperatures –> increases fluidity
   - high temperatures –> decreases fluidity

Question 26

what is a terpene?

Answer 26

a hydrocarbon polymer made of isoprene units (5 carbon long units)

we classify terpenes based on how many isoprene units comprise them.

Question 27

what is squalene?

Answer 27

squalene –> terpene with 6 isoprene units. Found in earwax and can be used to synthesise steroids.

Question 28

what is a terpenoid?

Answer 28

A terpenoid is a functionally altered terpene. For example, vitamin A (retinoic acid) is a terpene with a hydroxyl functionality at the end.

Question 29

what is a steroid?

Answer 29

steroids are derived from cholesterol and are comprised of a tetracylcic ring system.

Question 30

two orthophosphates bound together, via an anhydride linkage, form pyrophosphate (P-O-P). POP is a high-energy bond that may provide energy to enzymatic reactions. Why is POP high energy (n=3)?

Answer 30

1. the linked phosphates negative charges repel each other
2. orthophosphate offers increased resonance
3. orthophosphate has a more favourable interaction with the solvent (water)

Question 31

What is a nucleotide? what is it made of (n=3)?

Answer 31

nucleotides are the building blocks of nucleic acids.
each nucleotide has a
1. sugar group (deoxyribose or ribose)
2. a purine or pyrimidine base joined at the 1C of the sugar
3. 1-3 phosphate units joined at the 5C of the sugar

Question 32

what is a nucleoside?

Answer 32

a nucleotide without the phosphate group(s).

Question 33

t or f, triglycerides, phospholipids, cholesterol, steroids, and terpenes are all forms of lipids

Answer 33

true